MYE Technical Manual 1942
MYE_Technical_Manual_1942 MYE_Technical_Manual_1942
User Manual: manual pdf -FilePursuit
Open the PDF directly: View PDF 
.
Page Count: 409
| Download | |
| Open PDF In Browser | View PDF |
vke
HYE TECHNICAL,
. MAN nAL
MALLORY
.
Published by
P. R. MALLORY &
~O.,
Indianapolis, Indiana
IN~.
OUR SINCERE APPRECIATION TO YOUI
* ThuS do we ackn~wledge a special debt of gratitude for'generous, spontaneous, willing
help, ~nd permission to use articles, charts, and other information without which it would have been impossible
to make this MYE Technical Manual complete.
Air-King Products Co., Inc.
Alliance Manufacturing Company
Automatic Radio Manufacturing Co., Inc.
Belmont Radio Corporation
Brush Development Co.
Bryan Davis Publishing Co.
Buick Motor Co.
Capehart Division of Farnsworth
Television & Radio Corp.
Clough-Brengle Co.
Colonial Radio Corporation
Communications
Crosley Radio Corporation
Crowe Name Plate & Manufacturing Co.
Delco Appliance Division,
General Motors Sales Corporation
Delco Radio Division,
General Motors Corporation
Detrola Corporation
Electrical Research Laboratories, Inc.
Electronics
Emerson Radio & Phonograph
Corporation
Fada Radio and Phonograph Corporation
Fairbanks, Morse & Co.
Farnsworth Radio & Television Co.
Ford Motor Co.
Galvin Manufacturing Corporation
General Electric Co.
General Household Utilities Company
General Radio Co.
Gilfillan Bros., Inc.
Herbert Horn Radio Co.
Hickok Electrical Instrument Co.
Howard Radio Company
Hudson Motor Car Co.
Jensen Radio Manufacturing Co., Inc.
Ken-Rad Tube & Lamp Corporation
Magnavox Co., Inc.
McGraw-Hill Book Co., Inc.
Meissner Mfg. Co., In!!.
Midwest Radio Corp.
Mission Bell Radio Mfg. Co., Inc.
Noblitt-Sparks Industries, Incorporated
Pacific Radio Corporation
Pacific Radio Exchange, Inc.
Packard Bell Radio Company
Packard Motor Car Co.
Peter Plln Radio Corp.
Philco Radio & Television Corp.
For years it has been the Mallory-Yaxley pledge to retain
leadership in furnishing constructive, helpful information and
assistance to the radio service and engineering professionsand to make that information worthy of its confidence. In
this, the MYE Technical Manual, there is ample evidence of
the continuance of this pledge.
Radio Products Corporation
Radiotron Division of RCA Mfg. Co.
Raytheon Production Corp.
RCA Manufacturing Company, Inc.
Radio Engineering Handbook, by Keith
Henney (Copyright McGraw-Hill Book
Co., Inc.)
Radio Manufacturers Association
Sears-Roebuck & Co.
The Spar's-Withington Company
Stewart-Warner Corporation
Stromberg-Carlson Telephone
Manufacturing Company
Sylvania Electric Products, Inc.
Trav-Ier Radio & Television Corporation
Triplett Electric Instrument Co.
Troy Radio & Television Co.
United American Bosch Corporation
Utah Radio Products Company
Warwick Manufacturing'Co.
Webster Company
Wells-Garduer & Co.
W.lcox-Gay Corporation
Zenith Radio Corporation
In dedicating the MYE Technical Manual to the radio and
electronic industries, we are also dedicating it to those who
have made it possible.
You are always welcome at the Mallory factory, where you
may review and witness the continued research and development work-an activity which warrants your 100% confidence.
Reproduction or use, without express permissi;on, of editorial or pictorial content, in any manner, is prohibited,
No patent liability is assumed with respect to the use 01 the in/ormation contained herein,
Copyright 1942 by P. R. Mallory & Co" Inc., Indianapolis, Indiana, U. S. A.
Copyright under International Copyright Union
All rights reserved under Inter.American Copyright Union'{191O}, by P. R. Mallory & Co., Inc.
F Gurth Printing
PRINTED IN U. S. A.
· . . Up to This Time
N
one of our friends-evidently a
mation you could get to keep apace. So we brought
newcomer in the radio service field-wrote us
out the first complete Auto Radio Manual with quar-
for some help. "I knew you made parts, both original
and replacement," he said, "but how long have you
terly supplements to k~ep it up-to-date. The demand
for this book was terrific. Many of you still treasure it,
been is~uing technical literature ?"
even though it has been supplanted by more complete
When? It started a chain .of memories that ran
back eight years when vibrators were new and myste-
and up-to-date guides.
OT LONG AGO
rious; and service men needed information and help
That same year we gave you a greatly improved
and more complete Volume Control Manual-con-
to make repairs. Like every subsequent publication,
the Manual we issued then had a definite"purpose ...
cise, accurate and practical. It was widely imitated
filled a definite need of the industry.
announced thirty new replacement volume controls
but never quite equaled. More important to you, we
That same year, 1934, saw another help produced
that would service 98 % of the 3,200 set models then
in answer to your insistent calls for aid. The publication of a complete manu~l on replacement volume
in existence. Only four of the new controls would service 1938 models. It was the first move towards stand-
controls had been attempted but never before accom-
ardization of replacement controls.
plished. It became a reality with the issuance of the
Yaxley Replacement Volume Control Manual.
In 1935, we had not fully made up our minds
You have told us again and again that the time a-nd
money it has saved you is incalculable.
whether to issue further publications ... but you de-
In 1936, we introduced standardization of condensers with the announcement of 69 units for seryic-"
cided for us. Automobile radio was gaining ground
ing 100% of all radio sets using dry electrolytics.
with seven league boots, and you needed all the infor-
Over and above the many constructional features for
3
THE
MYE
TECHNICAL
universal replacement was an extra featur~the new
Mallory Condenser Service and Replacement Manual,
which gave in Qetail the universal app,lication ,of these
condenser~ in everyday service work. To guide our
planning, we had solicited your aid through personal
calls and extensive questionnaires. From a detailed
analysis of your problems, we made possible the first
practical system of condenser servicing.
But, in spite of the progress you had helped us
make, we were still dissatisfied. Too many of yo"\!
complained of the growing number of "guides," the
endless job of looking through dozens of books to get
the "dope'; you needed. A bright idea suddenly struck/
us. Why not lump all of our separate manuals into
one complete book-a book where you could find on
one page and on one line all the information you '
nee,ded for replacing controls, condensers and vibrators ? We could also put in the I.F. peaks of all makes
and models, the complete tube complement, perhaps
a reference to the transformer circuit. So, we started
to work.
In May, 1937" after months of almost insurmountable compilation and production problems, we
brought out the First Edition of the Mallory-Yaxley
Radio Service Encyclopedia. (You nicknamed it the
"M.Y.E.") Used daily by tens of thousands, this 'book
prompted your world wide testimony as to itJl indis-
MANUAL
pensable value. Many enthusiastic letters not only
bear witness to this fact, but als~ guided us in making,
important changes in subs~quent editions; changes
that, made their predecessors obsolete.
The Second Edition "M.Y.E." followed the firstfifteen months later. 'Automatic tuning, with its maze
. of complications to plague the service engineer, was
appearing on all new sets with infinite variations.
From our first-hand experience in the design and application of push-button switches with practically
e,very ma~or set manufacturer, we gave you the first
clear, detailed amdysis of all the systems-'with suggested servicing procedures. It was the hit of the year.
Again, you were profuse in your thanks.
In September, 1939, we presented the Third Edi- .
tion,free,of former ~'frills." It had to be. More new
models of radio receivers had been announced during
the period from March, 1938, to September, ~939,
than in any other comparable period. The listings of
makes and models alone required more than twice the
number of pages that had been devoted to them in the
first edition. It became obvious that it would be an
impossibility to have both listings and general technical information in ~ single volume. The book would
become too big, too bulky and too expensive. We
. had
,
4
,
THE
MYE
TECHNICAL
MANUAL
no choice but to omit the technical articles. However,
Almost a year had elapsed. from the time that the
the listings were made even more valuable by the addi·
twelfth, and final Supplement was mailed to you be-
tion of a number of new features, including a refeience by volume and page number to Rider's Manuals,
fore we issued our next publication ... the 4th Edition M.Y.E. During that year you showered us with
questions. The Engineering Application Section of
our Wholesale Division worked overtime to get you
the right answers-fast. Replacements were becoming
more complicated. Controls, particularly, were the
big headache. The variety of shafts and bushings were
enough to drive you "nuts." We purposely held up
the publication of the Fourth Edition M.Y.E. so that
we could give you thorough and painstaking replacement recommendations ... and also the maximum
universal replacement from the fewest number of indi-
and more complete information on tube cOJ;nplements.
You were grateful, and told us so.
vidual parts.
Although we started early in 1940, the further we
got into the job of gathering samples of original parts,
circuit information and other data that would enable
us to set up accurate recommendations, the more evident it became that we could not hope to publish the
M.Y.E. in 1940. It was September of 1941 before we
could get the Fourth Edition in your hands ... but it
was more valuable to you because of the delay.
There were twice as many pages of set and model
listings as in the Third Edition ... almost 400. We
had to change the shape of the book, too, in order to
New and vital developments in radio continued at a
dizzy pace. Shifts in frequei:lCY assignments for stations in the broadcast band necessitated your help in
the re-setting of automatic tuning receivers. Frequency modulation was coming in. Television, with
totally new complexities for the service man, was on
the threshold. Anticipating your troubles, we ha'stened
the first issue of the Supplemental M.Y.E. Monthly
Technical Service ... a service designed to give you
timely data in an unbiased, accurate and easy-tounderstand manner. As succeeding issues reached you
month after month, you hailed the supplements as
the one convenient, economical source of technical
information. You told us that they kept you abreast of
every current development, that one issue was worth
the price of the whole series.
5
THE
MYE
TECHNICAl.
MANUAl.
accommodate original part numbers on all products.
heat of the all-out defense effort, its progress con-
But this new feature saved you even more time and
tinued apace despite serious curtailments in our.
trouble in finding the correct replacement.
When we issued .the Fourth Edition M.Y.E. last
full-time technical staff as a re.sult of drafts and enlist-
fall, we did not announce a Second Supplemental
. mately 2,000 copies are being distributed to military
Technical Service. There were too many uncertainties
radio instructors. Once you look through the book,
ahead. We were in the midst of mounting defense
you'll understand why.
ments. As further proof of its timeliness, approxi-
activities. The future of the entire radio industry was
We are const~ntly studying your problems, work-
unplcdictable and we hesitated to commit ourselves
ing out new helps for you to meet the restrictions that
on a monthly service that we might have to suspend.
We sounded out a great number of you by personal
war imposes, bringing new ideas to you to make your
work more effective and more profitable.
letter on the idea of bringing the former supplements
We are in business to help ·you. Whether it be the
thoroughly up-to-the-minute, adding timely new ones,
selection of a volume control for a 1928 model re-
and binding the whole works in hard cloth covers.
.Your answers were so overwhelmingly affirmative
ceiver, the procurement of a switch for an aircraft
that we started immediately on the all-important revi-
address system, or any of the countless other problems
sions and new texts.
in service, substitution or procurement ... the recom-
crankshaft balancer, taking the hum from a public
Equally important as the enthusiastic "go-ahead"
mendations of the Mallory Engineering Department
signal were the many fine suggestions on the material
are yours for the asking. Sure, we're busy ... but not,
and subject matter for the new book. These sugges-
too busy to help you out.
We hope you'll find the M.Y.E. Technical Manual
a worthy companion to the other well-read books in
your library. Use it regularly-refer to it, and to the
Fourth Edition M.Y.E., whenever you are stumped.
If the answers aren't there, then write to our Engineering Application Section, Wholesale Division.
tions were all given the most careful consideration,
and wherever possible they have been incorporated to
make the M.Y.E. Technical Manual your book. In
presenting the M.Y.E. Technical Manual, we renew
again the responsibility we accepted eight years agoto provide you with factual, usable, reliable data that
would make your job easier and more profitable.
It is a war-time book in every sense. Begun in the
Remember, "Come hell or high water," we're here
to help you.
P. R. MALLORY & CO., INC.
6
e
THE
MYE
Section' I
TE~HNI~AL
MANUAL
Loud Speaker Design
and Application
MALLORY
7
Section 1 •
THE
MYE
TECHNICAL
MANUAL
LOUDSPEAKERDESIG.N AND APPLICATION
In spite of the fact that the most important part of a radio receiver, P. A.
system, electric phonograph, and similar sound reproducing systems is its
loud speaker, there has heen a dearth of practical technical information on this.
device. We~ave long felt that {l simple, straight forward, factual exposition
of loud speakers would be of real value to the service engineer.
It was with this thought in mind that we asked the Jensen Radio Manufac- .
turing Company, Chicago, Illinois, for' technical data suitable for preparation
of a text on this subject. They generously responded by furnishing this complete treatise, which we believe to be a real contribution to the technIcal literature of radio. We believe you will find this chapter to be both interesting
and valuable.
,
I. General Definitions, Physical
Characteristics
DIAPHRAGM
A loud .speaker is a device for converting audio-frequency electrical power
into acoustical power and radiating it
into a specific region"
The most common . type of loud
speaker is the moving coil or "electrodynamic" type. This type of loud
sp'eaker consists essentially of a radiator
or diaphragm to which is rigidly attached a coil, which in turn is immersed
in a steady magnetic field. This dia·
phragm and coil assembly is suspended
by flexible supports allowing vibration
parallel to the axis of the coil. These
vibrations are the result of passing the
audio-frequency electric current through
SOUND CHAMBER
.
VOICE COIL
Fig.2a
the coil. Figures 1 and 2 illustrate this
type of loud speaker.
Figures la, 11;>, and lc illustrate the
"direct-radiator" type. That is, the loud
speaker is designed in such a way that
when used in conjunction with a suit-
CLAMP
RI G
DUST CAP
ANNULUS
SUSPENSION
CONE
HOUSING
SPIDER
SUS
able "baffle" the diaphragm radiates directly into the surrounding air. In contrast, Figure 2 illustrates the class·in
which the diaphragm is coupled by
means of a "sound chamber" to a "horn"
'. which'in tum radiates into the air. This
latter class of loud speakers will be discussed in a later section.
Figure la illustrates a speaker in
which the magnetic field is supplied by
means of an electromagnet or field coil,
whereas Figures Ib and .lc illustrate
those in which a permanent magnet fulfills this duty.
II. The Magnetic Circuit; Field
Coils and Permanent Magnets
CORE OR - - ' i ? ? l
POLE PIECE
F'I ELD COl L
CASE
F'I ELD COl L
Fig.la
8
".
The operation of the loud speaker
does not depend upon how the magnetic field is supplied, providing this
• Section 1
LOUD SPEAKER DESIGN AND APPLICATION
ANNULUS
PENSION
CLAMP
RIN
TABLE 1
Field Coil Excitation
Power
(watts)
DIAPHRAGM
OR CONE
CONE
HOUSING
~:..-~----
RING
MAGNEr
Fig.lb
field has the required strength. This
latter point should be especially noted
since all further explanation concerning
the action of the moving parts will be
general, that is, the required magnetic
field strength is assumed.
Permanent magnet loud speakers are
generally available having magnetic
field strengths identical to equivalent
models using field coils. This equality
is a result of relatively recent develop·
ments in magnetic alloys. No apprecia.
ble deterioration has been noted in
original samples of magnets made from
these alloys several years ago. Thus
misapprehensions with regard to the
efficiency and stability of permanent
magnet structures need no longer exist.
For a given magnetic structure the
field strength depends on the magnet
weight. ijowever as the magnet weight
varies, the air gap (the region in which
the voice coil is situated) should be altered to give best results. A figure of
merit including all these factors is a
good measure of the effectiveness-i)f the
unit; one such measure is-the magrretic
energy iIi the gap stated in milliops of
ergs. Typical values are 0.19 "for a
~~mall inexpensive 5-inch perm'anent
mag-llet speaker, 1.36 for a good quality
lO-inch speaker and 7.5 for a high
quality 12-inch speaker.
For an electromagnet magnetic structure the field strength depends on the
power dissipated in the coil. The manufacturer specifies the normal power to
be dissipated in the field coil. Table 1
shows the field current or voltage required to dissipate a given power in a
field coil of given resistance. As a rough
guide, field-coil power dissipation
should be approximately equal to the
maximum audio-frequency power:han.
dling capacity of the device.
In choosing a loud speaker for a
given application, the decision as to
permanent magnet or field coil magnetic structures depends on several factors (see section 9). Cost is in many
cases a vital factor. Very small permanent magnet loud speakers cost from
the same to about 10 % more than
equivalent field-coil units. Larger permanent magnet speakers used for public
address and large radio receivers cost
approximately 50 % more than field
coil equivalents, while for very large
magnetic structures, such as used in
large public address installations, theatre work, etc., the permanent magnet
speaker may cost more than twice as
much as the field coil unit.
III. Baffles, Cabinets and Aconstic
Loading Networks
Loud speakers of the direct-radiator
type are invariably mounted on some
form of auxiliary structure. This may
take the form of a cabinet (radio console), a flat plan~ surface with an open-
Field
Resistance
(ohms)
Voltage
Field
Current
(rna)
3
3
3
3
3
500
1000
1500
1800
2500
38.8
54.8
67.2
73.6
86.6
77.5
54.7
44.7
40.8
34.6
4
4
4
4
4
500
1000
1500
1800
2500
44.8
63.3
77.5
85.0
100
89.3
63.1
51.6
47.0
40
6
6
6
6
6
500
1000
1500
1800
2500
54.8
77.5
95
103
122
110
77.5
63.1
58,2
49.1
8
8
8
8
8
500
1000
1500
1800
2500
63.3
89,5
110
120
141
126
89.4
72.7
66.6
56.7
500
70.8
100
122
134
158
141
100
82
74.6
63.3
10
10
10
10
10
~ '" 1500
' 1800
14
14
14
14
14
100015'00
1800
2500
83.8
118
145
159
187
167
119
96.5
81. 7
74.8
26
26
26
26
26
500
1000
1500
1800
2500
114
161
198
216
255
228
162
131
120
102
~OOO
250~
/;iit
ing through which the speaker radiates
(flat baffie) , or some more complex
System of acoustic loading. All of these
P PLATE
POLE PIECE
ICE COIL
LOUD SPEAKER HORN UNIT WITH ANNULAR DIAPH RAGM
Fig.2b
9
r
Section 1 •
H E
MY E r E C H N I CAL
MAN
ANNULUS '
NSION
SPIDER
SUSPENSION
CORE OR
POLE PIECE
VOl
COIL
SLUG
MAGNET
MAGN
CASE.
Fig. Ie
devices may be classed in general as
"baffles." Their primary function is to
acoustically "load" the loud speaker to
allow it to radiate more efficiently. This
improved efficiency usually occurs in
the low frequency range. It is important
to remember that the more "adequate"
the "baffle" the more improved will be
the low-frequency response. It should
be emphasized at this point that a loud
speaker cannot be considered as an iso,lated element because: (1) Any baffle is
definitely a part of the acoustical system; (2) The loud speaker may radiate
into a closed room which has its own
acoustic resonance characteristics reflected into the loud speaker; (3) The
accompanying audio-frequency electri·
cal circuits are definitely a part of the
composite system and must be consid. ered when we discuss the operation of
a loud speaker system.
The simplest type of baffle is a large,
flat surface with an' opening through
which the speaker radiates. However,
the simple flat baffle has the following
disadvantages: (1) Large size for adequate low-frequency response; (2)
Very poor low-f~equency response for
large angles from the speaker axis (that
is, as we approach the plane of the
baffle); (3) Limited acoustical flexibility (that is, limited oppottunity for
modification of response characteristics). The open-back radio console.cabinet has the same inherent disadvantages,
since it resembles a flat baffle. However,
'here a new form of difficulty arises
known as '''cabinet resonance." Cabinet
resonance actually modifies the response
characteristics of the system due to a
standing wave pattern in the, cabinet.
10
This results in emphasis of the 150 to
250 cycle response.
The closed box is an improvement
in that it eliminates the back-side radiation as such. In other words, if the
cabinet is rigid, all the sound at the rear
of the cabinet is due entirely to radiation from the front of the cone. There
is, of course, practically u~iform radiation in all directions at low frequencies. See Figure 3. The back-side radiation from the cone may be absorbed
by a heavy absorbent lining on the
interior of the box.
SOLID LOUD SPEAKER ENCLOSURE
SPEAK(R
UA
L
Still more elaborate acoustical loading I networks are in common use. In
one version a large volume is coupled
to the loud speaker and the acoustic
enolosure resonance is used to increase
low-frequency response. A modification of this method is one in which a
column at the rear of the speaker is
lined with absorbent material so that
the column acts as a long acoustic
'trans:q:tission line. '
Figure 4 shows an especially effective
type of acoustic loading in which a second opening or "port" in the otherwise
complete enclosure is adjacent to the
loud speaker diaphragm and is in effect
another radiator coupled to the loud
speaker diaphragm. This "secondary
radiator" (air in the mouth of the
port) moves with a given amplitude
and phase relative to that of the loud
speaker diaphragm in a ma~mer depending upon the spe~ker design and
dimensions .of the enclosure and opening. This is known as the ":Sass Reflex"
principle and results in considerable
advantage over the whole low-frequency
end of the acoustic spectrum. Only a
relatively small amount of sound absorbing material should be placed inside the enclosure, the object being to
have a very small absorption at low
frequencies. A modification uses a
series of short tubes instead of the simple opening in the enclosure.
It is to be emphasized at this point
that no effective equalization of the
electrical circuits in the driving amplifiers can give the same results as adequate acoustic loading and the subsequent high efficiency of the speaker
itself. This is true because: (1) the
poorly-baffled' loud speaker has inherently more distortion; (2) the highly
fig. 3
The stiffness due to the compression
of the air in the closed box acts as if
the stiffness of the speaker suspension
itself were made greater. Cabinet resonance may also occur and cause trouble
in the closed-box type of baffle if sufficient absorbent material is nbt used or
if the enclosure is not sufficiently large.
The totally closed-caliinet is sometimes
improperly called an "infinite baffle"
although the,behavior of the system is
quite different
ENCLOSURE
ABSORPTION
MATtRIAL
PORT
BASS REFLEX
ENCLOSURE
,
Fig. 4
I
• Section 1
LOUD SPEAKER DESIGN AND APPLICATION
100
S
10
....
b
""'",
horn, which has a straight axis with the
area expanding according to a definite
formula. Figure 6 illustrates this type.
A modification is the case in which the
complete horn is "coiled" or folded to
conserve space.
A second form of horn is known as
the multicell in which the area is
broken up into a number of sub-areas
each expanding individually-that is, a
group of individual cells forming an
array. These indiv.idual cells may be
formed by inserting partitions in a
simple or trumpet horn or they may be
completely separate sub-horns assembled in an array. Figure 7 shows an
example of the latter type.
FREQUENCV:HORN MOUTH
DIAMETER CHART I
V=1129 FEET PER SEC. AT
20° CENT.
)\.
" r\
I'.
""
"'I'..
" ""-
I
50
lOa
500
1M
fREQUENCY (CPS)
Fig.S
equalized amplifier may very likely
have limited overload characteristics
thus introducing considerable amplitude distortion.
IV. Horns and Horn Type
Loud Speakers
A horn is a device which is used to
couple a ,relatively small radiator efficiently to the surrounding air. It is
essentially a tube of varying crosssection, increasing in size from the loud
speaker unit to the open end. Relatively
high efficiencies are attained. Furthermore, the horn is relatively directional
at medium and high frequencies. (Contrary to popular opinion, horns are almost perfectly non-directional at low
frequencies.) The most common type
is the exponential horn in which the
area increases exponentially with distance along the horn. The lowest frequency effectively radiated by a horn
depends, first, on its rate of change
of area, and second, upon its mouth
area; the low-frequency end' of the
"" '"
r--...
5M
10M
Fig. 7
range is often called the horn "acoustic cutoff."
The mouth diameter for a horn of
circular cross-section should be about
one-third of a wavelength at the lowest
frequency to be radiated. This relation
is shown in Figure 5.
There are three common variations
of horns, depending upon their particular function. The most common form
is the simple trumpet, or projector-type
MULTICELLULAR HORN
=
=
=
Throat Area
1.718 in 2
Mouth Area 960 in 2
Cutoff Freq.
200 Cycles
The third form is known as the
folded or re-entrant type horn in which
,the axis along which the area expands
is no 10ng!3r a simple straight Of curved
line. Figure 8 shows one type in which
RE -ENTRANT HORN
Fig. 8
HORN LENGTH 10114
THROAT DIA.
.7.
MOUTH DIA.
12
CUT Off fREQUENCY
Fig.6
IN.
IN.
IN.
800 CYCLES
the area expands as a simple horn for
a short distance and then becomes an
annular area expanding back along the
exterior of the first simple horn section. This type of folding may be carried on even further. Figure 9 shows
a type commonly used with large diaphragm loud speaker! in which the
area expands along two channels each
11
Secti9n 1 •
THE
MYE
TECHNICAL
MANUAL
LOUDSPEAKER
SECTION A-A
r
A
)
WING jA'fLES ~
/
,I
,.,- -, \
\
\
....
'"
/
I
I
\
--"
/
, .....
,\
/
\
\
t
J
I
f-/
LOW FREQUENCY FOLDED HORN
Fig. 9
folded upon itself. Folded and re-entrant horns are used where economy of
space is essentiaL
Horns are often used with direct
radiator speaker!'!, the throat area being
approximately the same size as the
diaphragm, and are sometimes referred
to as "directional baffles." Below the
horn "cutoff" the loud speaker merely
radiates essentially as it would on a flat
baffle of the same area as the horn surface_ Thus small "flares" used in this
way add nothing to the low-frequency
response although they may enhance
the speech-frequency range.
'V. Power-Handling Capacity
Power-handling capacity of a given
loud speaker unit is generally determined by the amount of power that can
be handled by the speaker before an
appreciable amount of distortion is
introduced or by the physical ability of
the voice coil to dissipate a given
amount of power. In most cases, especially where the speaker or speaker system is the high-fidelity type, objectionable distortion will be introduced be12
fore the temperature of the voice coil
has risen to a point where permanent
damage will occur_ However, with the
standard-fidelity type speaker, i.e., one
whose high-freque;ncy response is limited to frequencies below approximately 5,000 cycles, the distortion will
not be as noticeable as in the highfidelity type and it is often possible to
damage the voice coil before distortion
is noticeable. One important fact to
remember is that most manufacturers
rate their speakers as to the amount of
musical or voice power that can be
deliver,ed to the speaker and not the
amount of power at a single frequency.
In the case of a metal diaphragm type
speaker, when used with a horn designed for the speaker; the powerhandling capacity of the unit will vary
with the frequency~ At the lower frequencies where the excursion of the
diaphragm increases as the frequency
deQreases (for constant power input) ",
the limiting factor is the distance that
the diaphragm can move before striking the 'walls of the sound chamber.
Thus, a unit that will handle 20 watts
at 400 cycles will handle only approxi-
mately 10 watts at 200 cycles or only
approximately 5 watts at 100 cycles.
In general, for cone type speakers,
the size of the diaphragm and the voice
coil will determine the physical ability
of the unit to handle power. The power-,
handling capacity of the voice coil is
limited by its operating temperature
rise. Therefore a permanent magnet
speaker of a given cone, voice-coil and
magnet size, having no field coil to
contribute heat, is capable of dissipating more power in the voice coil than
the equivalent field-coil design. See Figure 10. Since no universally recognized
standard method of rathlg power-handling capacity has been set up, some
manufacturers' ratings are highly overoptimistic, while other manufacturers
are ultra-conservative and their ratings
may oftentimes be exceeded by as much
as 100,/0 before the speaker willfail for
physical reasons.
One common misunderstanding is
the belief that a speaker rated at, for
example, 25 watts power-handling capacity and using a large cone, of say 15
to 18 inches diameter, cannot be driven
by a small amplifier satisfactorily. On
the contrary, the more efficient a speaker, regardless of its size, the more souna
output will be delivered by that speaker
for any giveri electrical input power. If
an amplifier is normally used with a
12" speaker having an efficiency of approximately 5,/0, it can also be used
with an 18" speaker having powerhandling capacity of 25 watts or more
and an efficiency of 20%, and what is
more, the sound output from the larger
speaker will be approximately four
times (an increase of 6 db) that obtained from the 12" speaker. In other
words a highly efficient speaker requires less power to drive it to a given
acoustical output than a small inefficient
speaker.
Where a speaker ,system is used in
conjunction with an amplifier having
response-equalization or volume-expansion circuits, it is of the utmost importance that the speaker be capable of
handling the maximum power that may
be delivered by the amplifier. For example, even though the unit may be operated on the average with only 2 watts
of power input, it must be capable of
handling 20 watts or more if the peak
power is increased by 10 db due to ex,
pansion or equalization.
LOUD SPEAKER. DESIGN ANP APPLICATION
• Section 1
hes~tancy of some manufacturers in releasing response curves which are likely
to be misunderstood by the reader. Of
course curves run on the same measur,.- 35
ing equipment under identical test
.-; 90
II:
z
conditions are directly' comparable.
VOICE COIL COPPER TEMPERW
w
0.
ATURE RISE
However, since the room conditions in
u
0.
RATED AUDIO INPUT 400 C.P.S.
the final installation play such an im/
~ 80
FIELD COIL SPEAKER
- 30 8I portant part in the quality of reproducw
PERMANENT
MAGNET
SPEAKER
W
II:
U
tion, it sometimes happens that the
CJ
Z
'W
curves of a particular laboratory show
/
070
~
that
speaker "A" is more desirable than
~
:z
en
- 25 w
speaker "B" from I:\. theoretical standII:
w
point, while actually it may be found
~ 60
~
~
that when the two speakers are comII:
1.1
pared side-by-side under living room
en
W
FIELD COIL COPPER _
20
«
II:
conditions, speaker "B" is audibly
TEMPERATURE RISE _
w
:> 50
II:
more acceptable to the listener than
!(
U
II:
z speaker "A." It is therefore suggested
W
0.
that rather than match a speaker to a
/
r
:E 40
15 z
w'
w given amplifier system and acoustic enr
U
vironment, the amplifier be adapted to
II:
match the speaker to that environment.
W
VOICE COIL COPPER_
30
0.
This can be done by incorporating comTEMPERATURE RISE
V
10
NO AUDIO INPUT pensation circuits (see Figure 15 )
F1E'ID COIL S,PEAKER
either in the form of equalizers or filter
20
'circuits, and adjusting them when the
I
speaker is located in the desired posiTEMPERATURE RISE IN
5
tion and all other conditions are identiLOUDSPEAKERS
10
cal with those under which the system
will be normally operated.
'\
There are several types of measurements made on a loud speaker in order
3
2
to show its frequency response characTIME IN HOURS
teristics. The most common is the ax",.10,
ial response curve run with speaker
mounted in some sort of baffie and the
so critical- that even using the same
microphone located directly in front of
VI. Frequency Characteristics
speaker and microphone, response
t!vJ speaker on its axis (generally 18 to
curves obtained under different condi36 inches from the baffie). A curve obThe frequency response curve of a
tions'may :not be similar. For example,
tained by this method, however, is not
loud speaker shows the sound pressure
the three response curves shown in Figconsidered a complete picture of the
output as frequency is varied. A conure 11 were run by three well known , speaker response since it does not take
stant voltage is applied to the grid cirlaboratories on t;4e same loud speaker.
into consideration the directional charcu~t of the power amplifier which in
Curve No. 1 was run by the manufacacteristics of the loud speaker. This
turn drives the loud speaker under test.
turer under outdoor conditions with a
type of curve sho\ys only what the listenIt is important to recognize that the
single microphone in fixed position in
er will hear when his ear is fairly close
frequency response curve of a loud
line with the speaker axis. Curve No.
to
the speaker and in line with the axis,
speaker is meaningless unless all of the
2 was run by another laboratory using
which condition is seldom if ever realtest conditions including the type of
the indoor rotating microphone methized in actual practice. Another method
room, driving amplifier and measuring
od.
Curve
No.
3
was
run
by
a
third
sometimes
employed is one in which the
system used, are known. It is impractilaboratory
using
the
indoor
multiple
output
of
the
speaker is measured by
cal for the average user to measure the
microphone method. The same speaker
the use of a moving microphone. A
frequency characteristics of a loud
was, used throughout but the results are
third method uses a group of microspeaker since the measuring equipment
radically
different.
For
this
reason,
unphones located at various positions
required is relatively complicated as
less the test method employed is known
through the room. In both of these latcompared to that required, for example,
and the room acoustics al'e also known,
ter methods, the output of the microin measuring the response of an audio
a curve run by one manufacturer canphone or microphones is averaged so
amplifier. Moreover, the acoustics of
not be compared with that run by' anthat the sound radiated by the speaker,
the room and the location of the microother manufacturer. This explains the
both on and off the axis, is taken into
phone and speaker under test, may be
TEM PERATURE RISE IN LOUDSPEAKERS
---
100
V
V
/
V
/
;
I
//V
/'
V
/
V
V--
.....-
I
V
13
Section 1 •
THE
MYE
TECHNICAL
MANUAL
12 IN. DYNAMIC SPEAKER CABINET SPEAKER
+2 0
+1 0
.,..
c::
c::
I-
m
c::
MEAN ENERGY DENSITY
MICROPHONE FACING SPEAKER
CONTINUOUSLY
0
"">
d
.-
'j -I 0
..
~
....
...
,
N
III
~ -2 0
.~
...J
..
..
"
....
..
.....
.'
MEAN ENERGY DENSITY
MICROPHONE REVOLVING ONCE
IN ACH QUADRANT
FREE SPACE
ON AXIS
>
....
..
...J
-3 0
20
3
4
5
6
8
9
1.5
100·
2
1.5
3456789
1M
FREQUENCY IN CYCLES PER SECOND
2.
3
4
5
6
7 8 9
12 14 16
10M
Fig. 11
consideration. Since the output of the
loud speaker at the higher frequencies is
considerably more directional than at the
lower frequencies the multiple or moving microphone method would show less
high frequency output from a given
speaker than an axial response curve of
the same speaker. However, since a multiple microphone curve gives a more
complete picture of the overall efficiency of the speaker at all frequencies, at
many positions within the room, it p~
vi des a more reliable indication of the
actual room performance than the axial
method. The frequency characteristics.
of a speaker are determined not only by
design of the. cone assembly but by the
method of baffiing, the location within
the room and the position of sound absorbent materials and reflecting s~r
faces. Thus speaker "A," having a tone
quality that is considered inferior to
speaker "B" in one particular room,
may sound much. better thal'l speaker
"B" if the location of the speaker within the room or the acoustics of the room
itself are changed.
It can be shown by means of frequency response curves that the frequency
characteristics of a loud speaker do not
vary with the amount of power delivered to the voice coil, assuming that the
speaker is nof overloaded. However,
14
due to well established characteristics
of the human ear, especially at low
sound intensities, the response does apparently change with power input. As
shown in Figure 14, the reduced sensitivity of the ear for low and high
frequencies relative to the middle frequencies at low sound intensities, is responsible for this effect. Therefore, in
listening tests, means should be provided within the amplifier or elsewhere
in the system to compensate for the apparent loss in low-frequency and highfrequency respon~e as the power level is
reduced.
VII. Impedance Matching
Since the required load impedance of
amplifier power tubes is relatively high,
and the impedance of loud speaker
voice coils (the load) is relatively low,
a transformer is generally used to match
these two radically different impedances in order that transfer of power
may be efficiently accomplished. It can
be shown that the ratio of the transformer primary turns to the secondary
, turns 'is the square root of the ratio between the speaker impedance and the
100
1
90
III 80
I
:E
a
z
-
w
~PEbA~C~J 1151~PEAKERII N
INFINITE BAFFLE
70
80
U
Z50
~
~ 40
:E
1---1--'
30
20
0
o
I-- V
20
J
30 40
~
'\
60 80 100
200 300 400 600 800 1M
FREQUENCY IN C.P. S.
Fig. 12
/'"'
2M
V
3M 4M
8M 8MIOM
• Section 1
LOU"D S,PEAKER DESIGN AND APPLICAtION
load impedance required by the output
tubes.
The amount of mismatch between the
, optimum load impedance required by
the tubes (tube manufacturers general.
ly list this value ~ their tube data
sheets) and that presented by the loud
speaker will depend upon the use to
which the system is put. In the case of
triode tubes tl}e load impedance presented by the speaker should be equal
to, or in excess of, the optimum load
resistance required by the tubes in order
to keep tube distortion low. Since the
impedance of a speaker varies with frequency (see Figure 12), the voice coil
impedance is approximately the minimum impedance above the resonant
frequency. In general the matching impedance is the 400 cycle impedance for
a conventional speaker intended to reproduce both high and low frequencies.
VIII. Audio-Frequency Transmission Lines and Transformers
When connecting speakers to an amplifier two factors should be taken into
consideration: First, the power loss,
due to line resistance, between the amplifier and speakers should be held to a
reasonable minimum value, and second,
the loss due to line capacity at the
highest frequency which is to be reproduced must not become appreciable.
Both effects are related to the length of
the line and the impedance at which the
line is operated. In general, if the distance between the amplifier and the
speakers is less than 25 or 30 feet, the
impedance of the connecting line (high
impedance, low impedance, or voice
coil) is not important and the most convenient impedance may be used. When
a distance greater than about 25 or 30
feet separates the amplifier and the
speakers, it is then necessary to take the .
resistance and capacity of the leads into
account.
Lines at J7oice-Callimpedance
The following table (Table 2) of
maximum lengths (2 wires) of voicecoil lines assumes a' maximum line resistance equal to 15% of the voice coil
impedance. This limits the power loss in
the line to about 15% of that delivered
TABLE 2
MAXIMUM LENGTH OF LINE, FEET
WIRE SIZE
(B & S Gauge)
No.
No.
No.
No.
No.
No.
12
14
16
18
20
22
Voice Coil Impedance
4 ohms
6 ohms
8 ohms
10 ohms
190 feet
120 feet
75 feet
47 feet
30 feet
19 feet
288 feet
180 feet
110 feet
70 feet
45 feet
28 feet
385 feet
240 feet
150 feet
95 feet
60 feet
37 feet
480 feet
300 feet
190 feet
118 feet
75 feet
46 feet
to the speakers. The capacity of the
lines is here considered negligible.
In the above table, the voice-coil impedance value is the total impedance on
one transmission line. If a single speaker is connected, then the total impedance .
is the voice coil impedan.ce of the one
speaker; if two 4 ohm speakers in series
are connected, then the total impedance
is 8 ohms and line lengths would be
read in the 8 ohm column. On the other
hand, if two 8 ohm speakers are connected in parallel, the resulting total impedance would be 4 ohms. If more than
two speakers are employed, the total
impedance of the group must be calculated. If the total impedance falls between values used in the table, the line
length can be estimated with sufficient
accuracy for practical purposes.
If the use of Table 2 shows insufficient permissible line length at voice
coil impedance, then the line length can
be increased by working at a higher impedance. For a given transmission line,
the higher the value of operating line
impedance, the lower will be the power
losses due to the resistance of the line.
However, the high-frequency losses in a
line due to the capacity between conductors are greater in a high-impedance
line than in a low-impedance line. A
"500 ohm" line will'usually afford an
acceptable compromise between the resistance losses and the losses due to the
capacity of the leads.
At this point, it might be well to define a "500, ohm" load. A "500 ohm"
load is one whose impedance is approximately (plus or minus 10%) 500 ohms
when measured at the ilmplifier end of
the line and includes all speakers, filters, level controls, and transformers
that may be connected across the line.
In other words, the impedance of the
total "load" including the line must
match that of the 500 ohm output trans-
.
former. This means that in order to connect several speakers together in parallel across a "500 ohm" line, the total
impedance of the "load" must be 500
ohms for all speakers, not individually.
For example: If four speakers with
their individual transformers are all
connected in parallel across a "500
ohm" line, each speaker with its own
transformer must have an impedance
of 2,000 ohms, not 500 ohms. Thus,
with four 2,000 ohm "loads" connected
in parallel, the resulting total impedance would be one-fourth of 2,000 ohms
or 500 ohms. Of course, four speakers
with 500 ohm transformers could be
connected in series-parallel across the
500 ohm line.
For the purpose of computing the
"effective impedance" of a group of
speakers connected in parallel, use the
following equation:
1
111
1
1
Z
Zl
Z4
Z5
-=-+-+-+.:..-+Z2
Zs
or in the special case of 3 impedances
in parallel:
-
Z
= ----------
Where: Z is the effective Impedance of
the circuit
Zl is the Impedance of the first
speaker
Z2 is the Impedance of the second speaker
Zs is the Impedance of the third
speaker
etc.
15
SectiOn 1 •
r
HEM YET E C, H N I CAL
MAN U
A
L
(
This reasoning applies to all types of
loads such as transformers, speakers,
filters and level' controls regardless of
the number used. The effectiv~ parallel
impedance of all the loads together,
when con'nected across' a "500 onm"
line, must be 50'0 ohms. The exception
to this is when a fiIt!:;r or level control,
etc., of the so-called 500 ohm input and
500 ohm output type is used. With a device of this kind the line is thought of
as simply, passing through the device
without its acting as a load. However, if
,two or more of these devices are connected in parallel across the line, they
must be 'considered as separate loads
and are treated accordingly.'
With this fact in mind, we may now
consider the methods of connecting the
amplifier and the "loads" to the line.
This is done by means of "impedance
matching" transformers. The transformers are so designed that, with a
given value of load impedance connected across one w~nding, the impedance measured across the other winding
is the required value. In a large welldesigned transformer, there will be
negligible loss of energy due to this
transformation (usually ab.out 10%).
Thus, a plate-t~-linetransformer is used
to transfer the output of the power
tubes at their inherently high impedance 'to a low-impedance line. For
example: If the plate-to-plate load impedance required for a pair of output
tubes in push-pull is 4,500 ohms, a
plate-to-plate transformer with an impedance ratio of nine to one will be
required in order to match these output
tubes to a 500 ohm line.
In order to keep the loss of the line at
a minimum, the total resistance of the
C Jnductors themselves and their capacity must be limited to reasonable values.
,The total resistance of the line should
not be more than about 5% of the load
and should preferably be less. Thus, if
a pair of No. 14 wires is to be used as a
500 ohm line, the line should not be
more than 5,000 feet long (10,000 feet
of wire, resistance 2.52 ohms per thousand feet) if the allowable. resistance is
not to be exceeded.
Upon this basis the maximum length
of line (2 'fires) for various sizes of
conductor is as follows ~Table 3) :
16
.,''::.
TABLE 3-500 ohm line
WIRE SIZE
(B & S Gauge)
No.
No.
No.
No.
No.
No.
12
14
16
18
20
22
MAXIMUM LENGTH
(R~sistance =
25 ohms)
8,000 feet
5,000 feet
3,100 feet
2,000 feet
1,200 feet
780 feet
The other factor controlling the permissible length of the "500 ohm" line is
the capacity of the leads which causes a
loss (attenuation) of the higher fre-
The transformer must be large enough
to handle the power involved and, with
all the speakers connected in parallel to
the transformer secondary, the primary
impedance must have the required value., Thus, if six speakers each having
6-ohm voice coils are to be connected
in parallel to a 500 ohm line, the resulting parallel impedance, of the voice
coils will be 1 ohm and the correct
transformer to use will be one with a
500 ohm primary and a 1 ohm secondary. If, however, the speakers are separated by more than one-half the allowable distance given in Table 2, or have
TABLE 4-500 ohm line
HIGHEST FREQUENCY DESIRED
MAXIMUM LENGTH
(Loss at highest frequency =3 db)
,
20,000 cycles per
15,000 cycles per
10,000 cycles per
7,500 cycles per
5,000 cycles per
second
second
second
second
second
quencies. Ordinary twisted pair or leadcovered cable has a capacity of approximately 50 mmfd. per foot. On this
basis a "500 ohm" line will be limited
in length to 600 feet if it is desired to
keep the attenuation at 10,000 cps. less
than 3 db at the highest desired frequency. This assumes, of course, that
the resistance losses due to the size of
the wire used fer the line do not exceed
25 ohms (see Table 3). The calculation
of losses at high frequencies takes into
consideration the capacity of the line
and the fact that the impedance of a
dynamic speaker is higher than the
rated value at the higher frequencies.
Thus if it is found necessary to run a
line longer than 600 feet and still reproduce frequencies up to 10,000 cps. without attenuation, it will be necessary to
use an equalizer (preferably within the
amplifier or its input circuit) to compensate for the loss due to the capacity
of the line, or ~o operate at a lower line
impedance.
The choice of transformers at the
load end of the line is dependent upon
the number and type of speakers involvea. If all the speakers have the same
voice-coil impedance at 400 cycles (400
cycles is the usual matching frequency
for dynamic, speakers) and all are
mounted close together, all the voice
coils may be connected in parallel and
through one, transformer to the line.
300
400
600
900
1,200
fee~
feet
feet
fellt
feet
different voice-coil imp~dances, it will
then be necessary to use separate lineto-voice-coil transformets for each
speaker. In this case, the primary impedance of each 'of the transformers
will have to be 3,000 ohms so that when
all' six transformers are connected in
, parallel, the resulting impedance will be
500 ohms.
This brings up the relative merits of
series and parallel connections. The
main objection to the series method of
connections is that, in case of the failure of one unit by open-circuiting, the
entire system becomes inoperative. The
use of series connections of speakers or
transformers is sometimes a practical
necessity, however, as in the case of
matching two 8 ohm voice coil speakers
to a transformer which has only a 16
ohm secondary. Then, of course, the
most econ'omical method is to connect
the voice coils in series.
Phtuing
When more than one speaker is used
in an installation, it is important to
operate all the voice coils "in-phase."
That is, all the diaphragms should move
in the same direction at the same instant. If they are not in-phase, the
sound output will be materially reduced
because the sound from one unit will
cancel that of the other. The mQst simple method of checking the phase of
LOUD SPEAKER DESIGN AND APPLICATION
speakers is to first connect and excite
the fields of all the speakers and then
short out the "bucking coils," if any,
temporarily. Then take a dry cell bat- '
tery (1112 volts) and touch the positive
side of the battery to one voice coil lead
and the negative side to the other voice
coil lead. The cone will "jump" either
in or out at the instant the battery is
connected. Test all the speakers in the
same manner, marking the lead on each
speaker which was connected to the
positive battery terminal when the cone
"jumped" out. For parallel operation,
connect all the leads that went to the
positive side together and all those that
went to the negative side together and
the speakers will be correctly phased.
If series operation is necessary, connect
between unlike terminals in the usual
manner. In order to reverse the phase
of any speaker, simply reverse the voice
coil connections, leaving the field connections the same as they were before.
If it is desired to phase several speakers
each having its own transformer attached, the same procedure as outlined
above is followed except that a battery
. of about 221/2 volts and the primary
leads of the transformer (instead of the
voice coil leads) are used (voice coil
leads are to be attached to transformer
secondary leads, and "bucking coil"
shorted out temporarily) .
IX. Applications
Replacements
When installing a replacement speaker there are several important points to
consider other than the obvious ones of
physical size, transformer impedance
and field coil resistance. Probably the
one least considered is the size of the
field coil. The amount of copper in the
field will have a direct bearing on the
amount of power that can safely be dissipated in the field without overheating
and causing a mechanical failure. It
will also have a decided 'effect upon the
efficiency and performance of the speaker. For example, if the original speaker
(say a 5 inch speaker) had a relatively
large field coil, say 2,500 ohms No. 35
wire (.73 Ibs. of copper) and dissipated
5 watts of power, if would be inviting
trouble to use a replacement speaker
having the smallest possible field coil
of the same resistance just because it is
less expensive. Using the smaller field
would cause the field to run very much
hotter (the original field was probably
hot enough) than advisable which
could easily cause the new field or the
voice coil to fail very soon. On the other
hand if the original field was relatively
small and failure was not due to overheating, there is little to be gained by
going to a large field coil unless, of
course, the power delivered to the new
field coil can be increased accordingly
without upsetting the plate voltages
throughout the receiver. Therefore,
whenever possible, use a replacement
speaker having a field coil of approximately the same physical size as that of
the 'original.
At this point it 'may be well to point
out the improved performance obtainable by replacing the field coil type
speakers supplied originally in the older
A.C.-D.C. sets with a P.M. type speaker.
This change will reduce the drain
on the rectifier tube and possibly improve efficiency. This should only be
done, however, when the original field
coil was connected directly from the
positive high voltage to ground, not
when it was used as a bias resistor or as
a choke in the power supply unless the
original field is replaced by an equivalent fixed resistor.
Oftentime when replacing the original speaker it is desirable to use a larger
speaker where it can be accommodated,
as for example in a 'large console. In
general, increasing the diameter of the
speaker cone will increase the bass response of the system, assuming of
course that the amplifier will pass the
lower frequencies. Here, too, the size of
the field coil must be considered for
there is little to be gained if the original
speaker had six watts in the field and
the larger replacement'requires fifteen
watts of field excitation. True, the lowfrequency response may be improved,
but it could probably be improved just
as much by using a less expensive
speaker with the same larger cone
diameter as the I5-watt speaker but
having 'a smaller field that would be
fully excited with six watts. However, if
means are available for increasing the
field excitation at the same time, then
use the larger field because the output
of the larger field coil speaker will be
greater and there will be less low-frequency distortion due to the increased
• Section 1
damping action of the larger magnet
structure.
The substitution of a larger speaker
than the original, especially in the case
of mIdget receivers, is a subject that
should be considered by every servicp
engineer. The chief objection to midget
sets is their lack of low-frequency response. Obviously with such a small
balRe and speaker the bass response of
the set will suffer. One solution to the
problem is to use a larger speaker in a
separate cabinet or balRe. Substituting a
twelve, fifteen or even eighteen-inch
speaker for the original 4 or 5-inch
speaker is indeed a revelation. Usually
it is only necessary to disconnect the
original transformer and substitute a
larger transformer to match the voice
coil of the new speaker to the output
stage. Leave the field of the original
speaker connected in the circuit in order not to upset the plate voltages and
use a P.M. speaker (or one with its own
power supply) for the new speaker. Increasing the bass response by this
method will increase the hum also, but
this can be reduced to an acceptable
amount by the addition of filter condensers or at the most by the use of a
second "30 henry" choke in the power
supply circuit.
P. A. Installations
The size and type of speaker system
in a P. A. installation should be governed almost entirely by the size, type,
location, audience to be covered, the
type of sound to be reproduced and the
psychological reaction desired of the
audience. This, of course, requires that
each installation be analyzed before the
installation is even started. Accordingly
the analysis of the job should cover the
following points:
INDOORS
Size of auditorium.
Area to be covered.
Dimensions.
Approximate size of audience and location
of same.
Actual volume of the room in cubic feet.
The reverberation time, if known.
Seating capacity.
Type and distribution of absorbing materials.
Location of orchestra or source of pickup.
Desired position of ,speakers and microphones.
Ambient noiSe level.
Type of service.
V oice or music reinforcement.
Remote pickup.
Symphony or jazz orchestra.
Point source illusion.
Fre9uency,characteristics of phonograph
pIckup microphone.
17
Section 1 •
THE
MYE
Amplifier.
Audio power available.
Desired coverage.
PERMISSIBLE COST.
TECHNICAL
MANUAL
ambient noise level outdoors and noise
level as well as the acoustics of the room
indoors will have considerable bearing
on the final choice of speakers. It is al~
ways advisable to have more amplifier
power available than the necessary
minimum as a margin of safety against
distortion. Adequate power-handling
capacity should be available in the installation of loud speakers. Since cost is
often '. of predominating importance it
may be necessary to arrive at some suitable compromise between location and
type of speakers finally used as compared with the ideal choice. Wherever
possible, if it is desirable to create the
illusion of the original source, the
speakers should be mounted in a cluster
and as near the source as possiblegenerally directly overhead. Outdoors,
of course, ~ this requires that higher
powered speakers be used than if the
sound were distributed at low level
throughout the audience but this may
be more desirable than the distracting
effect upon tpe audience of having the
performer in front of them and hearing
his voice coming from behind or over-
QUTDOORS
Area to be covered, in square feet.
Dimensions.
Approximate size and location of audience.
Desired location of microphones and
speakers.
Ambient noise level.
Loudes1;. hoise which system must override.
Type of service.
V oice or music reinforcement_
Remote pickup.
Symphony or jazz orchestra.
Point source illusion.
Frequency characteristics of phonograph
pickup microphone.
Amplifier.
Audio power available.
Desired coverage.
PERMISSIBLE COST.
If these facts are known it then becomes relatively simple to determine
the possible locations and types of
speaker system applicable in view of all
requirements. The amount of audio
power can best be determined by the
size of the audience-if outdoors
roughly 5 watts per thousand square
feet, or ~indoors in accordance with the
data given in Figure 13. Of course, the
1000
800
600
500
400
300
200
~K
.<~K~
III\~
100
80
(I)
II~
A
"')(
60
50
40
~~
I~
z
20
Ir
W
k'<
~~R
~
0..
10
8
V
)(
1'-<'
6
5
4
~
IX .'-'1
L¢X r'.'-' \j
~ ~~
3
~~f
2
~
20
3040
~
~
r
6080100
200
400 600 1M
. 2M 3M 4M 6M
SEATING CAPACITY OF AUDITORIUM
Fig. 13
18
v
lAX Y
.t<5 ~
3: 30
0
1)(
10M
head. Whenever it is necessary that
sound be distributed from some point
other than the point of origin, it is always advisable to operate the speakers
at as low a level as is consistent with
intelligibility.
Where the system is required to reproduce voice only, for example in a
football announcing system, it is not
necessary that frequencies below 150 to
250 cycles be reproduced by the speaker system. This permits the use of either
the new multicellular horns and driving
units or short trumpets. The former are
to be preferred, especially where a
highly efficient speaker system is advisable and where maximum intelligibility
is desired. However, where cost is the
more important factor, trumpets can be
substituted iInless, of course, the number of trumpets required is such that it
would be more economical to use a
multicellular horn.
Where the reproduction of both
music and voice is required, a large
horn, bame, ~or suitable speaker enclosure is of importance in order to reproduce the lower frequencies (see
section 4). Thus, in an installation
where at times only voice will be reproduced and at other times a full orchestra, it may be desirable to use a two-way
system consisting of suitable low-frequency unit and multicellular horn and
unit.' In this way the multicellular highfrequency system could be used where
voice only is being reproduced and the
entire system could be used for the
reproduction of music. This would be
by far the most economical use of all
possible components and at the same
time would result in the most efficient
possible speaker system.
Provision should be made, when using a speaker system outdoors, to prevent exposure to excessive humidity.
This would require that the system itself either be weatherproofed or that
arrangements be made to cover the system during rain or snow storms.
One important factor to keep in mind
is the distance over which sound must
be projected from a given speaker system, since sound energy diminishes
approximately as the square of the distance from the source. In other words,
if a speaker system will lay down the
desired sound power at a distance of
100 feet with an input of 10 watts, 100
times as much power or 1,000 watts will
LOUD SPEAKER DESIGN AND APPLICATION
-I-
_ _ F'tELING
200
~ .-/
/
...... :--..
i
I'---..
\
~ t'-.
-~
r\. ~ t'- ~
'\ ~ ~ ~ ~
~~~
/
r-
L
~ ~ ;:: ;:::;:::
t- ~
--
//
/,
J/ /
/
/
V
91%75°/0
1
50 %
~~
10 0/0
~J ~ ~ 5°
1.,
t'-- ~ ~ 1(/. /'
-
I-
20
/
/ /' 9~ Ofo
--- -- --....... r-')
~ ~ ::::::
20
/
"" -
1\
99 %
100
..............
II::
2 ~
:!lz
.02 ~
Z
!oJ
II::
.002
./
~
If
0 /0
2
10,000 20,000
1000
FREQUENCY IN CYCLES PER SECOND
Fig. 14
be required if the distance is increased
to 1,000 feet. As a result, both the am~
plifier and the speaker system must be
designed to handle the required power.
Phonographs
Recent developments in recording
practice and improvements in phonograph pickups make it definitely worthwhile to provide extended-range loud
speakers for high quality reproduction
of commercial phonograph records. Surface noise '( or "needle scratch") is, of
course, somewhat more noticeable as
the response range of the system is extended into the high frequencies. However, many listeners definitely prefer
the reproduction obtainable with such
equipment over that provided by standard fidelity speakers which usually give
predominant emphasis to the middle
high-frequency region. It is highly desirable to provide means for adjusting
the high-frequency response of the
system, so that fewer "highs" are reproduced when playing old or worn records. It should be remembered that
surface noise covers practically the entire audible frequency range, and it can
be reduced only by restricting the range
which is reproduced. The low-frequency
response of the speaker system should
be good and enclosures of the "Bass
Reflex" type are particularly suitable.
The new Single, Concentric and twoway extended-range loud speakers are
particularly suggested for high-quality
record reproduction.
Since oftentimes phonograph records are reproduced in the home at
much lower volume levels than those at
which they were originally recorded the
frequency characteristics of the human
ear must be taken into consideration. It
is therefore desirable to incorporate
both high and low-frequency compensation circuits (see Figures 14 and 15)
within the amplifier so that the quality
of reproduction may be adjusted in accordance with the level of reproduction,
the acoustics of the room and the listener's preference.
Volume Expansion
• With a properly designed volume expansion circuit the reproduction of
phonograph recordings, especially symphonic, can be made much more realistic since for practical reasons most
symphonic recordings are compressed
when originally recorded~ This compression is generally done automatically in the case of phonograph recordings,
whereas in the case of broadcasting stations the compression is done manually
in accordance with the best judgment
of the operator at the time. Volume expansion is, therefore, not generally used
for the r~production of radio programs
but is considered desirable or even necessary for high quality phonograph reproduction. It must be kept in mind,
• Section 1
however, that when compensation or
volume expansion is used in an amplifier, both the output stage of the amplifier and the speaker system must be
capable .of reproducing the loudest
passage without introducing appreciable distortion. For example, in the ordinary home living room and without
either compensation circuits or volume
expansion; an amplifier having an output of 2 to 4 watts is ample. However, if
compensation ·circuits or volume expansion having 10 db gain are introduced,
the output stage must be capable of delivering 20 to 40 watts power without
introducing distortion.
Custom Built Sets, Television and
Frequency Modulation Receivers
These receivers require a speaker
system having as wide a range of response as is practical, consistent with
the cost and performance desired.
Single diaphragm type speakers are
now available covering the range from
below 60 cycles to 10,000 cycles and
above. For most installations, especially
where cost is important, they will serve
very well. However, in general they are
less efficient than an equivalent sized
standard type speaker and they are
more directional at the higher frequencies than a specially designed tweeter.
This first objection is not too important
because most amplifiers have ample reserve power, but the highly directional
characteristics al}ove 5,000 cycles may
be quite objectionable.
In order to overcome this shortcoming and to provide an even greater frequency range, two-way speaker systems
are recommended. When using two
speakers to cover the audio spectrum it
is possible to design a speaker that will
do a better job of covering its portion
of the band than the single wide-range
speaker: In other words, the larger the
cone, in general, the better the low-frequency response; but the smaller the
cone the less directional t4e highs. This
does not infer that any small cone type
speaker is inherently a good high-frequency speaker. By using a metal
diaphragm high-frequency horn type
speaker a relatively small unit can be
made to reproduce the higher frequencies more efficiently and with less directional effects than a larger wide-.
range speaker. A two-way speaker system also requires a dividing network of
19
· Section 1 •
THE
some sort hut such a system can he
made quite efficient and need not he too
expensive. Thus, where it is desirahle to
MYE
TECHNICAL
MANUAL
fr~quency response, wide angle coverage and efficiency' is required, use a
multiple speaker system.
ohtain as wide a frequency· range ali!
pos;ihle, consistent with lo-w cost, use a
single speaker; and where the utmost in
VARIABLE COMPENSATION CIRCUIT
-
ISOLATE FOR
MINIMUM HUM
I MEG.
L I = CHOKE (30 HEN.)
L2 CHOKE (112 HEN.)
CI =.25 MF'D. TO RESONATE CI RCUIT
AT 60 CYCLES APPROX.
C2=.002 M rD. TO RESONATE CIRCUIT
AT 5000 CYCLES APPROX.
=
+15
O~--+----+----~----
NON-VARIABLE COMPENSATION CIRCUIT
ece
6J7
I MEG
~------------~B+
NOTE-IN ORDER TO PREVENT DISTORTION
THESE CIRCUITS MUST BE OPERATED
AT VERY LOW LEVEL (0.1 V. MAX, INPUT)
+10
DB
o
'---+---i----50
Fig. 15
20
400
F'REQ.
e Section 2
THE
MYE
TECHNICAL MANUAL
Superheterodyne
First Detectors
. and Oscillators
I
I
'
MALLORY
21
Section 2 •
THE
MYE
TECHNICAL
MANUAL
SUPERHETERODYNE FIRST DETECTORS
AND 'OSCILLATORS
A recent Superheterodyne incorporating
modern design practices (RCA 27K)
One of the /irst Superheterodyne
. Receivers (RCA Radiola 28)
Introduction
The heart of a superheterodyne is its
frequency-changer-the first detectoroscillator system which converts the frequency of any incoming signal to the
fixed frequency of an intermediate frequency or long wave R.F. amplifier;
where subsequent stages of amplification build up the signal to the desired
level.
It is the purpose of this article to review the developmenf of the various cirpuits which have been used or proposed
for this application, to point out the advantages and disadvantages of each,
and to give service hints, so. that the
service engineer or radio repairman
can proceed with confidence in making
any required adjustment.
Why the Superheterodyne?
Let us begin by briefly explaining the
advantages of the seemingly roundabout
way employed in superheterodynes for
the amplification and selection of radio
signals, as compared with the direct
method of amplifying the signal at its
original frequency (or tuned radio frequency amplification).
22
The advantages are:
1. Better adjacent channel selectivity
2. Uniform selectivity
3. Better. circuit stability
4. ,Uniform gain at various' frequencies
5. Lower cost for equivalent performance
The advantages listed above arise
directly from the use of a fixed tuned
radio frequency amplifier (I.F.) , operating generally, but not necessarily, at a
lower frequency or a longer wave-length
than the received signal. Precision
adjustment for optimum performance
is made when the receiver is constructed, and these adjustments will retain their correct setting for extended
periods of time. The amplifier constants,
such as the inductance of the coils, the
couplinK of the coils, and the value of
the tuning capacitors, have been selected
to give the best results at the desired
frequency. Physically such an amplifier
can be built with great compactness
since adjustable compression type mica
condensers or .small fixed condensers
'are used for tuning; as compared with
the bulky and exp~nsive air dielectric
, gang tuning condensers required for a
tuned radio frequency amplifier.
Even the least expensive superheterodynes usually have a total of five tuned
circuits contributing to the selectivity
of the receiver-a tuned antenna stage
and two tuned circuits in each I.F. transformer. A comparable T.R.F_ receiver
would have to employ a five-gang variable condenser-a form of construction
so expensive as to limit its use to only
the most expensive sets. Furthermore,
gang condensers are bulky, and require
long leads for connectio~s. This, in
turn, causes coupling between circuits
so that elaborate shielding must be used
to provide isolation and to prevent the
amplifier from oscillating. Such shielding is obviously costly_
When amplification occurs at signal
frequency, the amplifier must be tuned
to the signal, and in conventional engineering practice this is accomplished by
connecting a variable air dielectric capacitor across each inductance. Thus,
the LIC ratio (the ratio of inductance
to capacity) ~aries as the condenser is
adjusted for various frequencies, and
the selectivity characteristics are not
constant with frequency. The changing
LIC ratio varies the Q of the circuit.
The Q of a circuit is the ratio of inductive reactance to resistance and constitutes a figure of merit for a tuned circuit
since the higher the Q, the sharper the
tuning. The effect of variable -capacity
also makes it exceedingly difficult to de-
SUPERHETERODYNE fIRST DETECTORS AND OSCILlATORS
sign R.F. transformers having uniform
gain with frequency, since the gain is a
function of the impedance of the tuned
circuit, which varies with the Q. Even
more difficult is the designing of doubletuned transformers (tuned primarytuned secondary type) since coupling
varies with capacity.
The fixed tuned I.F. amplifier of a
superheterodyne is not open to any of
these objections.
There is another advantage of the
superheterodyne circuit which is inherent to all such receivers using an intermediate frequency lower than the
frequency of the received signal, namely-arithmetical selectivity. Radio stations on the broadcast band are located
with 10 kc. channel spacing. It is highly
desirable for a radio receiver to discriminate against interference from an
adjacent channel. The percentage of
difference between the frequency of the
desired signal and the signal on an
adjacent channel varies with the frequency, thus, at 550 kc. the adjacent
channels are off-resonance by 1.8%. At
1,000 kc. the difference is 1
while
at 1,500 kc. the difference is only
0.66%.
In a superheterodyne the incoming
signal is converted to the frequency of
the I.F. amplifier. An adjacent channel
station is still removed by 10 kc. at the
intermediate frequency. Thus, with
a 465 kc. intermediate frequency
the percentage difference between the
adjacent channels becomes over 2.1%.
This percentage difference is constant
at any portion of the broadcast band.
In this connection it is interesting to
note that the percentage difference in,creases with lower I.F. frequencies.
With a 175 kc. I.F. the adjacent channels are separated by almost 6%, while
at 50 kc. (a value used by some manufacturers in the very early days of the
industry) the percentage difference is
20%.
However, the problems of images
and spurious responses increases rapidly with decreasing I.F. frequency so
that the industry has largely standardized on values near 465 kc. The possible presence of such interference
constitutes the main objection to
the superheterodyne principle, and consequently the subject will be discussed
in a later paragraph.
ro,
How the First Detector·Oscillator
Works
The fundamental operation of the
first detector and oscillator is shown by
the block diagram, Figure 1. The
incoming signal is fed into a vacuum
tube, which may be a diode, triode,
tetrode, pentode, or one of the more
complicated types. The output of a local
oscillator is also fed into this tube,
where the two inputs are combined to
produce the intermediate frequency.
By means of special tubes or special
circuits it. is possible to combine the
oscillator and mixer functions in a single tube-however, the fundamental
operating principles remain the same.
INCOMING
INTERMEDIATE
SIGNAL
rREQLJ[NCY
FIG.
1
The local oscillator of a superheterodyne receiver serves two functions.
First, it provides a frequency which
will combine with the radio-frequency
signal and produce, through detection,
a new radio frequency wave called the
intermediate frequency. For this purpose the local oscillation need only be
of the same order of amplitude as the
signal.
When the signal and the local oscillator voltages are combined in the same
circuit, at a given instant they may be
either opposing or aiding one another.
If the frequency of the signal and
that of the oscillator differ (as is the
case in a superheterodyne receiver),
then the two voltages will be alternately
aiding and opposing each other at a
repetition rate equal to the frequency of
the new signal voltage. This combining
of the two radio-frequency voltages is
called heterodyning, or beating. The
beat frequency, called the intermediate
frequency, is not produced immediately
as a result of combining the two radio
frequencies. There are still only the
9riginal frequencies present but the
envelope of the combined wave is varying in amplitude at the beat frequency
rate. To create the new intermediate
frequency, this wave must pass through
a detector.
• Section 2
The second function of the local
oscillator is to raise the efficiency of
detection. If the incoming signal impressed on the detector is of the order of
1 millivolt and the local oscillator voltage impressed on the detector is of
about the same value, the rectified output would be practically zero. The
amplitude of the voltage impressed on
the detector must be of such a magnitude that the tube characteristic is different for the positive and negative half
cycles of oscillation. Increasing the
local oscillation voltage beyond the
requirements for producing the beat
envelope will result in raising the efficiency of rectification. The amount of
local oscillation required for most efficient conversion of the radio wave into
the intermediate wave .is determined by
the detector tube design and usually
runs between 5 and 15 volts in conventional circuits.
It will be seen from the above discussion that the efficiency of conversion of
a heterodyne detector in a superheterodyne receiver does not follow the customary square-law response as does the
second detector and that no matter how
weak the incoming signal may be, there
is no threshold below which the detector
fails to operate.
The first detector is operated over a
non-linear part of its characteristic. The
local oscillation may be supplied from
a separate tube and impressed on the
grid circuit of the detector through a
coupling in its cathode lead, or it may
be supplied from other tube elements
within the same detector tUbe. Some of
the tube elements may serve the double
purpose of both oscillator and detector.
In this latter case the local oscillations
may not appear in the signal input grid
circuit. They will, however, serve their
purpose of changing the operating
characteristic of the detector by altering the electron flow through the detector part of the tube as the local oscillation swings through its cycle. The
detector tube is, in effect, cut off on the
negative cycles. This is the condition
required for detection. In addition to
serving as a detector and sometimes as
an oscillator, the first detector tube also
acts as an intermediate frequency amplifier since the detection takes place in
the grid circuit. The amplification thus
obtained is approximately one-half the
23
Section 2 •
THE
value which would be obtained if the
tube were used as a conventional intermediate frequency amplifier. This is
due to the fact that the local oscillator
swings over the low gain part of the
MYE
TECHNICAL
MANUAL
tube characteristic on its negative half
cycle.
The first detector and the local oscillator of a superheterodyne receiver
each perform two important functions:
The detector creates and amplifies the
intermediate frequency; the oscillator
raises the efficiency of detection and
combines with the signal to produce the
intermediate frequency signal.
The Desired Signal, Images, and Spurious Responses
The Desired Signal
We have stated that the intermediate
frequency signal is produced by combining the incoming signal with R.F.
energy from a local oscillator. The combining of frequencies for the production of beats or heterodynes follows
simple arithmetic in that the two frequencies are simply added or subtracted. However, there are a number of
practical considerations which prevent
the dismissal of the subject with this
brief statemen't. We believe the matter
can be most easily explained by using
specific examples.
Let us assume that we have a desired
signal of 1,000 kc., and an intermediate
frequency of 465 kc. The conventional
way of producing the LF. frequency is
by operating the oscillator at a higher
frequency than the incoming signal.,.thus:
Oscillator - Signal = Output
1,465 kc.
1,000 kc.
465 kc.
Although the intermediate frequency
could be obtained by operating the
oscillator at a lower frequency than the
signal:
Signal - Oscillator = Output
1,000 kc.
535 kc.
465 kc.
The reason the oscillator is not used
on the low side for broadcast band reception is that a greater tuning range
would be required for the oscillator
than for the antenna or R.F. tuningthus:
Output
Oscillator
Signal
,465 kc.
95kc.
550kc.
465 kc.
1,035 kc.
1,500 kc.
A tuning range of 95 kc. to 1,035 kc.
would be impossible to secure without
band switching.
When using the oscillator on the
"high side" the tuning range of the
oscillator is less than tuning range of
the antenna.
24
Signal
550 kc.
1,500 kc.
Oscillator
1,015 kc.
1,965 kc.
Output
465 kc.
465 kc.
lt will be noticed that while the
antenna frequency tuning range has a
ratio of roughly 3 to 1 between maximum and minimum, the oscillator tuning range is approximately 2 to 1.
To provide the single dial control
required of modern receivers, some
method must be used to restrict the tuning range of the oscillator so that a
uniform separation of the value of the
intermediate frequency is maintained
between the signal tuning and the oscillator tuning. If a 465 kc. intermediate
frequency is used the ,oscillator tuning
must always be 465 kc. removed from
the signal. This cannot he accomplished
by simply using a smaller coil for the
oscillator, the effective tuning capacity
must also be reduced. This may be accomplished by connecting a condenser
in series with the oscillator section of
the tuning condenser to reduce its effective capacity. The series-connected condenser is called the low-frequency pad
and its adjustment is, or should be,
familiar to all servicemen. Another way
of accomplishing the same object is to
use a gang condenser in which the oscillator tuning section has specially
shaped plates of smaller area than the
'plates of the variable condenser sections used to tune the antenna and RF.
stag~s.
It is interesting to note that if the
receiver is designed with the oscillator
operating at a lower frequency than the
signal, the low frequency pad or pads
would be placed in the antenna and R.F.
sections of the circuit. This unorthodox
method of using a "low side" oscillator
would prove of advantage in designing
an ultra-high frequency receiver, since
the oscillator would have greater output and stability when operating at a
lower frequency. The difference between the "low side" or lower frequency
oscillator op~ration and "high side" or
high frequency oscillator operation
amounts to twice the intermediate frequenCY, and with a 465 kc. I.F. the
difference in efficiency would be negligible. However, with a 5 megacycle I.F.
th~ difference in oscillator frequency of
10 mc. between the two methods of operation could result in a considerable
improvement in oscillator performance.
Images and Spurious Responses
We approach the subject of "Images
and Spurious Responses" with some
hesitation, because in this section it is
necessary to point out the essential
defects of the superheterodyne system.
It is difficult to point out how various
forms of interference originate within
the superheterodyne without appearing
to condemn the principle of the receiver. Therefore we wish to st,ate emphatically that the superheterodyne is
truly the king of radio receivers, and
that while various improvements will
undoubtedly occur, the fundamental
design will remain. This fact has been,
recognized for many years.
The difficulty arises in the inability
to give a quantitative analysis of the
intensity of the various unwanted responses of the circuit as compared with
normal interference which .originates in
the turmoil of our broadcast band.
After all, it must be realized that
there are only 95 channels for broadcasting stations in the frequencies lying
between 550 kc. llnd 1,500 kc. and on
these 95 channels are located over 600
broadcasting stations. SatisfactOl;y reception can be obtained only on the few
clear channels; or from local stations
which have sufficient power to over-ride
interference originating from perhaps
a dozen other broadcasting stations
operating on the same wave length. An
• Section 2
SUPERHETERODYNE ',RST DETECTORS AND OSCIUATORS
unwanted whistle or squeal does little
harm when it lands on a channel which
at the location of the receiver is unusable anyway; so that most of the effects
to be described will never be noticed by
the average listener_
So far, we have been discussing the
desired signal. However, many signals
other than the desired signal reach the
first detector, since the selectivity of the
usual input circuits of the average
receiver is anything but perfect. Signals
from the adjacent channels are rejected
by the selectivity of the intermediate
frequency amplifier. However, there
are numerous signals and combinations
of signals that can produce heterodynes
which will pass through the LF. ampli-.
fier. These spurious responses can cause'
annoying interference, and a short
resume of their causes is of interest.
Images
Let us revert to the specific "example
used previously. Assume we have a
standard superheterodyne receiving a
1,000 kc. signal, and using a 465 kc.
I.F_ Then the normal operation of the
receiver is:
Oscillator
Signal
LF.
1,465 kc.
1,000 kc.
465 kc.
However, if a nearby station is operating at 1,930 kc. with sufficient intensity to produce an appreciable signal on
the first detector grid, the resulting signal will be passed by the I.F. Thus:
Undesired}
.
Signal
- ,OscIllator = LF.
1,930 kc.
1,465 kc.
465 kc.
The image is simply the "low side"
oscillator response, and the image is
always removed from the desired signal
by twice the value of the intermediate
frequency.
A corollary of this is that the higher
the intermediate frequency, the farther
the image is removed from the desired
signal. Naturally, the farther the image
is displaced from the signal, the easier
the problem of preselection. With receivers using the old standard 175 kc.
I.F., the image response to frequencies
between 550 kc. and 1,250 kc. was in
the broadcast band (900 kc. to 1,600
kc.), so that the possibility of spurious
response and interference is considerable. This is the reason why 115 kc. has
been largely dropped by the industry;
and why the better class of receivers that
employ this LF. frequency will be found
to use two, three, or even four tuned
circuits before the first detector. With
456 and 465 kc. LF. amplifiers the
image (except for a few channels) falls
outside the broadcast band; furthermore the percentage of difference between the frequency of the desired
signal and the image becomes so large
that the rejection of a single tuned circuit, such as a tuned antenna stage,
becomes adequate for ordinary household reception. The mathematical ratio
of the response of a receiver to a wanted
signal, as compared to the response to
the image, is frequently called the image
ratio, and the greater the ratio, the better the receiver.
Spurious Responses from
Harmonics
The strength of the harmonics
emitted by modern transmitters is very
small'in comparison with the power of
the fundamental wave, and in most
instances the actual harmonics cause little interference. The regulations of the
Federal Communications Commission
take care of this. 'However, strong harmonics of a signal may be generated in
the first detector tube; and the effect
will be exactly the same as if the harmonics originated at the transmitter,
except that the locally generated harmonics will be present only on the
stronger signals.
The production of harmonics by the
first detector generally occurs by reason
of grid rectification, the incoming signal having sufficient 'amplitude to override the grid bias. This effect and its
cure is described on page 10. It is the
purpose of this section to point out the
spurious responses which may result
from the harmonics. Thus the second
harmonic of a 1,000 kc. signal would
be 2,000 kc.; and if the harmonic possessed a reasonable intensity it could be
picked up when the receiver was tuned
to that frequency. In this example, little
harm "would result to the broadcast listener since 2,000 kc. is outside of the
broadcast band. However, second harmonics of stations from 550 to 800 kc.
fall in the broadcast band in fre-
quencies from 1,100 kc. to 1,600 kc. As
an example, the harmonic of a 700 kc.
station could spoil reception from a
1,400 kc. station-the effect would be
the same as two stations on the 1,400 kc.
channel.
Third, and higher harmonics are
occasionally encountered in high frequency reception-their intensity is
usually considerably less than the
intensity of the second harmonic, but
their presence may fool the listener into
believing that he is listening to a distant
short-wave station, when the signal
actually is originating in a local transmitter.
If the harmonics originate at the
transmitter, the harmonics are actual
radiated waves and they will be picked
up by any receiver of adequate sensitivity, regardless of its design. The
effect of generating the harmonics at
the receiver is more pronounced in the
first detector of a superheterodyne than
in other types of rlldio circuits. Proper
circuit design, including the 'use of preselection, provides a satisfactory answer
to the problem. A modern short wave
receiver with one or two stages of tuned
R.F. amplification before the first
detector rarely shows this defect.
Oscillator Harmonics
The oscillator of a superheterodyne
can, and usually does generate an abundance of harmonics. In fact, this effect
was deliberately used in the early
Radiola 2nd Harmonic Superheterodynes, in which the fundamental frequency of the oscillator was one-half
the desired frequency. The purpose was
to prevent interlock because the low
intermediate frequency employed would
normally place the resonant points of
the oscillator and the detector input
coils very close together. The second
and higher harmonics of the oscillator
are capable of beating with an incoming signal, and if the difference in fre·
quency between the two equals the
inteqnediate frequency the resultant
output will pass through the LF. amplifier. As specific examples:
Desired
Oscillator
Signal
I.F.
1,465 kc;
1,000 kc.
465 kG.
2nd Harmonic of 1,465 kc.=2,930
25
Section 2 •
rHE
MYE
rECHNICAL
MANUAL
\
kc. This 2,930 kc. oscillator input can
beat either of two frequencies" to the
I.F. frequency:
2,930 kc. - 2,465 kc. = 465 kc.
. 3,395 kc. - 2,930 kc. = 465 kc.
Heterodynes Between Stations
There is a very good reason why the
even numbered intermediate frequencies of 450, 460, 470, etc. are not gen3rd Harmonic of 1,465 kc. =4,395 kc.
erally
used in broadcast receivers.
4,395 kc. - 3,930 kc. = 465 kc.
Broadcasting stations are located in 10
4,860 kc. - 4,395 kc. = 465 kc.
kc. channels--and if two signals differThese examples will explain why a
ing from: each other in frequency by the
short-wave station will occasionally he
value of the intermediate frequency
tuned in on the broadcast band. The
enter the first detector, they will beat
input of such a station will be greatly
with each other to produce a third sigattenuated because the frequency is far
nal of I.F. value. The result would ,be a
removed from the resonant frequency
continuous backgl'ound jumble of the
of the detector grid tank (input tuning
two stations, regardless of where the
circuit), so that the effect is generally
receiver was tuned. Odd numbered
limited to very close stations. Many
intermediate frequencies are used, such
radio amateurs are blamed for spoil~g
as 465 kc., 456 kc., etc., since broadbroadcast reception when the real troucasting stations are never spaced by
ble"lies in the fact that the broadcast
such an odd' interval. Here is one of the
receiver does not have adequate presestrongest arguments to the serviceman
that his test oscillator should be acculection. Adequate preselection, plus reasonable shielding of exposed grid wires
rate, since a discrepancy of 4 or 5 kc.
will eliminate the trouble, or at least
will align a receiver so as to be susceptireduce the trouble to a negligible value.
ble to interference from inter-station heterodynes. Another point-an intermediate frequency amplifier does not
accept a single frequency-it accepts a
Harmonics Beating Harmonics
bimd of frequencies. Also, while the
unmodulated carrier has, or should
have a single frequency, the modulated
Although seldom actually causing
carrier with its side bands may occupy
trouble in receivers of modern design
the full 10 kc. allotted channel. Conseusing the higher intermediate frequently, in locations where the receiver
quencies and modern mixer tubes, it is
is very dose to two powerful broadcastperfectly possible for the harmonic of a
ing stations separated by an interval
station carrier to beat with the harmonic
approximating the I.F. frequency, say
of the oscillator to a value which will be
460 kc. or 470 kc. with a 465 kc. I.F., a
passed by the intermediate frequency
jumble of the two stations may be heard
amplifier. Because both,harmonics will
all over the dial. Assuming that the
have less amplitude than the fundamenantenna is of reasonable length, and
tal frequencies, such responses are genassuming that the receiver is properly
erally quite weak.
aligned, there is still one remedy left to
the serviceman. .Simply realign the
For those who are interested in a
intermediate
frequency a few kc. higher
pastime let us suggest that instead of
or lower than the specified value. In
working a cross:word puzzle, the reader
the example given above, realignment
try figuring all the various combinaat 475 kc. or 455 kc. will probably cure
tions and permutations by which an
,
the
trouble, and there is sufficient range
oscillator and its harmonics can beat on
in
the
trimmers of most I.F. transforma si~al and its harmonics to produce a
ers to permit this. Realignment of the
signal at intermediate frequency. The
I.F. will also call for readjustment of
practical value of such calculation is
the
gang condenser trimmers and low
doubtful, because the higher the ord~r
frequency
pad. After realignment the
of the harmonic the weaker the amphtude, but the number of such combina- . dial scale may be slightly "off" but this
can not be avoided, and is a small price
tions is amazing, and the read~r will be
to pay for the elimination of the interassured of a full evening of entertainference.
ment.
26
Overall Feed-back
There is one curious form of interference which is fairly common .in
receivers using a 175 kc. intermediate '
frequency, and that is the ·inability to
receive stations on 700 kc., 1,050 kc.,
and 1,400 kc. without a strong whistle
being heard. This whistle nas been
found to originate through overall
feed-back. Some of the R.F. energy at
175 kc. frequency passes from the sec:
ond detector through the output system
of the set and is picked up by the input.
The fourth harmonic of 175 kc. is 700
kc.; the sixth harmonic is. 1,050 kc.;
and the eighth is 1,400 kc. If this disturbance suddenly appears in a receiver
which has previously been free froni the
trouble, one should immediately suspect the failure of the R.F. bypass condenser connected to the plate of the
second detector tube, the opening of the
ground lead between the receiver chassis and the loud-speaker, or the failure
of other R.F. bypass conK8
R.F.
l'~PUT
\
6J8G
'6L7
"ABe.
•
P
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
full
0
0
0
osc S6
K
0
0
0
0
0
0
0
0
0
OSC. 05C 56
K
.\
INPUT
AlI01E
o
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
••
•
0
0
0
P
OSC •
0
0
0
0
0
0
0
0
0
0
0
OSC.
I(
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
•
0
0
0
0
0
0
~56
P
ANODE . \
~HfELD TIED
.
TO
0'-,
c:r- _ .....
rr ......"
"'..... "
rr ... ' \
a--
c:r- ......... ,
'\
,\ \
•
I I
,
,\
0,,\\\\
o
I \ ,
"", \\\
01
0.'
,
......
cr- ...
1
I
I
0./ 1 1 , 1
1
I I I
,. I I
,/ I
0.. ... ,. I
0.. ........ ,,"
0.." "
Q.._ ....
0.._ ....
0,.. ....
I
I 1
I,
/
0.. ........
,/
"
~
"' ...... ','\
(O'~
I
I
I
,
0./
11 /,1
o.."~ / I I
0,.......
0..- ...
I
I
I
I
',.0.,'
I
0.. ... "
"A"
,,# WI"""
\
,,~
i
lV'\
o0"\I \I 'I \I \I
I
"
'OIlP~/li6
(()IC "N ",,.0'" SIbil)
Fie. 14
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
10.' I
'....0 ..,.1
p
·'6"
..s'DII'.)
;~
The 6L7G construction, designed for
mixer service, uses five grids. The No.1
grid is the R.F. input grid, the No. 2
and No.4 grids are the screen, the No.3
grid the injector grid, and the No.5 grid
,
the suppressor.
The 6J8G construction is identical to
that of the 6L7 except that it has an
additional triode section mounted at the
bottom of the common cathode. The
grid of the triode is tied internally to
the No.3 grid of the heptode.
The 6K8 is of an entirely new construction best shown by the bottom
sketch at the right of the page. ~ single
flat cathode is used with a common No.
1 grid for the oscillator and hexode
section. A flat plate is used for both the
oscillator and hexode. The screen and
R.F. input grids are positioned approximately as shown on the sk~tch. The
shields as shown are placed to give a
suppressor action to the hexode section
thus raising its plate resistance and making p()ssible the use of the screen and
plate at the s~me potential.
The ability of the tube to develop a
current at an intermediate frequency is
given by the conversion conductance,
which by definition is the ratio of an
incremental change in intermediate frequency current to the incremental
change in R.F. signal voltage that produces the current. This conductance in
micro mhos is published on all converters
and its use to calculate stage gain is
analogous to the use of mutual with
R.F. amplifier pentodes. The gain equation for a single tuned load is:
,/
SPACE (IIAI(6E
CAMc/7:zJAlCC COt/Pt.lN6
(DII:.
I
,"
0- ........ ,
~ ..........
SHELL.
• Section 2 .
The above equation involves ':lnly one
other tube characteristic, and that is
plate resistance. Published values of
plate resistance and conversion conductance can therefore be used to calculate
stage gain.
In application there are certain phenomena that alter characteristics or
circuit parameters and th{) results are a '
gain value somewhat different than calculated from published data. These unpublished characteristics are essential
in selecting a tube for a particular
service.
Assuming the use of rated voltage!!
and oscillator grid current there are in
41
Section 2 •
THE
general the following effects that occur
in the several tubes:
1. Degeneration at the R.F. signal
frequency.
2. D.C. current flow in the R.F. signal grid circuit that upsets operating
conditions.
3. Oscillator voItageappears in circuits other than those associated with
the oscillator. This voltage may be in
phase or out of phase with the normal
oscillator voltage and the resulting
plate current at oscillator frequency
may be increased or decreased. As
conversion conductance' and gain are
functions of the plate current, the
measured gain is different from that
calculated.
4. Negative or positive loading in
the signal grid circuit affects. the antenna or interstage gain driving the
converter tube. Calculations are often
upset because of this phenomenon.
To facilitate comparison of the five
converter and mixer tubes, the chart
Figure 15 was prepared. It lists eight
separate plienomena found in the several tubes. In addition, a tabulation of
the more important interelectrode capacitances and of the two characteristics,
plate resistance and conversion conductance, is given.
The first phenomenon, capacity coupling from oscillator to signal grid, is
experienced with all tubes. The capacitance, not shown, is approximately .1
mmfd. for each type. The result of the
coupling is mainly that oscillator voltage appears across the signal grid tuned
circuit. At extremely high frequencies
the impedance of the signal grid circuit
to the oscillator frequency is quite high,
and the magnitude of the voltage becomes high enough to over-ride the bias
and cause grid current. If the voltage
does not produce grid current, the effect
is either to increase or decrease the conversion conductance and conversion
gain. If the voltage is sufficient to cause
grid current to flow, the D.C. current
upsets the operating conditions, with
attendant loss in sensitivity.
The oscillator voltage in the signal
grid return, as a result of capacity coupling, is in phase with the normal oscillator voltage if the qscillator is on the
high side of the resonant frequency of
the tuned circuit in the signal grid cirh:
70
-I-- ~- rI- t--I--
.......
'
a.
5-5
I-
r--.
.......
....... r-
r-
5-5
40
~
~
~
~
~
00
densers need be no higher than for the
half wave rectifier applications, 150volt working condensers are usually
specified for this type of circuit. Such
condensers are safely rated for all except unusual conditions of extremely
high ripple peaks as might occur with
low capacitance values and 25-cycle
supply lines.
It will be noted that condenser CB
has its cathode connected to the chassis and thus if it is of metal can construction the unit may be directly
mounted on the receiver chassis. Condenser CA, on the other hand, must
have its can insulated from the chassis
and be suitably covered to prevent
accidental contact of any grounded
parts with the can of the condenser.
One side of the power line is connected to the junction of these two
condensers designated as point 0 in
Fig; 4B. Since either side of the power
line circuit may be grounded depending on the direction in which the attachment plug is inserted in the power
outlet, it is evident that care must be
taken in the design of transformerless
sets such as the A.C.-D.C. and doubler tyPes from the standpoint of
shock and fire hazard.
The output condenser of the filter
(C 2 of Fig. 4), must of course be rated
at a value determined by the full output of the doubler less the filter drop
and is usually a 250-volt rated unit.
'-"' - I 0-10
r-... ....... ::::::: ~
rJ)
120
6::::
Fe :;.... I-"'"
~
::::::: I:::-.
160
oI:i
~
I-
50
6C
~
~
t-
~
~p
G: 200
<{
-- ~p
100
• Section 3
~ 20-20
0
0
60
- -- ....- '-"'
-
.....
~
~ :/'
P"
- I 0-10
1-
..-:: ~
..-::; .....
,~
-
SUPPLY SYSTEMS
~
00
00
IDC-LOAD CURRENT IN MILLIAM PERES
100
6A
Of importance from the performance standpoint is the effect of circuit
returns and power line grounding conditions on hum pick-up in the audio
circuits and hum modulation of the
oscillator. Either the metal chassis or
a negative bus wire is made the return
point for the RF, IF and audio grid
circuits as well as their respective
cathode or cathode bias circuits. The
heaters of all these tubes are connected in series with a suitable voltage
dropping resistor across the power
line. In half wave circuits such as are
shown in Figs. 1 and 2 the power line
can readily be connected directly to
55
THE
Section 3 ,.
the return side of the grid circuits
(negative side of filter output), if suitable protective measures are taken to
reduce shock and fIre hazard. In these
circuits the succession of heaters starting from the chassis is usually as follows: Second detector at ground on
chassis, then fIrst detector, if of the
converter type, or oscillator if of the
separate tube type, then in succession
the other heaters in order of the audio
and radio gain until the output tube
and the rectifIer are found at the other
end of the series string. By this
method the D.C. and A.C. differences
of potential between the heaters and
their respective cathodes are kept low
for the tubes most likely to introduce
either audio or carrier modulation
hum.
In the symmetrical doubler circuit
of Fig. 4A it will be seen that there
exists a D.C. voltage difference of half
the B supply voltage Between the
chassis and the fIrst heater of the
series string T 1 and that upon this
D.C. potential difference is superimposed the ripple voltage of CB. Fortunately modern tubes have very low
cathode to heater leakage as well as
improved heater constructions which
keeps this source of hum at a minimum. As mentioned above certain
recent receiver models employing this
type of doubler circuit have departed
from the usual symmetry of capacitance and have made CB twice the
capacitance of CA~ This reduceR the
RF impedance between chassis and
power line, as well as reducing the
ripple voltage between heater and
cathode o( the fIrst tube in the series
string.
FIGURE 7
A
SCHEMATIC
TECHNICAl.
MY E
MANUAl.
COInmon Line
or Series Line Feed Type
of Doubler Circuit
Another general type of voltage
. doubler- circuit has been variously
called the common line, series line feed
type, or half wave doubler, is shown
in Figs. 7A and 7B. This circuit operates in a somewhat different manner
from the one just described and might
be, designated as a voltage addition or
multiplier circuit rather than a doubler circuit. It was proposed prior to
1933 and has found occasional application since that time. It will be noted
that this circuit allows one side of the
power line to be connected directly to
the negative side of the fIlter output
and thus overcomes the difficulty of
a high voltage difference between
heater and cathode of the high gain
tubes at the chassis end of the heater
series string. The circuit is shown in
schematic form in Fig. 7A and in simplifIed form as Fig. 7B. Only the portions of the circuit essential to an explanation of its action have been retained in Fig. 7B.
The operation 'of the circuit may be
explained as follows: Assuming point
1 to be positive with respect to point
2 during the initial half cycle, charging current will flow in the direction
shown by the solid arrows through
rectifier tube T 10 until capacitor CA
assumes a charge equal to the instantamlous potential of the line. During the next half cycle as point 2 becomes'positive with respect to point 1
the charge of condenser CA will add
its potential to that of the line and
current will flow through rectifIer
tube T 2, charging capacitor CB to a
potential equal to the sum of the
charge in CA plus the line peak. The
path of this action is shown by the
dotted arrows. This action would result in a charge of condenser CB of
twice the peak line potential if it were
not for the fact that this condenser
begins discharging through the load
the instant that current starts flowing
through rectifIer tube T 2. A cursory
analysis of this circuit would indicate
that since current seems to flow in
both directions through capacitor CA,
as shown by the solid and dotted arrows, a non-polarized type of electrolytic condenser would be required.
This is not the case and it is possible
to use a standard polarized type in
this position. After the steady operating condition is reached the net
charge, which capacitor CA receives
during the half cycle when T 1 is conductive, balances its discharge on the
succeeding half cycle, since CA acts as
a rese~voir to supply the loss of charge
of CB by current through the load. It
will be seen that the polarity of CA
never reverses and thus a polarized or
common type of electrolytic condenser
may be used.
Fig. 8 shows the general nature of
the voltage and current wave shapes
in this type of doubler circuit. These
are seen to be quite dissimilar to those
encountered in the half wave rectifIer
and symmetrical or full wave doubler
circuits and a word or two of explanation may be in order. The shape of the
pulses for the fITst two cycles are
somewhat conjectural since it is difficult to observe them on the cathode
COMMON LINE OR SERIES LINE FEED TYPE OF DOUBLER CIRCUIT
DIAGRAM
B
......
SIMPLIFIED DIAGRAM OF DOUBLER CIRCUIT
~-x-,~
SOLID _
-
'tHARGING
CURRENT FLOW WHEN
IS POSITiVE
56
Q)
DOTTED --~ --~CHARGI NG
CURRENT FLOW WHEN
IS POSITIVE
®
!
,
HALF
WAVE
AND
DOUBLER
POWER
FIGURE 8 VOLTAGE AND CURRENT WAVE SHAPES IN
COMMON LINE TYPE VOLTAGE DOUBLER
+
/,~'\
!.
/,
\
b~~\--~
I
\
\
I
\
\
--~\-- -+- - --+--- I - - --t
\
I
\
/
\
A
\ .. ..--1
/
\
\
I
\
/
/
' ....../
VOLTAGE ACROSS CA
\
\
,
"
I
SUPPLY SYSTEMS
• Section 3
ray oscillograph without elaborate
transient sweep devices. After the
steady slate operating conditions have
been reached, the charging current
pulses into condenser CA (through T 1)
are of very short duration since it is
only necessary to restore the loss of
voltage occasioned by the transfer of
its charge to CB during the portions
of the succeeding half cycles when T 2
is conductive. The discharge pulses
from CA are of longer duration· since
current not only flows into condenser
CB but also into the load resistor during this time period. A condition of
equilibrium is reached when the area
of the charge pulse is equal to the area
of the discharge pulse and then, due
to the difference in time duration of
the pulses, the current wave may be
quite assymetrical as shown in Fig. SF.
Typical Operating
Characteristics of the Series
Line or Half Wave Doubler
B
c+-
VOLTAGE ACROSS Ce
CURRENT THROUGH T(.
CURRENT THROUGH T2
CURRENT THROUGH CA
Unlike the circuits previously discussed, this doubler has quite dissimilar functions for the two capacitors
CA and CB. CA acts as a reservoir of
energy and adds its charge to the line
during the succeeding cycle. It contributes little to the filtering action
and therefore we need only concern
ourselves with its effect on output and
regulation. CB is similar in its function to the input filter condenser of
the half wave A.C.-D.C. circuit of
Figs. I and 2 except for the higher
working voltages encountered. Unlike
the symmetrical doubler, the voltage
ratings of CA and CB 'need be similar
since CA is never subjected to an instantaneous voltage greater than line
peak plus the ripple voltage shown in
Fig. 9C. The average or D.C. voltage
on CA approaches line peak only for
the conditions of low D.C. load currents and high values of capacitance
in both units. For these reasons it is
evident that CA may, for typical operating conditions at 60 cycles, be
specified as a 150-volt rating, especially if its capacitance is high, i.e.,
30 or 40 mfd. Capacitor CB, on the
other hand, is operating with the full
D.C. output voltage of Fig. 9A plus
the peak ripple shown in Fig. 9E. It
must therefore carry a working volt57
Section 3 •
THE
age rating of 250 or 300 volts, depending on load current and voltage.
In the series of curves shown in
Figs. 9A, B, C, D, E, and F, the"value
of capacitor CB has been fixed at 40
mfd. as being. a representative value
from the standpoints of regulation
and ripple voltage (hum). As previously stated, it will be observed that
the value of the line series condenser
CA has only a minor effect on the
ripple voltage and RMS current conditions of CB. The ripple current in
CB again does not exceed the "rule of
thumb" value of 2.4 times the D.C.
load value discussed for the half wave
rectifier case and consequently this
estimate of working conditions provides a generous safety factor.
The conditions of operation of the
line series condenser as shown in Figs.
9B, C and D distinguishes this general
type of circuit from those previously
discussed. It will be noted that the
RMS ripple current through this unit
as shown in Fig. 9B is much higher
in proportion to the D.C. load current
than for either of the other types of
circuits. The ripple current for low
values of load current is seen to approach a value of 3.2 times the D.C.
current. This value has been chosen
as a, convenient figure which again
provides a generous safety factor when
considering load currents of practical
usefulness such as 50 MA or more. It
will be noted that low values of capactance should not be specified for condenser CA wherein the current exceeds
the value of 10 milliamperes per microfarad previously cited as safe for
the type FP capacitor. Other considerations, such as regulation and output voltage, which would influence
the choice of this capacitance value,
would also result in a capacitor value
which would lie in a safe operating
region as far as ripple voltage and
current are concerned. An upper limit
of capacitance is determined only by
the effect of capacitance on- peak ripple current through . the rectifier as
shown in Fig. 9D. In this instance the
D.C. currentlimitof75 MAisreached
before the peak ripple limit .of 450
milliamperes. As previously stated it
has' become standard practice to employ two rectifier tubes in parallel for
the higher D.C. load current conditions.
58
M YE
TECHNICAL
MANUAL
FIGURE 9 COMMON LINE OR HALf WAVE DOUBLER
TYPICAL CHARACTERISTICS
E,.../V.Nv
o
RI
T,
T2
CAz
~.
1~1Jit111111 fItItTI~,~l
cr
°0
10
20
30
40
50
60
70
80
90
100
inttiHlllllillRll1 M~~
It
a:
.I
~
a:
00
10
20
30
40
50
60
70
80
90
100
~
50H--!;'~++-H-+-+-+-H-+-+-++-H-+-l
.;
c(
10
20
30
40
50
60
70
~~
80
90
100
98
~
~:::J150H-+-+-++-H~~+-HH-+-+-+-~~-l
00.
~
r- 10MFD
>~
,
~ 100rC~B~=~4~~M~P~D-+-+-H-+~,++-H-+-+-+-H
a~
'U
Jl
50~1_+-1~_+-1~-+~+-~~~~~+-~-+~
I I
0
0
I
I
I I I
10
20
"'-
30
40
50
60
70
80
I-t-I- 5MFD
90 100
IDe-LOAD CURRENT IN MILLIAMPERES
9A
HALF
WAVE
AND
DOUBLER
POWER
Series Line Feed or Half Wave Doubler
with Common Cathode Type Condenser
An interesting variation of the type
of doubler just discussed is the circuit
of Figs. lOA and B. This arrangement
of circuit components makes it possible to combine all of the fIlter capacitors in one common cathode type
unit. The resulting saving of both
space and economy of construction
are obvious. In this case the metal can
of a condenser of the FP type can be
mounted directly on the chassis and
it is not necessary to provide insulation of the conaenser can as in the
case of the high side condenser of the
doublers previously discussed. Since
both CA and CB carry ripple currents
of the magnitudes shown in Figs. 9B
and 9F, the ability of the particular
type of condenser construction to adequately radiate the heat occasioned
by the flow of this ripple current
through the series resistance of the
condensers, should be considered in
the choice of a suitable unit. When
these units both having ratings of 40
mfd. and the D.C. load current does
not exceed 75 MA, it is possible to
combine them with the output fIlter
unit in a single condenser of the type
FP construction.
It will be noted that this circuit
interposes between the heater and
cathode of the frrst tube in the series
string the terminal voltage of condenser CA. Since there is superimposed
FIGURE 10
A
• Section 3
SUPPLY SYSTEMS
upon the average voltage a peak rippleas shown in Fig. 9C it is obvious
that the value of CA should be made
as high as is practicable not only to
keep this ripple at a minimum but
also to provide a low impedance path
between the chassis and the power
line for both radio and audio frequency currents.
Voltage Multiplier Circuit
An interesting extension of the principles involved in the half wave type
doubler circuits of Figs. 7 and 10 is
shown in Fig. 11. In this case the
principle does not stop with a doubling of the voltage but is extended to
cover any desired multiple of the line
voltage. Condenser C 1 operates in the
same manner as condenser CA of
Figs. 7, 8, and 9, and delivers its
charge plus the line peak voltage of
the succeeding cycle to condenser C 2 •
This condenser adds its contribution
of double voltage to the line voltage
on the next half cycle when diodes Dl
and Da' are conductive. This action
continues in chain fashion through
condensers and diodes 3, 4, 5, and 6
in turn. It might at first appear as
though the chain of rectifiers when
conductive would short circuit the
charging action. This is not true be-
cause, once the series of condensers
are charged, current from the individual rectifiers flows for only that
portion of the cycle necessary to restore the loss of charge from the condensers due to current through the
load. Thus, after the steady state
conditions are reached, condenser C 1
is charged almost to line peak, condenser C 2 almost to twice line peak,
etc. It is obvious that condensers C1,
C a, C., and CN, may be combined in
one common cathode unit with proper
attention given to the required voltage ratings of the individual sections.
Similarly condensers C 2, C 4, and C 6
may be combined in another or second
common cathode type single unit.
This circuit has been included here
more for its interest as an extension of
the principles discussed than as a suggested practical power supply system.
Those familiar with the technique of
the art of constructing surge generators for lightning research will recognize similarity of this circuit with the
individual charge and series discharge
methods employed to produce very
high voltages. A practical limitation
of a chain circuit of this type is the
fact that if the tubes have their heaters connected in.a series string across
the power line there will exist dangerously high potential differences between heaters and cathodes of the
rectifier at the high voltage end of the
system. This difficulty of course might
be obviated by the use of heater supply transformers but this would destroy the simplicity of this system.
SERIES LINE FEED DOUBLER WITH COMMON CATHODE CONDENSER
SCHEMATIC DIAGRAM
B
SIMPLlF"lED
DIAGRAM Dr DOUBLER CIRCUIT
+
U S PATENT 2 172 962
CHASSIS
P R MALLORY 8. CO INC.
SOLID ___ CIiARGING CURRENT
f1.0W WHEN
IS POSI1"IVE.
+
I
DC
DC
L
VOLTAGE
DIVIDER
aM
~
FIG. log
01----·---i---'
Frc.2
65
MY E
THE
Section 4 •
TECHNICAL
MANUAL
lated from the base and from each
other, permitting independent circuits.
The two reeds on any vibrator had to
be exactly matched in vibrating frequency .. Each production reed was
matched to a standard on a master oscillator by removing a small portion
of the armature weight. The coil was
still a series type, depending upon
the load current for good amplitude,
the contacts of both pairs were closed
at rest, and the second set of contacts
were used for' mechanically rectifying'
the high-voltage AC instead of using a
rectifier tube. As can be seen in the circuit, Fig. 3, a "phantom-load" resistance
Dual Reed Vibrator
The next step in the development of
vibrators was the addition of it second
vibrating reed and associated spring
and contacts. This "dual·reed" vibrator
is illustrated by the line drawing in illustration No.3, together with the circuit in which it was used. The coil
position was changed, so that the armatures now included on the reed assemblies could swing past the end of the
core, 'instead of being attracted to it as
was the case with the original vibrator.
All of the reeds and springs were insu-
The following reproductions picture the Mallory dual·reed or self-rectifying Elkonode in
two positions; a side view showing the Elkonode with cover and rubber cushion removed, and
a front view with wver and cushion removed. Numbered arrows clearly indicate position of
Elkonode parts involved in installing new contact spring and new reed assemblies.
e
1
s
5
6
cg}
L.OCKING SCREW
1111
I
SCREW-DRIVER SI...OT FOR
AO.JUSTING STOP POST
ENLARGED STOP POST ASSEMBLY
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Coil mounting nut
Coil
Stop-post mounting block
Position contact spring behind
stop-post head
11. Contact points
Air-gap
Rppd counter wf'ights
Stop-post locking-screw
Stop-post
Reed Spring Assm.
Contact Spring Assm.
~
III~
#17005
,.. ~
#A-\70~"'---~_'"T-'lm;oo'
P~~~LQAO
#10746
~A~+--J~srG=T'~~=S=FO='M="~
S,",O~T L'ENGTH
# \
B
8t S
WIRE
o~~~
U!AQ CON-
NEC1.~~~~
A-
IN
~C-
TYPE CH SSIS S- IS GROUNDED A.MO
COHDENseR A,I'tO CHOI
........ 6.6V
6.3;;':.:..
-.j 6.0·:'0/Ju1
- -:b~.x...,
~3
V.lnput
v
0
0
i---I.
160
o
20
---- -
40
d.6 \:...
--
--I-~6.0v.'",~
~
~
TAPS 2 & 4
----80
5
---
~
.
1'--"-'0
.......
--·120
-~
-
@.
...... ~
---
-- ~
!"'-' ... ~.
~-
JAPS 1 & 3
I~
'--
200
I!:
:::>
--r
__
120
1"--_...... ~~6.6"
~"
...........
"'"
6.0" ' ,
~
~, 1--,
g
'-- "
~ 160
o
illustrated ~ the previous photograph.
Fig. 20 shows the tube-rectifying type
with tap·switch, and "A" hot, 'fB" plus,
and "B" minus RF or hash filters. Of
course, the tube.rectifying type is intended primarily where "S" minus is
desired off of ground potential. Fig. 21
shows the self-recti,fying type with tap·
switch aDd RF filters while Fig. 22
shows the same type of power unit for a
single range of voltage output, therefore
not requiring the tap.switch. Fig. 23
shows the interior arrangement of a
dual power unit, with .individual pri.
mary RF filters, fuses, apd output resist·
ance smoothing filter. An individual con·
nection and filter is' provided for the
tube heaters so that they may be con·
trolled separately with the heaters of
the tubes in the amplifier or trans·
mitter.
While the output characteristics and
input loads corresponding to same are
shown in Illustrations Nos. 25, 26, 27, '
circuit diagrams representative of the
three types of Vibrapack power units
are shown in Illustrations Nos: 28, 29,
30 on pages 83 and 84.
t,--
--·240
I-200
MAf'tIUAL
280
280
~
:!
TECHNICAL
60
Vm
3
- :I!<
2
--
11-"'"
100
~
4
~
~
80
-. ~
o
~
-&
~
20
~V
40
>
80
60
100
OUTPUT MILLIAMPERES
FIG. 25A-OPERATING CHARACTERISTICS OF VP·551
where they are unobjectionable. Each
vibrator then assumes its normal por'
tion of the load so that satisfactory vi~rator life is secured; and the combined
power output is amply smooth for any
practical application. This fact has
been amply substantiated in actual servo
ice by the performance records of dual
Vibrapacks types VP-555 and VP·557
which are widely used under heavy load
conditions to operate police mobile
radio +ransmitters, etc.
.
Chassis Construction
Illustrations Nos. 20, 21, 22, show
the methods of assembly and constructio~ for the interior of the Vibliapacks
Operation of Vibrapatks on A.C Lines
\
Fu~ing
380
While all vibrator power units should
be fused for protection to the various
components and the battery, it is essential that dual units be individually fused
with the proper fuse. There are two
reasOns for this. There is an appreciable
amount of resistance to fuse and its
holder. 'The use of ,separate fuses provides additional isolation for the two
halves of the supply through the elimination of ~omnion 'impedance. But a
more important consideration is the
fact that should failure of any component render inoperative one side of a
dual pack, the fuse for the other section
will blow and thus prevent a single
vibrator from assuming the full load of
the entire power supply. It is obvio'us
that a single ~section of a dual power
supply could not supply double output
for an extended period of time without
being damaged.
340
440
"'"
" ~,---......
6.0,,>.
........ f--.. --......
4.?v
1--_
6.31'
t--- "'-'
400
.......
..... "
'" 360
~
"--...... 1"--,
" , ~'
. loev, l'
i'- _..
l'
~ S->~~
. -....:.: ...
.
~
"'~......
- ' " ...........
1 r--.. t
r--::.
~3~
--
t--
280
601'
0/. UI
-~-
TAPS 1 & 3
f
!--"'" --~'6
o
~
20
40
....- ~ ~ --5·4
L-----"
1-~
t::::::- 2i"'" ---60
~...
tAPS 2 & 4
---8
~
•
-~II.~
240
I-
.
.....
1'-_
320
r--~-~
1--- 1- __ ~.7..!:...
220
"-,
r-.....
r-.. ....... ~N·J"
........
.~
-
1--_
a
80
plying an additional primary winding
on the vibrator transformer for con·
nectiop. to U5·volt AC lines has been
suggested, and in some instances d-one.
Considerable discussion has occurred at times regarding the operation
0.£ Vibrapack type of power units on
AC {lower lines.
, The possibility of sup-
80
100
o
20
40
OUTJ>UT MILLIAMPERES
FIG. 25B-QPERATING CHARACTERISTICS OF VP-552
60
--
~
@
--@)
I--'"
80
100
• Section 4
VIBRATORS AND VIBRATOR POWER SUPPLIES
fore the usefulness of the receiver was
gone. In this case a high-voltage AC
. winding was included, controlled by a
two-position switch which also controlled the primary DC circuits simultaneously. The heaters were run from
the battery when on DC operation, and
from a portion of the DC primary when
on AC operation, thus eliminating one
winding. It is also not necessary to remove the vibrator from the socket when
operating in this circuit.
6r---~--~----+----+--~
TAPS 1 & 3
.!SJ-
TAPS 2 & 4
---~-4"----
13 5 1----1----1----+----1----+----- 51---~--_I----+_--_+7""":::....j
!.
~
~
~
4
3
2
---
L--::::: - - -
.,;
"
r-...::;.
I"-... I-- .......~
~ 340
............. !2 .
6.3".
6.0V.,.
5
--1'
~
.......
0
~" .......
.
"""- - - -- --- -- ,---- --- -- - .:::- :::::-r-----
o~
~,
~
420 ..... ,
1- .......
1---...
,220
' .......
_6.!.!::.
v".pu,-_
®
"--r---'-t--_ --.
6.0
5.7
~
---
TAPS 2 & 4
TAPS. 1 & 3
,
----8
--::.. g)....-- --~.
@---
2
;l!;
,--
40
60
80
100
-----~
6
--~-4
~
20
,
r-............ " -
300
260
.......-:: ::---
ill Illus-
The circuit diagram shown
.....-::::
-2 ::;;.-
::::--
20
40
60
®
------®
80
100
OUTPUT. MILLIAMPERES
FIG.
25D-OPERATING CHARACTERISTICS ~F
yP.554
81
Section 4 •
THE
----'-
650
r-
'
d~ rr----
-.......S.;>3~
~,-
-
....
$$0
1--
400
--
MYE
425
1- _ _
375
r- -__
1
--
~
~
=::::
TECHNICAL
I-
~
-~-~l
MANUAL
Vibrator Wave Form
with AC Load
- r-
75 It Inpuf
1---~r---r- r -
r-_
325
Here it' is seen that as soon as the
contacts open, at the bre~k, the load
which is connected to the transformer
drains the power from the circuit beyond the capacity of the timing condenser to supply. This reduces the volt-·
age across the primary to zero, thus
.closing the contacts, at the make, with
the full input voltage across them.
Naturally, this condition is somewhat
detrimental to good vibrator performance and life. An inductive load applied
to the transformer creates a worse condition, and therefore, unless comparatively light, is not a recommended, or
approved, load for a vibrator.powered
inverter. Operation of motors, etc., universally re~mlts in damage to the vibrator unless the inverter is expressly designed for that purpose, because of the
extreme starting load imposed by such
devices.
0
275
;
20
MinimlllTl Starting
---- 20
/
V
~
--~
.
/"
10
vV
.
---- 5
Minimum OuTput
V
Current ~5 MA.
;
50
75
100
125
I~I
014 Tubes 140 MA.
---:15
!
/
/
:IS
V
Cu'''",wUb
150
25
4
~
VI
V
V
,
/"
Minimum Output
~
Current 40 MA.
50
75
125
100
175
150
:ItO
OUTPUT MILLIAMPERES
FIG. 26-0PERATING CHARACTERISTICS OF
tration No_ 33, page 85, gives a satisfactory method of operating one vibrator
power-supply on more than one voltage
input. The percentage voltage range
covered should not be too great, or too
large a per cent of die input current
will be coil current, in as much as the
coil of the vibrator must be wound for
the lowest voltage of operation. This
high current on the highest input voltage has the tendency to unbalance the
primary magnetization characteristic.
The unit shown was dev~loped to provide a power sourde for operating 110volt DC razors from a 6-, 12-, or 32volt battery, using a self-rectifying vibrator. By using a more complicated
switching means, the primary could be
made a series-parallel arrangement for
6- and 12-volt operation, reducing the
transformer slightly, but in this case it
was not felt to be worth the involved
switching required_ Rl and R2 are resistors switched into the coil circuit to
permit operation on the higher voltages, with C4 used to by-pass the AC in
the coil circuit.
Illustrations Nos. 34 and 35, pages 85
and 86, are circuit diagrams for inverters to supply AC output voltage from· a
DC source, usually 110 or 220 volts DC.
The former is a simplified circuit using
the shunt-type of vibrator capable of carrying a medium load, with Rl being the
series coil resistance, (this type of vibrator requires a .coil' of such high
resistance that small enough wire to
attain same in the regular coil·dimensions is not practical), and Ca being the
,82
VP-557
AND
VP-555
AC by-passing condenser. C2 are primary point condensers of very low capacity, and C1 is the timing capacity.
When operating into an AC load, it is
necessary to know the type of load,
(whether' capacitive or inductive), and
its value before being able to accurately
set the values for C1 and C2 , as well as
design the correct transformer. For
operating into a resistance load, similar
to the power-supply of an AC radio receiver, the primary voltage waveform
becomes as shown in Illustration No.
35.
The final circuit diagram of illustra·
tion No. 36, page 86, shows an inverter
, using a larger: separate' driver type of
vibrator, capable of handling higher
powers than the one just described. In
this case the coil requires no added resistance for 110 volts, but does require
same for higher voltages, being Rl in
480
1'.........-...
380
440
340
."
5
0
----r--~V.I.'"
---- --' ----I"--.
---... " ... "
'~
~
'5
_~.o~
...
300
260
220
--
.
--" r--~
-- t-!.l.!!':...,
~
TAPS 1 &
~
...... ,!1.$"
-...:.
....,
"
N
..........
..................
'5
............
5320
'0
!!:gil
...:....
,280
---~~
1----__
./"
J
11
~1I:.....
-
TAPS 2 & 4
---·4
@
3
~ I.---
2
.~ 1 ..--=::
:;;.-
20
k::::::= ---Q)
-
"
---- ------ --- ------- --r
- -...
t---.......... _
240
4
o
~ 360
U~"
85
;>
·. . r
440 I---I--~....::.._.d_--+--I--_l
r-__
I...-
I--~
::::- -
280
I---
~6~
_
---....~
I
_
j
t-..
--. r-....
r-- --
--'I~
__
-~L
j
v.......... C"'p.
I'
r __
I~.!::
3201---+-::::..,,-I-._'"""".:.::...-lh.._
-_
-_
1---l
L36
I---f---
- - -!!t.. f-- __
280
16 0
-.... _ L
·1" tJl
__ 0360.....
51
2<101-r.--_-+---+---F::O"...:.;;:""--=---=1
~
....... ~v
::>.
'--. __
I
r-- ~ ...
,~ 400...........
r"-......J l ) . o - ,
I
'-- ~,:-f-__
I--- I~noui
- -......
CD -_
200
-....~
--~~...............
~I
320
50
RF Interference
Suppression
~~
--.il6 V
. In
r---t-
"i---- +----- ®
1
-
240
""f:-~-::._
32V
28"
-.J
___
1-_ 1- __ _
TAPS 2 & 4
TAPS 1 & 3
1.6,1---+--+---1f---t---+---1.61---+--+----If---b;:-~
.,;
I@ ___
1. 2 1---+---+---!--+~®E""""'1-
~ L21---+---+---!-__.::r;pr".---I
--=:::~ ~~
1--+-_-+~-=-,.......j:-::::"....-.9===---I_
8
4~
o
20
-------~
.81--+-..---:::::--_+-::--,.....,::.'--±.--'=-i---I
_.4~
40
60
80
100
40
20
60
80
100
OUTPUT MILliAMPERES
FIG. 27B-OPERATING CHARACTERISTICS
the diagram. In this circuit a transfonner and switching arrangement is
provided for operation on either no
or 220 volts DC, with C1 being the
timing condenser and C2 the point condensers. Cs and Rs are used across the
driver·contacts to prevent erosion and
transfer. Again, the primary may be
made a series·parallel arrangement
with more involved switching.
Other possible applications will come
to mind of the reader. Among them will
be the operation of neon (and other
luminous gas) tubes as signs, warnings,
etc. This has been done very successfully in the past by means of high leakage inductance types of transformers,
,imilar to the AC types used for the
~ame purposes, wherein the tube is ig'lited by the high induced voltage of the
unloaded secondary but which has its
maximum load current controlled by
leakage strips of transformer iron inserted in the window between the primary and the secondary windings which
'ire wound in separated coils. This type
of construction furnishes magnetic
shunts which limit the output.
OF
VP-F558
ply have been barely touched. What the
future may bring, no one knows. Each
year brings new applications wherein
the vibrator power supply serves better
than any other forms of power conversion equipment. The Mallory Laboratory is always on the alert for new
developments, and progress is governed
only by the necessary economic consideration that the potential market justifies the development expense.
TRANSFO;RM~E:!!R_ _--"-<~--'(;:-D):_--___:=:;f....-~
SWITCH
LEGEND
TRANSFORM
C-I
C-2
SECONDARV LEADS TO BE TWISTED
INTO 4 PAIRS. LEADS OF SAME
LEiTERS TO BE PAIRED
Future Developmeuts
From all this, it will be evident that
the design possibilities and the field of
application for the vibrator pow~r sup-
Perhaps the biggest "bugaboo" or
difficulty in the application of Vibrator
power-supplies to radio receiver operation, even for engineers and designers
experienced in the art, is the matter of
RF interference suppression. Fundamentally there are only a few basic
rules that must be observed, with a
considerable number of variations that
must be predicated upon the nature of
the particular application under consideration. In other words, methods
that would be ideal from the standpoint
of suppression may not be practical
from the standpoint of cost in lowpriced receivers, methods that may be
used on heavy current drain power
units may not be acceptable on light
power applications where efficiency is
important, and in general some compromise is usually necessary.
These basic fundamentals can be
listed as follows, although probably
none are more important than others:
First, proper and complete magnetic
and electrostatic shielding of the components of the power unit and of the
complete unit; second, proper selection of grounds in both the power-unit
and the receiver to reduce or eliminate
coupling and radiation; third, proper
VP-551
AL 0
VP-552
PT N MALLORV P
VP-G556
NO MAL
B-44617-1
RF-481
A-40980-2
TP-415
B-44617-2
RF·481
A-409BO-1
TP-435
RF-562
A-40919-1
Rf-563
A-40919-1
A-40389-3
725
A-40921-i
A-40922-1
B-111202-1
A-40389-6
725
A-4092H
A-40922-1
B-1I1202-1
A-40389-6
R'I'
N
B-44617-4
RF-481
A-40980-1
TP-435
A-42097-1
RF- 563
A-40919-1
A-403B9-3
G725
A-40921-1
A-4092Z-1
B-1 II 202-1
FIG. 28-SCHEMATIC WIRING DIAGRAM FOR VIBRAPACKS
Nos. VP-551, VP·552, VP-G556
83
THE
Section 4 •
MY E
TECHNICAL
MANUAl.
T RANSFORME;R_ _---:.RE~D_;:(:D~J_;:::::j._--,
and complete filtering in the leads to
and from the power-unit; and fourth,
proper orientation and shielding of the
receiver coils and transformers, etc., to
prevent coupling to the power-unit.
SECONDARY LEADS TO BE TWISTED
INTO 4 PAIRS LEADS OF SAME
LETTERS TO BE PAIRED.
Shielding of Components
sa
Shielq.ing methods have been dis·
cussed at a previous point, but to sum·
marize briefly, we find that the power
unit should be provided with some
method of securing a good magnetic
shield for all chokes and transformers,
including leads, and an electrostatic
shielding means that provides for a
short·circuited turn in the shield in
each plane or direction. This may take
the form of a separate chassis and cover
with all sides enclosed and electrically
V -
LEGEND
M l. OR
TRANSFORM.
C-I
C-2
C-3
C-4
C-5
CH-I
CH-2
RRECTIFIER
VI BRATOR
VI B. SOCKET
TUBE SOCKET
TERM STRIP
SWITCH
11-1
C·6
'A'GROUND
FIG. 29-SCHEMATIC WIRING DIAGRAM FOR VIBRAPACKS
V-54
3
PT.NQM
OR
-FS56
NO M
8-44617-1
RF·461
A-40960TP-415
TP-436
8-44617-2
RF·461
A-40960-1
TP-435
TP-436
R F·5 2
A-40 9-1
R F·563
-40919-1
A-40389-3
TVP oZ4
Y 625
A- 211-1
A-40978-1
A-40943-1
8-111202-1
A'40l89-6
TYPE e 5
T PE 825
A-I 211-1
A-40978-1
A-40943-1
8-111202-1
A-40l~'8
Nos.
0
8-44617-3
RF·461
A-42086-5
T P-435
T P- 438
A-42097-i
RF-562
A·409 9-1
A-40369-3
TYPE 024
TYPE F626
A-IS 11-1
A-40978-1
A-40943-1
B-II 1202-1
! ,~
Tp·410
VP-553, VP-554, VP-F558
1,1
LEGEND
"A
C-I
C-'
C-3
Co,
Co,
RF481
A-409SQ-6
A-4l0eO-2
A-42080-1
CH-3
J 01411
A-42204-1
A-4208]-!
A-40J89-3
A-1521i-l
A-40978-1
A-40922-S
A-40922-4
OZ4 A-40977-2
TYPE 825
A-40389-4
A-42092-1
fUSE
~AG 12~.t.4P
CH-I
,.,
CH-2
VIS SOCKET
TUBE SOCKET
TERM.STRIP·A"
TERM STRIP"B
RECTIFIERlU
VIBRATOR
R-3
I'~
OFl~5p;NOM vP~~NQ
V
TRANSfORM 8-44247-5
8-44247-6
RF 481
A-42G86-1
A-4Z080-Z
A_4l080- t
X-26080
A-42204-1
A-4208J-1
A-40389-]
A-15211-1
A-40978-1
A-40922-5
A-40922-4
6X5A-40977I
TYPE825
A-42092-1
3A_G 12 AMP I
FIG. 30-SCHEMATIC WIRING DIAGRAM FOR VIBRAPACKS
Nos.
VP-555 AND VP·557
A C / BATTERY-INPUT VI BRATOR POWER SUPPLY
connected, with radiating parts either
enclosed therein or mounted on same
with individual covers. Or, the power
unit may be mounted op. the main receiver chassis, as is more commonly tl;te
case in present stage of designing, with
partitions either welded, screwed, or
soldered in place to provide a cover for
components and leads. Or, again, the
power unit may be mounted upon the
receiver chassis, with few or no parti.
tions provided, and the outer case providing the additional shielding to a
more or less satisfaCtory degree, with
metal spring-wipers, bonds, screws and
studs, etc., completing the electrical cir-
A.C.SWITCH
~
A ..C.
PRIMARY
A: ~ :: ~'----'
/
'):'CHOKE
BOTTOM
VIEW OF
SOCKET
FIG. 31
84
SECONDARY
=-
VIBRATORS AND VIBRATOR POWER SUPPLIES
cuit to provide satisfactory suppression.
In general it can be stated that the' degree of difficulty in manufacturing a
receiver built in any of the above manners is directly proportional to the
elimination of shielding in the direction
of the steps outlined. Quite a few receivers of the last type mentioned have
been produced in large quantities, it is
true, but in order to secure satisfactory
uniformity after production started, experts devoted many hours of additional
labor to "remove the bugs" that could
not be foreseen, or if foreseen, the precautions necessary to prevent them arising were considered too much added
cost.
CIRCUIT FOR OPERATING VOLTAGE DOUBLER FROM VIBRATOR
HEATER
SECONDARY
#1
FIG. 32
CIRCUIT FOR UNIVERSAL INPUT POWER SUPPLY
USI NG SPECIAL SELF -RECTIFYI NG VI BRATOR
A
B
RI'
I
I
I
BATTERY
,
B BOTTOM
VIEW or
SOCKET
PILOT LAMP
OR
INDICATOR
-:-
I
I
~----------------
D.C.
OUTPUT
.----.
SMOOTHINC CHOKE
It is usually desirable to ground the
filament, or heater, "string" at one
point on the receiver, and to avoid
a loop effect formed by the "hot"
filament leads and this ground. Often,
dividing the flow of filament current
from a mid-point on the string will be
of assistance in preventing "hash" interference being carried into the highsensitivity end of the receiver. Selection of a ground on the antenna circuit
out of the region of any possible stray
field from the power unit is extremely
important.
A
I
• Section 4
FIG. 33
TYPICAL CIRCUIT FOR DCI AC INVERTER USING
TYPE 90 OR 627 SERIES VIBRATORS
Selection of Grounds
Universal rules for the placement of
grounds cannot be given as hard and
fast methods, because each design of
receiver must be considered as a separate problem. In general, it is wise
however, to have just one ground in the
power unit, if possible, at least for the
"A" or primary circuit components.
Another ground for the "B" circuit is
often permissible, as the magnitude of
the current in this circuit is such that
small radiation or ground currents can
be expected. If a separate power unit is
being used, this should be grounded to
the receiver chassis at one point only,
selected if possible to prevent a loop
being formed by the "hot" "A" lead
and the ground, or chassis, and to
ground as far from the RF end of the
receiver, or antenna coil, as is possible.
TRANSFORMER
A.C.
OUTPUT
(BOTTOM
VIEW OF
SOCKET)
Cz
r-I
C!.J...
,
<...,
::'
-r- <
<...(1
I
r
""'.
FIG. 34
DC
INPUT
85
Section 4
+fc
.
THE
BREAK
:
I
I
I
I
I
MA~E
TECHN"CAL
MANUAL
there is never an excuse for increasing
the number and cost of the filtering
components used over that required for
the purpose in question. Each case
must be considered again as an individual problem, yet there are certain
components that MUST be used as a
minimum for hash suppression. The design and quality of these components
are important factors, yet all types from
poor to excellent are often selected with
only the thought of cost, size, or availability as the determining factor. The
minimum amount of filtering· takes the
form shown in Illustration No. 37 in·
which an RF "A" choke is inserted in
I
I
I
I
I
I
I
0
MYE
WAVEFORM WHEN OPERATING INTO RESISTANCE LOAD-NO TANK CONOENSER
FIe. 35
Filtering of Leads
The term proper and complete filtering of the leads to the power unit may
be interpreted several ways. Naturally,
OCTO A C VI BRATOR POWERED INVERTER
USING TYPE 40 SERIES VIBRATOR
TAPPtD
AUTO-TRANSf'ORMtR
'-E---'\~~
BOTTOM Slot
Of SOCKtT
FIe. 36
r-~------~~B+
~----------------------~~B-
r----+x
HEATERS
~'AHOT
FIe. 37
86
senes with the center-tap lead of the
transformer, with a paper by-pass condenser connected from the center-tap to
ground, and a second by-pass condenser is connected from the "B" plus
high-voltage to ground. On receivers
with low sensitivity this may be sufficient, even with low grade components,
but as the sensitivity and compactness
of the receiver increases, the effectiveness decreases. The choke usually consists of a multi-layer coil of No. 16 or
smaller wire, with the "A" by-pass a
condenser of 0.5 mfd. The "B" con-.
denser is usually from .01 to .. 1 mfd.
Compare this circuit with the one
shown in Illustration No. 38, which
shows an improved form incorporating
the features found inJatest receiver designs, including improved chokes and
condensers. Choke No.1 is now a special bank-wound design instead of the
multi-layer type, and, while having approximately the same number of turns
and physical size, has much greater suppression power at radio frequencies
because of the elimination of high distributed capacitance between layers.
Choke No.3 is similar in construction
but may be of smaller wire size, since
voltage drop to the heater string is not
as important as to the vibrator. Choke
No.2 is usually a single-layer coil of
comparatively small number of turns
used primarily for ignition suppression.
However, in conjunction with its condenser it also aids in hash suppression.
Chokes Nos. 4 and 5 are small RF
chokes of small wire for hash suppres':
sion in the plate circuit leads, with
Choke No.5 used where B minus is not
at ground potential.
Condenser No.1 is the primary buffer condenser, required on 12-volt or
higher input voltages, but which may
take the form of an optional mica condenser on some 6 volt or lower applications for hash suppression. No.2 is
the timing capacity, in series with a
medium size resistance, as outlined previously, or in the optional arrangements
shown as dotted lines. No.3 is a patented type of hash-suppression RF·condenser (Mallory Types RF481, RF482),
which definitely eliminates the inductance loops formed by the leads on ordinary condensers. It will be noted that
the primary current to the transformer
and from the reed of the vibrator must
fl<~w directly across the plates of the
condenser, this being the best possibl ..
,~
!
• Section 4
VIBRATORS AND VIBRATOR POWER SUPPLIES
s+
COLD CATHODE
'-----_HEATERS
----- A HOT
CH.
FIG. sa
means of secui-ing a short-circuited path
for the RF currents. The vibrator reed
is grounded after the condenser in this
method, as shown. No.4 is a special
type of condenser developed recently,
and known in the trade as a "sparkplate," since its first application was
for the use of eliminatng ignition interference without reducing signal
strength, etc., in the antenna circuit.
Naturally its capacity is very low, but
the lack of inductance in its leads, and
close proximity to ground create an exceHent RF filtering device. Originally,
this condenser took the form of one or
more plates of metal separated by fishpaper insulation and riveted to the
chassis. The current was fed in one end
and out the opposite end of the plates,
in the same manner as No.3, thus eliminating the inductive effects. No.4 has
taken the form of a small mica insulated condenser which is soldered, rivetted, or screwed to the chassis, and has
been found to give excellent results in
difficult cases of hash elimination. No.
5 and No. 6 are ordinary RF by-pass
condensers, but may be of paper or
mica construction as the case demands.
OrdinariIy, little difficulty arises from
interference arising in the "B" circuit,
because subsequent filtering in various
parts of the receiver is usually sufficient
to minimize this source of difficulty. As
pointed out previously, where a coldcathode rectifier tube is used, No. 7
'condensers may be required if sufficient
filtering is not provided in the "B" circuit.
Two additional pointers are shown,
which may be of service in hash elimination. It is usually desirable to, connect the "hot" rectifier heater terminal
to the center-tap of the transformer
~"f
rather than to the heater string, unless
this involves carrying a long lead into
the receiver proper. The rectifier tube
is always "hot" with interference and
enough may be conducted through the
heater connection to nullify all of the
other filtering provided. The use of resistors Rl across the contact points of
the vibrators has great benefit in reducing, or eliminating, the type of interference known in the trade as "pop hash,"
that being the sharp intermittent variety, in contrast to the "tone hash" which
is the continuous, more or less regular,
type. The value of these resistors will
vary in different applications. Where
input current is not so important, as in
automobile receivers, or where chargers
are available for the battery, values
from 50 to 200 ohms have been used,
with probably 100 ohms being average.
This is for 6-volt applications; where
12-voIt applications would require resistors, approximately four times the
6-volt resistance is required to limit the
wattage to the same value, and for
higher voltages, the required size of the
resistance removes its effectiveness.
In general, where a design requires
intense hash elimination work, the best
rule is to provide every bit of suppression that is available and secure quiet
operation. Then, remove one component at a time until a change in interference level is noted, then replace that
particular part, and proceed. It is a
practical impossibility to judge the
value of a single component by inserting it alone when the interference may
be arising from a number of omissions,
or locations. Care should be taken that
the resistance of the vibrator "A" circuit be kept as low as possible, in order
to secure good starting, good efficiency,
and regulation. Added capacitors are
to be preferred rather than added
chokes.
Long-wavelength (low-frequency)
bands in communication or "all-wave"
receivers are usually the most troublesome to completely cure of hash interference. Here additional chokes and
high capacities are usually required
along with the other suggestions given
above.
r- -- - ------------ -----------------,
I
I
I
I
I
I
' - - : - '...+
L---L:;~~-=-~-:-_ _ -~+
I
L __ - - - - - -
.:r:
:::r::
:
----=--- - - - - --=---- --1
oV.
FIG. 39
87
Section 4 •
THE
MYE
TECHNICAL
MANUAL
portable receivers filament type tubes
are employed, one side of the filament
or cathode circuit automatically becomes connected to B-.
Very successful solutions have been
made to the problem, arid the discussion
following will make clear the principles
employed so that service procedure can
be confidently carried on in a logical
manner.
OSC.MOD.
608C
r - - - - - - - - - - - - - - - - - - - - - - - - ,I'
:
I
I
Types of Tubes
'--~---+_B+ TO "CT~R
L
T _____
_______
± _______
I
I
J
FIG. 40
Bias Supply Systems
Offhand it may seem a bit unusual
that a treatise on Vibrators and Vibrator
Power Supplies would treat grid biasing methods of radio receivers. However
the widespread usage of the deservedly
popular synchronous or self-rectifying
vibrators has led to the adoption of new
biasing methods, necessary in vibrator
power supplies employing synchronous
vibrators because' B- must be at
ground potential, and consequently bias
resistors cannot be inserted in the highvoltage negative lead of the power supply system. When heater type tubes are
employed, conventional cathode resistors will provide bias; but when for reasons of current economy in farm and
CONVERTER
6D8G
A-
A-
A-
c-
r----------- ---- -------- - - -
c--~
I
I
I
A-C
,
-
-
I:I
I
I
I
I
I
I
~-~--~----:-r---------------- _J
FIG. 41
88
-=--
B+
In using vibrator operated powersupplies to furnish plate voltage for
portable and battery-operated radio receivers for farm homes, or for places
where no AC power is available, current consumption must be held to a
minimum to secure g09~ life from the
batteries. Tube manufacturers have developed a considerable number of special types of tubes for this class of
service with the general characteristic
of low filament or heater P9wer, and
comparatively low plate and screen
power requirements. The cathodes of
these tubes are both indirectly and
directly heated in various tubes, being
either the common "heater" construction or filament types. Filament voltages are 1.4 and 2.0 volts, and heaters'
are 6.3 volt types. Quite often these
types of tubes are mixed in a receiver
for various reasons to obtain special
results.
Where the same cells of the battery
supply both the vibrator and the filaments of the tubes, it is usually necessary to isolate the filament "string," or
circuit, from the effects upon the battery of the hum "ripple" voltage impressed upon it by the vibrator pulsations, as illustrated at a later point.
This is usually done by placing an ironcore choke of low resistance (similar
to the voice-coil winding of an output
transformer), in the power lead to the
filament supply. This must not be in
the vibrator circuit. ,Quite often it is
also necessary to connect from the filament side of this ~hoke a high-capacity,
low-voltage, electrolytic condenser, of
elt least 1000 mfd., to ground or to the
other side of the filament circuit. This
filtering is usually not necessary if all
the tubes are of the heater-type unless
the system has unusually high gain, in
which case it may be that the first tubes
I"
I
!
• Section 4
VIBRATORS AND VIBRATOR POWER SUPPLIES
in the amplifier will require isolation.
Complements of tubes used in typical
radio receivers for this class of service
include types requiring: 6.3 volts for
the heater at currents of 0.40, 0.30, and
0.150 amperes; 2.0 volts for the filament at currents of 0.120 and 0.060
amperes, and 1.40 volts for the filament at currents of 0.100 and 0.050
amperes_ The maximum plate voltages
used are under 200 volts on the older
receiver designs, and as low as 60 volts
on recent portable units.
Circuit Diagrams
Shown in Illustrations Nos. 39-48,
are simplified circuit diagrams of the
tube complements, vibrator powerunits, filament or heater circuits, and
bias circuit connections for ten production models of battery-powered home
radio receivers that have been produced
in recent years. These diagrams offer <.
wide variety of combinations of tubes
and biasing methods that permit the
satisfactory operation of these receivers
with a "solid-reed," self-rectifying, vibrator power-supply in which the "B
minus" connection must be at supplybattery potential.
All Heater Type Tubes
The circuit shown under Fig. 39 illustrates a receiver equipped with all 6.3
volt, heater-type tubes of various
heater-current requirements. The Vibrator power-supply is conventionally
built into a separate unit consisting of
a sheet-metal box grounded to the radio
chassis at one point. A separate Type
6LSG. tube is used for Second-Detector
and A VC supply and a Type 6S7G tube
is used in addition for the lst-Audio
Amplifier tube. All of the heaters are
connected, of. course, directly across
the 6-volt battery. Bias voltages (negative) for the control grids are secured
for the converter, IF-amplifier, and
power-output tubes by self-biasing resistors in the cathode circuits. The first
audio tube is biased by means of a
Mallory Bias Cell, which is a primary
battery type of unit with extremely high
internal resistance, which generates approximately 1 volt on open circuit. It
is interesting to 'note here that a drain
FIG. 42
of only several micro-amperes will reduce the voltage read across the terminals of the cell, and thus a vacuum-tube
type of voltmeter is required to accurately measure the cell. However, in
the grid-circuits of radio receivers, no
current drain is required, and an AC
current passing through the' cell does
no damage to it, perhaps charging it
to a slightly higher voltage. A shortcircuit to the cell for a short period does
not damage it either, and the voltage
will rise to the original value as the cell
recovers. However, it is not recommended for u!le as bias for the output
",
6570
CQNVE:R'TE:R
6080
I.
eS7C
stage, inasmuch as continuous (DC)
grid-cl\rrent flow will change the cell's
characteristics to too great ~ degree for
satisfactory performance. To conclude,
the second -detector tube, being a
diode, -does not require grid bias. In
most respects, this design of receiver is
similar to most automobile receivers in
which vibrators have been used for
many years.
The circuit in Fig. 40 is quite similar
to that of Fig. 39, with two major
changes. The two. tubes used for
second-detector, A VC, and 1st-audio in
Fig. 39 are now combined into one tube,
OtT Ave
6LSCi
AUDIO
6S70
BIA$ CELL
+
'-r-+----+
B+
A+
FIG. 43
89
THE
Section 4 •
M Y E
TECH N , C A I.
MAN UA I.
Fig. 42 also shows a receiver with all
heater-type tubes, but with a zero-bias,
"Class-B" dual o,utput tube substituted
for the previously shown biased-type
tube. This tube requires a driver tube
preceding it to secure the maximum
power-output which it is capable of- delivering. The other tubes are biased as
in Fig. 40.
r-----------
-------~-----------1
I
I
I
I
I
I
I
I
I
I
I
I
,
,,
Heater and Filament Type
Tubes in Combination
B+
FILTER
rlLAM[NTS
,":""
,
I
L.. _ _ _ _ _ _ _ _ _ _ _ _
-::r; ___ -- =t='- _____
I
~
A-
FIc.44.
the Type 6T7G, and the negative gridbias supplied by the Mallory Bias Cell
for the 1st-audio tube is now omitted,
this circuit now being controlled by a '
10 megohm resistance.
The circuit shown in Fig. 41 is a
further variation of Fig. 40, in the manner of securing fixed bias for the tubes
other than the 1st-audio tube. The
cathodes of these tubes are now
grounded, as is the positive side of the
6-volt battery. The output-tube control grid connects to the negative of the
battery for a bias of minus 6 volts.
CONVERTER
1ST I.F.
le6
34
A+
2 NO I.F'.
34
The converter and IF -amplifier tubes
connect to the same point through a
voltage-divider to secure the desired
bias, and the diode of the AVC circuit
also receives a certain negative bias
from the same source. Iron-core "A"
circuit chokes are shown in the powerunit, but it should be pointed out that
these are of the high-frequency powdered-iron type, of comparatively low
inductance. The iron permits the use of
fewer turns of wire, making for a
smaller choke with lower primary-voltage drop.
I ST AUDIO
DIODE OET.
30
DRIVEft
30
30
A+ ,
I
MALLORY
BIAS CELL
~-~---------------------,
H
i
I
I
I
,
:
I
,
JI-+-=-+
B+
I
I
I
.i:ti~~~~~~~~~~~~;;~~
_______________________
FIG. 45
90
A+
OUTPUT
I.
In the circuits shown in Fig. 43 and
Fig. 44 it will be observed that a combination of heater-type amplifier tubes
and filament-type power:output tube
has been adopted, the latter being the
Type 19, a "Class B," dual output tube.
The Mallory Grid-Bias Cell is again
used for negative-bias on the 1st-audio
tube control-grid in each circuit. The
difference between the two circuits is
that in Fig. 43 the output tube operates at zero grid-bias (inasmuch as the
filament dropping resistor is on the
positive side of filament), while in Fig.
44 the output tube operates with 4 volts
negative bias (because the filament
dropping resistor is now in the negative side of the filament, raising the
filament 4 volts positive above ground
with the control-grids connected to
ground). The Type 19 is primarily intended for zero-bias operation; therefore, the use of the negative 4-volts bias
in Fig. 44 is for the purpose of further
reducing the "no signal" plate current.
In each circuit it is again necessary to
provide a: driver tube preceding thE
power-output tube to provide sufficien!
energy to attain full audio power.
Fig. 45 circuit diagram shows a combination of one 1.4-volt and six 2.0volt filament type tubes operated from
a 6-volt battery. This circuit shows the
simplest method of using this type of
tube, with each having its own filament
dropping resistor, but it should be
pointed out that the maximum conservation of battery current is not attained
to any degree with this system, in contrast to the possible series-parallel combinations which could be made. No
hum-filtering for the filaments has been
provided other than the dropping resistances. Inthe biasing of these tubes
I
}
• Section 4
VIBRATORS AND VIBRATOR POWER SUPPLIES
CONVE.RTER
I C70
OSCIL.LATOR
I H4G
OET 1ST A
r
IF7GH OR IF7GV
....---.,
r---------------------l
OUTPUT
6G6C
,..-----,
A-
I
I
I
I
B+
I
I
I
I____,iJ
I
t
• VOLTS
I::r:
::I::
1__
+~--:...-----------
FiG. 46
you will note a similarity to some of the
preceding diagrams. The power-output
tube is opera,ted at zero-bias, again being the type 19. The Mallory Bias
Cell is again used for negatively biasing
the 1st-audio tube control-grid, but in
addition adds one volt to the bias of the
driver tube control-grid, which receives
in addition 4 volts negative from the
fact that the filament dropping resistor
for this tube is on the negative side of
the filament.
The circuit shown in Fig. 46 is decidedly different from the others shown,
in that a combination of filament-type
amplifier tubes and a heater-type
power-output tube is used, and in that
a series-parallel filament circuit is used
to conserve battery current and secure
bias. The oscillator and second-detector
tubes are in parallel, as are the converter and IF-amplifier tubes, with the
two groups in series. An equalizing resistor is placed in parallel with the first
group to secure equal current and voltage distribution. The remaining 2 volts
of battery is dropped in the filament
iron-cored choke used for hum-elimination, as shown. The converter and
IF-amplifier tubes receive control-grid
negative bias by returning the grids to
the filament choke, thus securing negative 2 volts bias. A Mallory Bias Cell is
used for the 1st-audio control-grid,
while self-bias is used for the heatertype output-tube.
All Filament Type Tubes
The circuit of Fig. 47 shows a tube
complement of all 1.4 volt filament type
tubes, with push-pull triode poweroutput tubes. Here again the full con-
Ir
IOSC;
C-I ___________
servation of battery current is not attained, with all filaments in parallel, the
remaining .4.6 volts from the battery
being consumed in the series combination of resistor and iron-cored filter
choke. A high-capacity filter-condenser
has also been used in this receiver in
combination with the filament choke
for better hum-elimination. Two voltage dividers are placed across the 6-volt
battery to provide various bias voltages
for the control-grids of the tubes, with
the positive of the battery grounded.
The divider for the "RF" end of the
receiver is high in resistance, totaling
11 megohms, while for the audio end
of the receiver the divider is comparatively low in resistance, totaling 6000
ohms. This system provides a maximum
of 4.5 volts negative for biasing the
output tubes below the filaments. Again
a driver tube is required preceding the
output tubes.
The final circuit shown in Fig. 48 is
considerably different from the others,
and in many respects is the best from a
power-supply standpoint. One cell of
the 3-cell, 6-volt storage battery is used
exclusively for heating the filaments of
the tubes. The other two cells of the
battery are used exclusively for operating a 4-volt vibrator power-unit. This
isolates the filament circuits from the
pulsations impressed upon the battery
by the vibrator, and, by grounding the
negative side of the filament circuit,
permits the 4 volts of the battery used
2 NO Or.T
I H4C
~_=_
cc__________
:. _______________________
-IA-
I
t
I
t
I
I
I
I
I
t
t
I
6V
I
-,;-
IiI
-I
-=-
I
I
t
:=I=
L..::. _______~
-=- _______ ~
_______________________ :
~
.J
FIG. 47
91
a-
THE
Section' 4 •
for vibrator power to be used for biasing the control.grid of the output tube.
By filtering' this voltage through a
IC70
A+
TECHNICAL
M Y,E
MANUAL
single Mallory Bias Cell provides suffiCient negative bias for the tUbes requiring it.
resistor-capacitor netwo,rk, it could be
used as bias for the other tubes also.
However, in this receiver the use of a
IDeo
I"G
A+
A+
c:r-------------------------------------~----,
II
I
:'
I
I
I
I
I
I
I
1
I
1
I
1
:
'I
a+
I
I
':-
_
-
-
'::'
'::'
:
1
L-'------~n -~~~:---~-c--------n m_'
FIG. 48
Features of vibrators illustrated and described in the preceding section are covered by U. S. Patents 2,187,950,
2,190,685, 2,197,607 et al. of P. R. Mallory & Co., Inc.
, 92
e
THE MYE
Section
5
TE~HNI~AL
MANUAL
Phono-Radio
,
Service Data
MALLORY
93
Section 5 •
r H,E
M'YE
r E C H N' CAL
MANUAL
I
"'\
PHONO·RADIO SERVICE DATA
Crystal Pickup Installation
A large portion of present day phono-radio
combinations (either built as a single unit
or radio receivers converted by the use of
record playing apparatus) employ crystal
pickups. Since the pickup medium is actually
the heart of the reproduction system, the
first logical step is to become familiar with
the characteristics, 'Operati'On, and care 'Of
these units. The foll'Owing discussi'On illustrates these points.
r:.
'
,If y'OU are called upon to select and install
a crystal pickup for record reproduction you
have available a c'Onsid~rable choice 'Of styles,
types and prices. The final quality of repr'O, duction, however, depends not 'Only on the
pickup itself but als'O on the meth'Od of installation. The response of the yery finest
crystal pickup can be ruined by failure t'O
observe a few basic, simple installation precautions. Actually, pr'Oper installation is a
simple matter, and by f'Ollowing the suggestions in this 'article, you sh'Ould obtain the
really fine reproducti'On for which quality
crystal pickups are noted.
Electrically the crystal is the equivalent
'Of a condenser with a capacity of ab'Out
1,500 mmfd. The impedance of the device,
therefore. is quite high (100,000 ohms at
1,000 cycles and 1 meg at 100 cycles) and
the lower the frequency, the higher the impedance. Instead 'Of a power generator, the
crystal pickup may be th'Ought 'Of as a
voltage generator which requires a very
high-impedance load so tha:t the greater part
'Of the generat'Or v'Oltage, at all frequencies
'Of interest, will appear across the load.
Terminal Impedance
Since the impedance of the pickup is highest at low frequencies, it is evident that the
ch'Oice of load resistance will directly g'Overn
the low frequency response. This effect of
terminal impedance 'On low frequency response holds regardless 'Of any other considerations. It is inherent in the use of the
crystal with its capacitive internal impedance. Crystal microph'Ones, of course, display
the same effect.
Fig. 1 sh'OWS how the terminal voltage is
affected by load resistance alone for a crystal
of 1,500-mmfd. capacity. A resistance 'Of
5 meg introduces practically n'O frequency
discrimination while lower values reduce the
l'Ow-frequency resP'Onse as sh'Own.
Fig. 2 illustrates the effect of load re-
Tran$i+ion LO$s ..
201og~
eo
0
Mmfd,
1500
e
o
---r
R
eL
~
1000
FIG. 1. Since the impedance of the crystal pickup is highest at the low frequencies, the choice of load resistance will directly govern the low frequency response.
94
sistance 'On the response curve of a representative high-quality pickup. Experience
has shown that for h'Ome reproduction 'On
sets with g'Ood speakers, most listeners prefer
the elevated bass' response obtained with
terminations of 0.5 meg 'Or more, and theref'Ore the service man sh'Ould make certain
that the point of c'Onnection to receiver or
amplifier presents a sufficiently high resistance to the crystal pickup. On the other
hand, if the speaker is very small, elevated
bass response in the pickup is likely to result
in bad distortion due to excessive speaker
stiffness and poor radiating ability at low
frequencies. In such cases, the practical solution is to reduce the bass response of the
pickup until the overall performance is suitable. Try 0.5, 0.25 and 0.1 meg terminations
until the best results are attained.
Since the,crystal is a capacitive generator,
the effect of shunt capacity is merely to reduce the voltage output of the pickup uniformly at all frequencies. No frequency dis>
crimination is introduced by capacity only.
Actually, however, the use of a resistance
potentiometer volume control, in the presence of various circuit capacities, may introduce some high frequency loss. This, how- ,
ever, also occurs with sources other than
crystal pickups. The effect can be minimized
by methods which will be discussed.
Many modern receivers have input termi·
nals which will accommodate a crystal pick.
up. The arrangement is frequently as shown
in Fig. 3 where the receiver volume control
is a potentiometer in the first a-f grid circuit.
The phono.radio switch simply shifts this
potentiometer from the phono input termi.
nals to the detector output and vice versa.
The receiver volume control also controls
the volume on phonograph. The potentiom.
eter should have a resist!lllce of 0.5 to 1.0
meg as explained previously for proper bass
response. Sometimes tone compensating cir·
cuits are tapped into the potentiometer. They
will not ordinarily affect the phono repro·
duction adversely, but if the quality of reo
production is poor, or if the frequency
response appears to vary considerably as
the volume control setting is varied, it is
advisable to test the effect of disconnecting
the tone compensating networks from the
potentiometer. If they prove to be the cau/je
of the trouble, they should be switched out
during phonograph operation. If the receiver
employs the volume control method shown
in Fig. 3 but has no provision for phono
I
PHONO.RADIO
SERVICE
ai
~
c
o
0..
'"
~
500
40
100
1000
er Second
Frequency- Cyc1eS P
FIG. 2. Experience has shown that most listeners prefer the elevated bass
response obtained with terminations of 0.5 meg or more across the pickup.
input, a single-pole double throw switch can
be mounted on the chassis and wired as
shown. The switch should be located near
the potentiometer so that leads will be short
and hum pickup possibilities minimized. It
is advisable to shield the lead from the
phono post to the switch. The switch should
make on the phono position before breaking
the radio circuit to avoid a t1J.ump due to
momentary removal of grid bias.
Occasionally the audio system will have
such high gain that the pickup will overload
the first stage at full volume and necessitate
working at such a low setting of the potentiometer that volume adjustments are critical
\ and quality of reproduction may be poor.
The remedy is a shunt condenser of 0.001
mfd or larger across the pickup at the input
terminals. Increase the condenser capacity
until there is no overloading apparent on
listening test with the receiver volume control wide open. Pay particular attention to
the bass reproduction during the listening
test, for the maximum peak levels occur at
FIG. 3. If the receiver employs the volume control metluxl shown, a single-pole double-throw
switch can be wired for phono operation.
the lower frequencies. Increase the size of
the shunt condenser until the bass is clean.
It is always good practice to attain normal
volume with the audio control of the receiver almost wide open. At medium and
low volume settings, the input capacity of
the tube plus stray circuit capacities form an
L network in conjunction with the resistance
in the upper section of the potentiometer
with a resulting Joss of the higher frequencies. This effect is largely avoided by
operating at near-maximum settings.
When a volume comro] is provided on a
simple crystal record player which is located
some distance from the receiver, there will
almost always be a Joss of highs due to the
effect of the connecting lead capacity in
conjunction with the potentiometer resistance whenever the volume control is turned
down below maximum. There is less loss of
highs with a relatively low resistance potentiometer (of the order of 0.25 meg) but this
may be offset by poor bass response, especially if the record player volume control
and the receiver volume control are in
parallel and combine to present a still lower
terminal resistance to the pickup. When the
feature of volume control at the record
player is not absolutely essential, t)te reproduction will usually be improved considerably by disconnecting the record player
control entirely, depending on the control at
the receiver. Of course these remarks do not
apply to record players of the wireless type
or to those which incorporate an audio amplifier tube following the pickup; in these
cases the tube associated with the pickup
may effectively isolate the pickup volume
control from the connecting line and subse-'
,quent equipment.
. Many receivers of early vintage haye no
provision for phonograph pickup connections; others have phono connections which
are only suitable for magnetic pickups. '1;'he
alert service man can build up his profits by
adding crystal record players to such receivers and by modernizing yesterday's phonograph combinations with improved pickups. Circuit changes to accommodate the
crystal pickup are not difficult if a few fun7
,DATA
• SectiC?n 5
dar6entais are kept in mind. In the first
place, transformers are not required. They
will not provide the proper terminal connections for high-quality crystal pickup performance. Connect the crystal pickup in the
grid circuit of an audio stage across a resistance of 0.5 meg or more (which may be
the radio volume control) and make certain
that no low-impedance circuits are across
the pickup.
A common receiver layout includes a
power detector feeding the output stage.
Radio volume control is probably effected
in a preceding r-f circuit. The best solution
is to switch the detector tube grid to a 0.5
meg pickup volume control mounted on the
chassis (or motorboard if a combination) at
the same time switching the bias to the
proper value for Class A audio amplification
instead of detection. Fig. 4 shows one possible arrangement.
As before, the switch blade connected to
the grid should make in the phono position
before breaking the radio circuit to avoid
switching thump. The shunt resistor R2
must have the proper value to make the
parallel combination of resistors afford correct amplifier bias. Measure the applied plate
voltage and then consult your tube manual
for the correct bias voltage and plate current
for amplifier operation.
Divide the required bias voltage by plate
current to find the resistance which the
parallel combination of' Rl and R2 must
provide. After installing the correct resistor
R 2, recheck bias voltage and plate voltage.
L.
L.~
~~
00..
Q.E
<
Rt
Original self-bios resistor (proper
value for detector operation.)
C t - Original bypass condenser
-
R t - Original self- bios resistor.
R2 - Resistor to lower effective bias
resistance in phono position to proper
value for amplifier operation.
C t - Original bypass condenser.
C 2 - Lorge bypass condenser (may be
high cap., low voltage electrolytic.)
FIG. 4. A common receiver layout includes a
power detector feeding the output stage. The
best solution is indicated.
95
THE
Section 5 •
MY E
TECHNICAL
MANUAL
trolytic or other suitable condenser at C 2•
Both the switch and volume control should
be located as close to the tube as possible.
After these parts are mounted and the set
operates properly on phonograph, it is wise
to realign the tuned circuit feeding the detector which will p.robably be a little high in
capacity due to that added to the circuit by
the switch.
POS'TION A
POSITION B
234
M]116UJ
I
. II
~
RE:VISE
THUS FOR
( FIXE:D BIAS)
\ .
Ftlter Condo
r----~
---------------,
CRYSTAL
PICKUP
~,:
\.
RADIO
J ••••,..
,k'
•0 5 t
:,
•
0
f.O MeS' I
Single·", PHONO.q
•.. ' ..
pole, I
..a.."*'"
.-:double- I
.,. Add .Of Mfd.
I
throw'
.0
Blocking condo
I
switch
PICKUP TERMINALS
I
Shield
.
--f--n-t\!
I
Chassis
I
~-------------------~
FIG. 5. In grid circuits employing fixed bias a
blocking condenser should be used to prevent
the application of the bias to the pickup.
Occasionally the applied plate voltage will
drop and necessitate a slight change in the
bias resistor.
The lowered bias resistance for amplifier
operation will require an increase in cathode
by-pass capacity. This can be provided by
installing a low-voltage high capacity elec-
.1
FIG. 7
Diode-triodes
TYPICAL
DUPLEX DIODE
TRIODE CIRCUIT
1234
Frequently the detector and first audio
element are combined in a single tube, the
familiar duplex-diode triode. Circuit variations are numerous and a careful study of
the individual circuit of the particular receiver is strongly indicated before the work
is started. The problem is to get at the grid
of the triode section, making use of the receiver volume control if possible. Particular
attention must be paid to the method by
which the cathode is biased.
A circuit in which fixed bias is employed
is shown in Fig. 5, together with the p~oper
switching circuit for crystal pickup. The
only modification is the provision of a singlepole double-throw switch to shift tbe highside of the volume control potentiometer
from the radio circuit to the phono input
with a blocking cpndenser in series to prevent the application of bias voltage to the
pickup.
FIG. 8A-Diode Load
I"
I
1,1
It should be remembered that even the
most complicated circuit can be licked .by
switching grid and cathode to a separate
phono volume control and self-hias resistor
and by-pass condenser, respectively. Keep
leads as short as possihle and shield wires if
hum is encountered.
FIG. 8B-First A-F
Typical Switching Circuits
Immediately following is a series of 23 circuits, Figs. 8 through 31, representing a
condensation of past and present methods
for wiring phonograph pickups, magnetic
and crystal, into radio rec.eivers.
These circuits have heen universalized to
the extent that sections of switch wafers or
gangs not directly concerned with the phonoradio transition are not included. This applies to such features as tone control position, wave band change, etc., where these
operations have been combined in a multipurpose switch.
FIG. 6.' Special needles provide some scratch
reduction because they cut-off earlier at the
'high frequency end.
96
A second treatment is the use of a standardized method of swit~h schematic drawing.
As far as we know this system has no name,
'hut we have referred to it as a "linear 'block"
switch illustration. We believe it represents
the most flexihle and at the same time, most
SCREEN
GRID
PHONO
OR'-'
PLATE
,-8+
~-
FIG. 9A-Diode Load
~ '"~O
~ORI.F.
B+~ SCREEN
~-
GRID
OR PLATE
FIG. 9B-First A-F
PHONO-IADIO
SIIVIC,
DATA
• Section 5
easily undwstood method of switch layout.
It is not original with U8; we first saw it em·
ployed in schematic diagrams of the Bel.
mont Radio Corporation and we are in·
debted to them for its use here.
Fig. 7 shows an e~ample of this system.
A88uming it is desired that a particular application have two leads connected in one
position, one of these leads to be unu8ed in
the second p08ition, and the second lead to
join two new leads not used in the first posi.
tion, the wiring in Fig. 7 would apply.
FIG. lOA-Diode Load
FIG. l2B-Fir.t A·F
In position A, leads 1 and 3 are connected,
leads 2 and 4 are out of the circuit. In position B leads 2, 3, and 4 are connected to·
gether with lead 1 open.
Figures 8 through 27 show circuits in
which the phono-radio switching operation
is incorporated either in the diode load circuit of the 2nd detector or the first a-f grid
circuit.
FIG. lOB-First A-F
FIG. 13
Figure 8 shows the most common switching circuit in use, namely that of circuit
transfer only. The switch is shown in radio
position and when pressed or turned it
transfers the a-f lead of the volume control
from the radio input to the phono input.
Fig. 8A is diode load, Fig. 8B fir8t a·f.
In Fig. 9 the second portion of the 8witch
serves to break the screen or plate supply to
an i.f or r-f stage to render the r-f portion
of the receiver inoperative, thus preventing
any radio signal from feeding through by
lead or part capacitance. Fig. 9A-diode
load; Fig. 9B-first a-f.
FIG. llA-Diode Load
FIG. llB"':"First A.F
Fig. 10 shows a further variation in that
the second portion of the switch breaks the
cathode circuit of an r-f or i.f stage to pro·
vide the result outlined above. The dotted
lines indicate the possibility of using the
same switch to provide a shorting action for
the unused input. Fig. lOA-diode load;
Fig. lOB-first a·f.
In Fig. 11 the second function of the
switch i8 also of a transfer nature. When the
switch is in the radio position the lower
section shorts out the phono mput and when
the switch is moved this shortout is transfemd to the radio input li3l1d. This circuit
is an even m!>re positive method of prevent.
ing any capllcitive tranllfer of the unuied
input lellds. It is ufiually incorporated in
receiver8 where the phono or diode leads
are by necessity rather long and possibly
parallel to Jellds in the a·f stage.
Fig. 12 illustrates an application combin·
ing circuit transfer and motor control. When
the a-f lead transfers to the phono input the
second switch sectian cuts in the motor
supply.
FIG. l2A-Diode Load
II ...
R.F..loIllC~R.
-=-
ORII: SCREEN
-
~
YlG.17
Fig. 13 is a combination circuit transfer,
cathode break, and m~tor control system.
97
1HE
Section 5 •
MY E
1ECHNICAL
MANUAL
When the first section transfers the a·f lead
to the phono input, the second seCtion trans·
fers the common or ground lead from the
cathode to the motor thus making the radio
section inoperative and turning on the motor.
Fig. 14 is similar to Fig. 13 except that a
three·section switch is used and the plate or
screen supply of an r·f or i·f stage is broken
instead of the cathode asin the case of Fig. 13.
FIG. 18
FIG. 19
FIG. 20
In Fig. 15 the functions of receiver on.off,
circuit transfer, B+ break, and motor con.
trol are combined in a three.section, four·
position switch. In the first position the
receiver power is off. In the sooond position
the radio section is used. In the third posi.
tion, the a·f lead transfers to the phono
input, the plate or screen supply of an r-f
or i·f stage is broken, and the motor is at
rest position for changing records. In the
fourth position the a·f lead.phono input
contact is maintained, the B supply still
broken, and the motor operates for playing.
Fig. 16 employs a three.section four.posi.
tion switch to provide receiver on-off, circuit
transfer, and motor control. Position 1 is
receiver -off, position 2, receiver on·radio
use, position 3 phono use.record change, and
position 4 phono use-record play (motor on).
Fig. 17 illustrates a system of circuit
transfer and removal of r·f, i·f or mixer
screen voltage. The second section of the
switch when in phono position grounds the
scret"n of the desired stage. In scts employing
this circuit, the screen voltage is low enough
or rather the screen dropping resistor suffi·
ciently high in value to prevent excessive
current flow through the resistor.
I
ANTENNA
FIG. 23A-Diode Load
9!--vvv'v'--,
AN~
-*
~
~~
~
FIG. 23B-First A·F
FADE~
.,-
CONTROL
FIG. 24
The system shown in Fig. 18 has the
following functions: circuit transfer, coil
change, radio shortout in phono position,
and motor control. Position 1 is radio receive
on a certain frequency;' position 2, radio
receive on a sccond frequency; and position
3, phono with motor cut in and diode return
lead shorted out.
98
FIG. 21
Fig. 19 combines the circuit transfer,
radio shortout and a·f load change opera.
tions in a three.section, two.position switch.
In radio position, sections 1 and 2 provide
an a.f load consisting of the volume control
"R." In the phono position, sections 1 and 3
provide a shunt circuit RI and R2 across the
control with the phono input entering at the
junction of Rio Rio limiting the voltage ap·
,plied to the a·f stage hecause of the series
connection of R2 and R," and further pro.
viding a load match for phono input, of RI
shunted hyR2 and R.
FIG. 22
Fig. 20 illustrates a circuit transfer type
with a second section transferring the ground
or common to the diode return lead. Thus in
phono position the cathode of an r·f stage is
broken and the diode return lead grounded
to provide positive radio cut out.
"HONO
FIG. 25
FIG. 26
PHONO-RADIO
SERVICE
DATA
• Section 5
CATHODE
FIG. 27
FIG. 32. Equalization for relatively flat response can be provided by means of a
fixed condenser and a resistor.
FIG. 28
FIG. 29
FIG. 30
~
j
PHOND
-
'\
"
FIG. 31
In Fig. 21 a three.section, two.position
switch provides for circuit transfer, diode
return lead shortout, and bias circuit change.
In radio position the high side of the volume
control connects to the diode return lead and
the low side of the control is connected to
the cathode. In phono position the high side
of the control connects to the phono input
and the low side of the control is grounded.
The diode return lead connects directly to
the cathode.
The circuit shown in Fig. 22 provides
circuit transfer, cathode break, and load
change for phono use. In radio position, the
a·f lead connects to the diode return and the
cathode circuit is complete. In phono posi.
tion, the a·f lead transfers to the phono
input which has a resistor shunted across it,
thereby lowering the grid resistance to a
value comparable to the specific pickup unit.
Also, the second section transfers the ground
or common to open the cathode circuit and
ground the low side phono input.
• Fig. 23 illustrates a different method of
silencing the radio section in that a second
pOFtion of the switch performs an antenna
shortout in the phono position. The first
section is the usual transfer on the a·f lead.
Fig. 24 can't logically be called a switching
circuit since no switch is employed, but it
does transfer from radio to phono by using
a center tapped control, tapered both ways
from the center. When the variable con·
tactor is on the lower half it controls the
phono input. As it passes the center ground
point the phono input gradually reduces to
zero and the radio input is controlled in the
upper haH.
A clever system for use in battery.pow.
ered receivers is illustrated in Fig. 25. In
this circuit the first section of the switch
transfers from diode to phono, while the
second section opens the filament leads of
the oscillator and i·f stages, rendering the
r·f section inoperative, and keeping the bat·
tery drain at a minimum.
Fig. 26 illustrates a system of circuit
transfer and grid load change. The second
switch section in phono position shunts reo
sistor R\ across the grid of tube, thus lower.
ing the input resistance of the stage.
In Fig. 27 the first section of the switch
performs the transfer operation while the
second section alters the cathode circuit.
Fig. 28 shows a transfer action employed
in a biased detector circuit, while Fig. 29
illustrates a combination shortout and motor
control system also employed in the biased
detector stage.
The system shown in Fig. 30 is another
which can't be termed 'a switching circuit.
The phono input is series inserted in the grid
return of the tuhe and the setting of the
control effects the trailSfer. This circuit is
also that of a biased detector.
Fig. 31 shows a simple transfer circuit for
use with a grid lead type detector, and com.
pletes the circuit examples for the phonoplaying switching opel'ations.
Equalizing
It has been intimated, elsewhere in this
article, that a large percentage of radio set'
buyers have been educated to prefer excessive
bass response. This fact probahly accounts
for the elevated bass response which il! char·
acteristic of most present.day commercial
crystal pickups.
Equalization for relatively flat rEll!ponse is
easily provided, should an occasional customer prefer high.quality music. As shown
in Fig. 32, all that is required is a fixed con·
denser and a fixed or preferably variahle
resistance, connected as indicated. If a vari·
able resistor is employed, any response curve
hetween the fully equalized and the normal
unequalized can be obtained at will. The
curves shown have been matched at the
high frequency end and therefore indicate
only the relative frequency response.
99
THE
Section 5 •
Scratch Noise
It has been a common notion that sharplytuned rejector circuits would eliminate needle scratch or surface noise in phonograph
reproduction. The reasoning seems to have
been that the disturbing noise was localized
in a naJ,"row band around 2500 or 3000 cycles
and that the removal of the audio components in suhstantially this band alone, would
considerably lessen the reproduced surface
noise with minimum effect on the general
quality of reproductiou.
Without going into detail regarding special cases that are of little practical interest,
it appears that there are no appreciable
benefits in narrow band-elimination from the
noise reduction standpoint. Surface noise
components are of random character and
are distributed throughout the entire audio
M YE
TECHNICAL
MANUAL
range. Effective noise reduction goes handin-hand with reduction in quality of reproduction. Special needles (such as halftone,
cactus, bamboo, etc.), provide some scrat~h
reduction because they cut-off earlier at the
high frequency end, with of course a corr~
sponding elimination of what may have been
recorded in the lost frequency interval. Ad·
justment of the ordinary tone control of the
receiver or amplifier, with its adjustable,
tapering high frequency loss, will probably
completely satisfy most listeners.
Additional Hints
Crystal pickups, crystal cutting heads,
and crystal microphones will not withstand
temperatures above 125 OF. for long periods
of time. Make sure that adequate cabinet
ventilation is provided. Deflect heat from
power and rectifier tubes if necessary with a
sheet of asbestos board or other heat insulating material. Such a baffle can be made
more efficient by cementing a piece of tin
foil to it on the side opposite the pickup
unit. Check-up with a thermometer placed
at the pickup position. Long experience has
proved that the temperature limitation is
easily satisfied if it is recognized and given
attention.
Should it be necessary to replace the
crystal cartridge or cordage, apply minimum
heat when un soldering and resoldering connections at the cartridge terminals. Cool the
lug with a cotton swab dipped in illcohol
immediately after removing the soldering
iron. Heavy-handed sweating-in of soldered
joints at the cartridge terminals is practically
certain to ruin the crystal. Quick soldering
with minimum heat, immediately cooling
the joint, is ahsolutely safe.
Wireless Record Players
Keeping in mind the infor~ation obtained
from the preceding discussion of crystal pickups- we can gp a step farther and see
how these units are employed in commercial
wireless players.
The popularity of wireless record players
is undoubtedly due to a numher of factor-so
In the first place, the mystery feature,
i.e., the fact that they play through the
radio without direct connection, is intriguing. In addition, the record player may be
placed at any convenient location, the location being limited only by the distance from
the receiver and the convenience of an AC
outlet. Further, these wireless players are
,
ffO-120V
It""...,
60-
'"
FIG. 33. WILCOX-GAY (A56, A57, A60).
100
relatively inexpensive and simple to operate.
When properly designed they are capahle of
good quality.
The principle of operation of these units
is quite simple. A~ pointed out previously,
these record players are nothing more than
a low-power broadcast transmitter. Referring to the typical circuit, such as Fig. 33, it
will be seen that the unit contains two tubes,
one operating as an oscillator-modulator and
the other as a rectifier. The oscillator-modulator. generally a 6A7 or similar tube, is
modulated with audio by means of the crystal pickup and the phonograph record being
played. The oscillator is tunable over a small
range in the broadcast band, this tuning being accomplished hy means of a trimmer.
Microphone connections are provided in
some of the units as an additional feature.
Crystal pickups are used in all cases. The
turntable speed is, of course, 78 rpm and all
units are designed to use either 10 or 12 inch
records. In most cases self-starting induction
motors are used to drive the turntable. although in some instances a manual-starting
synchronous motor is employed. As a result,
operation is from a 1l0-volt, 60-cycle po~er
supply. Detailed information as to trade
names, tubes used, turntables, pickups, etc.,
is given in the chart which accompanies
this article.
Various record players and their circuit
diagrams are shown in Figs. 33 through 44.
In referring to the schematic drawings a
number of rather unusual circuits will be
FIG. 34. G.E. (GMll).
noticed. One unit, for example, uses a 12A7
tube as a combined rectifier and oscillator.
(See Fig. 34.) Another unique feature of this
same unit is the method of obtaining heater
voltage. Instead of employing the more conventional method of obtaining heater volt-
FIG. 35. RCA (VA20, 21).
PHONO·RADIO
SERVICE
DATA
• Section 5
FIG. 39. SONORA.
FIG. 36. PHILCO (RPl).
age from the supply line through a ballast
resistor, it is tapped off the motor winding.
In this connection, it is interesting to note
that another unit employs a similar method
for obtaining voltage for its pilot lamp
(Fig. 35).
290w
line cord
A high·impedance magnetic or crystal pick·
up is recommended for use with this OSC.
FIG. 37. MEISSNER.
In Fig. 36 is shown a unique method for
automatically starting and stopping the
turntable by means of the lone arm. When
insulated from case
the pickup is placed on the record, it automatically closes the motor switch and starts
the turntable. Similarly, when the tone arm
is removed from the record, the motor switch
is automatically opened.
Also of interest is the phonograph oscillator shown in Fig. 37. This Iype of unit is
designed for operation through a direct connection to the receiver antenna circuit and
will not ordinarily supply sufficient radiated
signal to provide satisfactory wireless operation, even if the coil shield is removed. There
is no reason, however, why the same components and exactly the same circuit would
not prol'ide wireless operation if a simple
addition were made.
A radiator connected to the oscillator coil
(indicated as an antenna in the circuit of
Fig. 37) will provide satisfactory results,
especially if this radiator is included in the
power line cord. Four to six feet of wire
should provide ample radiation. Some difficulty may be experienced from broadcast
interference with the 8ign~18 from the record
play cr. In general tbe wireless units use a
radiation frequency which is more free from
such interference.
Particular attention is called to the Dewald Modcl 411, the schematic of which is
shown in Fig. 44.
[[ is a 2-tube wireless record player that
permits the owner to play recordings through
a remote radio receiver or directly through
an a-f amplifier and a small speaker incorporated in the playback unit. The device
employs two new multipurpose 0.3 amp
FIG. 41. ESPEY (922)
tubes, the 12B8GT r-f pent ode-triode and
the 32L7GT beam power amplifier-rectifier.
The high-mu triode section of the 12B8GT
amplifier tube serves as an audio amplifier
in both modes of operation. With the switch
.0001 Mfd.
MIca
FIG. 42. KNIGHT.
in the r-f playback position, the a-f amplifier is necessary to provide a high percentage
of modulation. In wireless playbacks where
the pickup operates directly into Jhe r-f
oscillator the percentage of modulation is
IOIHISV.
ISO-A.C.
On-Off Sw shown
counter~clockwjse
posrtion
Y
For 220V 50 cycle operatlon,break cIrcuit In
Place mark.ed PX· and use input resistance cord
A·f4962 shown dotted in place of A·j469S·/
FIG. 38. SPARTON (219P, 219PD).
FIG. 40. ADMIRAL (A Wll).
FIG. 43. LU"A YETTE.
101
FIG. 44. DEWALD 411.
often too low. This makes it necessary for
the listener to turn the receiver gain up
higher in order to obtain normal room volume even though a strong carrier is being
received from the oscillator. Excessive carrier hum results.
In addition. low percentage modulation
requires more radiation to produce a satisfactory signal at the receiver. Also. the interference range of the transmitter varies in-
-
TECHNICAL
M YE
THE
Section 5 •
MANUAL
volume control in the a-f position and the
modulation level control in the r-f position.
The high-mu triode feeds the beam-power
tube in the a-f position or the screen grid of
the pentode oscillator section in the r-f position. The plate of the power tube is returned
to the input of the filter while the screen is
connected to .the second filter section to reduce hum. In the a-f position, the oscillator
is cut off by opening the'screen grid lead.
In setting up a wireless record player, the
general procedure is as follows:
The radio receiver should be turned on
and tuned to it quiet spot in frequency range
covered by the oscillator. The oscillator
should then be tuned to the frequency of the
receiver. Adjust the volume controls on 1he
receiver and record player to the proper
levels. In very noisy locations, it may be
necessary to wrap several turns of the oscillator antenna around the antenna lead-in to
the receiver. In receivers having push-button
tuning, one of the buttons may be set up for
the oscillator frequency.
Figures 45 through 73 show schematic
diagrams of later types of wireless record
players. Most of these units have prototypes
already covered in this discussion, and no
commentary has been attempted. The general features of these players are listed in
the complete table following this record
player text. The chart also lists equipment
previously discussed.
versdy as the depth of DlOdulation. Too
high a modulation level. however, would
cause frequency modulation. and consequent
distortion. ··To prevcmt this a modulati~n
level control is incorporated. as an element
of the .pickup tone corrector.
With the switch in . the audio playback
position, a complete record player and amplifier is available with no additional equip-.
ment required. This' feature is. obtained !it
only a slight additional cost over an ordinary
wireless recorQ player, since the power supply, heater resistor and cabinet are required
even if this feature were omitted. A. power
output of 1.4 watts is available to the permanent magnet dynamic speaker.
Two controls are used, one for level with
the on-off switch incorporated and the a-f,
r-f switch. The carrier frequency is adjustable over a small range around 550 kc.
The padder is accessible through a hole in
the top of the panel.
A 4-wire line cord is used, 3 wires for the
power and filament resistor and the fourth
is the antenna. This arrangement with the
antenna coupled to the hot end of the oscillator tank through a 0.0001 mfd condenser,
allows satisfactory reception as a wireless
unit up to about 40 feet. A 0.1 mfd by-pass
condenser across the line keeps the r-f energy
from the lighting circuit.
A crystal pickup is employed with a tone
correcting load circuit. The resistor is the
Tvbe.
--
f-_...,..'_"_,"_"'_b"..-__+__....,._"_'_"-,-P--;==_I 01'..
f-_c._''';--'·_I'---;_·_'''_·"T''_I0_·~'-r__
.~~--~---f--------'f-------I------f------r-------~-,----f----f_----f-----r----.f--'·-!~_••_J.f--~s_'"-=~~--__ I-®-C'-~-I~-O_r·~=~~~~~··_r'_Io-.-~O_.__. ~
vm~ L---f--I---1--~:.=:
--:.
AJlId J,tacHa Corp.
N~~·~r
Knight
Contfrt._lbdkJ&
1'.~.~
Adflllral
hwold hdfo Mfg. COi1).
'
C,..,ttol
78
78
to'" or 12"
10" or 12"
Cry,hil
H.
78
10" Of 12"
Cty.tal
Ves
Cryd,!!
6A?
12A8GT
70L701
110·120
110·120
.0
""
1288Gr
32L70T
110·)20
60
S,lf Stort
25Z60T
110·120
60
S.lf Start
78
10" or 12'"
1I0·12D
60
78
10'" or 12'" Mognetic 3,000 @
110.120
110·120
60
60
78
78
10" or 12"
10'" or 12"
,No..
CW13
1.575
Dewald
411
550
.........
922
1475·1750
I1A
1200-1750
No
21,.,
22A
1300-1750
1250·175'0
No
No
GE
No. 47
.A7
2525
6A801
2SA7G
176
6K6GT
6SK7GT
OMII
1400·1600
No
HM21
11()()'1600
No
6A8G
.tN.23
1100·1600
No
6A8G
530·580
Ve.
Ve.
6A7
...
RPI {Cod., 111,
122,1231
-41·ap6
PlfotIin llectrk Corp.
Pilgrim
RCA
530·580
530·570
930
6JSGT
'0
v..
12A1
84
U
100,0000
~a9~etlc
400 Cy.
C:...,lfol
80,0000
1~
Crystol
C'1.tol
,~
"
,-+--f---f--INo
Ves
Yes
No
No
No
Ves
Ves
Ves
No
No
No
No
No
V..
Y.,
Nt»
No
No
V..
14
78
78
9
10"'Q112"
IO~Or 12"
CrySftll
S.1f S'ort
78
8
10":QI'1"2"
C')'sfell
10" or 12"
10" or 12"
10'" or 12"
"ymr
No
Crystal
No
Y..
Y..
Y.,
No
No
No
10'"
No
Ye.
No
60
60
60
No
. .7
76
110-120
60
530·625
No. 47
6A7
530·625
No
6S,4,7
25%6G
25!6G
110·120
110-120
60
60
$848
540·700
540·750
No. 51
No. T·46
35L6GT
3.,z6GT
2SZS
110·120
110·120
600
No
V..
SOL6GT
6 ...7
UZ5GT
2$Z$
110.120
110.120
60
1200·1700
Y.,
611.7
25t5
110·j20
540·750
No
3516GT
35Z.5GT
78
78
78
78
Cry.tal
12"
Cryttol
18
18
10'" er 12'"
10" Of 12'"
Crystcd
Crystol
60
78
10" or 12'"
60
1.
10'"
12'"
Crystctl
Cryltol
No
7.
78
10" or 12'"
10'" Of 12"
Cry.tol
Cr,.stal
JICo
Ve.
No
Combined
60
78
10'" or 12'"
Cryttal
Yel
V•• ~
1l0~120
60
78
10'" or 12"
\:rydal
Yu
60
78
10"
12"
Crystal
~:
:g: : :~:
~~~::
78
78
78
78
10'"
10'"
10'"
10'"
or 12"
or 12'"
or 12"
or
12"
Crystal
Cry.ral
Crystal
(r)'I'ol
78
78
10'" or 12'"
10" 0112'"
Crystal
Crystal
Manllal Start
Gr
Of
100,0000
1Yt
Ne
No
No
10
c.mb'-,.••-f--.--I-'-'!4--I--"-14+-,0-
S.rfSlori
hlfStart
110·120
110·120
110·120
'4
I--f--+--I--+--
60
84
16
Combined
60
s.
611.7
V..
Cryttol
60
0.7
U
Combined
110-120
110-120
. .7
·l-O
No
110·120
VA20, VA21
Ose.22
6226
r
LoCld
2SZ:;
Ves
______ f-:-_____ II-~:_3lC-'-.'_'_IIC_W_+'_'5_0_.'_"_O+_"".:...+6_'_K7_G_'___ "-6J_5_G_'_+'_'O_.'_'0+_.:.,:O_f-____ ~--78--.I_--410.. or 12"
CkMr.oI&ctricCo..
Imp.danc.@looon.e-OI\VoIH't.Wdth.Depth(w,.....,.J
Record
COflIblned
Combined
10*
14K
14~
6-h
3"
12Y2
8\4
.$
7Yt
4Y2
9
lTn
2~
71,4
Combined
Combined
~ko_"_'_h~.,-.~.__--r---------lr·-~-33-------~-5'-0-.'-25__ I--N_O'_'__
4 r'_'A_8_G_'__+_3'_U_G_'___f_'-'O-.'-20-r-6-0__ 'f_M_o-~-o-'~_o_rt.r-_78__.f--___ I-,o_·_o_'1_2_·f-C_'~r._~_' r'_·~O~_O_O_.+__'~__.r-N_0-t_C_~_b~"_'d__II__-1----I----r--T• ..,Jdon Corp.
Senelro
KVU-8S, KVU·97
P8W
60
S.lf Start
No
J.
114
13V.
10M
:-~~~~~~~______ I~W~I=~~W='=~_W_2_'_r~'~~~_I-__""___f-______32_r'_7-,-____ if_'-'.~"-20_f__.-O--I__--__-r--78__+----r'-0~·"--I2~·crO~'-~-'-~----_r---ll-y-e-.-~V-.--s ~I__--I____II__--I--__
$porb-Wlthlngton Co.
Spartan
219f,219PO
SflworI'.-.r0rntr
Stewott·Wcuner
11·211.1
Cqmblned
: W-:-' ' '~' '-:-' =I•.:--:c:-w-P.--I-:w:::-.'''';.,.~,---+::-::~=~------r:~~~:-:o~::"';~:-:g+--~-o-r:-:-:'-7~--f-~-~Z-4G-,-_~~~f-_:-:._.-:_:-~_g~rf-_~:~g~~rf-_~-_~-_~~+II-'~-~_:-_~·I:~~~~·:I:-g::_"'-o_,-:_~-~:-~~~~<'I~:_::~:-~~~~-_~~~I-_~~~~~I-_v-v_:-:~I:_~-:_-:_~!--_!--__II--_I___
Whotu.al\ Radio
Sarvlc. CO.
K2196S
Wlfeoll.OCIIY
:::
AU
8K2
8P2
540
Ne
6 ... 80T
76
110·f20
540·750
~
:~,~ 3516
~:~:
::g:!:~:~
No
540·730
V.,
1211.8
6A7
6A8GT
35Z4
2.5Z5
.5Z4GT
110_120
110-120
110-120
Yes
60
60
60
:-:::-::-::--::___I-:--:::-____1-:9:-:A2=:-:-____r--.::.54:.,:0_.7.:.50:..-f--.:.N::.O__ J-'::.'::.A8:..-__ j-:35::.Z::.4_·__+'~'O::..'::.20+ 60
ZenfHl
Redio Corp.
,'"I
I Z~nlfh
[,'::':"
1;lk.: ~
;" \,~!' }\;- r1.'
102
86622
$7000, S7001,
57002, S7003
S8500, S8501
1.540
{::·::o
Yel
6L7G
6X5G
110.12-0
No
No
12SA1GT
125A70T
35Z4GT
lSZ4GT
110.120
!to·120
hi' $tart
Self Start
Of
150,0000
3-"*
Ve.
No
1~
"""" V..
No
No
Y.I
No
Ve.
No
""
No
No
13
Contbtnecl
ColI'Ibined
V..
V.s
No-
-60--·f------11--7-8-11---+,O~.:-0<-,-,~. f-ery,-=--,o-' f----·f-----r-""-f-y.-.+-""-II----I---t---r-60
60
No
No
Y...
No
PHONO-RADIO
FIG. 45. CONTINENTAL CW13.
SERVICE
FIG. 50. PHILCO RP1 (122).
DATA
• Section 5
FIG. 55. RCA OI!lC.
~2.
FIG. 56. SEARS·RoEBUCK 5848.
FIG. 46. GALVIN llA.
FIG. 51. PHlLCO RP1 (123) .
....
......
FIG. 47. GALVIN 21A.
FIG. 52. PHILCO RP3.
FIG. 57. SEARS·RoEBUCK 6226.
mpmC. ,11~
FIG. 49. G. E. HM21, JM23.
FIG. 53. PHILCO 41·RP6.
FIG. 58. SEARS·RoEBUCK 6233.
FIG. 54. PILGRIM 930.
FIG. 59. SEARS.RoEBUCK 7061.
103
\,
rHI
Section ,5 •
MY I
rICH~'CAL
MANUAL
!--'
,,',
FIG. 60.
8BAltB.RoBBtICK
7063.
FIG. 65.
WARWICK
9·28.
"
"
FIG. 71. ZBNtTH 86622.
FtG. 62.
SoNOitA
FIG. 63.
SnWART,WARNBR
FIG. 64.
104
~.
'.
W17, W19, W24.
WARWICK
ll..2Al.
9·21.
FIG. 67. WILCOx~GAY 9A2.
FIG. 68. WILCOX·GAY
FIG. 69.
WILCOX.GAY
A·95.
A-63, A·64.
FIG. 72. ZENITH 87000, 87001,
81002, 87003.
PHONO-RADIO
SERVle.
DATA
• Section 5
It has often been noted that in the radio
industry and its allied fields, certain features
fan to become popular during the Beason of
their introduction. Then, after a number of
years of disuse, they are reintroduced with
improvements and experience immediate acceptance. Home recording, a feature introduced about eight years ago, has been dormant· until the recent introduction of lowpriced, improved recording systems. A typical example of this type of unit is the
Wilcox-Gay "Recordio."
.Home Recorders
EXTRA RECORD
HOLDeR
CUTTING
HEAD
This unit makes poeeible the recording of
{oice or music originating locally, as well as
providing a means of recOtding radio programs.
The appeal of this, and similar types of
equipment, ill further enhanced by the avail.
• ability of inell.pensive record blanks.
These recorders are extremely popular,
not only for their value as a home entertain.
ment device, but also because of their possi.
ble uses in the fields of public address, education, voice culture, .and personal correspondence.
The following discussion deals with the
components of the system, its operation, and
the procedure for servicing.
TURN TABLE
MICROPHONE
MOTOR SWITCH
There are numerous general types available such as the phono.player, recorder, and
P.A. system; another with these same fea·
tures plus radio·receive and radio.record;
completely portable types, etc. Since this
discussion is primarily concerned with reo
cording and reproduction the unit employed
for illustration is the Wilcox.Gay Portable
Recordio model A·72 pictured in Fig. 74
with schematic as in Fig. 75. The A-72 is of
the portahle type without radio-receive and
record, and was one of the first popular price
units to reach the market.
VOLUME CONTROL
AND ON-OFF SWITCH
FIG. 74
FIG. 75
Controls
Viewing the top of the A 72 Recordio there
will be found four controls, designated as
"Play," "Volume," "Tone," and "Motor."
The control labelled "Play" is a selector
switch that in its extreme right hand position
connects the equipment for public address,
in which position anything spoken into the
microphone will he heard to issue from the
loud speaker in an amplified state-degree
of amplification being controlled by the volume control. In the center, or play position
the equipment is connected for phonograph
reproduction, in which condition the recordings that have heen made cim he played
back, and, also any phonograph record may
be reproduced. Both the tone and amplitude
of sound will be controlled by the tone and
volume controls respectively. In its left hand
position or when the yellow dot is opposite
105
THE'MYE
Section 5 •
"cut," the equipment is connected for recording, at which time by .following the
directions below, a recording may he made.
The controlillbelled "Volume," is for the
purpose of controlling the volume of both
recording and playing back records as well
as when the unit is used for 'public address~
During the first portion of its clockwise tum
it operates the off-and-on switch connecting
the power supply to the equipment. Through
the remainder of its clockwise turu, the
volume is increased.
The control labelled "Tone" is for properly controlling the fidelity or tone of the
Recordio. Turned in a clockwise direction
the bass notes are emphasized. Turned in a
counter-clockwise direction the treble notes
are emphasized. THIS OONTROL SHOULD ALWAYS BE IN THE LEFT HAND OR HJGH POSITION WHEN RECORDING. Fai1ur~ to do this
result in a very poor recording.
The control labelled" Motor" is for starting and stopping the turntable. Turned to
the right it connects the power supply and
the table will rotate. Turned to the left the
supply is disconnected and the table will
stop.
TECHNICAL
MANUAL
FOLLOWER ARM STOP
LATERAL FEED SCREW
FOLLOWER ARM
l'i
I.
I'
will
MOTOR
BOARD
Figure 76 shows the Recordio with the escutcheon removed and the motorboard raised
to a vertical position. The components to he
later referred to under care of the instrument
are clearly identified in the illustration.
Recording
- - - 6Q7
---6J7
I
,~
MOTOR BOARD AND AMPLIFIeR, FIG. 76
To use this equipment as a recording
mechanism, whereby radio programs and
various other activities picked up on the
microphone can be preserved on a record,
first of all the "Play" control should be
turned to "Cut" and a blank record should
be placed on the turntable. A small pin is
located near the center of the turntable. It
will also he noticed that the record blank has
three holes in the center. The record should
be so placed on the table that the pin engages one of these holes. After this procedure,
the cutting arm, which is the arm on the
right of the equipment, should be raised up
to an angle of approximately 45 degrees and
the cutting head swung over 80 that the
cutting stylus will come in contact with the
'near outside of the record hlank when the
arm is lowered.
!
I,
Recording Microphone
To use this equipment for recording anything that is picked up by the microphone,
the controilahelled "PA," "Play," "Cut,"
106
eb
FIG. 77
PHONO·RADIO
mentioned above should be turned in its left
hand direction so that the dot is opposite
"Cut." If the microphone is going to be
spoken into, a few words should be spoken
into it while adjusting the volume. The
magic eye should be watched; and the volume should be adjusted so that the magic
eye just closes on the loudest words. The
turntable should now be started and whatever it is desired to record spoken into the
microphone in the same tone and level of
voice as used in initially setting the volume.
If it is found that during this process some
slight adjustment of volume is necessary,
this should be done, maintaining an adjustment so that the magic eye just closes. All
other efforts, such as speeches, recording of
orchestras, bands, etc., ..hould be accomplished by first of all noting and adjusting
the level and then turning on the motor and
making the record cut.
SERVICE
previously recorded material will be repeated. When it is desired to play ordinary
phonograph record!! on this equipment, all
that is done is to position the switch to
"Play" as above, place the record on the
turntable, at which time the pin on the turntable will disappear and allow the record to
lie flat on the table. A NEEDLE THAT HAS
BEEN USED TO PLAY A REGULAR RECORD
SHOULD NEVER BE USED TO PLAY A WILCOXGAY RECORD. Use a new needle.
To use this equipment for public address,
the selector switch should be turned to
"PA." The microphone should be used as far
to the side and rear of the equipment as
possible to prevent acoustical feed back between the loud speaker and microphone.
There are available 12}1 foot extension microphone cords for this equipment.
Cutting Arm and Head Adjustments
Recording Radio
Inserting Cutting Stylus
To record radio programs, the microphone
should be set up directly in front of the loud
speaker of the radio receiver supplying the
program and the radio receiver adjusted sO
that it is operating at normally low room
volume. The left hand control should be set
on "Cut," the tone control should be turned
to "high" and the volume adjusted so that
the magic eye just closes on the louder parts
of the -program. Any slight adjustment of
volume can be made, however, the individual expression of orchestras, as well as
of vocal selecti~ns, will be impaired if loud
and soft passages are compensated for by
either decreasing or increasing the volume.
Do not use any other make of cutting
stylus than Wilcox-Gay. This stylus is especially designed for this equipment.
After the cut has been made, there will be
seen to have bet\ll cut a small shaving out of
the record material. This will pile in the
center of the record. The machine is cutting
correctly if, after having completely cut a
6~" record, the wadded up shaving has a
total diameter of approximately % to ~
inch. THIS SHAVING IS NOT FLAMMABLE AND
THEREFORE THERE IS NO FlRE HAZARD IN
DISPOSING OF IT IN ANY MANNER.
Phonograph Play Back
The control marked "Play" should now
be turned to "Play," and the phonograph
arm, which is the arm at the left of the
equipment, should be equipped with a new
needle and placed in the outside groove of
the record. The motor should be turned on
and the volume and tone adjusted by' the
respective controls. After this procedure the
When this equipment leaves the factory,
the cutting stylus is packed in a small envelope to avoid its becoming lost. To prqperly install the cutting stylus, it should be'
pressed into the cutting arm in such a
manner that the flat side on the shank of the
cutting stylus is in front and is the surface
that the retaining screw tightens up on.
When the cutting stylus is correctly placed
in the cutting head and the cutting nead placed
on the record a small shaving will be seen to
be cut out of the record material. If the
needle is in backwards, it will not in any
crse operate correctly.
Extreme care should be exercised to see that
thJs cutting stylus is held in the cutting arm
tightly. Owing to the fact that the cutting stylus
is of very hard Norwegian ra1XJr steel and that
the retaining screw is hardened also, there is a
tendency for the cutting stylus to become
loosened in the head. It is suggested that the
retaining screw be given a little tightening turn
each time a recording is made.
Under no circumstances allow the cutting
stylus to rest on table top or any other metal
because its point is ra1XJr sharp and it will be
dulled if this precaution is not taken.
Effect of Dull Cutting Stylus
DATA
• Section 5
being dulled so that replacement is necessary.
Many times it may seem from casual observation that because an incorrect cut is
being made, an adjustment is in order to
bring about correct depth of cut. Actually
the trouble may be due to the cutting stylus
having become dulled, either accidentally o~
through natural wear.
It is well to FIRST TRY A NEW CUTTING
STYLUS before making any adjustments, to
preclude the necessity for a complete readjustment. Adjustments made with a dulled
cutting stylus being used will have very
little effect upon the depth of cut.
Depth of Cut
The depth of cut may be observed by
holding the record in such a position that a
light is reflected from the groove. If the
depth of cut is correct, the grooves will appear to be about as wide as the spaces between them.
The correct depth of cut will produce a
thread cut from the record surface that is
firm, although neither coarse and stiff, nor
light and "fluffy."
Provided a new cutting ,stylus, or one
known to be in perfect condition, is being
used, the correct depth of cut may be
gauged by permitting the cuttings to remain
upon the record until completed, then rolling
the cuttings into a hard ball. The size of the
ball thus obtained should be approximately
% inch in diameter for the 6~ inch record.
The depth of cut is regulated by an adjustment of the flat head screw on the top of
the recording arm, Figurt'l 77.
Turning the screw to the right (clockwise)
increases the depth of cut.
Turning the screw to the left (countercl~ckwise) decreases the depth of cut.
Important Notes
Leveling:
To derive the best operation from this
equipment, it should be very nearly level in
all directions. Because of the fact that many
floors are not level, it is suggested that
something round, like a round lead pencil, or
a marble, be placed on the top of the equipment to test which way it is low. The top
may be levelled by shimming the low side.
Both the operation of cutting the records
and reprod.ucing them will be improved if
this precaution is taken.
Groove JUInping with Offset Head:
With proper care the cutting stylus will
cut dozens of records satisfactorily before
Some phonograph instI'uments are
equipped with an offset, reproduction head.
107
;'
Section 5 •
TH.
By this is meant a head that is at an angle to
the pickup arm. If it is desired to play
records on this type of phonograph reproducing equipment, it is suggested that a
minimum internal diameter of 372 inches be
used. Otherwise the needle may have a
tendency to jump out of the record groove.
Groove Depth:
In some of the early Recordio models the
adjusting screw was threaded throughout
its full length, although only the lower portion of the screw over a span of approximately % inch contributes to the useful
range of adjustment. If the adjusting screw
is turned in a clockwise direction so a8 to
raise the spring holding lug to the upper
threaded portion of the screw, the adjustment will have passed through a "deadcenter" position, which will cause a bobbing
up-and-down movement of the cutting head.
If it is found that when using a new cutting stylus, the depth of cut is too shallow,
and the adjusting screw has been turned to
the fuIl clockwise position in the later models, or to the upper limit of the useful range
in the older modeJs, this is an indication that
the balance spring"is too strong. Its tension
may be decreased by spreading the coils of
the spring with II pair of diagonal cutting
pliers.
CAUTION: Care should be used in removing and replacing the cutting head, when
occasion arises, so that the balance spring is
not stretched to a length that will prevent
its returning to normal length and tension.
When the cutting head is in proper adjustment and the recording arm is raised to a
position approximately 25 to 30 degrees from
the vertical plane, the cutting head should
float freely in its mounting, with equ!l' up
and down movement. The balance spring
holding lug should be in a position on the
adjusting screw approximately U inch from
the shelf which holds the riveted end of the
screw. (Fig. 77)
Observe that the leads connecting to the
cutting head are shaped to form an "8,"
and that these wires are kept in the c1earnot touching the balance spring. Also, the
wire leads should not be permitted to droop
(arm horizontal) so t~at they will rub on the
turntable. Also observe that the holding
tongues of the finger grips on the nose of the
recording arm are bent back sufficiently 80
as not to interfere with free movement of
the cutting head.
108
MY.
T.CHNleAL
MANUAl.
Height of Recording Arm Adjustlllent
The components of the recording arm as·
sembly are positioned so that the cutting
head is parallel, and the stylus is perpendicular to the record surface (Fig. 77), which
condition obtains ONLY with the nose of the
recording arm adjusted to the correct height
of U int;h above the record surface.
An adjustable stop (arm height adjusting
screw, Fig. 77) is mounted on the arm platform to provide a means for adjusting the
height of the recording arm. With a blank
record on the turntable and a WILCOX·GAY
cutting stylus inserted in the cutting head,
the arm height adjustment should be made
so that the bottom of the recording arm is
U inch from the record surface as shown
in Fig. 77.
The connecting wires from the cutting
head should not be allowed to double up between the arm and arm platform, but should
feed freely through the hole in the platform
as the arm is lowered. Otherwise, the doubled
up wires may prevent the arm from com·
ing to rest on the head of the height adjusting screw.
There is little likelihood that the arm
height adjusting screw will get out of adjustment due to the lock nut becoming loosened.
However, there is the possibility that the
recording arm may be roughly handled by
the operator. II the arm were to be forced
backwards after having been raised to its
vertical position-or if, while being lowered
to its horizontal position to the right of the
turntable, the arm were dropped or forced
downward, the plate on which all of the recording mechanism is mounted may be bent
or sprung slightly. This would destroy the
U inch height adjustment, and readjustment of the arm height adjusting screw
would' be necessary to bring the nose of the
recording arm to exactly U inch above the
record surface.
Also, the straddle plate (Fig. 77) may be
bent down, which would effect the arm
height adjustment. In this event, the straddle
plate should be removed and straightened.
This is most easily accomplished with t,he recording arm in the lowered position. Grasp
the heel of the arm with the left hand and
raise the arni horizontally, at the same time
removing the arm lift lever from the slots in
the straddle plate. The straddle plate may
now be removed by sliding it towards the
rear.
The importance of the arm height adjustment may be 'judged by a study of Fig. 77.
Note that the halance spring serves to hold
the knife.edge pivot of the cutting head
mounting fuIly seated in the "V" shape
trunnion hearing of the cutting head mounting hracket. Also, that the "pull" of the
spring is slightly downward, as well as horizontal.
The initial tension and length of the balance spring must be such that when adjusted
to the proper tension to produce the correct
depth of cut, the spring holding lug will be
positioned on the adjusting screw as shown,
to create a slight downward "pull" on the
cutting head mounting.
As the stylus end of the cutting head is
raised and lowered slightly, when cutting
records which are not perfectly flat, the cutting stylus varies from its perpendicular
plane, and the angle of the cutting edges of
the stylus also vary. This tends to produce a
varying depth of cut which would place a
varying load on the motor, resulting in a
variation in the average pitch or tone of,the
recorded music or speech. This effect is commonly ()ailed "wow." However, the spring
tension, and consequently the stylus pressure, also, "Varies. This variation in stylus
pressure opposes the effect of the varying
stylus position, resulting in a substantially
uniform depth of cut.
It can be seen that if the balance spring
were adjusted to a horizontal position with
respect to the plane of the cutting head(a) The downward "pull" of the spring
would be lost, resulting in a pronounced variation in the depth of
cut when cutting a record having a
slightly warped surface.
(b) The cutting stylus would have a
tendency to chatter or dig into the
record, due to the "dead-center"
position of the spring.
It can also be seen that if the arm were
adjusted to an incorrect height above the
record surface, the cutting stylus would not
be perpendicular, and the tendency towards
a greater variation in the depth of cut,
which would be more pronounced, would not
be fully corripensated by the counteracting
effect of the varying tension of the balance
spring.
PHONO-RADIO
SIRVlel
DATA
• Section 5
Record.Changer Service Data
Supplement No.5 to the 3rd Edition Mallory
Radio Service Encyclopedia, published in
Fehruary of 1940, contained complete service
material on Capehart, Farnsworth, Garrard,
Magnavox, RCA, and ·Webster record
changer equipment current at that time. It
was the first step taken in the direction of
supplying data on all types of changers for
use by the radio servicemen in this somewhat puzzling, but rapidly expanding and
lucrative phase of radio receiver maintenance.
The field has grown tremendously, with
wider application of mechanisms then in use,
and the introduction of new or improved
changer systems. A really comprehensive
treatment of service operations on all models
now existent would entail a large volume on
the subject of changer systems. We are
happy to say that Mr. John F. Rider has
certainly fulfilled this requirement with his
excellent book "Automatic Record Changers and Recorders." For all those servicemen
actively engaged or desirous of entering the
record changer maintenance field Mr. Rider's book is a
{'e
must .'"'
The response to publication of the changer
section of Supplement No.5 was so enthusiastic, and the numher of requests for reprints so large that we are including this
material in this Technical Manual. Many
of the types are basic, so that the service
material can be used for later models. However, on mechanisms not covered, we respectfully refer you to Mr. Rider's book just
mentioned.
( ape ha r1- Model 16· E De Luxe Record
1. To Locate and Adjust the Record
Tray. (6687) (Fig. 83)_ In assembling the
record changer, the first tooth of the driver
quadrant (3551) (Fig. 82) should mesh with
the second tooth of the driven quadrant of
the tray as shown.
With the two gears properly meshed,
loosen the. Allen set screws which hold pins
No. 34133, Fig. 78, in place. This will allow
you to move the record tray sidewise, adjust
tray sidewise until the turntable spindle is
exactly in the center of the 10" record level
of the record tray. (The 10" record level is
that part of the tray where the felts No. 4913
are indicated in Fig. 83.)
With the control lever in the "one side"
posiJion, run the record changer through its
cycle until the large hole in the main cam is
exactly half way past the upper edge of the
record tray cam follower, as shown at No. 82,
Fig. 1. At this position, the points of the
ten-inch felts (4913) (Fig. 83) should be level
with the top of the turntable felt. If this tray
is too low or too high, it may be adjusted to
the proper level by loosening the eccentric
screw (3237) (Fig. 78) No.4 and turning this
Changer
screw until the proper level is obtained. Be
sure to tighten the lock nut after adjustment.
If the tray is too high, at this position, the
ten-inch records will not be centered over
the turntable spindle. If the record tray is
too low, the ten-inch records will slide out
over the ten-inch tray shoulder and hot
properly center.
2. The Adjustments of the Record Magazine. Before attempting to adjust the magazine, be sure that the center of the magazine pivot pins (34132) (Fig. 78) is 8%"
above the base plate. This height is very
important and we recommend checking the
height of the right hand pin, when looking at
the magazine, before any adjustments are
made.
The record magazine is positioned by
moving it sideways on its bearing. or pivot
pins. The two set screws underneath the
pivot pins lock the magazine in position.
Loosen these set screws, then see that the
left hand side of the record reverse assembly
fork (part of 6228, Fig. 83) is between ~"
and is" inside the left hand side of the Reverse crank, when looking at the magazine.
That is, the left hand edge of the record
reverse fork is about ~" or
to the right
of the left hand edge of the crank. After
moving the magazine, lightly set up the set
screws. Then with the selector arm in the
"Repea·t" position swing the record reverse
arm around in front of the magazine, to see
whether the record guide strikes either of
the record support pins (34138) (Fig. 83). If
the guide strikes either of the support pins it
will be necessary to bend the pin away from
the guide so they can not strike. If it is necessary to bend either pin, set the control lever
in the "Repeat" position, then raise the
record tray by hand, with a 10" record on it,
observing the way the record strikes the
support pins, the record should hit both
pins about
from the end of the pin; if it
does not it will again be necessary to adjust
the pin until the record hits both pins an
equal distance from the ends. If it is necessary to bend the pins, check the clearance
between the record guide arms and the pins
and between the arm carrying the record
guide and the right hand pin. Also if the
magazine has been shifted it is necessary to
see that the two points, which extend downward from the magazine, have ample clearance in the channels, in the record tray,
which are provided for their passage. If
there is possibility of the points striking it
probably means the magazine has been
shifted too much.
If the magazine has been adjusted, it is
also necessary to see that the record separator hook (6226) (Fig. 78) does not bind in
the slot in the end of the record separator
arm (6445) (Fig. 83). If it does the section
covering these parts gives the adjustment.
3. Magazine Stop Screw. The magazine
stop screw No.2, Fig. 82, should be adjusted
so that the crank pin (part of 6230, Fig. 78)
is approximately
from the edge of the
record reverse arm fork (part of6228, Fig. 83)
which is furthest from the magazine, when
the record reverse guide is in front of the
magazine, that is, in the reversing position.
4. Magazine Link Adjusting Screws (No.
2) (Fig. 78). The record magazine should always come back snugly against the magazine
stop screw, No.2, Fig. 82. If it does not, it is
. necessary to loosen the two set screws (No.
2, Fig. 78) to a sliding tension imd run the
record changer through a cycle of change.
When the magazine has reached the horizontal position, as shown in Fig. 78, press
down on the lower end of the magazine; this
will lengthen the link assembly. Then when
the magazine returns to its normal position,
the magazine link will adjust itself so that
the magazine is snugly against the stop
screw. Then tighten the magazine link screws.
ro"
ron
ro"
109
rHI
Section 5 •
MY I
r I eH
N" CAL
MANUAL
Fig. 78
2722 Switch AC Line
3059 Escutcheon Plate Off-On
3237 Shoulder Screw-Record Tray Slide
3982 Spring-Separator
4018 Main Shaft Bushing
4020 Record, Magazine Bushing
4719 Magazine Link Upper
4720 Magazine Link Lower
4925 Record Tray Shield Felt-Outer
5044 Stop Lever Roller Tubing
5658 Pickup Arm Lever Hook
5765 Pickup Cover
6178 Chassis Plug
6226 Separator Hook and Arm Assembly
6228 Record Reverse Arm and Fork Assembly
6230 Reverse Pinion and Crank Assembly
6693 Record Bumper Guide and Felt Assembly
34132 Pin-Magazine Pivot
34133 Pin-Record Tray Pivot
34147 Pin-Record Tray Slide
43159 U "-28 Hex. Cap Nut
43160 Lock Nut for Pivot Screw
64197 Pickup Arm Stop Lever Assembly
(Specify color).
662p4 Steering Arm Assembly.
I
6-32x %" Pickup Stop Lever Screw
NOTE: In ordering any part that is painted,
please specify color wanted .
•
5. Record Reverse Guide (6444) (Fig. 83).
With a 12" record in the magazine the record
reverse guide assembly (6444) (Fig. 83)
should be parallel with the record when in
the reversing position, in front of the magazine.
If the record reversing assembly is parallel
with a 12" record as above, it should come
around and lay against the reverse guide pin
tubing (34134) (Fig. 83), if the eccentric cl1m
(3825) (Fig. 85) is properly adjusted. This
cam can be adjusted, by loosening the screw
through the cam and turning it so that the
record reversing assembly returns to the reverse guide pin tubing. Care should be taken
when making this adjustment so that the
crank pin (part of 6230, Fig. 78) does not
hold the reverse guide away from the pin
tubing. This cam should be turned so that
the reverse guide assembly just touches the
pin tubing; if the cam is turned too far it will
allow the reverse guide assembly to hit the
pin tubing, but in the reversing position the
assembly will not be able to ass\lme a position parallel with a 12" record.
6. Reverse Assembly Link Rod. Loosen
lock nut No.9, Fig. 80, while the record
changer is in the reversing position, that is,
when the reversing assembly (6444) (Fig. 83)
is in front of the magazine. Remove the
screw (3241) (Fig. 85) holding the 'reverse
segment link (34141) (Fig. 85) to the reverse
segment (3550) (Fig. 85) and lengthen or
shorten the link, by the link thread until the
reversing crank (6230) (Fig. 78) stands with
the crank pin just barely touching, but not
hinding, against the front side of the fork
(6228) (Fig. 83). After the adjustment has
no
J~
been made, lock the link in place with the
lock nut No.9, Fig. 80.
7. Rccord Separator Adjustment. The
separator stop No.3, Fig. 78, should he adjusted so that a small 10" record will positively clear the knife portion of the separator
lever as shown in the following illustration.
A standard to use is to make certain that
there is approximately -h" clearance between the edge of the small record and the
point of the separator lever, as shown at
"A" in illustration below. However, it may
be necessary to vary one way or the other
from this measurement, depending on
whether or not the slotted end of the record
separator lever goes over the hook (6226)
(Fig. 78) without binding.
8. Record Separator Hook Adjustment.
After adjusting the record separator it will
be necessary to check the record separator
hook (6226) (Fig. 78) to see that it enters
the slot in the record separator without
binding. This hook is threaded and by loosening the locknut the hook can be turned in
either direction, to raise or lower it. After
the correct adjustment is obtained, tighten
the locknut.
It should never be necessary to change
these adjustments on record changers unless
they have been tampered with by an inexperienced person.
9. Separator Hook and Arm (6226) (Fig.
89). Be sure set screw No. 10 in Fig. 85 is
screwed all the way in.
10. Record Magazine Bushing (4020)
(Fig. 78). If a ringing noise is heard while the
instrument is changing records, i.e., such a
noise that might be made by a spring, it will
be found 'that the Durex bushing (4020)
(Fig. 78) is too tight, in which case it will be
necessary to loosen the lock nut of the holding bolt, and back the bolt out, from a
quarter to a half turn, then tighten the
lock nut.
n. To adjust the Tone Arm Height.
To adjust the tone arm height, first place a
12" record on the turntable and adjust the
tone arm stop lever (64197) (Fig. 78) so that
the record hits the rubher roller (5044) (Fig.
78) in the center. Start the record changer
through a cycle and stop it when the tone
arm lever hook (5658) (Fig. 78) just touches
the stop lever assembly. In this position adjust tbe tone arm height so that the top of
the stop lever is the same height as the
center of the hook. This adjustment is made
by loosening the two Allen set screws at the
rear of the tone arm. These Allen set screws
are accessible by raising the tone arm by
hand. After making the height adjustment it
is necessary to make certain that there is a
clearance of approximately %" between the
pickup head and the record tray. This distance may be checked between the bottom
of the record tray and the bottom of the
pickup when the record tray is approximately
parallel with the pickup.
12. To adjust the Pickup Elevation.
When the tone arm swings in towards the
record, the pickup arm lever hook (5658)
(Fig. 78) comes to rest against the pickup
arm stop lever (64197) (Fig. 78) and when
the tone arm lowers the pickup toward the
PHONO·IADIO
SEIVleE
DATA
• Section 5
Fig. 79
3243 Shoulder Screw-Repeat Lever
3244 Shoulder Screw Clutch Throwout Lever
3317 Screw-Clutch Throwout Cam
3319 Screw-Turntable Shaft Collar
3995 Spring-Reverse Arm
5333 Main Clutch Fork Lever
6326 Worm and Bushing Assembly
6450 Reverse Cam Arm and Roller Assembly
6460 Clutch Throwout Lever and Spring Assembly
6719 Turntable Drive Shaft Assembly
•
record it pauses momentarily before the
pickup arm lever hook goes through the stop
lever. H the record changer is stopped during
this pause, it will he found that the ball in
the end of the pickup arm lift shaft (6457)
(Fig. 86) is at the point marked "L" in
Fig. 86 on the lift cam (6449) (Fig. 86).
Now if the pickup, with a needle in the
proper position, is moved beyond the edge
of the record, the point of the needle will
extend below the top surface of the record a
distance equal to half the thickness of the
record. The correct elevation of the pickup
is made by the screw in the underside of the
tone arm fork against which the pickup
cover rests. Loosen the locknut, adjust the
screw to bring the needle to the position
mentioned above, then lock the locknut.
13. Pickup Feed in Adjustment. Tht;
collar of the pickup arm swing lever and
collar assembly (6232) (Fig. 86) should ride
on the leather facing of the friction cam
(6691) (Fig. 87) until the pickup arm lever
hook (5658) (Fig. 78) has engaged the stop
lever (64197) (Fig. 84). Then a slight amount
of friction should be maintained after the
ball at the end of the pickup lift arm (6457)
(Fig. 86) has engaged with tlfe lift cam
(6449) (Fig. 86). This friction should be
maintained until the needle has touched the
record, otherwise the pickup arm may move
away from the stop lever and the needle
miss the record. H the friction be maintained
too long the needle may be forced beyond
the first playing groove. To adjust this, the
pin locking the friction cam to the main cam
shaft should be driven out and the Allen
set screw loosened to a sliding tension. The
cam is rotated forward, in the direction of
rotation of the main cam shaft, to maintain
the friction a longer time and backward to
maintain it for a shorter time.
14. To Adjust the Pickup. After
removing the pickup cover, it should be
noted whether the stylus (5610) (Fig. 87) is
centrally located in respect to the pole pieces
(569) (Fig. 87). To center the stylus loosen
the locknuts (99·11.1) (Fig. 87), then loosen
the two headless set screws (99.28.3) (Fig.
87). These set screws hold the spool assemJt.ly
(6711) (Fig. 87). The spool assembly should
be shifted until the stylus is centralized with
the pole pieces, then tighten the 3et screws
carefully, so as not to crack the spool, then
tighten the lock nuts.
H for any reason it is necessary to shift
the pole pieces, which are held to the back
by two screws, the two set screws holding
the spool should be loosened before attempt.
ing to move the pole pieces. H any adjust.
ment of pole pieces is made, carefully check
the centering of the stylus before replacing
the cover by means of its three screws.
15. To Adjust the Stop Lever Hook
(5658) (Fig. 78). Always adjust the tone arm
position on a 12" record before adjusting for
a 10" record. Adjust the tone arm stop lever
hook (5658) (Fig. 78) by m~ving it in or out.
This hook is locked in place by a set screw
in the stud whose nut is shown in Fig. 78 as
No. 43159. This set screw is at the bottom
of this stud. Adjust the hook so that it will
pass through the notch in the pickup arm
lever (64197) (Fig. 78) without binding
against the top or bottom of the notch,
. when in the playing position. With a 12"
record on the turntable, the rubber roller
(5044) (Fig. 78) against the edge of the rec·
ord and the stop lever hook (5658) against
the blade of the stop lever (64l97) the
needle should stop on the record exactly h"
from the edge of the record.
With the record changer in exactly the
same position as described above, and with
a 10" record on the turntable and the hook
(5658) (Fig. 78) against the blade, the stsp
lever should allow the needle to stop on the
record :l{2" from the edge of the 10" record. A
6·32 screw shown in Fig. 78 is provided for
making this adjustment, simply by screwing
it in or out. A check should be made for
clearance between the roller and the tray,
this roller should never bind on the record
tray. This can he taken care of by slightly
bending the tone arm stop lever (64197)
(Fig. 78) up or down. If it is necessary to
bend the stop lever it will be necessary to
readjust for 12" records.
111
THI
Section 5 •
MY I
TECHNICAL
MANUAL
i
1\
Fig. 80
2764 Switch Assembly-Solenoid and Motor
3550 Record Reverse Pinion Segment
3977 Spring-Magazine Slide Arm
3986 Spring-Solenoid Lever Torsion
5326' Record Reverse Cam Shaft Lever
6178 Chassis Plug 5 Prong
I,
6713 Solenoid Assembly
34140 Pin-Long, Reverse Segment
•
!~
I
I,
16. To Adjust the Clutch Throwout
Lever and Cam. The clutch throwout lever
cam is shown at 15 in Fig. 79 and is adjusted
by loosening the shoulder screw (3317) (Fig.
79) to a sliding tension after the record
changer has been stopped in the playing
position. The clutch throwout lever cam
should just clear the point of the turntablc
throwout cam (6448) (Fig. 87) with the
clutch disengaged. Unless clearance between
the turntable throwout cam and the clutch
lever throwout cam is maintained the record
changer will jam. If too much clearance is
allowed the turntable throwout cam will not
disengage the clutch and the record changer
will continue to change records without
playing them.
17. To Adju~t Solenoid Wedge Spring.
This phosphor bronze spring is located on one
of the three spacers used to mount the solenoid plate bracket to the solenoid bracket.
It is used to prevent clutch ch,atter or bounce
when the clutch engages. The only adjust·
ment is to bend the spring to a snug fit with
a long screw driver 80 as to increase or de·
112
crease its pressure on the solenoid to clutch
lever (6455) (Fig. 88).
18. To Adjust the Reverse Cam Shift
Lever (5326) (Fig. 82). This lever is moved
by the record control shaft (3724) (Fig. 89)
and is held in position by an Allen set screw.
It should be positioned on its shaft 80 that
the record reverse cam (6325) (Fig. 81) is
firmly engaged with its pin (34144) (Fig. 85)
in the "Both Sides" position. In the "One
Side" and "Repeat" positions it should have
good clearance with the pin. If any adjustment of this lever is made be sure to check
the setting of the Reverse Cam Arm and
Roller Assembly (6450) (Fig. 85) as instructed in Section 7 of the instructions on
replacing a reverse cam.
19: To Adjust the Record Repeat Lock
Lever (5334) (Fig. 89). The purpose of this
lever is to prevent accidental shifting of the
Selector Arm while the instrument is not in
the playing position. In the "Repeat" position this lever is on the side of the Solenoid
to Clutch Lever (6455) (Fig. 88) away from
the main cam. In the "One Side" and "Both
Sides" positions it is on the main cam side
of the solenoid to clutch lever. With the tone
arm in the playing position (Main Clutch
Disengaged) this lock lever should clear the
solenoid to clutch lever by approximately
!oN when moved under it.
20. To Adjust the Reverse Cam Lock
Lever (5339) (Fig. 89). This lever should he
on the main cam side of the solenoid to
clutch lever when in the "Both Sides" posi.
tion. And on the opposite side when in the
"One Side" and "Repeat" positions. With
the main clutch disengaged the lock lever
should clear the solenoid to clutch lever by
approximately 'h" when moving under it.
21. To Adjust Reverse Cam Arm and
Roller Assembly (6450) (Fig. 81). See Section 7 under Instructions for Replacing a
Reverse Cam.
22. To Adjust Record Repeat Throwout
Lever (4663) (Fig. 89). No adjustment of
this part is necessary.
'
23. To Adjust Record Repeat Clutch
Lever (5332) (Fig. 89). The adjustment of
I"!
PHONO-RADIO
SERVICE
DATA
• Section 5
Fig. 81
1173 Condenser-O.1 Mfd. 400-Volt (in can)
3238 Shoulder Screw-Magazine Slide Arm
3243 Shoulder Screw-Repeat Lever
3550 Record Reverse Pinion Segment
3826 Record Repeat Sliding Clutch Cam
3976 Spring-Record Separator Hook Lever
3977 Spring-Magazine Slide Arm
3978 Spring-Record Repeat Clutch
3995 Spring-Reverse Arm
6450 Reverse Cam Arm and Roller Assembly
•
this lever is made by loosening the Allen set
screw to a sliding tension then moving the
part along the shaft. The sliding clutch
should engage in the "One Side" and "Both
Sides" positions, but should be disengaged
in the "Repeat" position. The fork of this
lever should not bind the sliding clutch in
either the "Repeat" or "Both Sides" position.
24. Lateral Location of the Main CaIn
Shaft. Both end bearings of the main eam
shaft are movable, and are used to locate the
cam shaft in its proper lateral position, as
well as adjust the amount of end play. The
main cam shaft is located laterally so that
the ball in the end of the tone arm lift rod
(6457) (Fig. 36) travels in the exact center
of the tone arm lift cam (6449) (Fig. 86). As
shown at H in Fig. 86.
25. To Adjust the Stop Trip Switch
(2792) (Fig. 84). This switeh is accessible by
removing the turntable, which will expose
the switch cover. To remove the switch
cover it is necessary to remove the trip arm,
which goes through the switch cover and the
two flat head screws which hold the cover in
place. The clearance between the contact
points on the fixed and movable arms of the
switch should be +S". After replacing the
trip arm (6510) (Fig. 84) in the switch, after
the switch cover has been removed, set the
turntable on the spindle, push stop trip arro
(4533) (Fig. 84) slowly about 74:" toward the
magazine and then turn the turntable
through one complete revolution. This will
insure the fibre cam, on the turntable, resetting the trip switch, the clearance between the trip arm and the movable arm of
the switch should be +S". The distance between the trip arm and the switch trip
guard finger should also be +S".
To adjust the clearance between the trip
arm hook (6510) (Fig. 34) and'the movable
switch arm, loosen the screw in the bakelite
switch base, at the end nearest the tone arm.
Move the switch until +S" clearance is secured between the trip arm hook and the
movable arm of the switch, then tighten the
screw holding the switch. In making this adjustment be sure that the stationary arm of
the switch is not bent when tightening this
screw.
On some models a headless set screw, near
the end of the coil spring, is used to lock the
switch in position; loosen this screw, adjust
the switch, then tighten the set screw.
26. To Adjustthe Solenoid Motor Switch
(2764) (Fig. 80). After the switch cover has
been removed the switch is exposed. The
upper switch points should make good electrical contact, while the main clutch is disengaged, in this position the clearance between the bottom points should be approximately j, ". While the clutch moves from the
disengaged to the engaged position the upper
switch points should remain closed until the
lower set of points are closed. When the
clutch is fully engaged the lower points
should make good contact and the clearance
between ihe upper points should be approximately j,1I.
To adjust the switch loosen the screw
through the bakelite switch base at the rear
of the switch assembly. After the position is
found where proper clearance is secured,
with the clutch engaged and disengaged, the
switch should be locked in position with
the screw.
In some machines a headless set screw is
used to lock the switch in position. This
screw is near the point of the tapered bakelite insulating block. Loosen this screw and
adjust switch to 'get proper clearance then
lock the switch in position by the set screw.
The two upper contacts are in series with
the auto trip switch and the two lower contacts are shunted across the motor switch.
When the clutch is engaged the auto trip
switch is out of circuit and the motor switch
is shunted by the lower contacts thus insuring the completion of the change cycle even
though the instrument is switched to radio
or turned off.
27. To Adjust the Friction Joint of
Automatic Trip Switch. The amount of
friction necessary in the friction joint hetween the auto stop trip lever-long (6510)
(Fig. 84) and the auto stop trip lever-short
(4533) (Fig. 84) should be just sufficient to
close the automatic stop'trip switch (2792)
(Fig. 84). The friction is regulated by adjusting the screw which tightens the flat
113
rN.
Section 5 •
M YI
r.CNNICAL
MANUAL
Fig. 82.
3240
3243
3319
3539
3550
3551
3826
3976
3977
3978
3981
5326
Shoulder Screw-Reverse Segment
Shoulder Screw-Repeat Lever
Screw-Turntable Sp,aft Collar
Worm Gear-Main Drive
Reoord Reverse Pinion Segment
Record Tray Gear-Driver
Record Repeat Sliding Clutch Cam
Spring-Reoord Separator Hook Lever
Spring-Magazine Slide Arm
Spring-Record Repeat Clutoh
Spring-Record Reverse Cam Control
Record Reverse Cam Shift Lever
I:
I
I'
i
I
~
•
spring (3998) (Fig. 84). If the tension is too
great the instrument may trip hefore finishing a record, if not enough tension is had the
instrument will not change records when the
needle hits the automatic change groove.
28. RecoJ,'d Size Limit. The 16-E Series
record changer will play any lOR or 12"
record of IItandard size. The minimum sbe
for 12" record. is 111-1/". The minimum size
for IOu recordil is 9ft". Records smaller than
theae limits are very apt to miss centering
over the tumtable spindle and in most cases
are broken.
Theile record changers will automlltically
trip on any record hllving an automatic stop
chllnge groove, either spiral or oscillating,
where the blank space in the center of the
reoord i8 not more than 631" in diameter.
29. Records. Always inspect the records to
lee that no rough edges are present., Occasionally you will find a record which has a
rongh out"ide edge. This rough edge will
greatly intedore with the satisfactory performance of the recqrd ohanger. A small
,piece of No. 00 sandpaper wiD assist you
greatly in romoving this rough edge.
114
30. To Adjust the Vertical Bumper
Guide (6693) (Fig. 83). This guide is located
hack of the magazine cro'ss har (6685) (Fig.
83). After the records are separated from the
magazine they are guided in dropping off
the separator so they hit the center of the
record humpers (5081) (Fig. 83). This vertical humper guide al80 guides the records
when the elevating hook, on the rear of the
record tray lifts the record. The vertical
humper should he set hack just far enough
to allow a 12" record, to drop onto the record
humpers freely. The lower part of the vertical bumper, which extends into the record
well, should extend toward the center of the
well ruhher humpers far enough to make
sure that the upper edges of the records fall
hehind the points of the upper record support (5517) (Fig. 83). This adjustment is not
-critical. In most cases it will he found that
the upper end of the vertical humper will
just clear the elevating hook on the rear of
the tray. In cases where it is found that 10"
records are chipping ahout the edges, due to
bounding against the points of the upper
record support (5517) (Fig. 83) it will he
necessary to hend the vertical humper (6693)
(Fig. 83) hack at the top to a point where it
just harely clears the elevating hook at the
rear of the tray. It should never he hent
hack far enough to raise the front of the tray.
31. Clutch Clearance. The clearance hetween the driven (6326) (Fig. 87) and driving (3630) (Fig. 87) members of the clutch
should he approximately ~020" (twenty
thousandths), and is adjusted hy loosening
screw No. 16 (Fig. 80) to a sliding tension
and adjusting the clutch fork (5333) (Fig.
79) and the solenoid to clutch lever and pin
assembly until the proper clearance is ohtained. After adjustment is made lock the
screw No. 16 (Fig. 80).
32. Motor Connections (21131). The '
21131 motor is a synchronous motor and
will run equally well in either direction,
when properly connected. For this reason,
all motors shipped from the factory are
equipped with a terminal strip and cable.
However, if it should ever he necessary to
disconnect the leads from the terminal strip
the leads should he replaced in the following
order: With the cable extending to the right
of the terminal strip and the mounting lugs
pointing down\\l'ard, and the soldering lugs
towards you, the leads go on from left to
right in the following order-emall hlack,
hlack with yellow tracer, hlue and large
PHONO·RADIO
4915
SERVICE
DATA
• Sec:tlon $
Fig. 83
7
Shoulder-Screw-Magazine Link
Shoulder Sorew-Separator
Pickup Needle Screw (Magnetic)
Turntable Drive Shaft Cap
Automatio Stop Trip Quadrant Bracket
Reoord Reversing Ann Lock
Reoord Reverse Arm Look Stop
Record Tray Felt-La~e
Record Tray Felt-Small
Reoord Magazine Felt
Lower RecoM Ejupport Felt
Reoord BUmper Guide Felt
Magazine Side Felt
Reoord Way Shield Felt Outer
Record Tray Bumper-Front
Record Tray Bumper-Rear
Reverse Ann BUmper
Reoord Bumper
~82 Pickup Arm Base
5517 Record Support-Upper
5615 Record Reverse Guide
5766 Pickup Arm
6228 Reoord Reverse Ann and Fork Assembly
(Specify color)
6444 Reoord Reverse Guide Assembly
6445 Record Separator and Hub Assembly
6510 Automatio Stop Trip Lever Asl!6mbly
6669 Pickup Ann Assembly oomplete
6685 Lower Record Support ASilembly
6686 Record Magazine Assembly
6687 Record Tray Assembly
6693 Record Bumper Guide and Felt Asaem.
34134 Pin-Reverse Guide Stop
34138 Pin-Record Support
34145 Pin-Record Control Rod
39130 Record Reverse Guide Spring'
64197 Pickup Arm Stop Lever Assembly
.
(Specify color)
3239
3242
3356
4320
4431
4659
4664
4912
4913
4915
4916
4917
4923
4925
5036
5037
5042
5081
•
black. In that order they are ground, one
side of nO.volt line, one side of the condenser, and the remaining nO-volt and condenser leads. The motor terminal strip should
be 'mounted to the cabinet torminal strip 80
that the cable extends to the right, with the
soldering lugs towards you.
33. Oiling Inlltructions. Due to its careful design and precise workmafillhip, the
Capehart 16-E record Changer requires a
minimum of oiling.
About once each year a light coat of
vaseline or petroleum jelly should be applied to all moving surfaces which were
coated with graphite at the factory.
A very light coat of vaseline should be applied to the surfaces of the magazine, indicated at "A" in Fig. 83. It is best to apply
this coating every six months. The vaseline
should be applied with, and removed by, the
fingers, on the magazine faces. Do NOT USE
EXCESSIVE AMOUNTS OF LUBRICANT ANY·
WHERE ON THE RECORD CHANGJl;R.
A good grade of machine oil, not too light,
should be used on the sliding clutches, reverse cam shaft and all eccentric and
shoulder screws.
N EVER OIL THE "DUREX" BUSHINGS, AS
THIS WILL CAUSE THEM TO DISINTEGRATE.
Once each year the motor oil cups should
be oiled with a good grade of motor oil. At
the same time the gear box should he inspected, and the grease replaced if it has
become hard. A good mixture to use ,here is
75% vaseline and 25% SAE 40 motor oil.
34. IuauuctiQns for Replacing the Record Reverse Cam and itll AdjUlitmentll.
1. Set' record changer in the playing position. Carefully mark the drive gear (3516)
(Fig. 87) on the main shaft and the driven
gear shown as part of 6623, Fig. 87, by prick
punch marks or scriber, so that the same
teeth can be engaged after reassembly, thus
insuring proper timing.
2. Remove the two bolts, one (3238)
(Fig. 81) securing the magazine slide aud
roller assembly to the magazine slide 8l'Ill
Jever, and one (3237) (Fig. 78) securing the
record slide arm and stud assemhly to the
record tray drive crank.
3. Looking in from the rear of tho iUlitrument, remove the Piu-ex bushing from the
end of the main cam shaft. nea\'est the
motor drin shaft. This iii accomplililhed by
loo.ening the bolt to the right of the main
shaft. Care sbould he taken when replacing
this bushing so all not to tighten the bel}t
enough to crush the hUilhing; I linug fit only
is roq"ifed.
.
4. Remove lowtlf balf
boann, and
Durex bushing frmn the other end ()f the
main cam shaft and work the cam shaft OUt
of the record changer. The 8ame precaution
agaiust crushiug this bushing should he
taken with this one as with the obe in the
preceding section.
5. Remove taper pin from gear and lool16n
set screw in the collllr. hoth shown as 6233
in Fig. 85, of the reverse cam shaft al8embly.
as well a8 the pin (34144) (Fig. 8'1) OVtll'
which the reverse cam forks, when in the
m
115
rHI
Section 5 •
MY I
rlCHNICAL
"'
MANUAL
I,
I'
Fig. 84
2792 Record Trip Switch Assembly-complete
3988 Spring--Automatic Trip Lever Pin
4320 Turntable Drive Shaft Cap
4533 Automatic Stop Trip Lever--Short
5044 Stop Lever Roller Tubing
6018 Selector Knob
6228 Record Reverse Arm and Fork Assembly
(Specify color)
6510 Automatic Stop Trip Lever Assembly
6723 Pickup Brush Assembly
34134 Pin-Reverse Guide Stop
34145 Pin-Record Control Rod
39130 Record Reverse Guide Spring
64197 Pickup Arm Stop Lever Assembly
(Specify color)
'.
,~
•
6&10
reversing position. After removing the coIlar
and sliding the gear to one side, file all burrs
from the edges of the holes in the reverse
catp shaft. Slide the shaft through its Durex
hushing toward the rear of the instrument
far enough to aIlow the removal and replacement of the reverse cam (6325) (Fig. 87).
6. Reassemble the reverse cam shaft assembly, making certain that the taper pin
holes in the shaft and gear are correctly
aligned to permit the taper pins being properly inserted. The set screw in the collar at
the end of the shaft shlilUld be properly
tightened.
7. Remove the reverse cam arm and roller
assembly (6450) (Fig. 79) and make sure
that the roller pin and arm are not bent, if
either of these items are found bent we suggest that you replace the reverse arm and
roller assembly.
8. In reassembling the reverse cam arm
and roller assembly (6450) (Fig. 79) in its
proper position for alignment with the reverse cam, be sure the roJler is about
inside the ridge on the reverse cam, when the
cam is in the ~eversing position.
+."
116
9. Remove the taper pin from the gear
(3516) (Fig. 87) on the main shaft, which
drives the gear on tbe reverse cam shaft
assembly (6233) (Fig. 87) and remount the
main shaft to the record changer chassis,
pushing the above gear, from which the pin
was removed, to one side so that it will not
mesh with its driven gear.
10. Locate the main shaft so that the
lower end of the pickup arm left shaft travels
in the center of the pickup arm lift cam, as
shown at "H" in Fig. 86. With the main
shaft in this position, adjust the main shaft
Durex bushings so that there is no end play
in the main cam shaft IIssembly.
11. Rotate the main cam shaft to the
playing position so that the pickup arm is
lowered over the turntable.
12. Set the reverse cam in its lowest position, with the control lever in the "Both
Sides" position, so that the fork of the reverse cam is meshed with the driving pin.
13. Mesh the reverse cam assembly driver
gear (3516) (Fig. 87) with the reverse cam
assembly driven gear so that the identifying
punch marks correspond to the original posi-
tion. The taper pin for the driver gear
should be inserted next. If the assembly has
been properly made there should be approximately:h" clearance between the roller
or the reverse cam arm and the reverse cam.
See "A," Fig. 86.
'
14. Throw the control lever to the "One
Side" position and rotate the reverse cam
with the fingers until it is in the reversing
position. Again throw the control lever to
the "Both Sides" position. Now there should
be approximately :h" clearance 'between the
reverse cam and the roller. See "B," Fig. 86.
If the clearan~e is not approximately -h" for
both positions of the reverse cam it indicates
either the gears are not properly meshed or
the reverse segment link rod may be bent. A
careful check of the latter while the main
shaft is out will save time and troub)e later.
35. Instructions for Rellloving the 16-E
Record Changer. There is a great possibility, when removing the chassis from the
cabinet, to mar or scratch the cabinet. If you
will place a piece of cardboard around the
record changer it will eliminate, to a great
extent, the possibility of marring the finish.
PHONO·RADIO
SERVICE
DATA
• Section 5
Fig_ 85
3241
3243
3244
3317
3550
3825
3826
3976
3977
3978
3981
3984
3995
5046
5331
5332
5334
6230
6233
6326
6450
6460
Shoulder Screw-Reverse Segment Link
Shoulder Screw-Repeat Lever
Shoulder Screw-Clutch Throwout Lever
Screw-Clutch Throwout Cam
Record Reverse Pinion Segment
Reverse Segment Stop Cam
Record Repeat Sliding Clutch Cam
Spring-Record Separator Hook Lever
Spring-Magazine Slide Arm
Spring-Record Repeat Clutch
Spring-Record Reverse Cam Control
Spring-Tone Arm Lever
Spring-Reverse Arm
Stop Lever Collar Pin Tubing
Record Repeat Throwout Hook Lever
Record Repeat Clutch Fork Lever
Record Repeat Lock Lever
Reverse Pinion and Crank Assembly
Record Reverse Cam Shaft Assembly
Worm and Bushing Assembly
Reverse Cam Arm and Roller Assembly
Clutch Throwout Lever and Spring Assembly
6719 Turntable Drive Shaft Assembly
34141 Pin-Short-Reverse Segment
34144 Pin-Reverse Cam Shaft
•
A rubber auto mat, with a hole for the record
changer, the same size as the one in the
cabinet, makes an excellent pad. This pad
can be split and is easily put in position and
removed.
Remove the backs from the record changer,
radio and amplifier compartments.
Release the play control cable and cable
housing from the bracket on the record
changer chassis, by loosening the two set
screws. Care should be taken to prevent
breaking the control cable when removing
it. The end which has been kinked by the set
screw should be straightened before attempting to reinstall it.
Remove the screws from the partition between the radio and record changer compartments, so it can be moved back out of
the way.
Loosen the two Allen ,set screws in the
flexible coupling and allow it to slide down
the motor shaft, so as to' clear the record
changer shaft.
Remove the wood screw, under the turntable, also the three bolts which hold the
record changer down.
Move the play control as far into the
radio compartment as possible.
Remove the two wood screws that mount
the play control.
Remove the screw marked "Boo in the
illustration on page 109. This is the middle
one of the screws holding the upper record
support.
Remove the female chassis plug, from the
male chassis plug (6178) (Fig. 78), the pickup lead, which runs from the radio chassis to
the terminal block, then dismount the terminal block by removing the wood screw in its
center, the straps holding the shielded lead,
which runs from the shorting switch, and the
nO-volt leads to the Play Control.
Remove the magazine link shoulder screw
(3239) (Fig. 83). This will allow the magazine to be swung out of the way. As soon as
the record reverse arm and fork assembly
have cleared the reverse crank and pin
(6230) (Fig. 78) it should be swung over the
magazine and locked with the record reverse
arm lock (4659) (Fig. 83), to keep it out of
the way.
Lift the record changer up, until the tone
arm just touches the top of the cabinet,
carry it forward through the doors, tilting it
to keep the main cam clear of the shelf.
All parts of the cabinet liable to damage
should be protected by soft cloths while
removing or installing the record changer.
It is not necessary that the above operations be carried out in the above sequence.
36. Alignment of True-Tangent Pickup.
When adjusting the TRUE-TANGENT pickup
the pickup head and tone arm should form a
straight line, when the needle is exactly one
and one-half inches from the point of the
turntable drive shaft cap (4320) (Fig. 83).
To adjust the pickup angle, loosen the nut
at the rear of the steering arm assembly
(66254) (Fig. 78), turn the steering arm
either right or left until the correct position
for the pickup is found, then set the locknut
up tight. Then see that there still is %"
clearance between the pickup and the record
tray per Section 11.
117
THE
Section 5 •
MY E
TECHNICAL
MANUAL
50(73
6.32;/' R.,.,N,P'
I:
504-ti
f)-3l X
I
1Y4
'I
FHMS
1,1
67
I.'
67/9
6449
-S03S
4320 ---_
A
I ~Jr
I
,">I I
'l{x 2.0
HEX NUT
Fig. 87
8
Fig. 86
6232
632$
6449
6457
Pickup Swing Lever and Collar :\s""mbly
Reverse Cam
Pickup Arm Lift Cum
Pickup Arm Lift Shaft
118
3319
3356
3516
3539
3626
·3627
36:30
3820
3822
3984
4210
4233
4243
4244
4:312
4320
46213
50:38
SOH
5046
50173
.51a9
569
Screw-Turntable Shaft Collar
Pickup Needle Screw
Gear-Reverse Cam Shaft Driver
Worm Gear
Ball Bearing
Bull Bearing
Turntable Shaft Clutch
Magazine Slide Arm Cam
Pickup Arm Swing Cam
Spring-Tone Arm Stop Lever
Thrust Washer-Worm Shaft
Main Cam Collar
Pickup Arm Stop Lever Collar
Turntable Shaft Collar
Pivot Bushing
Turntable Driveshaft Cap
Magnet Holder
Turntable Driveshaft Cap Tubing
Stop Leyer Roller Tubing
Stop Leyer Collar Pin Tubing
Tone Arm Insulating Bushing
Terminal Block
Pole Piece
5610
5765
5768
61212
6233
6a25
6326
6448
Stylus
PickUp Cover
Pickup Back
Pickup Magnet
Record Reverse Cam Shaft Assembly
Record Reverse Cam and Pin
Worm and Bushing Assembly
Turntable Throwout Cam and Hub Assembly
6449 Pickup Lift Cam and Hub Assembly
64197 Pickup Arm Stop Lever Assembly
6691 Pickup Arm Friction Cam Assembly
6711 Spool Assembly
6719 Turntable Shaft Assembly
6723 Brush Assembly
34144 Pin-Reverse Cam Shaft
34147 Pin-Record Tray Slide
99-11- 1 6-32 Hex. Nut
99-18-21 6-32x % H RHMS
99-28- 3 6-a2x J4 n Headless Set Screw
99-28-21 rr-a2x V. H Headless Set Screw
99-a8- 2 :S-o. 2 Woodruff Key
SER.VICE
PHONO-R.ADIO
DATA
• Section 5
bl7S
5323
S,1t..ENCER,
3977
Fig. 88
/6257
I
565
3241
3fl26
3H2.S
a077
3!l7H
3\)Hfl
--
3825
401~
IO-24XYz}
R HM S
4018
4022
4a:n
443:3
5040
5:32:3
5331
617H
G257
433!
G450
G455
---'"-1-.-.--____
t>713
3'241 -----.:.-tI---5331
34141-'
6455
3626
6460
6460
6713
34140
34141
Clutch Throwout Cam
Reverse Aegment Link Shoulder Screw
Ball Bearing
Reverse Aegment Stop Cam
Magazine Slide Arm Spring
Record Repeat Cluteh Spring
Solenoid Lever Torsion Hpring
Main Shaft Bushing
Record Tray Hhaft Bushing
Bearing Retainer Plug
Holenoid Plate Bra('ket
Pi('kup Arm Brake Facing
Magazine Hlicle Arm Lever
Record Repeat Throwout Hook Lever
Chassis Plug
Record Tray Gear and Sliding Cam
AHHembly
Reverse Cam Arm and Roller Assembly
Aolenoid to Clutch Lm'cr and Pin Assemhly
Clutch Throwout Lever and Spring Assembly
Aolenoid Assembly
Reyerse Segment Pin, Long
Reverse Segment Pin, Sh~rt
•
Fig. 89
2722
3240
3243
3550
3724
3977
3981
3983
3984
3995
4020
4238
42:39
4243
4663
5046
5326
5332
5333
5334
5339
6221
6223
6224
6226
6230
6231
6451
50117
OOx %
Ox U
AC Line Toggle Switch
Reverse Segment Shoulder Screw
Repeat Lever Shoulder Screw
Record Reverse Pinion Segment
Record Control Shaft
Magazine Slide Arm Spring
Record Reverse Cam Control Spring
Separator Hook Spring
Tone Arm Stop Lever Spring
Reverse Arm Spring
Record Magazine Bushing
r." Collar
fg" Collar
Pickup Arm Stop Lever Collar
Record Repeat Throwout Lever
Stop Lever Collar Pin Tubing
Record Reverse Cam Shaft Lever
Record Repeat Clutch Fork Lever
Main Clutch Fork Lever
Record Repeat Lock Lever
Reverse Cam Lock Lever
Record Tray Drive Shaft Assembly
Record Re,-erse Arm Shaft Assembly
Solenoid Lever Shaft Assembly
Separator Hook and Arm Assembly
Reverse Pinion and Crank Assembly
Record Control Lever and Stud Assembly
Separator Hook Lever and Roller Assembly
Main Frame Pad
Taper Pin
Taper Pin
NtH
cUo
/
401.0
/
50117
1\I&X14 -2
lUi. CAP S/;,
tlZt!
AS'I.
424'"
2121-
00 X 5/S
3qQS
0223
ASY,
119
Section 5 •
THE
MY E
TECHNICAL
MANUAL
Farnsworth - Model S 30
SERVICE
1. To Remove the Turntable (5i79) (Fig.
90). The turntahle unscrews from the record
spindle (37140) (Fig. 90) hy turning the
turntahle counter·c1ockwise. If the main cam
(3869) (Fig. 93) turns hackwards, damage to
the starting lever release assemhly spring
may result. Hold the main cam while un·
screwing the turntable.
2. To Adjust Drive Pulley (3672) (Fig.
91). In case "wows" are heard in the repro·
duction, additional tension should he placed
on the turntahle drive hracket spring hy
turning the spring clip, which is held hy one
of the motor mounting screws (99.19·19)
(Fig. 91) so as to increase the tension on the
spring. On earlier models, it may he neces·
sary to bend the hairpin spring.
3. To Replace Drive Pulley (3672) (Fig.
91). Remove the hairpin cotler key (99-34.
12) (Fig. 91r) and the drive disk thrust
washer (50209) (Fig. 91). This permits the
removal of the turntable drive pulley. In
replacing this pulley, the long shoulder goes
toward the hase plate.
4 .. To Replace Turntable Driv'; Bracket
and Stud Assembly (64216) (Fig. 91).
Remove turrttahle drive pulley (see 92)
and remove screw (99-19·2) (Fig. 91) and
nut, locknut and washer under drive pulley.
In replacing this part (64216) (Fig. 91) he
sure the nut and locknut under the drive
pulley are set up so there is very little play
between the hase and the bracket (64216)
but the hracket should move sidewise freely.
Replace the drive pulley (See 92).
5. If Records Feed Incorrectly. Record
shelves may he out of line. Run changer
through its change cycle until the back rec·
ord shelves are in their lowest position.
Roller (4057) (Fig. 93) is on point C of main
cam (3869) (Fig. 93). The front shelves. do
not move during the cycle. With the shelves
in place for a 12" record, 10" shelves raised,
a straight edge from shelf to shelf should
just clear the shoulder near the top of the
record spindle (37140) (Fig. 91). The shelf
may he adjusted while in the lower position
by adjusting the four nuts holding the lower
link (54107) (Fig. 92). Care should be taken
not to run one nut farther than another ahd
so get the link out of line wi th the suppor t
rods (37138) (Fig. 92). The screw (99·20.45)
(Fig. 92) is to prevent the upper nuts on the
lowering link from hitting the main cam.
Probahly it will not require any adjustment.
6. Adjustment of Reeord Centering Pin
(34&10) (I<'ig. 91 and Fig. 94). The record
120
centering pin should clear the record spindle
(37140) (Fig. 94) by approximately fi".
When the record spindle is rotated hy the
turntahle,it will be seen the tip descrihes a
circle. When the tip is at that point in its
rotation where it is nearest the hack of the
record changer, the rear face of the tip.
should he exactly ;(4~ ahead of the rear face
of the record centering pin. When rotated,
the tip should leave and go back under the
centering pin in the same relative positions.
If it does not, it is necessary to spring the
centering pin sidewise until it does. If this
adjustment is made, check the other two
adjustments in this section.
7. Setting Tone Arm Drop. The needle
should drop on the record ahout V8" from
the edge. To adjust, make sure the record
changer is in the playing position, that is
the tone arm has moved over so that the
needle is on the record.
Set the hutton (66364) (Fig. 91) for ten.
inch records. Loosen screw (99-20.5) (Fig.
92) in the tone arm crank (54108) (Fig. 92).
Place needle on record V8" from edge.
Press tone arm return lever (64212) (Fig.
93) firmly against the main cam, holding
tone arm crank against side of square hole
away from record, at the same time hold
tone arm crank firmly against the collar
ahove it. Tighten set screw (99-20-5) (Fig.
92) making sure the tone arm still has a
lillIe up and down motion of the lift rod
(43182) (Fig. 92). Check the adjustment by
letting the record changer go through a cycle.
Load 12" records and set button (66364)
for 12".
Adjust screw (99-18.19) (Fig. 93) until the
needle drops properly on 12" records, ap·
proximately V8" from edge.
Never set for 12" records first and then
for 10" records as the 10" adjustment affects
the 12" setting.
8. Adjustment of the Record Trip.
Changer Will Not Trip. If the leject hut·
ton has no effect and the record changer will
not trip when the needle enters the change
grooves, see that the reject lever (46304)
(Fig. 93) is not caught on or behind the
starting le'ver release trip (64215) (Fig. 94).
The reject lever should he free to move, have
very little motion up and down and should
hi t the cen ter of the trip finger (46287)
(Fig. 93). The up and down motion of the
reject lever may be corrected hy tightening
the nut that holds it against the hase. Do not
tighten it so as to cause the lever to hind;
it must move freely.
If the changer will not trip when needle
enters change groove hut will change when
reject hutton is pushed, hend starting lever
trip spring (39226) (Fig. 94) towards motor
spindle gear. On £ecords where the recording
occupies only Va to Yz the available space, if
instrument fails to trip in change grooves,
it may he necessary to loosen the Bristol set
screw in the trip friction collar (43185)
(Fig. 92) and move the collar slightly. Use
6-32 Bristol wrench (6075) for this adjust.
ment. Turn the collar a small amount clock·
wise, when viewed from the bottom of the
changer. Check the operation of the changer
on standard records as it is possible to move
the collar too far.
Changer Trips Too Soon. If instrument
trips when only half the record has been
played, check the position of the starting
lever release trip spring (39226) (Fig. 94).
The dog, on the motor spindle gear (35102)
(Fig. 94) should throw the spring hack so
the starting lever release trip (64215) (Fig.
94) overlaps the starting lever (46288) (Fig.
94) approximately h". In case the overlap
is less, bend spring slightly toward the motor
spindle gear until proper overlap is secured.
If instrument trips near end of record: Set
needle I%;" from record spindle, loosen set
screw in collar, pin and set screw assembly
(66355) (Fig. 92), turn collar slightly coun·
ter·clockwise (viewed from hottom of
changer). This will decrease the tension on
the friction trip lever spring (39228) (Fig.
92); tighten set screw and check tripping
action on records again.
Adjustment of Trip Finger (42687) (Fig.
93). The trip finger must not ruh on the
base plate when tone arm is raised. It may
be bent slightly to clear base plate if neces·
sary.
The trip finger must move freely. If it
moves stimy or binds, tone arm cam (66366)
(Fig. 93) may he dropped slightly.
The trip finger stop (46293) (Fig. 93)
sh~uld he set exactly 2Yz" from outside of
base plate.
9. Adjustment of Tone Arm Height.
With a 10" record on the turntable, a stand.
ard needle in pickUp and 10" records in the
magazine, there should be approximately
%" clearance between the top of the pickup
and the bollom of the hottom record in the
magazine during the change cycle. This
clearance is adjusted by the screw (99·26.15)
(Fig:93).
Still with a 10" record on the turntable,
pickup in playing position, lift pickup off
record so that both brush and needle clear
record. The point of the needle should drop
three·fourths of the thickness of the record
below the top surface of the record. This
height is adjusted by bending the tone arm
support (64219) (Fig. 91).
I,',
I~.(
Ii
\'I{
I
I
I:
I
I
PHONO-R.ADIO
To adjust needle preR"Ure: Move tone arm
"0 all the hrush is on t he record but the
needle clears the edge. Adjust the hrush
(6725) (Fig. 91) by the screw in the pickup
head 80 the needle is halfway between the
top and bollorn faces of the record.
Care should he taken to see that there is
some slack in the pickup lead he tween the
pickup arm and hase. If the lead is too tight,
the needle will skip over the record instead
of stopping in the first groove.
10. To Remove Tone Arm. Loosen tone
arm crank screw (99-20-5) (Fig. 93); loosen
set screw in collar, pin and set screw assemhly (66355) (Fig. 92); loosen screw holding cord clamp at rear of tone arm; lift tone
arm straight up
(Fig. 92).
SER.VICE
DATA
• Section 5
Recover lift rod (43182)
erly. It may he necessary to hend the lever
to secure proper mesh.
n. Replacement of Crystal Cartridge.
On Farnsworth 530 changer, the entire cartridge, cord and plug m;'st he replaced.
On Capehart Panamuse, only the cartridge need he replaced.
14. A Squeak during the change cycle is
usually caused by a lack of oil on roller
(4058) (Fig. 93). A drop of oil placed on it
will usually cure it.
12. Removal of Main Cam. Remove turntahle according to directions in Section 1.
Remove nut (99-]4-5) (Fig. 91) which holds
main cam spindle. Pull record shelves down
and main cam will slip out. Reassemble in
the reverse order.
13. If Gears Jam, and changer won't cycle,
see that starting lever (46288) (Fig. 94) is so
positioned that when it engages with pin
(34309) (Fig. 94) the first teeth mesh prop-
Any rumhle occurring during the change
cycle hetween the motor spindle gear and
the main earn gear, can he minimized by
loosening the three screws (99-19-17) (Fig.
91) and properly positioning the motor
spindle. Retighten the screws.
GARRARD .... See Magnavox Models
Re5, RC8, RCIO,
RCn, RC50, and RC51
-4-6186
---5780
781 Complete
3-4-313
6636-4
Fig. 90
3167 Tone Arm Support
46286 Record Support, 12" Rear
3360 Needle Screw
46295 Record Support, 10" Rear
4639 Wire Clip
46300 Record Support Bracket, Front
5568 Record Support and Lowering Bracket
Assembly
50206 Grommet, Rubber
,
5779 Turntable
66349 Record Support Bracket Assembly,
Front
5780 Tone Arm
5781 Tone Arm, Complete
6725 Brush
34310 Record Centering Pin
34313 Tone Arm Hinge Pin
37140 Motor
Spindl~
54110 Tone Arm Support Housing
(Part of 6287)
66350 Record Support Plate and Pin Assembly
(Farnsworth)
66391 Record Support Plate and Pin Assembly
(Capehart)
66364 10 or 12 Stop Cam Knob (Late Production: 6069)
Decalcomanias: 50226 and 50227 used on late
production with Knob No. 6069.
99-19-18 8-32x /0" RHM Screw
99-22-35 6-32x ~" Bind. HM Screw
99-22-37 4-36x J.B" Bind. HM Screw
99-23-13 8-32x Vs" Hinge Pin Screw
Where (Capehart) appears -behind a part,
this part is used on Capehart Panamuse Instruments exclusively.
46284 Record Support Plate (Farnsworth)
43180 Record Centering Pin Nut
46330 Record Support Plate (Capehart)
46285 Record Support, 10" Front
66363 Reject Knob (Late Production: 6(69)
Where (Farnsworth) appears behind a part
this part is used on Farnsworth combinations
exclusively.
121
THE
Section 5 •
MY E
TECHNICAL
MANUAL
Fig. 91
2328 Crystal Pickup Only (Capehart)
715-1 Crystal Pickup, Lead and Plug Assem.
(Farnsworth) AK-59 Only
716-1 Crystal Pickup, Lead and Plug Assem.
(Farnsworth-76, 95, and 96)
3671 Motor Drive Pulley
3672 Turntable Drive Pulley
6725 Brush
34310 Record Centering Pin
34315 Record Support Hinge Pin
37140 Motor Spindle (Part of 6287)
39225 Idler Spring (Changed to 39245 on Later
Models)
39235 Spring-Pickup Wire Clip, Long
39237 Spring-Pickup Wire Clip, Short
43180 Record Centering Nut
46285 Record Support Front, 10"
46286 Record Support Rear, 12" (Part of
64213)
46295 Record Support Rear, 10'
46297 Record Support Front, 12"
46306 Drive Disk Bracket
50173 Tone Arm Bushing
50206 Grommet Rubber
50209 Drive Disk Thrust Washer
64216 Turntable Bracket and Stud Assembly
64219 Tone Arm and Bracket Assembly
66363 Reject Knob (6069 Used on Later
Models)
66364 10-12 Stop Cam Knob (6069 Used on
Later Models)
Decalcomanias Nos. 50226 and 50227
Used on Later Models With Knob
No. 6069.
I'
I;,
I,
,.
99-13- 6
99-14- 5
99-19- 2
99-19- 6
99-19-17
99-19-18
99-19-19
Hex Nut.
Ux28 Hex Nut
8-32xU' RHM Screw
8-32x~" RHM Screw
8-32xh" RRM Screw
8-32xh" RHM Screw
8-32xn" RHM Screw
99-2()"18
99-20-29
99-20-54
99-34-11
99-34-12
99-36-21
99-42-11
1()"32xU" RHM Screw
10-32x /t" RRM Screw
10-32x1 ~. RHM Screw
Hairpin Cotter Key
Hairpin Cotter Key
Washer
Turntable Stop Washer
I,
Fig. 92
37138
39224
39227
39228
43182
43185
45165
46288
46292
47124
50203
54107
54108
64215
Record Support Rod (Part of 64213)
Spring-Record Lowering
Spring-1)'ip Friction, Flat
Spring-Trip Friotion, Coiled
Tone Arm Lift Rod
Trip Friotion Collar, Upper
Friction Trip Lever
Main Gear Starting Lever
Tone Arm Lift Bracket
Base Plate
Trip Friction Drive-Cork
Record Lowering Link (Part of 63119)
Tone Arm Crank
Start Lever Release Trip and Hub
Assembly
66355 Collar, Pin and Set Screw Assembly.
Lower
99-14- 3 ~x28 Hex Nut
99-20- 5 1O-24x ~" RHM Screw
99-20-45 1()"24x2" RHM Screw
99-42- 5 Washer
122
I,
I,,',
'J
i:t
!'
PHONO-R.ADIO
SIR.VICI
DATA
• Section 5
42162
46287
46293
46304
64212
Fig. 93
3162
3868
3869
4057
4058
21151
21153
Main Cam Stud
Tone Arm 10-12 Stop Cam
Main Cam
Roller-Record Lowering (Part of 63119)
Roller-Tone Arm Lift
Motor-60 Cy., AC
Motor-50 Cy., AC
34308
34309
34312
35102
39229
39234
39236
Pin-Record Lowering (Part of 63119)
Pin-Motor Spindle Gear
Pin-Tone Arm Lift Lever
Motor Spindle Gear (Part of 6287)
Spring-Tone Arm Lift Lever
Spring-Tone Arm Return Lever
Spring-Reject Lever
Fig. 94
'4111
3869,
6287
34309
34310
35102
37140
39226
Main Cam
Spindle and Gear Assembly
Main Cam Starting Pin
Record Centering Pin
Motor Spindle Gear
Motor Spindle
Starting Lever Release Spring
462~8 Starting Lever
64215 Starting Lever Release Trip and Hub
Assembly
66359 Spindle Gear and Bracket Assembly
Shoulder Spacer
Trip Finger
Trip Finger Stop
Reject Levllr
Tone Arm Return Lever and Hub Assembly
66347 Tone Arm Lift Lever Assembly
66366 Tone Arm Crank and Clamp Assemby
66359 Spindle Gear and Bracket Assembly.
99-12- 1 8-32 Hej[ Nut
99-13- 3 10-24 Hex Nut
9943- 5 10-32 Hex Nut
99-18-19 6-32x n," RHM Screw
99-19-13 8-32x~" RHM Screw
99-20- 5 10-24x ~. RHM Screw
99-20-45 10-24x2" RHM Screw
99-26-15 10-32x~' RHM Screw
99-34-11 Hair Pin Cotter Key
99-34-12 Washer-~' ODx-hxH TH
99-36-14 Washer-Ji' ODx",x-h
7344--1 Gauge for AdjUsting 8-30
63119 Record Lowering Link Assembly, ,Complete
64213 12' Record Support and Shaft Assembly, Complete
34311 Shelf Pin 10'-12' Front and Rear Record SUpport Assembly
66351 Friction Trip Assembly, Complete
4949 Felt Washer for Motor Spindle
54109 Spindle Support'Bracket
6287 Motor Spindle and Gear Assembly
.,J
;
111\
14110 _ _
11140 - -_ _,"
123
THE
Section 5 •
MY E
Magnavox -
TECHNICAL
MANUAL
Model G 1
SERVICE
Operating Instructions
This record changer ,Plays seven 12" or
eight 10" records automatically. The last
record remains on the turntable and repeats
as long as the record changer is in operation.
Records may be repeated as often as desired by raising the record removing arm at
"A" (Fig. 95) to the upright position.
To reject a record and play the nex t record
below it, pull the latch lever at "L" (Fig. 95)
forward.
'
To adjust the record moving arm to
handle 10" records set the record removing
arm change lever at "D" (Fig. 95) opposite
the numher 10 stamped on the base plate.
For 12" records set the lever opposite the
number 12.
To adjust the pickup to play 10" records,
push the pickup stop at "K" (Fig. 95) back.
(Away from the pickup needle.) For 12"
records pull the stop forward (toward Ihe
needle) as far as it will go.
Some unils are equipI)ed with two speed
motors, and others with 78 rpm motors.
"hen the two speed motor is used change
from one speed to the other by simply moving lever at "F" (Fig. 95) to position desired.
To start motor, throw switch (supplied on
same models) at "N" (Fig. 95) on the "on"
position.
(Fig. 95) as far as it will go in the direction
of swing indicated by the legends "33~"
and "78" on the base plate.
'
If adjustment of the speed change lever is
required for any reason, proceed as follows:
First loosen the screw which clamps the
I~ver to the motor shaft. This shaft is proVIded with a screw-driver slot in the -end.
Next, uSing a screw driver, tnrn this shaft
in a clockwise direction until you feel it
strike the stop. The motor is now in the
"33%" Rpm. position. Now set the levllr
against the lug provided in the base plate
and opposite the legend "33~" and tighten
the clamp screw. This places the lever in the
correct position on the motor shaft. The
final step is the adjustment of the eccentric
hushing at "G" (Fig. 95) which limits the
throw of the lever. First loosen the screw
which holds the eccentric bushing. Next,
throw the speed change lever to its farthest
"78" Rpm. position, (using care that the
lever does not slip on the motor shaft).
Then turn the eccentric bushing around
until it touches the side of the lever, and
tighten it in place with the screw provided.
Trip Mechanislll
The trip mechanism is the trigger that
sets the record changer in motion. This is
done by allowing, the latch bar at "0" (Fig.
95) to drop in front of, and be actuated by
the cam at "P" (Fig. 95). This cam is drive~
by, the motor and is in motion as long as the
motor is running. If this mechanism does
not operate smoothly, the precautions outlined in succeeding paragraphs should be
observed. '
First of all, make sure that the square pin
in the latch lever at ",U" (Fig. 95) latches
properly in the notch in the lift lever a t "I"
(Fig. 95). When latched, the notch should be
engaged approximately one-half of its depth.
The depth of engagement is adjusted by
means of the eccentric washer and locking
screw at "}" (Fig. 95). Now run the record
changer through its cycle. If the square pin
fails to engage the notch in the lift lever,
first check the tension of the latch spring at
"II" (Fig. 95) to insure that the notch can
engage the pin. Next check the tension of
the reset spring at "E" (Fig. 95). This reset
spring should not be under tension when the
latch bar is latched but should have enough
tension when the latch bar drops back off of
the cam to cause the square pin to over
travel the notch in the lift lever. IMPORTANT
-Before attempting to change the tension
of any spring, be sure that the parts involved
work freely without any tendency to bind,
as of course any binding condition would
preclude proper operation.
The record changer is adjusted at the factory to trip on a spiral trip groove record
when the phonograph needle is I%;" from
the edge of the hole in the center of the
record.
'
When eccentric or oscillating trip groove
records are used, tripping is effected by
I
I'
1
I
Motor Lubrication
. The motor installed in the record changer
IS governor controlled, with all gearing enclosed, and leaves the factory lubricated for
pro~er operation. For maximum satisfaction,
lubrIcate the motor at regular intervals with
SAE No. 10 oil. Do not use any other
grade of oil.
The governor disc engages with a ring of
hard felt, This felt is impregnated with a
lubricating solution sufficient for proper operation for approximately a year under
normal c~nditions. It may be necessary,
however, If the motor shows a tendency to
chatter or waver, to apply a drop or two of
oil to this felt ring.
~
I,
Motor Speed
The motor speed is adjusted by means of
,a lever at "C" (Fig. 95) which is mounted
under the turntable. The direction of swing
to fast or slow is indicated by the legends
"F" and "S" on the base plate.
o
33 1/3 RPM-78 RPM Shift
\
(Two-speed Illotors only)
Move the speed change lever at
124
"Jf"
FIG. 95
,I
PHONO-RADIO
means of the hardened steel pin in the end of
tone arm lift crank at "S" (Fig. 96) engaging
the serrated block on the trip lever at "T"
(Fig. 96). There must be a minimum of b"
play between the end of the pin and the
block, when, with a short needle, (%" minimum length) the pickup is resting on one
record on the turntable. If the pressure of
the pin on the block is not sufficient to insure
operation, then check the pressure spring
which is located up under the pickup.
The oval head pivot screw at "R" (Fig.
95) serves as a pivot for the lift lever at "I"
(Fig. 95). This screw should allow the lift
lever to be raised by the latch bar to its
FIG.
DAfA
SE,RVleE
from the top of this record down to the base
plate. This distance should be one inch. Now
by pulling the reject lever at "L" (Fig. 95)
first, it will be found possible to swing the
record removing finger at "Y" (Fig. 97) ov'er
to where it just touches the edge of the
record. If the adjustment is correct, the
record removing finger should just barely
rise over the edge of the first record. If adjustment is required it can be made by
means of the stop screw at "Q" (Fig. 97). In
the event the record removing arm raises the
record from the turntable and drops it back
in place without removing it, check the lift
adjustment at "V" (Fig. 95). This adjustment consists of an eccentric stud which is
provided with a locknut, and is made by
loosening the locknut and turning the eccentric stud. The lift adjustment should be
set so that the hole in the cellter of the record
just clears turntable spindle when the record
changer is in operation.
96
maximum height without binding but also
without any additional play.
If the record changer fails to trip, see if
the phonograph needle is jumping out of a
worn record trip groove. Next make certain
that all parts of the mechanism work freely
and smoothly. If it is found that the latch
bar at "0" (Fig. 95) is not dropping in far
enough to engage the cam at "P" (Fig. 95),
then check the tension of the trip spring at
"B" (Fig. 95).
FIG.
98
Pickup Lowering Mechanism
The pickup lowering mechanism has two
functions. First, it lowers the phonograph
• Section 5
needle gently to the surface of the record.
Second, it feeds the needle toward the center
of the record so that it will enter the playing
groove.
If the pickup descends too fast or too
slow, adjust the speed of descent by turning
the knurled thumb nut on the dashpot sleeve
at "w" (Fig. 96).
The unit is adjusted at the factory so that
the needle will be set down approximately
%" in from the edge of the record. An adjusting screw is provided on the side of the
pickup at "M" (Fig. 96). If the needle is
being lowered onto the playing surface of the
record, and the adjusting screw at "M"
(Fig. 96) fails to correct the condition proceed as follows: First stop the record changer,
with the pickup in the maximum raised position and check the clearance between the
underside of the pickup shelf at "Z" (Fig.
96) and the tip of the dashpot. This clearance should be very small as otherwise the
pickup will tend to hounce as it is lowered.
There must be sufficient clearance however
to prevent the pickup shelf from rubbing on
the tip of the dashpot, or the pickup will not
swing out far enough to allow the adjustable
stop at "K" (Fig. 96) to come to rest against
the dashpot. Check this clearance in both
10" and 12" record positions. If adjustment
is required, the height of the dashpot may be
regulated by loosening the nuts on the bottom of the lift lever stud at "X" (Fig. 98)
and changing their position on the stud. To
raise the dashpot turn the nuts clockwise, to
lower the dashpot turn the nuts counte~
clockwise. Be sure to lock the nuts tightly
together after the adjustment is made.
Models RC5, RC8, RClO, RCn, RC50, RC5l, (Garrard)
FIG. 97
Similarity of service and illustrative material for these models has made it
possible to combine certain portions of the text for more rapid reference. A
table has been prepared to indicate the correct portion of the text for each
model.
If, for instance, it is desired to study the service methods for adjusting speed
on the model RC8, simply look under "Speed Adjustment"-follow this column
until it intersects the column beaded RC5, R~8 and the reference is found to
be' paragraphs AlO, and All.
Record Removing Mechanism
The record changer is adjusted so that it
will always leave one record on the turntable. This is done to prevent the phonograph needle from damaging the covering
on the turntable.
In case the record removing mechanism
fails to operate smoothly, proceed as follows:
First make certain that all parts work freely
with no binding in pivots or bearings, and
that the record removing arm assembly rests
on the stop screw at "Q" (Fig. 97). Next
stop the motor in such a position that the
latch bar at "0" (Fig. 95) can swing by and
clear the cam at "P" (Fig. 95). Place just
one record on the turntable and measure
Operating Instructions . .................. .
AutoJDatic Trip ........................... .
Operation of AutolDatic Trip .............. .
Striker Adjustment ............. , ......... .
Friction AdjustD1ent ..................... .
Oversize Records . ......................... .
Pickup Arm Adjustment ....... ,., ........ ,
Pickup Arm Adjustment ....... , ..... , ... ,
Aut.omat.ic St.op . ......................... .
Speed Adjustm.ent ............. , .......... ,
Irregular Speed ....... , .............•......
Lubrication of AC Motor .................. .
Universal Mot.or . ......................... .
Aut.oDlatic Switch . ...................... .
Record Dropping ......................... .
Binding .. , ...... , ........ , ...... , ... , ..
Pickup, ...............................
ReDloving Changer . ......................
Replacing Tone Arm Baae ... ..............
.
,
.
.
Models
RC5, RCS
Models
RCIO, RCll
Models
RC50, RC5I
Al
A2
A3
A4
A5
A6
A7
A8
A9
AIO, All
Al2
Al3
AI4
AI5
A16, A19
Al
A2
A3,B3
A4
A5
Bl
A2
A3,C3
A4
A5
B6
A7
B8
A9
AIO, Bll
·A2i.~·A22·
A23
A24
····87····
CS
B9
AIO, BIl
Al2
Al3
Al4
·Bi.6~·Ai9·
. .. Ai:i ...
Al4
C3
A16, A17,
A18, Al9
A20
A21, B22
B23
125
THI
Section. 5 •
AI. This record changer plays eight 12"
records or eight 10" records (not intermixed)
automatically, and the changer stops oper.
ating after the playing of the last record. A
record may be rejected before playing the
entire selection by turning the right.hand
knob on the motorboard to the REJECT
position.
.
To operate the changer, first turn the left.
hand knob on the motorboard 80 that the
indicator is pointing to the 10" or the 12"
designation, depending on the sil'le of the
records to be played. With the record spindle
in position-angling section toward the rec·
FIG. 99
MY I
MANUAL
done by rotating the mQtorbollrd knob to
the STOP position.
A2. The automatic trip plays lin important
part in the operation of the reco~d changer,
and upon the certainty of the automatic trip
coming into action depends the whole opera·
tion of the record changer. The automatic
trip mechanism will operate on all makes of
records having a "run·off" groove, either
eccentric or spiral.
A3. The trip lever "A" (Fig. 99) is connected
to the pickup arm through a series of levers
and is moved forward towards the main
spindle a distance proportional to the ad·
vance made by the pickup. The striker arm
"B" (Fig. 99) is fiUed on the main spindle in
order to push back the trip lever, preventing
the automatic trip from functic;ming while
the record is being played. When the pickup
reaches the end of the playing grooves and is
carried into the "run·oW' grooves, the move·
ment transmitted to the trip lever is too
great to allow its being pushed back by the
striker arm. The striker arm then contacts
the metal trip lever which in turn operates
the changing mechanism.
B3. If the trip mechllnism does not operate
at the end of some records, projection "A"
should be bent towards point "c" on lever
"B" (Fig. 103) so that when the mechanism
is in the p,laying position (and the chan~er
stopped), the tone arm mlly be moved In.
wardly to a point where the needle is 1711"
from the edge of the motor spindle.
ca.
Old platform-place from one to eight rec·
ords of either the 10" or 12" type on the
record spindle. Rotate the right.hand knob
on the motorboard to the START position,
placing the changer in operation.
T.CHNICAL
If the automatic switch does not op·
erate at the end of the last record, make
certain that all of the levers are free and that
all the springs are in place. Also ;Qake certain
that the turntable 8pindle is frec in the mdin
spindle-it should move about Ya" when
depressed and should rise the same distance
when released. This" test should be made
while the changer is in the playing position.
Switch tripping adjustment can be obtained
by means of a small quadrant adjustment on
the top of the spindle operated by lever
"P" (Fig. 100).
A4. The correct functioning of the trip
mechanism depends on the rubber bushing
"H" (Fig. 99), on the tl'ip lever arm "G."
When the bushfng becomes badly worn, a
tapping sound will hecome apparent, and
the trip lever may operate before the end of
the record. This con!fition may be correeted
by turning the rubber bushing on the spindle
in order to present a new surface to the
striker arm "B."
A5. If the changer fails to operate at the
end of a record, the record apindle should be
removed and the turntable lifted from the
motor shalt so that the friction adjusting
screw "E" (Fig. 99) may be readjusted. Before adjusting this screw it is advisable to
make certain that the operating trip lever
"A" is not rubbing on the base plate, setting
up additional friction. To adjust the friction,
give the friction adjusting screw "E" a small
turn in a counter-clockwise direction to in.
crease the friction. If the changer 'trips be·
fore the pickup has reached the end of the
playing grooves, or if a humping noise is
heard in the speakers, the friction adjusting
screw should be turned in a clockwise direc·
Bl. Models RC.50 and RC-51 play eight
10" and 12" records, intermixed in any
order, automatically, and the changer stops
operating after the playing of the last record.
A record may be rejected hefore playing the
entire selection by turning the motorooard
knob to the REJECT position.
To operate the changer, raise the forked
arm and place IIny number of records-not
exceeding eight--on the record spindle and
lower the forked arm until it rests on the top
record. Turn the pickup head one·half turn
in a counter-clockwill6 direction lind in.ert a
phonograph needle, returning the pickup to
itll normal position. The needle IIhould be
inserted onl, when the IIrm is locllted on the
rest, a8 movement of the arm when it is in
IIny other position may affect the mechllrusm.
Tum the motorboard knob to the START
position, setting the changer in operlltion.
Be lIure to hold the knob in' this position
until the motor has started and becomes
engaged with the changer mechanism.
Should the changer be stopped for any
reason during, the record changing, it may
be necessary to give it help in restarting hy
turning the turntable by hand, due to the
excessive load imposed on the motor when
it is stopped in such a position. If it is desired
to stop the motor at any time, it may be
126
:\
PHONO·RADIO
tion to decrease the friction. This adjustment is very sensitive and the screw should
be turned not more than a quarter of a turn
at one time.
A6. The record platform, opposite the pickup arm on the motorboard, is normally adjusted to the correct position for all average
records, however if a very large or small
record is encountered, it may be necessary
to make a slight adjustment to the platform
position to accommodate these records. This
is accomplished by removing the nut, washer,
and screw "K" (Fig. lOlA) and turning the
bushing "L" clockwise to accommodate
larger records, and counter-clockwise for
smaller records. Replace the screw, washer,
and nut and check the .platform position by
placing a record on the spindle. If it is correct
the record edge should rest on the platform
just clear of the studs when the changer is in
the playing position.
B6. The record platform, opposite the pickup arm on the motor board is normally adjusted to the correct position for all average
records, however if a very large or small
record is encountered, it may be necessary
to make a slight adjustment to the platform
position to accommodate these records. This
is accomplished by removing the nut, washer,
and screw "Q" (Fig. 100), and turning bush.
ing "N" clockwise to accommodate larger
records and counter-clockwise for smaller
records. Replace the screw, washer, and nut,
and check platform position by placing a
record on the spindle. If it is correct the
record edge should rest on the platform just
clear of the pushing pawl, "12" (Fig 1(4),
SERVICE
when the changer is in the playing position.
A 7. Should the lowering position of the
needle require adjustment, the turntable
should first be turned by hand to bring the
pickup from the loading position to the
point where the needle has descended to
within
of the record. The screw "R"
(Fig. 102) which is accessible through a hole
in the motor board, should be turned either
to the right or to the left according to the
requirements-a quarter turn in either direction will give the maximum adjustment
obtainable. The adjustment should then be
checked by operating the changer and noting
the lowering position of the pickup.
ro"
B7. Should the lowering position of the
needle require adjustment, the turntable
should first be turned by hand, after the
STOP-START lever has been set to the START
position, to bring the pickup from the loading position to the point where the needle
has descended to within
of the record.
If it is seen that the lowering position must
be shifted either to the left or to the right,
the tone arm should be returned to the
"rest" p'osition by hand, at which time the
adjustable screw, whICh is accessible through
a hole in the motorboard near the tone arm
base, should be turned either to the right or
to the left according to the requirements-a
quarter turn in either direction will give the
maximum adjustment obtainable. The adjustment should then be checked by operating the changer and noting the lowering
position of the pickup.
ro"
A8. When making adjustments to the pickup arm, it should never be forced into posi-
DATA
• Section 5
tion, and when the turntable is turned by
hand it should never be turned other than in
a clockwise direction. If the pickup is lowered so that the needle contacts the smooth
surface of the record and does not run into
the playing grooves, check to make certain
that the motorboard is tilted slightly to the
left. Then check the lead to the pickup,
making certain that it is not twisted in any
way to prevent free movement of the tone
arm. Also check levers "S" and "Q" (Fig.
102) to see that they are free and that the pin
at the eRd of lever "Q" i~ not rubbing on the
bottom of the cam grooves. If required, the
pickup height can be adjusted by looseniug
the set screw in the counter-balance weight
"MOO (Fig. 100), and turning the weight while
holding the spindle. If this adjustment is
changed, see that the tone arm lifts high
enough to clear eight records on the turntable.
B8. If, after the playing of the last record
(when eight are played), the needle scrapes
across the surface of the top record as the
tone arm moves to its rest position, the
pickup height must be adjusted in the following manner. Loosen screw "8" (Fig. 102),
and rotate the counter-balance "7" a few
turns in a clockwise direction. The adjustment should be such that at the completion
of the last record, the pickup will move
across the top record with the needle at
least one-half inch above the surface of the'
top record. Tighten set screw "8", completing the adjustment.
CS. If the pickup is lowered so that needle
contacts the smooth surface of the record
and do~s not run into the playing grooves,
check to make certain that the motorboad
is level or tilted slightly to the left as ad·
justed at the factory. Then check the lead to
the pickup, making certain that it is not
twisted in any way to prevent free movement of the tone arm. If the needle scrapes
across the surface of the last record at the
completion of the playing of that record, the
pickup height requires adjustment. Loosen
the set screw in the collar at the bottom of
the pickup arm, lift the spindle and turn the
collar while holding the spindle. A few turns
in a counter·clockwise direction should be
sufficient. Tighten the collar set screw, completing the adjustment.
If the tone arm lowers to the record and
then immediately returns to the rest, it is
possibly due \0 the fact that the STOP-START
lever at the right side of the motorboard is
rubbing on the under side of the motorboard,
preventing the clutch from disengaging.
Bend the lever downward so that it operates
freely.
A9. The record changer automatically stops
after the last record has been played due to
the fact that there is no longer any weight
on the turntable spindle. The weight of a
127
Section 5 •
THE
MY E
TECHNICAL
MANUAL
the oil-retaining type, and with average use
will require lubrication about once every
three months. All oiling holes are accessible
when the turntable is lifted from the motor
spindle and are indicated on Fig. 99. A
few drops of fine oil may be helpful in the
tone arm pivot, if the tone arm shows signs
of sluggishness in moving into the playing
grooves after it has lowered to the record.
i' ,
I I..I' · , ;
I:
A14. The lubrication and speed adjustment
for the universal (AC-DC) motor is the same
as for the AC motor. If the brushes are allowed to become dirty and worn, brush
noise will develop. The brushes may be removed by unscrewing the bakelite caps on
the motor body and pulling out the brushes
by means of the springs. The brushes can be
cleaned by sanding them with a fine grade
of sandpaper or crocus cloth and cleaning
the dust from the surface before replacing
them. It is important that the brushes be
replaced in the same way in which they were
originally installed. The brushes when new
are -to" long under the springs-when they
have worn down to %", they shonld be
replaced.
record on this spindle moves lever "0"
(Fig. 100), which interrupts the movement of
the switch lever "P" (Fig. 100) from the cam,
so preventing the switch from operating.
When the record is removed from the center
spindle, the spindle raises and allows lever
"0" to move so that it does not interrupt the
switch lever "P," thereby allowing the
switch to operate.
B9. The record changer automatically stops
after the playing of the last record, due to
the fact that there is no longer any weight
on the turntable spindle. The weight of a
record on this spindle moves lever "J" (Fig.
101), which interrupts the movement of the
switch lever "K" (Fig. 101) from the cam, so
preventing the switch from operating. When
the record is removed from the center
spindle, the spindle raises and allows lever
"J" to move so' that it does not interrupt the
switch lever "K," thereby allowing the
switch to operate.
A10. Due to the differences of line voltages
in various localities, a slight adjustment of
the speed indicator lever (that projects from
the edge of the turntable) may be necessary.
To make this adjustment, first set the motor
speed to 78 Rpm., using the stroboscope
disc (on AC models) furnished with the unit.
To set the speed on the AC-DC unit. operating on direct current, place a piece of
paper under a record on the turntable and
count the revolutions in a period of 30
seconds. If there are more or less than 39
128
revolutions the speed adjustment lever
should be moved a slight amount in the required direction, and the process repeated.
All. After the motor has been set at 78
Rpm. the turntable should be removed and
the quadrant screw (near the spindle on the
speed-control lever) should be loosened very
carefully and the lever moved until the
pointer is in position on "78" on the indicator plate, holding the quadrant stationary while making this adjustment. Now
tighten the quadrant screw and replace the
turntable.
BU. After the motor speed has been set at
78 Rpm., the turntable should be removed
and the set screw in the collar of the speed
control lever should be loosened very carefully. The speed control lever should be
moved until the knob is in position on the
center mark of the escutcheon. Now tighten
the set screw. Be sure that the screw stud
does not move during this adjustment.
A15. If the automatic switch does not operate at the end of the last record, make
certain that all of the levers are free and that
all the springs are in place. Also make certain
that the turntable spindle is free in the main
spindle--it should move about Ys" when
depressed and should rise the same distance
when released. This test should be made
while the changer is in the playing position.
Switch tripping adjustment can be obtained
by means of a small quadrant adjustment on
the top of the spindle operated by the switch
lever "P" (Fig. 100).
A16. If the first record does not drop when
the changer is switched ON, this is due to the
leather brake pad becoming worn and not
braking the turntable sufficiently when the
previous record was completed. To adjust
this pad, loo,sen the two screws "F" (Fig. 99)
and turn the brake lever slightly to bring the
leather pad nearer to the turntable rim.
Tighten the screws and check to see that the
switch breaks contact before the leather
brake pad touches the turntable rim.
e
A12. If an occasional "slowing up" is noticed
in the reproduction, the trouble is most
likely due to the record slipping, due to its
being warped. If a record slips while it is
being played, examine the center hole for
burrs. These burrs should be carefully removed with a penknife. Warped records
may be flattened by subjecting them to a
warm temperature and pressing them.
A13. The motor should always be "elilubricated, as noise will develop if the bearings
are allowed to run dry. All bearings are of
FIG. 102
I~
P H 0 N 0 - I A D I. 0
SEIVleE
DATA
• Section 5
one record to feed to the turntable at one
time, depending on the direction of the bend.
Extreme care should be tlSed in bending the
sl?indle back into position, should this be·
come necessary, as it may be broken very
easily.
-
=--
A20. If the mechanism should bind during
operation, it may he possible to free it by
depressing the pushing pawl "12" (Fig. 105)
FIGURE 103
BEND LEVER"A" SIDEWAYS TOWARD"B"APPROXJMATELYII16'
AT THE SAME: TIME BEND IT OUT SO THAT IT CONTACTS
"B"NEAR THE CORNER"C~
B16. If the first record does not drop when
the changer is switched QN, this is due to the
leather brake pad becoming worn and not
braking the turntable sufficiently when the
previous record was completed. To adjust
this pad, loosen the screw "F" (Fig. 99) and
turn the brake pad slightly to present a new
surface to the turntable rim. Now tighten
the screw "Ji''' and L-heck the adjustment.
A17. If the records do not drop properly, it
is possible that the forked arm is sprung to
the right, preventing the pushing pawl "12"
(Fig. 105) from pushing the records from the
platform. To correct this condition, spring
the foeked arm to the left a slight degree and
check to make certain that the bottom rec.
ord contacts the smooth surface of the
record platform. The vertical motion of the
record platform may he controlled by adjust.
ating the mechanism. If the motion of the
platform is still not sufficient to push the
records to the turntable; the bushing should
be turned a few revolntions to further
lengthen the lever arm, however, it is not
probable that a second adjustment will he
required.
A19. Occasionally a record may stick to the
spindle and not drop to the turntable as it
should. The record may be excessively thick
and must be removed from the stack. The
reason for the "thick" record sticking is that
the slot at the angle in the spindle is not
sufficiently wide to let the record slide into
place. Never attempt to file this groove as it
will then be possible for two "thin" records
to drop to the turntable at one time.
If the spindle should be hent, it will
either cause records to stick, or more than
and allowing the pickup to come to the rest
position. Tum off the motor and slide the
nameplate that covers the mechanism in the
record platform from its holder, exposing a
small set screw in a stop lever. Loosen the
set screw and move the stop forward a slight
amount. Tighten the set screw and check
the adjustment. If the mechanism still binds,
the stop lever should be advanced a little
more. This position is quite critical and the
lever should not he moved more than -I."
during each adjustment. If the mechanism
should bind as a result of the turntable being
rotated manually, it is probably caused by
the fact that the motor end.hearing has been
forced from its correct position in the end of
the motor frame, allowing the motor gov.
ernor set screws to strike the main gear of
the motor. To correct this conditiOll, loosen
the small set screw that holds the motor e&d.
bearing in place---located adjacent to the
nameplate on the motor frame-press the
bearing in as far as it will go. and tighten
the set screw. This adjustment should per.
mit the motor to operate properly, however,
if it still binds it may be necessary to loosen
this set screw again, rotate the end.hearing
a fraction of a turn and tighten the set screw.
This adjustment may be necessary to keep
the spacing around the armature equal at
all points.
A21. If the quality of reproduction is di&torted, or if the volume of the signal is unusually low, it may be due to a defective
ing the bushing "V' (Fig. 100), after the
nut, screw, and washer at ••K." have been
removed.
A18. If the records do not feed properly
from the spindle, it is possible that the hori·
zontal motion of the record platform is not
llufficient to push the lower record from the
stack on the spindle to the turntable. To
increase the distance of motion, the lever
arm with bushing "N" must be lengthened
by removing the nut and screw "Q," sliding
the bushing "N" from the lever and rotating
the bushing a few turns in a counter-clock.
wise direction. Slide the bushing back to the
lever and install the nut and screw "Q" in
place. Now check the adjustment by oper.
'3
~-~~~~"~ ~ ;(
... ..
lFiG.10~
129
Section 5 •
THI
MY I
TICHNf'CAL
'M A N U A L
crystal pickup. If no signal is heard when the
pickup is used and the radio is operating
,properly, it is probable that the pickup lead
is broken or shorted on the pickup arm. ,
II
A22. To remo'\>e the pickup cartridge assembly. remove screw "I" (Fig. 104) and
pull the cartridge from the arm, examining
the connections to the bakelite terminal
block. To remove the cartridge from the
assembly, remove the two retainer plates
"2" and "3" (Fig. 1(4), and Unsolder the pigtail connections from the bakelite block.
:/
I,',',
I
I'
I,
II,!,
I~
!,
i
B22. To remove the pickup cartridge as·
sembly, remove screw "I" (Fig. 105), and
pull the cartridge from the arm, examining
the connections to the bakelite terminal
block. To remove the cartridge from the
assembly, remove the two retairler plates
"2" and "3" (Fig. 105), and slide the cart·
ridge from the housing.
C22. To remove the pickup cartridge as·
sembly, remove the four screws securing the
cartridge rj'ltainer plate and pull the cartridge
from the arm, examining the connections to
the bakelite terminal block. Pull the plugs
from the bakelite block to free the cartridge
from the arm.
A23. When removing the record changer
unit from the cabinet, first remove the two
connecting co.zds from the radio chassis by
withdrawing their plugs from the sockets.
Disconnect the ground, lead from the radio
chassis by sliding the spade lug from the
securing screw that has been loosened a few
turns. Remove the nuts and springs from the
four mounting screws and lift the unit from
the cabinet. When replacing the mechanism,
be sure that the heavier springs are used on
ibe top of the mounting cleats and the
lighter springs on the' bottom. The changer
should be tilted slightly to -the left, 80 that
the needle will slide into the first grooves of
the record easily.
When replacing the pickup lead plug in the
chassis (on Windsor style numbers CPAR.
320, and CPAR-352 and on Regent style
numbers CPAR-319, CPAR-329 and CPAR356), be sure that the felt ~asher is used
to prevent the metal cap of the male plug
from contacting the radio chassis. If this
rule is not observed, a distinct hum will be
heard in the speakers when the phonograph
is used.
B~.
When removing the record changer
unit from the cabinet, first remove the two
connecting cords from the radio chassis by
withdrawing their plugs from the sockets.
130
I':
FlO) 105
Remove the nuts and springs from the four
mounting screws and lift the unit fr<;lm the
cabinet. When replacing the mechanism, be
sure that the heavier springs are used on the
top of the mounting cleats and the lighter
springs on the bottom, being careful to
mount the unit so that the turntable is
perfectly level.
after the plug has been unsoldered from the
lead.
C23. When removing the record changer
unit from the cabinet, first remove the two
connecting cords from the radio chassis by
withdrawing their plugs from the sockets. If
the metal motorboard of the changer is secured to a wooden sub-base and the entire
assembly "floated," remove the nuts and
springs from the four mounting screws in
the wood sub-base and lift the unit from the
cabinet. If the metal motorboard has beenI
"floated" in the cabinet, remove the nuts
and springs from the mounting screws and
remove the changer in the same manner as
described above. When replacing the mech·
anism, be sure that the heavier springs are
used on the top of the mounting cleats and
the ~ighter springs on 'the bottom. The
changer should be tilted s~ightly to the left
SO that the needle will slide into the first
groove of the record easily.
4. Remove the screw from the casting and
rotate the base 180 degrees exposing another
screw which should be removed from the
casting.
A24. If the bakelite tone arm base should
need replacement, it can be removed by
following the instructions outlined below:
1. Loosen the small set screw "4" (Fig.
104), and punch the pivot pin "5" from the
tone arm using a small punch and ha~er.
2. Lift the tone arm from the base "6"
and pun the pickup lead up from the bottom,
3. Remave the two mounting screws that
secure the tone arm base to the motorboard,
and rotate the base until the large hole in
the rear of the base is directly over a screw
in the casting beneath the motorhoard.
5. Slide the assembly to the rear of the
hoard, removing the lever pins from their
guide slots.
6. Remove the counter-balance weight
"7" by firs t removing the s~t screw "8" and
then turning the weight in a counter-clock.
wise direction until it drops from the shaft.
7. Now loosen the set screws in the bushing "s" and remove the lever arm from the
shaft, holding the assembly over a small box
so that the ban bearings will not be lost.
S. Slip the casting from beneath the base,
off the shaft and replace the bakelite base.
There are fifteen bearings above and fifteen
bearings below the base, that should be replacell before the assembly is reassembled.
9. Reassembly of the unit is not difficult,
however the counter-balance "7" will reo
quire adjustment to allow proper lowering
of the tpne arm to the record. Instructions
for this adjustment are given in paragraph
AS.
PHONO-RADIO
R ( A-
SERVICE
DATA
top of record shelf, the vertical spacing between the knife, in its lowest rotational
position, and the shelf, is .072-.078 inch.
Models RP139A and RP14S
SERVICE
A. Main Lever. This lever is basically im·
portant in that it interlinks the various
individual mechanisms which control needle
landing, tripping, record separation, etc. Ro.
tate the turntable until the changer is outof-cycle; and check rubber bumper bracket
(A). The roller should clear the nose of the
cam plate by approximately -h inch.
B. Friction Clutch. The motion of the
tone arm toward the center of the record is
transmitted to the trip pawl "22" by the trip
lever "7" through a friction clutch "5." If
the motion of the pickup is abruptly accelerated or becomes irregular due to swinging
in the eccentric groove, the trip finger "7"
moves the trip pawl "22" into engagement
with the pawl on the main gear, and the
change cycle is started. Proper adjustment
of the friction clutch "5" occurs when movement of the tone arm causes positive movement of the trip pawl "22" without tendency
of the clutch to slip. The friction should be
just euough to prevent slippage, and is adjustable by means of screw "B." If adjustment is too tight, the needle will repeat
grooves; if too loose, tripping will not occur
at the end of the record.
C. Pickup Lift Cable Screw. During the
record chauge cycle, lever "16" is actuated
by the main lever "IS" so as to raise the
tone arm clear of the record by means of the
pickup lift cable. To adjust pickup for proper
elevation, stop the changer "in-cycle" at the
point where pickup is raised to the maximum
height above turntable plate, and has not
moved outward; at this point adjust locknuts "c" to obtain 1 inch spacing between
needle point and turntable top surface.
D. & E. Needle Landing on Record. The
relation of coupling between the tone arm
vertical shaft and lever "20" determines the
landing position of the needle on a 10 inch
record. Position of eccentric stud "E" governs the landing of the needle on a 12 inch
record; this, however, is dependent on the
proper 10 inch adjustment.
To adjust for needle landing, place 10 inch
record on turntable; push index lever to
reject position and return to the 10 inch
position; see that pickup locating lever "17"
is tilted fully toward turntable; rotate mechanism through cycle until needle is just ready
to land on the record; then see that pin "V"
on lever "14" is in contact with "Step T" on
lever "17." The correct point of landing is
4% inches from the nearest side of the turntable spindle; loosen the two screws "D" and
adjust horizontal position of tone arm to
proper dimension, being careful not to disturb levers "14" and "17." Leave approximately -i> inch end play between hub of
lever "20" and pickup base bearing, and
tighten the blunt nose screw "D"; run mechanism through several cycles as a check, then
• Section 5
tighten cone pointed screw "D."
After adjusting for needle landing on a
10 inch record, place 12 inch record on turntable; push index lever to reject and return
to 12 inch position; rotate mechanism
through cycle until needle is just ready to
land on the record; the correct point of
landing is 5% inches from nearest side of
spindle. If the landing is incorrect, turn
stud HE" until the eccentric end adjusts lever
"14" to give correct needle landing. The
eccentric end of the stud must always be
toward the rear of the motor board, otherwise incorrect landing may occur with 10
inch record!!.
F. & G. Record Separating Knife. The
uppeJ plate (knife) "25" on each of the
record posts serves to separa!e the lower
record from the stack and to support the
remaining records during the change cycle.
It is essential that the spacing between the
knife and the rotating record shelf "27" be
accurately maintained. The spacing for the
10 inch record is nominally .055 inch, and
for the 12 inch record is .075 inch.
To adjust, rotate the knife to the point of
minimum vertical separation from the record
shelf and turn screw and locknut "F" to give
.052-.058 inch separation. Screw "G" must
not be depressed during this adjustment.
After setting screw "F," adjust screw "G"
so that when its tip is depressed flush with
H. Record Support Shelf. The record
shelf revolves during the change cycle to
allow the lower record to drop onto the turntable. Both posts are rotated simultaneously
by a gear and rack coupled to the main lever
"IS," and it is necessary that adjustment be
such that the record is released from both
shelves at the same instant. To adjust, place
a 12 inch record on the turntable, rotate
mechanism into cycle to the point where
both separating knives have turned clockwise as far as the mechanism will turn them;
lift record upward until it is in contact with
both separating knives. Then loosen screws
"H" and shift record shelves "27" so that
the curved inner edges of the shelves are
uniformly spaced approximately -h inch
from the record edge. Some backlash will be
present in the rotation of these shelves. They
should be adjusted so that the backlash
permits them to move away from the record
but not closer than the approximate -h inch
specified above. Tighten the blunt nose
screw HR," run mechanism through cycle
several times to check action, then tighten
cone pointed screw "H."
If record shelves or knives are bent, or not
perfectly horizontal, improper operation and
jamming of mechanism will occur.
J.
Tone Arlll Rest Support (not shown).
When the changer is out-of-cycle, the front
lower edge of the pickup head should be fo
inch above surface of motorboard. This may
be adjusted by bending the tone arm support
bracket, which is associated with the tone
arm mounting base, in the required direction.
FIG. 106
131
THI
SectIon 5 •
K. Trip Pawl Shop Pin. The position of
the trip pawl stop pin "K" in relation to the
main lever "15" governs the point at which
the roller enters the ~am. By bending the pin
support either toward or away from trip
pawl bearing stud, the roller can be JIlade to
enter the cam later or earlier, re~pectively.
This adjustment should be made so that the
roller definitely clears the cam outer guide as
well as the nose of the cam plate.
Lubrication. Fetrolatum or petroleum jelly
should be applied to cam, main gear, spindle
pinicm gear, and gearR of record posts.
Light machine,oil should be used in the
tone arm vertical bearing, record post bear.
ings, and all other bearings of various levers
and pulleys on underside of motor board. The
turntable spindle bearing of RP·145 must be
lubricated from the top of the motol'lboard.
Using an oil can with a long spout, reach in
between the turntable and motorboard and
apply oil directly to the spindle.
On Model Rp·139·A apply a few drops of
light machine oil (SAE·IO) to the motor oil
hole adjacent to the spindle bearing after
each 1,000 hours' of operation. Tbe oil hole
has a screw plug.
Do not allow oil or grease to come in con·
tact with rubber mounting of tone arm base,
rubber bumper, rubber spindle cap, or rub·
ber parts of friction drive mechanism of
Model RP·145.
MY I
TECHNICAL
MANUAL
E. Adjust at "EO. to provide approximately
-h of an inch between outer end of "Liuk
Slot" and screw when rubber "Bumper" is
ir. contact with stop bracket.
F. and G. Remove rubber silencer at "F"
and adjust "F" and "G" so ejector tip "F"
is in line with "Spindle." Longitudinal move·
ment, with respect to "Ejector Arm," may
be effected by loosening hex. head at "F."
Lateral movement of "Ejector Arm" may
be effected by adjustment "G."
H. Adjust "H" so under side of pickup head
can be raised 2Yz inches above motorboard.
J. Adjust screw "J" until friction will just
force "Trip Finger" to mov;e "Trip Pawl"
when "Index Lever" is in "12" inch position.
N. Adjust needle pressure by turning screw
under center of "Pickup Arm" so that a
force of 72 grams (2.5 ounces) is reqnired to
lift needle from the record. Hook scale under
needle screw to measure force.
I
Mount motorboard on a level support.
Remove turntable and cover at rigbt of
turntable. Adjustment locations are desig.
nated on Fig. 108 as "A," "B," etc. The ad·
justments are explained under corresponding
symbols below. Perform adjustments in the
following order:
A. Trip rod "A" should be engaged in
"Switch Lever" slot. Adjust trip rod "A" to
obtain about U of an inch clearance from
motorboard.
B. Adjust "B" to the position shown.
C. With "Index Lever" in "Manual" posi.
tion. "Pickup Arm" rotated to extreme left,
and switch tripped to open contacts "C,"
adjust contact points "C" by bending the
stiff contact arm until points are opened 10
to 30 thousandths of an inch.
D. With "Index Lever" in "Manual" posi.
tion. release set IIcreW "P" lind force "Man.
ual Index Finger" as far as it will go towards
"Trip Pawl Stop Pin." Tighten set screw.
27
FIG. 107
132
\
I,
I.,I
RECORD CHANGER ADJUSTMENTS
III
I
K. Adjustment "N" must be performed
prior to this adjustment. With a 12" record
on turntable, turn on "Motor Switch," place
"Index Lever" to "12" position and adjust
Model UI09
COliER
I
FIG. 108.
AUTOMATlC RECORD CHANGER ADJUSTMENTS.
(Top and bouom views.)
PHONO·RADIO
"K" so that "Cable" tension will allow
needle to lower slowly on start of record at
completion of eject cycle. Turn "Motor
Switch" oft" aher eject cycle i8 completed and
check to see that "Cable" is slightly loose
when "Pickup Arm" is moved against
"Spindle." Replace turntable and put a
needle in "Pickup."
L. Adjust "L" so needle will drop into
center of smooth portion at the start of a 12"
record when "Index Lever" is in "12" inch
position and "Pickup Arm" is to extreme
right.
M. Loosen three screws "M" and rotate
"Spacer" untll pointer on "Spacer" is in line
with ICrew to right of "Pickup Arm."
P. Adjust turntable height by insertion or
removal of thrust washers at "P" 80 ejector
wlll not eject bottom 12" record but will
eject second from bottom record.
Q. Adjust position of shorting switch at
"Q" so switch closes wh~ needle is just
outside a 12" record.
R. Adjust screw "R" upward just enough
80 that with one record on 'turntable and
ejector tip "F" resting on record surface,
there is if of an inch clearance between
screw "R" and "Ejector Arm."
RECORD CHANGER SERVICE HINTS
1. "Ejector Arm" goes through normal
cycle but does not eject records. Adjust "F"
and "G." See that "Spindle" slides freely.
S.RVIe.
2. Ejects bottom record. Lower turntable
by removing thrust washers at "P."
3. Ejects records properly down to second
from bottom of pUe. Raise turntable by
placing thrust washers at "P."
4. Eject cycle does not start aher needle
reaches eccentric groove. Adjust "1" (turn
screw clockwise).
5. Eject cycle starts before eccentric record groove is reached. Adjust "1" (turn
screw count~r-clockwise). Set "Index Lever"
to "12" inch or "10" inch position after
starting to play record. Do not jar motorboard during automatic operation.
6. Lateral movement of "Pickup Arm"
has no control over starting and stopping.
Adjust clearance of rod "A." See that rod
"A" engages in Illot of "Switch Lever."
7. Fails to eject top record of a pile because "Ejector Arm" strikes record in returning to center at end of eject cycle. Ad.
just screw uR" upward to provide greater
incline so that roller in "Ejector Arm" will
roll back 'during cycle.
8, Pickup strikes record during eject cycle.
Adjust "K" and "H."
9. Starts playing record several grooves
in from beginning or needle millses record
entirely. Adjust "L."
10. Needle falls on smooth portion at start
of record but does not move into playing
groove. Adjust "M." Check to see that
motorboard is level.
DA1A
• Section 5
11. Automatic stop does not operate after
needle reaches eccentrc groove. Adjust "B"
and "C."
12. Motor does not restart when "Pickup"
is returned to rest position. Adjust "C." See
that switch mechanism parts move freely
and springs are functioning.
IS. Starts eject cycle although set for
"Manual" operation. Adjust "D."
14. Noise in loudspeaker while changing
needles. Clean "Shorting Contact" and adjust "Q."
IS. "Wow" in record reproduction-In.
strument should be warmed to about 65 0 F.
Ejector tip should be centered and free to
rotate (adjustments "F" and "G"). There
should be no solid particles on gear teeth or
in grease; no tendency to bind. Turntable
plate should be in dynamic balance and
"Spindle" should be straight. Proper lubrication is important.
Lubrication. Clean motor gear-box thoroughly before regreasing. Apply less than a
tablespoonful of a grease, sucb as "Cities
Service No. 70SS.Al" or "Koolmotor Uni·
versal Trojan .No. 1," directly on gears
taking care to get none in rotor bearings.
Put medium motor oil (S.A-E. No. SO) in
the oil holes. Cover main gear and cam of
automatic mechanism with a light grease
such as "Sooony.Vacuum No.2." Any good
household oll, Lluch as "S·IN -ONE" is sultable lor the ejector,-tip "F" bearing.
MALLORY TECHNICAL INFORMATION SERVICE
• Throughout its long association with the radio
and electronic industry the Mallory organization has
consistently given its services or advice on technical
problems submitted by those who have seen or heard
of our ofters to help to the best of our ability. That
we have made good on 'our ofter is evidenced by the
many letters of appreciation we'have in our files for
services large or small.
There is no charge or obligation for this servic~,
and many have asked how we can justify the cost of
such a service without direct monetary return. Our
answer has been essentially as follows:
1. Any help which we render to the field, the
serviceman, or the ultimate consumer reflects as a
general credit to the industry of which you and we
are a part.
2. In many past cases, our work and study on
problems submitted has been of real value to ourselves in obtaining a dearer picture of maintenance
operations, in finding new applications, or substantially iqtproving product features for existing ones.
In view of the present restrictio,!s on the design
and manufacture of electronic parts, we realize that
the field will be faced with an increasing number of
problems relating to changeover, adaptation, etc.,
with the limited types available. We reaffirm our
desire to help, and ofter the benefit of the experience
and knowledge of our technical personnel, to all
who request it.
Add,.",
TECMNICAL INFORMATION IIRVICt
Who,••a'. DIv,.'on
P.
R.
MAL LOR Y
&
CO.,
INC.
3029 I. W..hlnato.. • Indlonopoll.
133
THE
Section 5 •
MY E
. Webster-Chicago SERVICE
The changer plays twelve lO-inch or ten
12-inch records. To reload, revolve the two
posts sJightly, 'grasping them underneath the
shelf plates. Turn them back after the played
records are removed; they will fall and lock
when they are in the proper position. Place
the new records on the shelf plates and push
hutton "R" to put changer in operatiou. To
play the other size records, turn the knob at
the top of each post until the proper figure is
opposite the pointer. Press the "10" or "]2"
button, to agree with the pointer setting. To
reject a record (or to start a change cycle as
for testing purposes) simply press the "R"
(release or reject) button, at any time while
the needle is upon a record. To play manually, turn plates out of the way as for reloading, and press button "M."
The photos illustrate all the vital parts of
the changer. Letters are used alphabetically,
to refer to points on the photos; thus, motor
oiling holes "AK" are found by glancing
down column "A" (left side of Fig. 109) to
leiters "AK."
TECHNICAL
MANUAL
Models 11 and W1270
, the proper points; through the hole marked
"AM," see felt wick and drpp the oil directly
upon it; through the hole marked "AN," see
felt wick and drop the oil directly upon it.
l { squeaks are heard compare the squeak
with and without a load of records; any
stack of wax records in motion is likely to
squeak a little against a pin through their
'Center. ,See that all five wicks are in position,
including three %-inch round wicks in frame
of motor, one washer-shaped wick on lift
"CV," and one on cam lever "CS." See that
each wick is thoroughly saturated (as it may
not be if insufficient oil or too heavy oil has
been used). Lift out all three motor wicks,
with tweezers; see if old oil has become
gummy (commonly due to use of low-grade
oil or low-viscosity oil). If necessary, clean
gummed-up wicks with Kerosene. See that
each is saturated with good oil; then, before
replacing them, drop a little good oil into the
holes. The gearbox of the motor is packed
with a semi-fluid grease at the factory, and
it should not be necessary to take it apart
for lubrication purposes.
Change Cycle
Oilin~
The changer should be lubricated once a
year with about a dozen drops of good light
machine oil at each of the following 6 points:
(All points can be reached from above,
through holes in the mounting plate.) Three
oil holes ou motor gear housing; reach all
three through two holes "AK;" through hole
marked "AL," drop the oil upon the flat
surface of the cam, it will distribute itself to
PI./SH BUTTON ASSEMBLY hR"
, II
,,'
1\
, II "
I!" " ,
II
'II.
\I
"M"
"t2~
"10"
An automatic record player for records of
two sizes has three principal duties to perform. These duties are here performed by
three mechanisms, interconnected and built
together but largely separate in their operation.
(I) The record-changing mechanismbrought into operation originally by the
contact oflifter cam "DG" with pawl "DH"
-is the simplest of the three. It is driven by
the cam groove (not visible) on u,mler side
(in Fig. 110) of cam gear "DF." As cam lever
"CS" is forced, by the pawl, out underneath
lift "CV" (which is shown revolved to the
right for visibility) the lift rises and forces
roller "DJ" into the under groove in cam
gear. The motion is transferred to rear
changer shaft (at "ED") through cam connecting rod "DE" ("EC"), thence through
changer connecting rod "FD" to front
changer shaft "BB."
(2) The pickup-operating mechanismlikewise brought into operation originally
by the cam-and-pawl action upon cam lever
"CS" is driven in part by the groove in upper
(visible) side of cam gear "DF." As cam
lever is forced out, at the beginning of the
change cycle, against link "CG," it causes
the link to push upward upon pickup plunger
"DA," thus lifting needle from rec~rd. The
same pressure upon link "CG" works,
through guide arm "CD," to force stud
"DD" down into the groove on the cam
gear. This rotates the pickup arm, while
pickup plunger "DA" holds it up off of
record. It is rotated first out beyond the
turntable until selector plates "BL" have
dropped the next record, then rotated back
to proper position to start playing.
(3) The mechanism for bringing needle
into correct starting position must operate
accurately for both lO-inch and 12-inch records. Partly due to this requirement, the
starting position is not determined by the cam
action. The upper groove on cam gear is designed so that it, acting alone, would carry
the needle farther back toward record pin
than would ever be desirable as a starting
adjustment. Travel of pickup arm toward
record pin is then stopped, at proper point
for lowering onto the record, hy action of
lever hub "CL." The stopping takes place as
lug "EW" (upon the lever hub) strikes the
shoulder on rod "EX." This enables the entire mechanism rotated by cam action on
guide arm "CD" to travel on past the proper
point of rotation for record-starting, while
the pickup arm itself, which is held rigid to
BA CHANGItR
8a·
\I"
. SI'~.A11II'"'I"\ ..
Be
CHANGER POST'
,PICt
. ' ...'
~~ ~~f~G~R CONNl!C'tING !roo.
EA
EB
EC
ED
E'e'
e'F
EG
~~ rlL~~~tl:RSI;:EEVI!:
(a R!U'D)
FH MANUAL KEY ROO '
F'I REuECTJON ROO
F.) MANUAL
FUt..!. ROO SPRINt).
FK EXTENSIQN. ROo .
FL KEY CONT. BRACKET.
a
~r
1M) SUe-pL.ATE AND GEAR ASSM .. E.!
AD", ROO ASSM.
EK
CONNl!:CT1NG ROO LIFT (CY) El.
CONNECTING ROD L.iFT SPRING EM
CHANGER MODEL NUMBER EN
n
SERIAL
U
EO
RE.JECTlON 1>,00 SUPPORT
Ep
AD". ROO LEVE:R SPRING
EQ
PICKUP LEADER SPRING (CO) ER
PICKUP CORD ES
POST NUT ET
SHAXEPROOF WASHltR EU
MALE PLUG
EV
LUG ON LEVER-Hue ASSM. EW
AD..). ROD EX.
FIG.
UNIT
FN AD.). ROO sPRING
FO CONT. UNIT TRUSS SAl"!
FP NEEOLE LANDING AOu'lNG CAM
FQ AO,JUSTING ROD SRACKtt
FR PICKUP CARTRIDGE
FS CARTRIDGE CLAMP
f'T TONE ARM LIFT PLATE
FIJ HINGE PIN SPRING
f'V TONE ARM HINGE PIN
IlL The correct adjustment for the starting position of the pickup arm requires only the correct adjustment of rods EX and FK.
not have been properly done; old oil may
have become gummy.
(b) Changer may have been in a very cold
place, and may not yet have reached room
temperature. Give it a fair chance to get
warmed up before concluding that motor is
defective.
(4) Squeaks or other noises, during playing
of records.
(a) Check oiling.
(b) See that all setscrews are tight.
(5) Motion of pickup toward recoril pin
will not trip clwnger mechanism.
(a) (Only on models not having trip adjustment hole "AR:') It may be found that,
instead of trigger being actuated, there is
stretching of swivel spring "CK," allowing
the spreaders to open. Increase tension of
the spring, by bending the lug on either
spreader slightly. If this increased tension
causes needle to jump across the record,
needle may he a little out of vertical, radially-it may lean toward center of record.
To remedy this, grasp pickup arm and twist
it, very slightly, in a clockwise direction
(looking from needle end) so that it stands
vertical, or even leans a little in outward
direction.
(b) ] f trigger is being properly actuated,
prohahly cam lever "CS" is hinding against
suhplate "CU." Look for dirt or ohstruc, tions; see that pawl "DH" and trigger "CP"
are working freely on their rivets. If the
lever engages the pawl so that lift "CV"
forces roller "DJ" up into the under groove
on cam gear, and, if setscrews are tight, the
change cycle must operate, as cam gear
turns.
(6) Pressing button" R" doesn'ttrip changer
mechanism'.
(a) Check key control unit "FM": see
whether there is an obstruction or a bent
part which prevents operation of button
"R" clear down to the end of its travel.
(b) Examine reject. rod "FI." If it does
not trip, even when properly revolved by
complete depressing of button "R," the rod
has probably been bent, and must be restored in same way. Grasp the two ends and
twist it slightly.
(c) If trigger "CP" is being properly actu-
136
fM
ated but without starting a change cycle,
see directions above.
(7) Pressing button "M" jails to put
changer mechanism out of action so as to
enable manual operation. First see that button goes clear down; then follow its action
through manual rod "FH."
(8) Motor stops immediatply when changer
switch is turned off during a change cycle
(instead of continuing to run, as it should,
until needle is again upon a record, and
then stopping). Or(9) Turning on-off switch jails to stop
changer at all. Either of these two conditions
would indicate flliture of cycling switch
"EH." Cycling switch operates normally
to short-circuit the manual on-off switch
(which may be located in position shown
at "FA" or elsewhere) during change cycle
only. Such damage to cycling switch (not
likely to occur) would necessitate returning
either the subplate assembly or the entire
changer to factory.
(10) Needle lands properly on record but
fails to move over into record groove. Pickup
arm is normally impelled toward center of
records by lead spring "ER." Should a
slight increase in its tension be found necessary, this can be easily obtained by bending
the lug, to which it is attached, down against
main plate. If tendency then appears for
needle to jump acrOS8 record, check angle
of needle.
(11) Records jatl unevenly upon turntable.
Seldom objectionable (some unevenness may
even be advantageous); this is due to record
pin not hei~g correctly centered between
changer posts. If necessary, it can be corrected as described above.
(12) Last record drops on one side only.
This suggests a changer post bent out of
perpendicular to main plate. Test as directed above. If post must be straightened,
be careful not to bend other parts.
(13) Changer continues cycling. Probably
due to failure of lift "CV" to be drawn back
out of engagement with c.am gear. Check
the various rivets at which motion occurs,
to find the point where friction or binding
is interfering with freedom of motion.
(14) Record is driven, but not heard, or
not heard with proper volume. See that pickup
cord is plugged in. Check amplifier· and
speaker and connections to them, thoroughly. If then trouble is still suspected in
pickup, test its output with a vacuum-tube
voltmeter. Playing an average record, output
should test 1 to 2.5 volts if pickup cartridge
is of crystal type, or 0.5 volt if of magnetic
type. If pickup cartridge is found not to
deliver proper output, remove it and install
another.
•
(15) Selector plate jails to separate bottom
record from stack. This is due either to a
badly warped condition of the record, or
to its being of a thickness very considerably
different from those now in standard use.
The design of both selector and shelf plates
is such as to accommodate a maximum
variation in thickness and flatness of records,
but certain records may be found which are
so far out as to be impracticable for use in
automatic changers.
If Necessary to Disassentble the
Changer
First detach the entire changer mechanism
(except changer connecting rod assembly.
"FD" and cam connecting rod assembly
"DE," also seen at "EC") from main plate
"ED." To do this, first take out shoulder
screw "CT," to free the rest of the mechanism from assembly "DE." Then remove the
three screws "AO," which hold subplate assembly "DJ" to main plate "EB." Also remove screw "BN," which holds cam gear
"DF." Pull off the four key control buttons.
Remove the two screws that hold key control and "FM". to main plate. Now remove
control unit truss bar "FO," rejection rod
support "EP," and extension rod bracket
"FQ"-this means taking, out five screws.
Remove flat spring "FJ," by taking out one
screw. Rods "FH" and "FI" can then, with
due care, be extracted without bending.
Free the cam connecting rod assembly" D E,"
by loosening setscrew holding spreader hub
"EE" to rear changer shaft. In reassembling,
reverse the prO'cedure, taking care to ge t all
springs properly connected as shown in the
photos, without stretching any of them.
I.
1
I
I:
e Section 6
THE MYE TECHNICAL MANUAL
Automatic Tuning
MALLORY
137
Section 6 •
THE
MYE
TECHNICAL
AUTOMATIC
The past four years have witnessed the widespread
adoption of automatic tuning systems by practically
every radio receiver man,ufacturer. The appeal of this
feature to the public has been fostered by intensive
sales promotion and advertising campaigns which have
established it as a necessary adjunct to a modern receiver. It presents to the radio service engineer a
unique opportunity for the establishment of closer
customer contact since the original setup of selected
stations as well as the maintenance of continued satisfactory automatic operation is a function which he
alone is technically capable of rendering.
As everyone acquainted with radio receiver details
will realize, automatic station selection is not a new
development but rather a refinement and perfection
of principles which have been in use for several years
past. It is interesting to note that the continued progress
towards the ideal of simplification of the tuning requirements of radio receivers has been the result of a
series of cycles in which improvements in mechanical
design have in every case followed and been initiated
by the introduction of new radio circuits. In the present
case the development of automatic frequency control
of superheterodyne oscillator~, stabilization of drifts
due to temperature and humidity and the expansion of
IF amplifier circuits have simplified the design of automatic tuning devices by allowing considerable latitude
in the mechanical and electrical precision of selectors.
The present article is a combinat,ion of the texts appearing in the 2nd Edition Radio Service Encyclopedia
(pages 249-274), and the Automatie Tuning Supplement Number 8 to the 3rd Edition Radio Service Encyclopedia. In each of these articles a system of listing
all models in table form with reference to specific portions of the text applying to the particular model was
used, and the present article continues this method.
The present article has a greater utility not only because of integrated form but also because it combines
the basic theory of operation as covered in the 2nd
Edition with the specific set-up and service information appearing in the Supplement.
In setting up this reference system it has been nec138
MANUAL
TUNING
essary to classify the material under nine headings as
follows:
Section 1
Section 2
Section 3
Section 4
Section 5
Section 6
Section 7
Section 8
Section 9
Mechanically Operated Manual Types
Tuned Circuit Substitution Types
Motor Operated Types
Electric Tuning Motors
Station Selector Switches
Transfer Devices
Silencing Equipment and Operation
Station Selector Commutator Devices
Special Mechanisms
Some of the sections have subdivisions to cover the
many variations of a basic operation and references in
the table are made directly to the subdivision in such
cases. Two subdivision references are frequently given,
one for theory of operation, and the second for specific set-up data.
The column headed "Type" in the reference table
actually names variations of the three main types, that
is, manually operated, circuit substitution, or motor
operated. For instance, it is more informative to refer
to a particular system as dual mica, or mica and permeability type rather than to the general classification
of tuned circuit substitution.
The column headed, "Number of Buttons,." refers to
the number of sele~tors actually used for station reception. Transfer buttons, tone control buttons, etc.,
are not included in the number shown.
The "Special Descriptions" column refers to portions of the text devoted to transfer devices, audio
silencing systems, etc., applicable to models carrying
the reference. Altogether there are seven subheadings
under the Special Description classification as follows:
Button Indexing Adjustment, Tuning Motor, Push-Button Station Selector Switch, Transfer Device-Manual
to Automatic, Audio Silencing Circuit and AFC
Release During Tune, Station Selecting Commutator
Device, and Stop or Lock-In Mechanism.
It should be noted that the method of referring receivers of one manufacturer to those of another manufacturer for illustrative purposes does not indicate that
the receivers are identical or even similar; only that
the automatic tuning device operation is basically the
same.
AUTOMATIC
TUNING
REFERENCE
MANUFACTURER
AND MODEL
AIR KING
910,911 ............... .
ALLIED
A9757, A9758 .............. .
B10525, BI0526 ... '" ..... .
BI0537, BI0538, BI0539 .... .
BI0540, BI0541, BI0542 ... .
BI0580, BI0581, BI0582 ... .
BI0799 .................... .
EI0704 .................... .
EI0705, EI0706 ........... .
EI0707, E10708 ........... .
EI0709, EI0710 ......... '"
EI0711, EI0712 ........... .
EI0718, EI0720 ........... ..
EI0721, EI0722, EI0723 .. .
EI0726 .................... .
EI0727 .................. .
EI0728 ................... .
EI0740 ................... .
£10741, EI0742, EI0743 ... .
EI0744, EI0745 ........... .
EI0751 ................... .
EI0773, EI0774 .......... .
EI0786, EI0788 .......... .
EI0790, EI0794 .......... .
EI0795 .................... .
EI0797, EI0798, E10799 .... .
EI0800 .................... .
EI0806 .................... .
EI0807, EI0808, EI0809 .... .
E10810, EI08H, EI0812 .... .
E10813, EI0814, EI0815 .... .
E10825, EI0826, El0827 .... .
EI0828, E10829, EI0830 .... .
EI0840, EI0841, E10842 .... .
EI0850, EI0851. ......... .
EH)870, EI0872, EI0874 .... .
E10875, EI0876, EI0877 .... .
E10880, EI0881 ............ .
EI0882A to EI0887 A ....... .
EI0890 .................... .
EI0893, EI0894, EI0895 .... .
EI0897, EI0898, EI0899 .... .
EI0900, EI0901, EI0902,
EI0903 ................ '"
EI0905 ................... .
EI0906, EI0907 ............ .
E10920 ................ .
AUTOMATIC
855,892 .................. .
No.
of
But·
Sec-
tons
tion
SubDivision
Dual Mica ......... .
5
2
2A,2B
Telephone Dial. .... .
Motor Operated .... .
Motor Operated .... .
Telephone Dial ..... .
Telephone Dial ..... .
Rocker Bar ........ .
Cam and Lever . ... .
Rocker Bar ........ .
Rocker Bar ........ .
Dual Permeability .. .
Dual Permeability .. .
Rocker Bar ....... "
Rocker Bar ........ .
Dual Permeability .. .
Rocker Bar ........ .
Dual Permeability .. .
Rocker Arm ....... .
Dual Permeability .. .
12
8
8
10
12
6
4
6
6
7
7
6
6
7
Type
1
3
3
1
1
1
IE
"aD' .....
1
1
2
1
2
1
Cam and Lever ... .
Rocker Bar ........ .
Rocker Bar ........ .
4
6
7
6
7
6
6
4
8
6
6
8
4
5
4
6
1
lC
IE
IB, IBI
lA,1Al
IB,1B1
IB, IBI
2B
2B
IB, IBI
IB, IBI
2B
IB, IBI
2B
IB, lBl
2B
3B
1A2
2B
1B
IB
IB
2B
1A1
IBI
2B
IBI
2B
IBI
lBl
lAI
3B
2B
2B
3£1
1B
lA2
IBI
IBI
Dual Permeability .. .
Dual Permeability . . .
Rocker Bar ..
Rocker Bar ..
9
4
6
4
2
2
2B
Permeability & Mica.
6
2
~a~O!2rL~~t::
. . :::
Dual Permeability .. .
Rocker Bar ........ .
Rocker Bar ........ .
Rocker Bar ........ .
Dual Permeability ..
Cam and Lever . ... .
Rocker Bar ........ .
Dual Petmeability .. .
Rocker Bar ........ .
Dual Permeability .. .
Rocker Bar ........ .
Rocker Bar ........ .
Cam and Lever . ... .
Motor Operated .... .
Dual Permeability .. .
Dual Permeability .. .
:t::k!r~::.a.t~~:::: :
6
7
4
6
8
5
5
4
4
5
9
1
1
1
2
2
1
1
2
1
2
1
2
3
1
2
1
1
1
2
1
1
3
2
2
3
1
1
1
1
1
• Section 6
SPECIAL DESCRIPTION
Button
Indexing
Adj.
Tuning
Motor
PushButton
Station
Selector
Switcb
5B
1C4
.. 'ic~i'"
.. ·4B· ...... ·SB· ....
4B
5B
Transfer
Device
Manual to
Automatic
Station
Selecting
Commutator
Device
t,::r-'i~
Mechanism
60
6B
60
60
... 6B.. · ..
lC4
Audio Silencing
Circuit and
AFC Release
During Tune
7D,7K2
7H,7K4
7H,7K4
7A
7D,7K2
8C
8C
... 4B" ... . .. SB" ... . .. 6D .... . .. 'iii,' 7K4 .. . ..
8C
.. ,4B" ...... i;iJ ....... iiD .. .. .. 'iii,' 7K4 . .. ..
8e
2B
IB
IB
5B
6B
................
1-------1----------1-----
BELMONT
408A ....................... Cam and Lever.
5
1
IA1
418A ....................... Cam and Lever.
6
1
1Al
501A ....................... Cam and Lever.
5
1
1Al
5HA ....................... Cam and Lever.
6
1
1A3
517A, 519A, S20A, 52lA ...... Cam and Lever.
6
2
2B
524A ....................... Cam and Lever. . . ..
6
1
lA3
526, 527, 529, 531B. . . . . . . . .. Cam and Lever. . . . .
5
1
lAl
553A ....................... Cam and Lever.....
6
1
lAl
577A, 577C, 579 ............. Cam and Lever. ....
5
1
IA4
582, 583A, 6lIA, 612A. . . . . .. Cam and Lever. . . . .
6
1
IAI
632A, 633A, 634A, 63SA, 636. Cam and Lever. . . . .
5
I
IAI
637 A, 638.. .. .. .. .. .. .. .... Cam and Lever.. .. .
6
1
1Al
665A ...................... Cam and Lever. .. ..
6
I
lA3
676A ....................... Cam and Lever. .. ..
6
I
lAS
677. . . . . . . . . . . . . . . . . . . . . . .. Cam and Lever. . . . .
6
I
lA4
678. . . . . . . . . . . . . . . . . . . .. .. Cam and Lever. . . . .
6
I
IA5
751A ....................... Cam and Lever.....
6
I
lA6
761A, 765A ............. , . .. Cam and Lever. , . . .
6
1
lA3
767A ....................... Cam and Lever. ....
6
1
lA6
791A ....................... Cam and Lever.. ...
6
1
IA3
792, 793. . . . . . . . . . . . . . . . . . .
Cam and Lever. . . .
6
1
lA7
6
1
lA8
794 ......... '............... Cam and Lever.....
796,797 .................... Cam and Lever....
6
1
lA3
·'iB.. · ........
860 ........... , ..... , ...... Cam and Lever. . ...
8
1
lA3
7B
860A ....................... Cam and Lever.. ..
8
1
lA3
867A........ ............... Cam and Lever ....
6
I
lA6
1075A, 1075B. . . . . . . . • . . . . .. Dual Permeability. . .
6
2
2B
.. ·'iB···········
1175... ............ ........ Cam and Lever. . . ..
8
1
lA3
7B
1175A ...................... Cam and Lever.....
8
1
1Al
....................................... .
BUICK
1---------------1--------1-------1--------1-------1-------1-------1------------1-----980598, 980620 ......... , ... . Rack and Pinion . ...
5
9
90
CADILLAC
1433970 ................... . Permeability Tuners.
S
2
2B
CHEVROLET
985283 ................ , ... .
985425, 985426 ........ , ... .
8
5
8
1
8D
IB2
5
4
5
2
2
2A
2A
2A
CLARION
55A, 57A, 58B. .............
70X. . . . . . . . . . . . . . . . . . . . . ..
93,1105....................
---------------1---Dual Mica ......... .
Dual Mica ......... .
Dual Mica ......... .
2
........................................................................
139
THEM Y E
Section 6 •
TECH N I CAL
MANUAL
REFERENCE
MANUFACTURER
AND MODEL
Type
No.
oE
But·
Sec~
Sub.
tons
don
Division
Button
COLONIAL (Sea.... -Roebuck) .
4610,4666,4686 ............ .
46111 ...................... .
4786 ...................... .
4787 ...................... .
4791,4792 ............... .
Telephone
Telephone
Telephone
Telephone
Telephone
Dial .....
Dial. ....
Dial. ....
Dial. ....
Dial .....
.
.
.
.
.
11
11
11
11
11
CONTINENTAL
SA ........................ .
5B ........................ .
6B,6C .................... .
6G ....................... .
6K ...................... ..
7G, 8A, 8AU .............. .
9G, 11A, 118, 16R, 16S.
55 ..................... .
Cam and Lever ....
Rocker Bar ........
Motor Operated ....
Dual Permeability ..
Rocker Arm .......
Dual Permeability ..
Motor Operated .. .
Cam and Lever.
.
.
.
.
.
.
4
4
6
6
4
6
8
5
I
I
3
2
I
2
3
I
IA1
lBI
3B
2B
IB1
2B
3B
lA2
Rocker Bar ........ .
Rocker Bar ........ .
5
5
4
5
1
1
1
1
1
1
1
IB3
IB3
IB3
1B3
IB3
IB3
IB3
CROSLEY
A158, A168, A169, A258 ..... .
A268, A3S8 .......... .
418,428 ................•....
438M, 448 ................. .
458 ....................... .
548 ................. ..
588,598 ................. ..
617 ....................... .
628,638 ................... .
648 ....................... .
718,758,818 ............ .
828 ....................... .
1018 ...................... .
1118 .................... .
1127 ...................... .
1137, 1227, 1237 ....... .
5628 ................. .
Rocker Bar ...... , .
Rocker
Rocker
Rocker
Rocker
Bar ........ .
Bar ........ .
Bar ..... .
Bar ....... .
4
5
4
Motor Opera ted .... .
Rocker
Rocker
Rocker
Rocker
Rocker
Bar ........ .
Bar ........ .
Bar ........ .
Bar ..... .
Bar ........ .
'Motor Operated .... .
Motor Operated .... .
tt:ctk':r ~ae:~.t~~.' . : ..
SPECIAL DESCRIPTION
Push·
IC
lC
lC
lC
lC
3
1
5
4
5
8
5
8
1
3
8
5
3
1
1
1
I
3
Button
Indexing
Tuning
Station
Selector
Adj.
Motor
Switcb
ICI
ICI
ICI
lCI
lCI
Transfer
Device
Manual to
Automatic
6A
6A
.. ·4il....
·sii ....
Audio Silencing
Circuit and
AFC Release
During Tune
Station
Set".:'.!!~g t:tI~
mUtator
Device
7A
7A,7Kl
7A
7A,7Kl
7A
Mech ..
ani8m
lC8
IC8
lCS
Ica
lC8
6D
... 4il ... . .. S»" ... . .. 60
3A
4C
IB3
IB2
IB3
IBa
IB3
3B
3A
3B
IB3
.. '4C"
4C
4C
5D
·7G· ...... · .. "80'
7G ...... · .. · . '80"
"SA"
50
5A
----------1------1----1---1------------------1·-DELCO
R667, R669 .......... .
R675, R677, R678 ...... .
Rll~.. ............. .
RU34, R1135, RU39 ....... .
R1140 ................ ..
R1141, R1l42, R1143, R1144.
Delco-Matic
Rocker Bar ..
6
5
8
Delco-Malic.
Cam and Lever..
..
Dual Permeability ..
Dual Permeability ..
5
5
6
9
1
9
1
2
2
9B
IB4
9B
lAI
2B
2B
-----------1----·--- ---------1--- - - - - - - - -----1------1--DETROLA
175, 183, 185 ............... .
191, 192, 193, 195(C4), 204.
209, 210 ................ .
220, 221, 222 ....... .
223,225 ........... .
226, 227 .................. .
228 ..................... .
231 ....................... .
Motor Opera ted ... .
8
Motor Operated ... .
Dual Permeability ..
10
3
6
4
6
4
6
8
6
2
I
1
1
1
3
1
6
2
Rocket Bar .... , .. .
Rocker Bar ....... .
Rocker Bar ....... .
Rocker Bar ....... .
Motor Operated .. .
233 ....................... . Rocker Bar.
258, 259, 270 ....... .
Dual Mic•...
3
3B
3B
2B
4B
4B
5A
5A
7G
7G
.4»'
SA
7G
8C
8C
IBI
IBl
IBI
IBI
3B
IBI
2A
--·--·---------1-------·-- - - - - -------1·----1----- - - - ---·--1-------1---ERLA
11 Tube 3 Band ........... .
11 Tube 3 Band ........ .
76A ...................... .
78B, 78BE, 82A, 82AE, 86AE.
91B, 95B .............. .
Flasb Tuning .
Telephone Di.1.
Flash 1'uning .... .
Telephone Dial ..... .
Telepbone Dial .... .
12
10
12
10
10
Automatic Dial. ... .
Automatic Dial .... .
Automatic Dial .... .
Single Adjust. Mica ..
Single Adjust. Mica ..
Rocker Bar ........ ,
Single Adj ust. Mica ..
Instamatic ......... .
Instamatic ......... .
Instamatic ......... .
Rocker Bar .... .
FADA
A66PC, A66T, A76PC ...... . Dual Mica ......... .
A76T,6A39 .............. . Dual Mica ........ .
358, 366, 366PT, 368 ........ . Ftashomatic.
FAIRBANKS-MORSE
9AC4, 9AC5 ............... .
12AC6 .................... .
10
10
10
1
1
1
6
6
2
2
6
6
2
9
6
6
4
9
9
1
6
6
6
2
2
2
4
--------------1---·-
IC4
ICa
lC4
IC3
lC3
IC
lC
IC
2C
2C
IBI
2C
9E .
9E
9E
IBI
lCI
lCI
lCl
6B
6B
6B
6B
6B
7D,7K2
7D,7K2
7D,7K2
7D,7K2
1D,7K2
-----1-----1------1----1----1------- - - - - -
-----1---------1---
EMERSON
ARI7I, AR173, ARI74 ...... .
AR176, AR180, AIU85 ...... .
AT170, ATI7:!, AT181. ..... .
AV193, AY194, AY195 ...... .
AZ196 .... ~ ............... .
BB208, BB209 ............. .
BDl97, BDl98 ............ .
B0223, B0225, BQ228. . ... .
B tt224, B tt226, B U229 ...... .
BU230, BW231. ........... .
CA208, CA209, CA234 ..... .
IE
lC
IE
IC
lC
1
15
15
2A
2A
IC
lC
lCll
lCll
lCll
.....
lCI
,
....
7A,7Kl
7A
I,
lC8
-------------1--------1--- ---1----1----1----1-----1----1----- - - - ---FIRESTONE
S7407·5 ... : ............... .
1175 ...................... .
01009,01010 ............... .
01029 ..................... .
01030 ..................... .
015040, 015050, 015060, ...... .
015070 .................... .
015080,015090 ............. .
015100, 015110, 015120 ...... .
015130 .................... .
100502 ....... ,' ............ .
FORD
FI740, 6MF490 .............
140
Ratchet Switcb ....
Cam and Lever ....
Cam and Lever ....
Cam and Lever ....
Cam Ilnd Lever ....
Rocker Bar ........
.
.
.
.
.
.
6
8
5
8
6
4
Cam and Lever .... .
Cam and Lever .... .
Rocker Bar ........ .
Rocker Bar ........ .
Cam and Lever .... .
4
4
6
Ratchet Switch .... ,
5
2
1
1
1
1
1
1
1
1
I
I;
20
lA3
lAI
lAl
IAI
I,i,
~~
i
IBI
......... .
IBI
......... .
lA3, lA8 ......... .
1A9
......... .
IBI
......... .
1
1M
2
20
......... .
AUTOMATIC
TUNING
REFERENCE
MANUFACTURER
AND MODEL
No.
of
But·
Type
tODS
GALVIN
1938 Auto Models .......... .
8.60.8.80 ............... .
IOn. 12Y. 12Yl. .......... .
9·49. 9·69. 15F ............. .
16C ...................... .
170. 17DA. 180. 19B ....... .
20P. 21L, 22S. 24K. 25N ... .
89K1. 89K2. 89K3, I09Kl ... .
109K2 ................. .
Spot Tuning .......
Motor Operated ....
Motor Operated ....
Motor Operated ....
Rooker Bar ........
Rooker Bar .......
Motor Operated ....
Motor Operated ....
.
.
.
.
.
.
.
.
Motor' Operated .... .
GAMBLE-SKOGMO
AI. A2. A3. A6 ............. . Motor Operated ....
Cam and Lever ....
527A, 527C ............... .
CMO ...................... . Cam and Lever ....
645 .....•.................. Dual Mica .........
648 ...................... . Rooker Har ........
677 ...................... . Cam and Lever ....
678 ...................... . Cam aad Lever ....
735 ....................... . Dual Mica .........
761 A. 796. 797 ............ . Cam and Lever ....
867A ...................... . Cam and Lever
Any
No.
6
19
6
5
6
6
6
6
.
.
.
.
.
.
.
.
.
8
5
6
GAROD
782.782.1 ................. .
Prestomatic ........ .
GENERAL ELECTRIC
F96 ..................... .
FI07. FI09. FI37 ........... .
G50 ...................... .
G53 ...................... .
G55 . . . . . . . . . . . . . . . . . . . .
G56. G6l. GM. G66, G68 ... .
G69. G75. G76. G78 ........ .
G85 ...................... .
G86 ...................... .
G95 ...................... .
G97 ...................... .
G99 ...................... .
mos. GI06 ................ .
G655 ..................... .
GA62 .................... .
GD51. .................. .
GD52. GD52A. GD60. GD63.
GD610 .................. .
H73, H77. H78. H79. H87 ... .
H116. H118..... . ....... .
H634. H638. HMO ..... I • • • • .
HJ905. HJ908 ............ .
HJlOO5 ................... .
HJl205 ................... .
Touch Tuning .... .
Motor Operated ... .
Telephone Dial. .... .
Dual Mica ......... .
Telerhone Dial. ... .
Dua Mica., ...... .
Dual Mica ........ .
Dual Mica ........ .
Dual Mica ......... .
Motor Operated .... .
Dual Mica ......... .
Dual Mica.... . ..
Motor Operated .... .
Dual Mica ........ .
Rocker Bar ....... .
Cam and Lever .... .
Dual Mica ......... .
Cam and Lever ... .
Permeability & Mica.
Permeability & Mica.
Permeability & Mica.
Permeability & Mica.
Permeability & Mica.
Permeability & Mica.
GENERAL HOUSEHOLD
UTILITIES (Grunow)
585 ..................... .
588., .................. .
Teledial. .. . .... .
Teledial ......... .
Teledial. ......... .
622 ..................... . Teledial. .......... .
623 ...................... . Teledial. .......... .
624.632 ................... . Teledial. .......... .
63S. 1067... .......... . .. Teledial. . . . . . . .
1081. 1091. 1181. 1183. 1185
Teledial ....... .
1291.1293 ............ .
Teledial .......... .
589 ...•...•...............
13CS-E .................. .
HERBERT H. HORN
I1A ...................... .
Motor Operated.. .
9
9
9
6
6
I
2
I
I
6
2
2A
2
2A
9A
IB2
2A
IB2
2A
2A
2A
2A
3B
2A
6
8
6
8
6
6
8
6
I3
9
1
1
1
I
9
1
2
I
2
2
2
2
3
6
8
2
2
I3
3
2
1
1
6
5
5
5
5
6
8
5
5
6
8
2
1
2
2
2
2
2
2
10
8
10
8
10
8
10
16
15
.
Indexing
Adj.
IC6
.. ·iC2····
Tuning
Motor
Button
Station
Selector
Switch
5C
2A
3B
3
3B
2
2
2
2A
2A
2A
2A.2B
3B
2A.2B
9
9F
... 6C·····
f.:tI~
MechaniSM
. 'iC'lS"
lel3
~.
4C
7G.7K2
... 5ii ....... i;ri ... .
···4A.... ·
5B
6B
5B
5B
60
60
... 7E,"7K.S······
8B
···i;B·· .. ·
.. ·i;ii· .. ·
6B
6B
6B
. ··6B·····
6B
3B
2A
lBl
IA1
2A
IAI
2A.2B
2A.2B
2A.2B
2A.2B
2A.2B
2A.2B
2
3
Station
Audio Silencing Selecting
Circuit aod
Com·
AFC Releaoe
mutator
During Tune
Device
.......... .......... . ......... ',E'··········
4B
5A
2~
lC
IC
IC
IC
IC
IC
IC
IC
IC
Transfer
Device
Manual to
Automatic
"'6B" ...
···5B.... · ..........
60
1C3
ICl
7A.7KI
7A.7KI
7A,7K1
7A.7KI
7A.7KI
7A.7Kl
7A.7Kl
7A.7KI
7A.7K1
Ica
ICl
IC3
IC3
IC3
ICI
IC1
.. 4B.. ···
5B
5B
60
6A
5B
60
. .. iii······ .. ·
1C8
ICS
ICS
1CB
1CB
IC8
lC8
ICS
ICS
..............
BC
I---------------~---
HUDSON
SA40 ....•................. Solenoid ........... .
MAJESTIC
62A ....................... .
639. 639B ................. .
6S1-EB ................... .
739 ....................... .
1056X. 1058X ............ .
1356X. 1656X ............. .
11056 ..............•........
11058 ..................... .
11356 .................... .
11656 ........... .
3
9
1
1
6
5
Motor Operated ....
8
1---------------1---HOWARD
210 Adapter. 211 Converter•.. Dual Mica ........ .
8
8
240.240.2 ............... . Dual Mica ......... .
318, 3180. 3250. 368A .... .
8
Dual Mica . . . . . . . .
375 ...................... . Permeability & Mica.
6
4OOA.425A ............... . Motor Operated .....
8
6
418. 468. 525. . .. . ......... . Permeability & Mica.
MAGNAVOX
CR10IM. CRI08M ......... .
CR121 .................... .
CRl22 .................... .
CRl2s .................... .
CR124 .................... .
CRl28 .................... .
10
3B
3C
9G
IB
1B
9G
9G
9G
1
3
2
6
8
Dual Mica ........ .
Sub.
DivisioD
5
6
6
GILFILLAN
5TH ...................... .
Button
9C
IAI
1AI
2A
1BI
1M
IA5
2A'
lA3
lA6
13
SPECIAL DESCRIPTION
Push·
Sec.
tion
• Section 6
Motor Operated ....
Dual Mica .........
Motor Operated .. .
Rocker Bar ........
Dual Mica .........
Rocker Bar . . . . . .
6
.
.
8
.
.
6
6
Rocker Bar ........ .
Rocker Bar . . . . . . . .
Dual Mica ........ .
Rooker Bar . . . . . . .
Dual Permeability .. .
Dual Permeability .. .
Motor Operated .... .
Motor Operated .... .
Motor Operated .... .
Motor Operated ... .
6
8
6
4
6
4
4
5
7
6
8
10
12
2
2
3
S'
2
3
1
2
I
I
1
2
I
2
2
3
3
3
3
4B
4B
5B
5B
5B
5B
7H.7K4
8C
60
.. ·60 .. ··
... 60·· .... ·iH··· .. ·· .. ·
"'SC'"
3B
· .. 6:8·· ..
2A
3B
IB
.. ·6B·····
2A
IB
1----1-------1------·1------11-----1·---------- - - - - - IBI
IBI
2A
IBI
2B
2B
3B
3B
3B
3B
..........
6B
141
'Section 6 •
THE
MY E
TECHNICAL
SPECIAL DESCRIPTION
REFERENCE
MANUFACTURER
AND MODEL
MIDWEST
VTl6, VTI8, VT20.
No.
of
But·
tons
Type
Motor Operated .....
18
Cam and Lever .... .
Cam and Lever .... .
Motor Operated .... .
Dual Permeability ..
Cam and Lever. , .. .
Cam and Lever, ... .
Cam and Lever .... .
Cam and Lever.
Dual Permeability, , .
Dual Permeability" .
Motor Operated .... .
Cam and Lever .... .
Motor Operated .... .
Cam and Lever .... .
Cam and Lever .... .
Dual Permeability .. .
Dual Permeability .. .
Cam and Lever .... .
Cam and Lever .... .
Cam and Lever .... .
Cam and Lever .... .
Cam and Lever .... .
Dual Permeability .. .
Cam and Lever .... .
6
6
8
----------1---------------1----
MONTGOMERY-WARD
62·274,62-280,62.282"", ...
62-284, 62-288,62·290"" .
62.303, 62-321 " .... ,.,.
62·322 . . . . . . .
62.323, 62-324. , ..... , ' . ,
62.350 .. , .... , ... ,., ..
62·361 ... , , . , ...... ' . , .
62·362 ........ ' . . . . . ,
62.363, 62·370, 62·390 ... , .. , .
62·401, 62·403, 62.422 ... , . , ..
62·433. , ... , , . , ' .. , ..
62.434,62·435.,.,.,., .... ,
62·451, , . , . , , . , ... , . , .. , .. .
62·453 .... , . . .. ." .. ,.,.,.
62·459 ......... .
62·463,62·470,62·479", .....
62·490 ............. ..
62·501, 62·502, 62.504A
62·505A, 62.552, 62·553.
62·554 ", .. ,'
62·558. , , ..... , , , ' , ... , .
62·601. , ...... , .. , .. .
62·650
62.651, 62·652 .......... ,
62.653 ."
....... .' __ ..
62.654, 62.655, 62.656. , . , .. .
62·700 .. ,'., ... , .. '...... .
62·713 ....... ,..... ., .. .
62·750, 62·751 ..... .
62.900, 62.1100 ... .
62·1558 .. ,., .... .
04BR.609A."., .... .
04BR678C .... " ..... , ... , ..
93BR462A ... , ...... " .... .
93BR508, 93BR509 .. , ...... .
93BR560A ........ , .. ,.,
93BR561A, 93BR563A .. ,.
93BR564A ..... , ..... ,.,.
93BR657A ............. , ... .
93BR658A, 93BR659A .. , .. .
93BR660A .. , .. , ........... .
93BR713A.. . . .. . _...... .
93BR714A, 93BR714B .. , .,
93BR715A, 93BR717A ... , ..
93BRI20IA, ....
Cam and Lever.
Cam and Lever.
Dual Permeability ..
Cam and Lever ....
Cam and Lever
Dual Permeability ...
Cam and Lever.
Cam and Lever.
Cam and Lever.
Cam and Lever.
Cam and Lever
Cam and Lever.
Cam and Lever .....
Cam and Lever .. , .
Cam and Lever
Cam and Lever.
Cam and Lever.
Cam and Lever.
Cam and Lever
Cam and Lever
Cam and Lever
6
6
4
6
6
6
6
8
6
8
6
5
6
6
6
6
5
6
6
6
6
5
6
6
6
6
6
6
6
6
6
4
6
6
6
6
6
6
6
'6
6
6
Sec~
tion
Sub.
Division
3
3B
I
I
IAI
IAI
9C
2B
IA3
lAI
IAI
IA3
2B
2B
9C
IA3
9C
IAI
9
2
I
I
I
I
2
2
9
I
9
I
I
2
2
I
I
I
I
I
2
MANUAL
Button
Indexing
Adj,
Tuning
Motor
4B
Puoh·
Button
Station
Selector
Switch
5A
Transfer
Device
Manual to
Automatic
6F
Audio Sil~ncing
Circuit and
AFC Releaoe
During Tune
7C
Station
Se~:c.!!~g f~~tI~
mutator
Device
Mech·
anism
SC
tAl
I
I
I
2
I
I
2
I
I
I
I
I
I
I
I
I
I
I
I
1
I
I
2B
2B
IAI
IAI
IAlO
IA3
IAI
2B
IA6
IAIO
IA6
2B
IAll
IA6
2B
IA3
lAI
IA5
IA3
IAI
IAll
IAI4
IAI
IAll
IAI4
IA14
IAll
IAI4
lA14
IAI4
2
2
1
2
2
2A
2A
IE
2A
2A
I
1
---------1-------------- - - - - - - - - - - - - - - --------1-------1-----1-----------1----NOBLITT-SPARKS
6,68" ......... , .. , ..
92 . . . . . .
818AT, 828AT. 838AT ..
1237,1247, 1247A ....
1427 .....
Dual Mica ....... .
Dual Mica .. ,.
Phantom Tuning ..
Phantom Tuning
Phantom Tuning
OLDSMOBILE
982126,982127.
Rocker Bar.
6
IB2
PACKARD BELL
160.
Motor Operated ....
8
3B
PACIFIC (Chicago)
Converter Unit .......... .
SeJectro~Matic
6
PACIFIC (Loa Angele.)
37, 37A ..
Dual Mica .....
6
PACIFIC
8AC. .. ..................
501, 601, 602 ....
Rocker Bar, ...... ..
Rocker Bar, .... , ..
6
4
6
6
10
6
10
.. 6iJ
5B
5B
6A
-'AO'_" tIP-3S
LEFT END VIEW OF MECHANISM
FIG. 87
tuning shaft causes the star wheel to
force down the kickout arm. This releases the depressed button and slides
back the friction roller into engagement
with the friction wheel for manual
tuning.
The flywheel on the back end of the
tuning shaft provides a "spinner" action while tuning manually.
The station selector cams are prevented from turning on their shaft by
an expansion and contraction type
locking mechanism. The assembly is
locked when the device is expanded or
unmeshed as shown in Fig. 90B. Unlocking is accomplished by pulling out
the set-up knob and turning it clockwise
until a click is heard. This contracts the
MOTOR MOUNTING
SCREWS
BRACKET MTG,
SCREWS
15
_==#;==;==FRICTION
~~~~~~ WHEEL
/ AI1II,,-1"tII.!!'<:t--. AND - 18
MOTOR
PINION
28-PAWL
FRICTION_ 16
ROLLER
12-COLLAR
CLUTCH-II
ESCUTCHEON SUPPORT
6-
BRACKET
FRICTION SPACER
WASHER-17
J.
10
~
KEY
TOP VIEW OF MECHANISM
FIC.88
185
- Section 6 •
THE
MY,E
TECHNICAL
MANUAL
b. Allow the set to warm up for twenty minutes before settIng it up.
c. Set up the buttons from left to
right, that is, the' right hand buttons
should be the last to be set up.
d. Avoid setting buttons on weak or
fading signals.
e. Tune cart;.fully when setting up.
f. After a button is set up, do not
push that button again until the mechanism is locked. To do so will spoil the
setting of that button.
g. Lock up tight. Continue to force
the set-up knob in a' counter-clockwise
direction even after it seems to reach a
definite stop. If you do not use force,
the settings of the buttons may change.
en
Z
o
t=
fd
z
z
o
o
0::
LLI
:r:
.....
o
II:
0
0::
Q
f2
~~
..:
u
U)
-...
~
~CD
CD
is
AUTOMATIC
5 t-~~~~__-+-+_P~I~lO~T_l~I~GH~T~~~~~~~--~
en::(3
'-SMAll ~LUE
SCHEMATIC WIRING DIAGRAM
OF TUNER WITH MECHANISM
IN MANUAL POSITION
~
INSULA TION---
II:
o
~ (EARLY TYPE BACK & SIDE SWITCHES)
L------------'3I:%
Fie. 89
locki:t;lg mechanism and allow~ the selector cams to turn on the shaft for setting up.
Pawls
If a Pawl does not fall completely into
the notch on the station selector cam,
check the setting of the back switch. It
is probable that the Power contacts are
opening too soon. Notice that in order
to fall into the notch, the pawl must
work against the bar carrying the bakelite cam. Anything that makes this bar
operate hard should be corrected. See
that the end of the pawl and notch on
the station selector cam are smooth and
~ree from burrs. Then try closing up the
Power contacts on the back switch a
little more, but only after checking the
above points. This may be done by
bending the Power blade so the Power
contacts are closer together. Do not
change the outline of the pawl or cam
notch.
186
I,
I,
Setting Up Procedure
z
II:
....
I
Setting Up
The following points must be ob,served during the setting up and use
of the automatic mechanism if best
results are to be obtained.
On some models the tone control
broadens the tuning when in the treble
position, maximum clockwise, therefore
, this position positively must not be used
during set-up.
a. Use a good antenna.
, In brief, the setting up procedure is
as follows:
a. PuII off the tuning knob. This reveals the set-up knob (Fig. 87). Pull
the set-up knob out. Unlock the mechanism by turning the set-up knob clockwise until a slight click is heard.
b. Push in a button. After the pointer
has stopped moving, grasp the set-litknob and tune in the station to which
the button is to be set.
c. Push in another button. After the
pointer has stopped moving, again
grasp the set-up knob and tune in the
station to which this button is to be set.
d. Continue to push in buttons and
tune in the stations until as many are set
up as desired. Then release the last button set up, by pushing the set-up knob
part way in.
e. Pull the set-up knob back out.
Lock up the cam assembly by turning
the set-up knob counter-clockwise as far
as it will go. Continue to force the setup knob in a counter-clockwise direction even after it seems to reach a definite stop. If you do not use force, the
settings of the buttons may change.
LATCH ARM
LATCH SPRING
SPRING
RETAINING
WASHER
CAM ASSEMBLY LOCK
FIC.90A
FIG. 9GB
I
i f~
I,
I
AUTOMATIC
f .. Push in the set-up knob and reo
place the tuning knob.
In case of complaint that a button set
for some frequency, does not tune to that
point within 10 K.C., or more, after locking up, it usually develops that the station selector cam has inadvertently been
moved before it was locked. This may
come about by turning the set-up knob
slightly when releasing the button, preparatory to lockin~ the mechanism. Another possibility, if the back switch is
not adjusted properly, is that by pushing a second button the motor will start
before the pawl falls clear of the first
cam, thus causing this cam to be shifted
slightly before it is locked in place.
A short may occur in the unit due to
the tuning shaft bearing stop (Fig. 87)
getting out of place. It then catches
on the set-up gear. When the gear is
turned counter-clockwise it forces the
bearing stop against the hot blade of the
side switch. Solder the bearing stop in
place.
• Section 6
TUNING
rotation. Fig. 91B shows the tuning
button depressed with the stop lever
bearing agaihst the outer periphery of
the brake shoe. The ball on the end of
the switch lever is depressing the switch
plunger causing the motor to run. The
motor will run the system until the stop
lever drops into the notch and allows
the switch lever ball to leave the switch,
thus stopping the motor with the setting
disc firmly locked in place, as shown in
Fig.91C.
Fig. 91D shows the manner in which
the setting disc is released from the
brake drum to allow it to be set at the
correct point for station tune. The station is tuned in manually with the system as shown in Fig. 91D. The brake
drum turns freely within the setting disc
until it is clamped in place by the cams
on the drum release and auxiliary lever,
as the setting button is withdrawn.
Study of the position of the various
parts as shown in Fig. 91 will disclose
the sequence of operation.
Audio silencing is obtained by a
switch operated by axial movement of
the motor shaft.
.
SECTION 9D
Buick Sonomatic
The push-button tuning mechanism
of the Buick Sonomatic Model 980620
is illustrated in Fig. 92. One button
is removed to show the lock screw.
SECTION 9C
Wells-Gardner
"Electric Drive"
The Wells-Gardner "Electric Drive"
is a combination of mechanical and
electrical interlocks which allows station "set-up" from the front of the receiver. The station stop mechanism consists of a series of discs which are geared
to the condenser drive system and are
encircled by brake shoes having notches
which co-operate with stop. levers as
shown in the sequence of drawings of
Fig. 91.
Above each station tuning button IS
a setting button used. only when it is
desired to change the pre-set tuning
choice. The station tuning buttons are
interlocked by means of a side-acting
latch in such a manner that the act of
depressing a station button will move
the latch and release any previously held
button. This side-acting latch or locking
plate is also actuated by the manualelectric transfer control.
Fig. 9lA shows the system of rocker
arms and stops in position corresponding to a released plunger. It will be seen
that all parts of the stop system are clear
Qf the brake shoe and will allow its free
(Al
I
ELECTRIC MANUAL LEVER IN L
L&E\..~~
ELECTRIC POSITlON--BOTH
BUTTONS OUT--SWITCH IN
TUNING
S.PRING
","UTTON
LOWER-OFF' POSITlON-- STOP
LEVER AND ROCKER ARM STOP
FREE DF SETTING DISC.
-Setting Disc-Off Position
-Setting Disc-On Positfon, Stop Lever on Edge of Di.c
SET1'ING
OISC
(e)
(0)
TUNING BUTTON DEPRESSED
PAWL PUSHED BACK
STOP LEVER IN NOTCH OF SE TTING DISC
ROCKER ARM STOP RIDING ON SETTING
OISC"SWITCH IN UPPER OFF POSITION
BOTH BUTTONS OEPRESSED--SETTING
BUTTON ENGAGING ROCKER ARM-ROCKER ARM ENGAGING DRUM RELEASE
LEVER--STOP LEVER IN NOTCH OF SETTING
DISC--SWITCH IN UPPER OFF POSITION
~Settjng
Disc-Stop Lever in Notch
~Setting
Disc-Setting Button Depressed
Fie. 91-Wells-Gardner "Electric Drive" Details
187
Section 6 •
THE
MYE
It is important that this set be connected to a six-volt battery before any
attempt is made to operate the tuner.
Magnetic clutch "E" (Fig. 92) must
operate to remove the load of the
manual tuning system before the push.
buttons will operate.
In set-up anll operation this tuner is
very similar to the rocker bar types._
Pushing pawl "F" pushes against the
.. "C"
pair 0 f racks "D" to turn pInIOn
to the desired position.' Pinion "C" is
connected directly to the dial mechanism and geared to the condenser side of
the magnetic clutch "E." The switch
contacts which operate the clutch are
closed by the very slightest touch of a
button.
To set up stations on this receiver
proceed as follows:
First remove the push-button by
pulling the button spring to the right
and pulling straight out on the button,
Then loosen lock screw "A" wit4 a
coin or screwdriver. Carefully tune in
the desired station ~y ~eans of the
manual control, then push the loosened
screw in as far as possible and retighten.
TECHNICAL
MANUAL
SECTION 9E
Emerson Instamatic
PUSH IN THE BUTTON
WITtt A flRIIt·RAPO
MOTION. AS FAR IT
WILL GO, SO THAT IT
REMAINS OEPRESSED.
'The six push-buttons provide a choice
of six favorite broadcast stations for
Miracle Instamatic Tuning. Adjustments for any particular station must
be made by means of the small crossslotted button immediately below the
chosen push-button. The following procedure must be carefully observed in
making these adjustments:
Insert the line plug in the- electrical
outlet. Turn the receiver on by rotating the tone control knob clockwise
until the switch is heard to click and
then rotate this knob to the extreme
clockwise position. Wait about a minute for the tubes to warm up. Turn the
wave-band switch to the broadcast position, clockwise. Turn the volume control clockwise to about half of its full
rotation.
I~
I
11
II,:"
~~:,v~~~~~foaid
Ii
by meons ot c..:IJusting
, button.
I
when tuning station
,:
"
'~~~~jib
U
TURN THE SLOTTED
ADJUSTING SUTTON
JiITH A COIN ANO
OBSERVE DIAL FACE.
TUNE IN STATION IT
MEANS Oil' THIS
AOJUSTING BUTTON
I'
I'
II
i~
I
I
FIG.~3
FiG. 92
188
Push in the manual selector knob
(second from right). When pushing in
the selector knob or one of the pushbuttons best results are obtained by using a firm rapid action.
With the selector knob depressed
tune in the desired station. Rotate the
selector knob until the mark on the dial
face corresponding approximately to
the frequency of the station appears at
the black indicator line on the conical
escutcheon window. Identify the station and note the approximate position
of the dial face,
Push in the button to be adjusted for
this station. (See Fig. 93.)
Insert a small thin coin in one of the
slots of the adjusting button immediately below the push-button. Turn the
adjusting button until the mark on the
dial face corresponding approximately
to the frequency of. the station again
appears at the black indicator line on
the conical- escutcheon window. Once
the station is heard, tune it in carefulJy
I,
I'
AUTOMATIC
UP
DOWN
FIG. 94
TO UNLOCK: Turn Manual Tuning
Control down about 70 to 100 strokes
after word UNLOCK appears. Turn until control turns hard after turning
easily. Never force control after this
point is reached.
by turning the adjusting button back
and forth slowly. From the standpoint
of performance it is of paramount im·
portance to tune in the station accu·
rately. (See Fig. 93.)
.
It is very important, when tuning in
a station by means of the adjusting but·
ton, that the last turning motion of the
adjusting button be in the counterclockwise direction, as indicated in
Fig. 93.
Check the results by moving the dial
face, using the selector knob, to a dif·
ferent position and then pushing in the
·button. The station should be received
clearly and with maximum volume.
Adjust the remaining buttons, one at
a time, following the procedure out·
lined above.
SECTION 9F
TO LOCK: Turn Manual Tuning Control up about 711 to 100 strokes after
word LOCK appears. Turn until control
turns hard after turning easily. Never
force control after this point is reached.
(c)
(d)
(e)
(f)
Hudson Feathertouch Tuner
IMPORTANT PRECAUTION: In order to
assure perfect results you must observe
all instructions. One very important
precaution during set· up is to never
touch a button already set while control unit is unlocked. For example, if
some buttons are set and while work·
ing on the remainder you accidentally
touch one already set, the setting on
this button will change. This will ne·
cessitate resetting of the button acci·
dentally touched.
How to Set Up Push·Buttons
(a) Operate set for about ten minutes
before setting up buttons.
(b) To Unlock Tuning Mechanism:
Rotate right (tuning) control downwards until word Unlock shows at
(g)
• Section 6
TUNING
the left side of diaL Continue to
'turn until wheel tightens. (70 to
100 strokes will be required.) A
more complete description of this
procedure is given below under
the heading "Unlocking Tuning
Mechanism. "
Tune in desired station with (tun·
ing) control.
Hold down the button selected and
move tuning control up and down,
leaving it in position where tone
is deepest. Release button.
Follow same procedure for other
buttons. IMPORTANT: After setting
any button, it must not be touched
until after mechanism has been
locked as in (f). Otherwise it is
necessary to reset it as in (c) and
(d) .
To Lock Tuning Mechanism: Ro·
tate tuning control upwards until
word LOCK appears at right side
of dial. Continue to turn until
wheel tightens (70 to 100 strokes
will be required). A complete de·
scription of the locking operation
is also given below.
Insert station call letter tab in
front of each button. The tabs are
inserted by flexing them and al·
lowing them to snap into place in
the buttons.
2. Now hold the manual tuning can·
trol and push the button to be set
up several times.
•
3. After pushing and releasing button
several times, hold button down
and again tune station carefully by
turning manual tuning control back
and forth slightly.
4. Repeat for other buttons.
The essential difference between this
procedure and the one given above is
that the button is pushed and released
several times in quick succession after
desired station is tuned in but before
final tuning adjustment is made.
Unlocking Tuning Mechanism
In setting up this mechamsm, you
must understand the action of the con·
trol during locking and unlocking.
The l)-nlocking operation begins after
the tuning control is turned to the point
where the word unlock appears. To
complete the unlocking operation, the
tuning control must be turned quite a
bit after this point is reached. When
unlocking begins, the tuning control
may turn quite hard, but then it begins
to turn quite easily. You must continue
to turn it downwards until it again
turns hard. Because of the high gear
ratio, it may require 18 to 24 complete
turns of the tuning control to reach this
point. Since you can turn this control
only a quarter of a turn at a time, it
may require 70 to 100 strokes of the·
finger on the control to completely unlock the mechanism. The tuning control
will not reach a definite stop when the
mechanism is unlocked. However, when
the control turns easily for quite a
while, then turns harder, the unlocked
position is reached. In this position the
tuning control wiH spring back when
you take your finger off after turning
it. At this point, the tuning indicator
will function if you turn the tuning con·
trol back (up). Important: When this
position is reache.d, do not force the
tuning control further down.
Setting Up Early Radios
Locking Tuning Mechanism
Some of the earliest radios produced
require a slightly different set·up pro·
cedure than given above. This same
procedure can be used on later sets
though it is not necessary.
After unlocking the tuning mechan·
ism, proceed as follows for each button:
1. Tune station in manually.
The locking action begins when you
continue to turn the tuning control up·
wards after the word lock appears.
The action is much the same as de·
scribed 'under unlocking and it will reo
quire as many turns of the tuning con·
trol to lock the mechanism as were
needed to unlock it.
189
Section 6 •
THE
M YET E C H N " CAL
MAN U A L
PUSHBUTTON
FI.,. 95-Magnet Plunger in "OUT" Position
Fu;. 9O--Magnet Plunger in "IN" Position
Refer to Fig. 95 and Fig.' 96. When a
push-button is depressed, it makes mechanical contact with the cam operating
bar located under it, and depresses the
bar so that the gathering bar can make
contact with it. At the same time, the
key forces the contact plate downward,
making electrical contact through the
contact screw. When the contact screw
makes contact, it energizes the winding
of the magnet assembly causing the
plunger to be drawn completely into
the magnet as shown in Fig. 96. The
plunger is mechanically coupled to the
gathering bar and gathering bar shaft,
'so that when the plunger is drawn into
the magnet, it causes the gathering bar
to be forced ahead. The gathering bar
engages the cam operating bar which
is depressed by the push-button key and
drives it forward as shown in Fig. 96.
This position of the cam operating bar
is indicated by the ends of. the cam
operating bar extending from the mechanism frame (see Fig. 98). When the
cam operating bar moves forward, the
cam stops attached to the bar engage
the cam, rotating it until it is in the position indicated in Fig. 96. The rotation
'of the cam causes the cam shaft and
gear segment to rotate likewise, rotating
the gang condenser to a position corresponding to the station to which this
particular key is set..
threaded collar is turned upon the
threaded section of this cam shaft, exerting pressure upon the cams and friction collars, thus locking them securely
in position. When the cams are unlocked, this threaded collar is turned
so as to unscrew it and exert a minimum of pressure on the cams and friction collars. The only pressure then exerted upon the cams to hold them in
position is that exerted by a spring
washer near the threaded end of the
shaft. Thus the cams are. held so they
cannot move of their own accord, but
are still loose enough to permit them to
be set to correspond to the desired station.
The threaded collar is connected
through the clutch to the manual tuning control, permitting adjustment of
the cams from outside the tuning unit.
How the "Locking-Up"
nlechands~ ~orks
The cam shaft assembly consists primarily of a shaft on which five cams
are alternately spaced between friction
collars. On the clutch end of this bar is
a short threaded section upon which
screws the collar which is part of the
clutch and clutch spring assembly.
When the cams are locked, this
190
Operation of Clutch and De-Clutch Arin
The clutch mechanism of this tuner
(see Fig. 98) functions every time a
push-button is depressed. Its purpose
is to de-couple the manual tuning control and its associated gears from the
automatic portion of the tuner when
tuning electrically. The clutch is a dual
unit, providing positive mechanical
coupling between the manual tuning
gears and the cam shaft, and it also has
CAM ON
GATHERING BAR
SHAFT
DE~g~~C~~-G--":-'::::-.='-'T-_--r'_...J
ARM
FiG.97A
Correct Position of
Cam on Riser
a leather friction disc which operates
in conjunction with the positive coupling element to remove ex~essive backlash when tuning mechanically.
When the plunger is drawn into the
magnet, turning the gathering bar
',shaft, the cam attached to the shaft
(Fig. 98) moves downward on the riser
of the de-clutch arm, releasing the pressure on the de-clutch arm, which bears
against the inside section of the clutch.
When this pressure is released, the
clutch return spring contracts, separating the two halves of the clutch, thus
disengaging the manual tuning gears.
When the push-button is again released, allowing the plunger to be withdrawn from the magnet, the cam on the
gathering bar shaft moves upward on
the de-clutch arm riser, again exerting
pressure on the de-clutch arm, and in
turn on the clutch, thus engaging the
two clutch sections, and making manual tuning possible.
Set Tunes
I:
I'
I
I~properly
If the set fails to tune in stations
properly, first check the set-up of the
various buttons. If the set-up is incorrect, the set will tune consistently to
the same point, and thIs condition can
. be remedied by res~tting the buttons.
If the set will not tune in stations,
although the plunger tends to move,
make sure the Bristo headed set screws
in the retaining collar are tight. This is
the collar which is almost touched by
the condenser drive gear sector when
the condenser plates are unmeshed. A
loose set screw may strike the unit
frame, causing the plunger to stick in
either the IN or OUT position.
If the set fails to tune properly, and
the djal stops at different points when
approaching the station from opposite
ends of the dial the mechanism may
not be properly locked up (see "Locking Tuning Mechanisms"). The. next .
step is to check for binding of the
~-~~
.~ ~R ~
FIG.97B
Position of Cam
Too Low
I'
FIG.97c
Position of Cam
Too High
..
FIG.97D
Correct Position of
Cam on Alternate
Type Riser
I
I
I
AUT 0 MAT' C
• Section 6
TUN ,'N G
mechanisms. Below are enumerated
some of the reasons for binding:
SET
GANG
CQUNTER-
Rubbing Light Diffusion Plate: Two
types of light diH usion plates were
used, the new tyPt' being riveted to the
cover, while the old type is mounted
on the unit itself (see Fig. 99). If the
new type light diffusion plate, which is
mounted in the cover of the control
head, rubs against the dial scale due to
warping of the celluloid, cut this plate
as shown by the shading in Fig. 99. This
can be done without removing the
shield from the cover. In' some early
units, this diffusion plate was mounted
on the unit itself. In this case, enlarge
the notch fitting over the dial lamp
wire as shown in Fig. 99. Exercise care
when enlarging the notch, as the celluloid is quite brittle and may break.
Then cement the diffusion plate to the
front of the contact plate assembly so
that the shield rests flat against this
metal plate.
SPRING
FIe. 98
mechanism (see section on "Binding").
This trouble also may occur if the pulling force of the magnet is not great
enough. This may occur when the battery voltage is low (below 5 volts).
It may also be due to too large a gap
between the plunger and the pole piece
of the magnet assembly. On later sets
the gap can be adjusted as described in
paragraphs 5 and 6 of "Replacing
Magnet Coil Assembly." The adjqstable magnet assemblies are identified
by the Gap Adjusting Screw and Locking Nut shown in Fig. 98.
In the early type of magnet assemblies the gap is not adjustable. If one
of these magnets is found to have insufficient pull, the remedy is installation
of the new type magnet assembly.
. However, before replacing a magnet
assembly, make sure that improper
tuning is not due to low battery voltage
or the other causes mentioned above.
Mechanism Where Tuning Control Fails
to Reach Stop Dudng Unlocking
This is probably due to the shearing
off of the "C" washer on the clutch end
of the cam shaft (see Fig. 98). On the
earlier mechanisms, this "C" washer
holding the clutch and gear assembly
to the shaft was made of a fairly soft
steel. Occasionally these washers may
shear off if the customer continues
turning the tuning wheel after the
mechanism has become completely unlocked. This continued turning forces
the gear and clutch assembly against
the "C" washer, shearing it off completely. Replace this washer with the
new hardened washer. This can be done
without removing the tuning unit from
the case. First lock the mechanism,
then remove the nuts holding the triangular plate on the clutch end of the
tuner. Unhook the plunger return
spring so that no pressure will be exerted by the clutch. The washer can
now be removed and a new washer installed.
On all early sets, replace this "c"
washer even if the old one is still all
right.
Shearing or partial shearing of this
washer may cause slipping of the
clutch or sticking of the plunger in the
OUT position.
.
If a bronze washer is present between the "c" washer and the gear, nimove it and discard it. If a steel
washer is present, it must be left in
place. On early mechanisms, a nil
steel washer was used in this position
and it must be left in place.
Binding
If the radio tunes improperly, check
for binding in the dial and tuning
~I
OLD TYPE
I~
PORTIONS SHOWN SHADED TO BE CUT AWAY
FIG.
99'--Illustration Showing Method of
Cutting Light Diffusion Plate
Ends of Drum Rubbing Brackets:
The dial drum should have a slight
amount of end play. If it doesn't, it
may be binding. This may be due to
improper placement of the volume control mounting bracket. To correct this
difficulty loosen the two screws holding
this bracket and move it slightly farther
away from the drum.
.
Similar binding may also be due to
a loose end cap on the dial drum. In
this Gase, force the cap back on the
drum and punch-mark the cap to hold
it in place on the dial drum.
In a few cases it may be found that
dial end bearing is out of line or
slightly off center. The bearing can
generally be benr slightly to restore it
to its proper position. If this cannot
be done, replace the dial scale assembly.
Binding of the drum on the mount·
ing brackets may be due to the fact
that the control units fitted too tightly
191
Section 6 •
THE
in early cars. This causes the escutcheon to be forced sideways, thus pressing on the tuning controls, which may
move the dial drum brackets. This
binding can generally be eliminated by
bending the brackets slightly outward.
Similar difficulties will be encountered if the control head is not properly installed. / When mounting the
head, tighten the wing nuts evenly, so
the control head will not have a tendency to hind against the dash opening,
which would push the escutcheon
,against the controls.
Drive Pulley Striking Antenna Coil
Shield: Check to see that the dial drive
pulley is properly located on condenser shaft. Its bushing should touch the
condenser pinion gear.
Also, the antenna coil shield can
may be moved slightly away from the
drum by loosening the two nuts holding down the can.
It may also be possible to move the
entire tuning unit slightly away from
the shield can. Loosen the four screws
holding down the unit and shift it. '
Chassis Wiring Improperly Placed:
, If the leads from the on-off switch and
other leads in the vicinity of the "A"
filter assembly are not properly located,
they may interfere with free motion of
the dial cord or the condenser drive
gear sector. Dress these leads so that
they cannot touch these moving parts.
, Binding Between Sector and Pinion
Gears: Excessive friction between these
gears can be reduced by changing the
position of the pinion gear so that the
set screw indicated in Fig. 10 points upward when the gang is completely
closed. This draws the pinion gear
slightly farther away from the gear sec- .
tor, reducing the pressure between
them.
Counter-Weight Strikes Case: Should
the gang counter-weight strike the wraparound case, loosen the four screws
holding the tuning mechanism to the
chassis and shift the tuning mechanism slightly so counter-weight clears
case. Keep in mind that !;he case side
may be pulled in slightly when the
cover is put on. If the case is warped'
inward, bend it slightly outward till
counter-weight does not strike it.
Slipping Clutch (Backlash)
A slipping clutch is indicated by ex, cessive backlash during manual tuning.
192
MYE
TECHNICAL
MANUAL
First check to see that the correct
plunger return spring is used_
The correct type of spring may be
determined from the following table
giving the dimensions of the three types
of springs which have been used.
No. Length
Outof
of Overall side
Turns Body Length Diam.
Correct Spring... 36
%"
,Light Spring.34 or more %"
Heavy Spring.
24
H"
1%"
1JA,"
1%"
is"
*"
If"
If the unit has the light or heavy
spring, replace it with ,correct one.
When changing springs, it is also desirable to replace the magnet assembly
if it does not have the Locking Nut and
Gap Adjusting Screw shown in Fig. 10.
Ho}Vever, this is only necessary when
there is insufficient pull of the solenoid
to operate the mechanism.
Next check the position of the cam
on the end of the gathering bar shaft
(copper plated shaft) with relation to
the riser of the de-clutch arm while the
plunger is out. See Fig. 98 and Fig. 97A.
The cam should be halfway up the
curved portion of the riser as shown in
Fig. 97A.
If the cam is not halfway up the
riser while plunger is out, as shown in
Fig. 97A loosen the two Bristo set
screws in the retaining collar on the
other end of the gathering bar shaft and
move the retaining collar on the shaft
until the cam is properly positioned on
the riser. A special set screw wrench is
needed to fit the Bristo set screws.
In all cases wher,e slipping clutches
are reported, check to see that there is
no excessive friction in the gang condenser, dial or gang condenser drive
gea~s. See section on "Binding."
plunger and the pole piece is 'adjustable. Adjustable magnets are identifi,ed
by the gap adjusting screw and locking
nut on the end of the magnet assembly
(see Fig. 98). In these sets, loosen the
locking nut on the rear of the magnet
and turn the gap adjusting screw,
outward {counter-clockwise) one-half
turn, and re-tighten the locking nut. If
this sticking occurs in early units, replace the magnet with the newer type
assembly. Read the paragraph "Replacing Magnet Coil Assembly" for instructions for replacing and adjusting
the magnet assembly.
The plunger may stick in the OUT
position, if the "C" washer on the
clutch end of the cam shaft (Fig. 98) is
totally or partially sheared off. Check
this washer, and if found defective, replace with the hardened type of washer. A faulty "C" washer allows the
plunger to come out too far, ~d also
allows the cam to reach a position too
high on the de-clutch arm riser (see
Fig. 97C).
After checking the "C" washer, check
the adjustment of the cam on the riser,
as explained under "Slipping Clutch."
If the cam is too far up on the riser
(see Fig. 97C) it lets the plunger come
out of the magnet too far and this may
cause sticking. If the cam is not far
enough up on the riser (see Fig. 97B) the clutch may slip.
If the position of the cam is correct
as shown in Fig. 97A, but the plunger
still sticks, loosen the two screws holding
down the magnet and shift it slightly
until the plunger moves freely, then retighten the screws. If this does not
clear up the difficulty, replace the entire
magnet assembly.
Sticking Magnet Plungers
Replacing Magnet Coil Assembly
If the automatic tuning mechanism
does not operate, but manual tuning is
possible, the plunger may be stuck in
the OUT position (see Fig. 95). If manual tuning control turns easily but does
not tune stations, the plunger may be
.stuck in the IN position (see Fig. 96).
A loose set screw on the retaining collar on the gathering bar shaft may
strike the frame and cause the plunger
to stick, so check the set screws first.
If the plunger sticks when the plunger is all ,the way in, it is sticking against
the conical pole piece of the magnet assembly.
On the later sets, the gap between the
To replace a magnet coil assembly,
proceed as follows:
1. Remove top and bottom' covers of
tuning unit. Unsolder red and
black magnet wires froni points to
which they connect.
2. Take out two round headed screws
holding magnet to mounting plate.
3. Lift off old magnet assembly and
install new assembly.
4. When replacing this magnet assembly, before tightening the screws
holding down the unit, check to see
that thll plunger moves freely inside the magnet coiL If it has a
I',
I
I~
AUTOMATIC
tendency to bind, shift the position
of the magnet slightly until the
plunger moves freely, then tighten
down the holding screws.
5. It is now necessary to set the large
adjusting screw on the top of the
new magnet. Loosen the nut and
turn the screw out several turns.
Now push down one of the push.
button shafts next to the drum dial.
Then with a screwdriver, push the
plunger into the magnet as far as it
will go.
6. While holding the plunger in very
tightly, you can now release the
push-button shaft and turn the magnet adjusting screw in, until you
feel the screw striking the plunger.
When this happens, back the screw
out one complete turn and retighten
the locking nut. This adjustment
must be made very carefully, since
if the threads are tight it is difficult
to notice the exact point where the
screw strikes the plunger.
Important: To get proper adjustment, a push-button shaft must be depressed before pushing in the plunger
so that the plunger operates the tuning
mechanism as indicated by one of the
cam operating bars extending from the
frame (Fig. 98). If the above adjust~
ment is done while the power is on the
unit, the plunger will pull in by itself
as soon as you depress one of the pushbutt~n shafts. It is then merely necessary to hold the plunger in tightly with
a screwdriver and release the push-button shaft. The adjustment can then be
made.
• Section 6
TUNING
bly. When the gang condenser or any
of its associated parts are replaced or
otherwise . adjusted, before tightening
the set screws holding the condenser
drive pinion gear to the shaft, set the
rotor plates so that their upper edges
are flush with the top edges of the stator
plates. Then turn the condenser drive
gear segment until the stop arm on the
cam shaft strikes the fixed stop on the
frame, then tighten the set screws.
When this adjustment is properly
made, and when the stop arm adjusting
screw is correctly set, no strain is put
on the rotor plates of the condenser in
either the open or closed position of
the gang condenser.
tion is to counter balance the weight of
the gang condenser. When the weight
is in correct position the edge of the
weight nearest the set screw is approximately straight up and down with the
gang condenser fully meshed. When replacing the dial drive drum, always
check to see that this weight is in the
position described above, or the tuning unit may not operate satisfactorily.
SECTION 9G
Motorola Electric
Automatic Tuner
Adjustment of Contact Screw
NOTE
Th~
contact screw, once properly set,
seldom requires readjustment. Improper adjustment may be identified by the
following symptoms:
Contact Scr.ew Too Far In: When a
push-button key is depressed, the magnet will operate, but the cam operating
bar may not be pushed through as
shown in Fig. 98.
Contact Screw Too Far Out: This
may permit the push-button key to exert too much pressure on the cam operating bar and cause it to stick.
Chattering of the mechanism may be
caused when the screw is either too far
in or too far out. Adjust the screw un. til the unit operates properly when any
one of the push-buttons is depressed.
All seven tuners are identical in construction, except for the condenser
gang.
E5T has a 3-gang condenser and is used
in Models 9-49 and 9-69.
E6T has a 2-gang condenser and is used
in Models 15-F, 20-P, 21-L, 22-S,
24-K, 'and 25-N.
E7T has a special high frequency condenser gang and is used in Police
Cruiser Model P-69-14.
Ell T has a 3-gang condenser and
used in Model 500.
IS
E12T has a 3-gang condenser and
used in Model 700.
IS
Position of Gang Condenser
Counter-Weight
E13T has a 2.gang condenser and is
used in Models 34K6 and 34K7.
Refer to Fig 98. The purpose of the
counter-weight shown in this illustra-
E14T has a 3-gang condenser and is
used in Model 550.
Stop Arm Adjusting Screw
The function of this screw (Fig. 98)
is to prevent damage to the gang condenser plates when the rotor plates are
fully opened. This screw is adjusted so
that the stop arm on the cam shaft will
strike it just before the gang condenser
plates open so far as to strike the sta·
tionary plates. Set this screw so the
stop arm will strike it when the rotor
plates are approximately Y8" from the
stator plates. Then tighten the locking
nut so as to hold the screw in this position.
There is also a fixed stop whose purpose it is to stop the condenser plates
just before they strike the fixed plates
when the plates are fully meshed. This
fixed stop is part of the frame assem-
FIG-IOO
193
Section 6 •
THE
M Y ErE C HI N I CAL
MAN U A 1
Motor Does Not Run
Mot~r Fails to Reverse
4. Die Cast Hub Expanded. This usual-
1. Motor Contacts in Control Head Not
Closing. Open the control head and in·
spect the motor contacts. If the gap is
too great, contact will not be made when
the button is pressed. Adjust by bending carefully.
1. Reversing Switch Not Properly Adjusted. See instructions on page 195.
ly causes the two outside rings to bind.
Can be corrected by filing hub.
2. Open Circuit in Motor. If one side
oLmotor circuit is open, motor will run
in one direction only.
Fails to Stop at Station
2. Poor Contact at Push-Button Plug.
Inspect the contacts between the plug
and the receptacle on the chassis.
3. Open Circuit in Motor. Check all
connections to motor and check motor
winding for continuity.
4. Motor Brushes Not Making Contact.
Check contact between brushes and
commutator. Clean dirty commutator
with carbon tetrachloride.
5. Low Battery Voltage. A weak or defective battery in the car would not deliver sufficient voltage to run the motor.
6. Flexible Tuning Shaft Binds. Binding in the flexible tuning shaft places
an additional load on the motor. If this
load is too great, it will prevent the
motor from turning the mechanism.
7. Magnet Fails to Release. If the magnet which. has previously been energized, fails to release the latch bar for
any reason, the motor cannot turn the
mechanism.
Mechanism Runs Sluggishly
1. Low Battery Voltage. A weak or defective.battery will not deliver sufficient
voltage to turn the motor at normal
speed.
2. High Resistance C~ntact in Control
Head. High resistance at the push-button contacts will cause a voltage drop
which will prevent the motor from turning at normal speed. _
3. Poor Contact Between Push-Button
Plug and Receptacle. This will also result in voltage drop, and lessened motor
power.
4. Binding in Tuning Shaft. Binding in
the flexible tuning shaft will place an
additional load on the motor which can
slow it down considerably. Install tuning shaft with minimum amount of
bending and check alignment where the
tuning shaft enters the receiver housing.
5. Gears Not Properly Meshed. Check
all gears in assembly for binding due
to improper meshing.
6. Defective Motor.-Replace.
194
3. Open Magnet Winding. An open
magnet will not pull latch down; consequently will not cause motor switch
to reverse.
4. Latch Bar Spring Too Tight. If the
latch bars operate under too much tension the magnet may not be able to pull
the latch down.
Fails to Retain Original Setting
1. Latch Rings Not Locked Securely.
The locking screw must be pulled down
securely, otherwise, the shock of the
sudden stopping will tend to slide the
rings away from the original setting.
2. Original Setting Not Accurate. Resetting of magnets may be necessary
after several days' use, during which
time the mechanism goes through a
"shaking down" process.
3. Electrical Drift. This is usually the
result of a great change in temperature.
Automatic compensation is provided in
the circuit to take care of the normal
operating temperature range. Before
making original setting, turn the set on
and permit it to play long enough to
arrive at a constant operating tempera'
ture. In zero weather do not expect the
set to tun~ "on the nose" until after a
constant temperature has been reached.
In severe cases of electrical drift occurring at normal operating temperature,
change the compensating condenser.
Impossible to Set Up Stations
. 1. Too Much Tension on Locking Levers. When the automatic locking screw
is loose, the station rings should move
freely. If the levers still hold the station rings partially locked, the screws
which hold the levers in position should
be loosened one-quarter to one-half
turn.
2. Latch Rings "Out of Range." If the
1. Open Magnet Winding. Check for
continuity and replace if necessary.
2. Magnet Contact in Control Head Not
Closing. Inspect contacts. Adjust or
clean if necessary.
3. Latch Bar Defective. Inspect latch
bar to make sure that it has not been
damaged. Replace latch bar, if required.
4. Poor Contact at Push-Button Plug.
A poor contact here means a voltage
drop which reduc~s the pulling power
of the magnet.
5. Improper Spacing of Magnet. Check
the spacing between the latch bar arma·
ture and the magnet pole. When the tip
of the latch bar is seated all the way
down in the notch in the latch ring, the
armature should not quite touch the
magnet pole. A hair line of light should
be visible between them.
6. Latch Rings Not Locked Securely.
If the latch rings are very loose the
motor will continue to turn the gang until the plates are completely meshed.
Latch Bar Sticks in Notch
1. Manual Tuning Shaft Binds. Bindin the tuning control shaft causes
the latch bar to press hard against one
side of the notch and may prevent it
from releasing as the magnet is deenergized.
~ng
2. Latch Bar Spring Weak. Check latch
bar tension spring to make sure it is
pulling away from the magnet with
sufficient force. Spring tension is adjustable.
3. Magnet Contact in Control Head
Stuck. Check the magnet switch in the
control head to make sure it breaks
contact when pressure is released on the
button. Check for frozen contact points,
or for sticking button.
4. Armature Rivet Wom. There is a
loosened latch rings slip ort the drum
until the notch falls out of reach of the
latch bar, they can be brought back to
position by following exactly the "setting procedure" outlined on page 195.
brass rivet at the tip of the armature, to
prevent the armature freezing to the
magnet. If this rivet is worn down, permitting the steel armature to actually
touch the magnet pole, it may freeze in
that position.
3. Die Cast Rings "Out of Round." In-
5. Burr on Tip of Latch. Lat~h tip
stall new rings.
should be smooth and shiny.
i
AUTOMATIC
6. Binding in Latch Bearings. Latch
must move freely but not sloppily.
. 7. Latch Tips Not Centered on Latch
Rings. Latl?h tips must not rub bake·
lite guide rings. The latch bar bearing
shaft is adjustable.
8. Friction Clutch Too Tight. A tension
washer between the motor pinion and
the brass pinion collar acts as a friction
clutch to absorb the shock of stopping
the motor quickly when a station is
tuned. If the tension is too tight, thl'!
torque of the stopped motor will hold
the latch bar tip in the notch.
9. Motor Brushes Too Tight. Too much
friction between the motor brushes and
the commutator will cause the same
thing.
TUNING
down. A faint "click" should be heard,
indicating that the tuning magnet has
attracted the latch bar.
5. Holding the magnet energized,
turn the dial manually all the way to
the high frequency end (1550 K.C.)
and then all the way back to the low
frequency end (535 K.C.)
6. Still pressing on the button, tune
in the station to be set on that button.
7. Proceed to set the remaining five
stations. For each station follow steps
3, 4, 5, and 6, as outlined above. At no
time in the setting up procedure should
the Tuning Motor be permitted to run.
8. Tighten the automatic locking
screw very securely. Do not hold the
tuning knob while locking the auto-
Setting StatioDs
NOTE: Before setting any station, let
the set warm up for not less than ten
minutes. If you wish you can "set" the
automatic tuner on the service bench
before installing the radio in the car.
Use a short aerial and peak the antenna
trimmer to it: Then readjust the antenna
trimmer after the installation in the car.
IMPORTANT-You will note that the
9·contact plug on the end of the control
head cable has one pin that is shorter
than the others. For the "setting up"
procedure, this plug should be inserted
in its receptacle on the receiver only
half way. This will cause all of the mag·
net terminals to De connected, but will
not permit the tuning motor to run duro
ing the adjustment, since the'short pin
will not make contact, thereby holding
the motor circuit open. The motor
should not run at any time during the
"setting up" procedure.
1. From the set of call letter tabs
provided, detach the proper ones for
the six stations. The station tabs should
then be inserted in the space provided
in the face of station tuning buttons.
Cover the tab with a small rectangular
piece of celluloid. Both tabs and celluloids snap into position.
2. Loosen the Automatic Locking
Screw. This screw should be turned
counter-clockwise four or five revolu. tions-far enough to assure plenty of
looseness.
• Section 6
matic, but allow the mechanism to turn
to its natural stop.
9. Push the plug all the way into the
receptacle on the receiver housing so
the short motor pin will also make contact.
Reversing Switch
NOTE: Four adjusting screws extend
upward through the switch mounting
plate, three of them in line, and one set
off by itself. (See Fig. 101.)
1. Turn the rotor assembly until the
High sides of all latch rings rest opposite the latch tips.
2. Turn screw "A" in until all latch
bar tips touch High side of ring and
then turn the screw back one-half turn.
(Spacing between latch tip and high
side of ring at point "X" should be 8
to 12 thousandths of an inch.)
3. Hold any latch bar tip down on
High side of ring and adjust screw "c"
(center screw) until the bakelite insulator on the center switch leaf just
Q:
UTING. MAGNET
MUTING ARMATURE
~
,
BOTTOM VIEW
'8"
.RONT
CENTEit
RCAR
3. Turn the dial all the way to the
low frequency end (535 K.C.)
4. Press the fint button and hold it
FIG. 101
195
Section. 6 •
THE
barely misses touching the heel of the
latch bar at point "Y." (Check adjustment by pressing other latch bars. The
depressed latch bar must not lift the
center contact even slightly.)
4_ With latch bar at rest position adjust screw "B" (front screw) until top
motor contact is lifted from center
contact by 12 to 15 thousandths of an
inch at point "Z." (15 thousandths =
1/64".)
5. Turn rotor until Low side of ring
rests under latch tip. Press any latch
bar down and make sure switch actually reverses. (Bottom contact must break
and top contact make sufficiently to lift
the top switch leaf slightly from the
bakelite spacer.)
6. Turn screw "D" (rear screw) until muting relay armature rests 15 to 20 .
thousandths of an inch from the mag-·
net pole. (Too close spacing will cause
intermittent muting due to vibration.)
(15 thousandths = 1/64".)
To Remove Latch Bar Assembly
1. Back up on front switch adjustment screw (A) until latch tips rest
outside the diameter of the bakelite ring
separators.
2. Remove comb shaped latch tension
spring. (E) Fig. 102.
3. Remove the hex-head machine
screw' which extends through the small
angle bracket into the brass latch bar
bearing shaft underneath the tuner.
4. Pull out latch and shaft assembly.
(F)
NOTE: To re-assemble, reverse the
above procedure, and take particular
care that:
1. Latch bar tips center on latch
rings. They should not rub bakelite
ring separators. (Spacing is adjustable
through elongated hole in small bracket under tuner.)
2. When readjusting screw (A),
turn it all the way in until latch tips
touch high side of rings; then back
screw up one-half turn. (See reversing
switch adjustment on page 195 ..
MYE
TECHNICAL
MANUAL
4. Lift the locking nut off the end
of the rot~r shaft.
5. Carefully loosen the three screws
(J) which hold the ring assembly to
the rotor hub, and remove all rings
and separators as a unit, being careful
to keep the three screws in position
through the assembly.
NOTE: To reassemble, reverse the
above procedure. Work carefully-do
not let the rings and separators get off
the screws.
To Replace Defective Latch Ring
1. Remove the entire latch ring assembly from the rotor hub. (See instructions above.)
. 2. Lay assembly on flat surface with
screw heads down.
3. Remove rings; separators, and
brass spacing collars, one at a time, until the defective ring is exposed.
NOTE: Reassemble parts one at a
time, being careful that rings, separators, and spacers are in the correct position.
CAUTION: Be careful to replace rings
in original position. Turning the ring
over will reverse the position of the
notch and will result in faulty tuning.
To Remove Defective Bub and Gear
A.
B.
C.
D.
E.
F.
G.
H.
J.
K.
L.
M.
N.
P.
R.
S.
T.
Fig. 102
Switch Adjustment Screw
Switch Adjustment Screw
Switch Adjustment Screw
Switch Adjustment Screw
Latch Spring (6 finger)
Latch Assembly Complete
Automatic Locking Screw
Clamping Lever
Ring Assembly Screw
Idler Gear Assembly
Motor Pinion
Pinion Collar
Tuning Motor
Relay Magnet Assembly
Reversing Switch
Manual Drive Shaft
Tuning Magnet
2. Loosen the four Bri!1to set screws
in the rotor hub ..
3. Loosen the one Bristo set screw
in the bakelite flexible shaft coupling.
. 4. Pull the rotor hub off the gang
shaft. The manual tuning gear and
coupling will have to be removed at
the same time. The brass collar on the
motor shaft may also need to be removed.
NOTE: When installing a new hub,
turn the gang to full mesh and the hub
gear against its stop before tightening
set screws.
SECTION 9H
Flash Tuning
1. Remove the entire latch ring assembly from the rotor hub. (See instructions above.)
I,
I
!
I
. The Flash Tuning mechanism consists essentially of the toothed disc at
-':0...
To Remove Latch Ring Assembly
I
1. Back up on switch adjustment
screw (A) until latch tips rest outside
the diameter of the bakelite ring separators.
2. Remove locking screw. (G) .
. 3. Remove the three locking levers.
(H)
196
I.'
I.
F'Ic.102
AUTOMATIC
the rear of the variable condenser
and the relay. The function of the
toothed disc is to operate the relay
when the variable condenser is turned
to the various pre-selected stations. The
relay contacts close the Flash Tuning
light circuit, illuminating the station's
call letters. At the same time they remove the high negative bias which
blocks off the audio, keeping the receiver silent until the pre-selected station is tuned in.
The relay coil normally is energized.
It is short circuited by the bent up tooth
of the disc contacting the movable arm.
This is why the Flash Tuning light
flashes for a second or so when the receiver . is first turned on-the rectifier
has not heated sufficiently to furnish
current to energize the relay.
Turn the Flash Tuning and Selectivity Switch knob to the "SHARP" position. Then tune in the first station on
your list of selected stations.
Leaving your station tuned in, go to
the rear of the radio. You will see a
semi-circular toothed disc, as illustrated
in Fig. 103. There is also a flat spring
arm, with a small rounded projection
near its end, that moves over the teeth
of this semi-circular disc as the Station
Selector knob is turned. Still leaving
your station tuned in, carefully not~
which tooth on the semi-circular disc is
directly under the rounded projection
of the spring afI~. Mark this tooth with
a pencil. Note that there is a double
row of teeth and either the tooth that
faces you or the tooth that faces the
front of the radio may be bent up, depending upon which one is nearer the
rounded projection of the spring arm.
After you have marked the tooth, turn
off the radio. Then tune away from the
station (with the Station Selector knob,
not the movable arm) and bend this
marked tooth straight up, using the
slotted end of the tool provided. See
Fig. 103. It is important that the slot
of the tool fit as far down as possible
on the tooth before bending. This is
necessary so that the complete tooth
will be bent up instead of just part of
the tooth. When this is properly done,
the projection of the spring arm will
touch the bent up tooth when the
toothed disc is rotated by turning the
Station Selector knob.
Turn the radio on again and tune in
• Section 6
TUNING
the next station on your list of selected
stations. Mark the tooth that now is
under the projection of the spring arm
when this station is tuned in. Turn off
the radio, tune away from the station
so that the spring arm will not be in
the way and bend up this marked tooth,
using the tool provided. Proceed in the
same manner for each of the other stations on your selected list. Turn off the
radio each time before hending up the
tooth. Otherwise a slight spark may
occur, although there is no danger of
shock. When properly done, the spring
arm will touch each of the teeth that
has been bent up but will not touch any
of the other teeth, as the Station Se,
lector knob is turned. Since the mechanism will already be set up on teeth
close to the ones· you will want to use,
these old teeth must be bent back down.
Turn the Flash Tuning and Selectivity Switch knob to the "FLASH" position. Now again tune in the first station
on your selected list. As its position is
reached, the bent up tooth will'touch
the spring arm and a light will flash on
the' dial at a position opposite the end
of the dial pointer.
SECTION 9J
Packard 333915
First turn the receiver on and allow
it to operate for twenty minutes before
making these adjustments.
POSITION OF TOOL
AFTER SLOTTED END
HAS BEEN USED TO
BEND UP TOOTH
Press in the "DIAL" button and hold
it in until the tuning motor stops, indicating that your receiver is now connected for manual tuning.
Using the tuning knob, tune in the
station whose call letters appear on the
extreme left hand button (Button No.
1, Fig. 104). This is done so you can
identify the station by its program.
Remove the front cover on the receiver case. Two slots are provided at
each side of the case so that the cover
can be pried off easily. CAUTION: If
cover is pried off with a screwdriver,
do not push screwdriver too far into
case. After the cover has been removed,
you will note two rows of adjusting
screws in the receiver (See Fig. 104).
Press in the button bearing the call
letters of the station you have just
tuned in manually (Button No.1 on extreme left). Hold this button in until
the tuning motor stops running. Then,
using a screwdriver, adjust the screw
marked lA (in the receiver case) until
the station you were just listening to is
heard again.
Adjust the screw marked IB for
maximum volume. Repeat adjustment
of lA, making sure you set it to the
point where the tone is the deepest, also
where hiss and noise are at a minimum.
These adjustments must be made very
carefully to assure good reception.
The set-up for this station is complete and you can proceed to set up the
next station which you have labelled on
the push-buttons. Proceed as follows:
(a) Press in "DIAL" button, and hold
it in until tuninl? motor stops.
SCREW
IMPORTANT
TOOL MUST BE
PUSHED AS FAR
POSSIBLE ON
TOOTH BEfORE
BENDING
POSITION OF TOOL
PRIOR TO BENDING
U~ TOOTH
REAR OF RADIO
FIG.
103
\
'197
Section 6 •
THE
FREQU!NCY RANGE
55. @
c::.
®
"='
2A @ 550® 2B
lA c::, -
TO -
950KC
V
7 ••
@
3A (j) - 1250KC
<0 (JJ) 3B
60
z
Z
I.IJ
is
t- 50
:r
C)
z
«
I.IJ
0
1&.4
0
II:
I.IJ
t-
C)
z
~
t-
~
z
10
i:i 2600
:r
2200
<
III
iii
W
10.1
.'!> 3500
t3000
:r
c).
:i 30
r/)
600
500
'z 400
<
II:
20
1600
1600
1400
1200
1000
800
t-
300
200
I:
1
I
...ii'
"
1*
I
10
FIG.
Receivers
FIG. 6
transmitting antennas are usually located on tall buildings, mountains or
other high elevations. Special antenna
arrays are also employed with the intention of concentrating the signal in
the horizontal plane. Such an array is
the "turnstile" antenna, illustrated in
Fig. 6. The height of the receiving antenna is of equal importance with that
of the transmitter, as, in general, trans'mission is essentially limited to "line of
sight" distances. Fig. 7 is a chart for
obtaining this distance, knowing the
heights of the receiving and transmitting antennas. By laying a ruler between the proper points on the outside
scales, the line of sight distance will
be given by the interception on the
middle sc'ale.
204
The design of a receiver for F.M. is
similar in many respects to that employed in A.M. practice, but is somewhat more complicated. The superheterodyne circuit is used universally, but
the different fr~quency coverage brings
in many variations from usual A.M.
practice and, in addition, there is included such features as limiters, discriminators, etc. Let us start at the antenna ,end of an F.M. receiver and discuss the salient design points of the
various major component divisions.
In standard broadcast reception a
makeshift antenna is frequently adequate; in F.M. reception this is not so.
While it is true that good F.M. reception is often obtainable using the least
possible bit of antenna in the immediate locality of the transmitter, out in
the more remote sections field strengths
are of the order of a few hundred
microvolts per meter or less. In an
F.M. rer:eiver there is a definite advantage in getting all possible pick-up, as
the noise-reducing ability of the set is
a direct function of this factor. All
modern F.M. receivers give acceptable
noise reduction on signals of only a
few microvolts, but at these low signal
levels ,the noise reduction is not absolute. Thus any improvement in the sig-
100
50
7
nal delivered by the antenna to the receiver proper means just that much
more increase in the signal to' noise ra·
tio, until ultimately we reach the level
at which reception is practically noise
free. For this reason most up.to.date
F.M. installations utilize dipole antenna
installations. This consists of a hori·
zontal rod assembly, cut in the middle,
one-half wave length long (about 11112
feet), and connected to the receiver by
a twisted pair transmission line. Such
an antenna is most receptive to signals
coming from a direction at right angles
to its plane, a fact which is of great
value in those areas where two stations
of the same frequency and essentially
equal strength are received, as previ.
ously described. By orienting the an·
tenna to favor pick-up from one station
over another the favored station alone
will be received devoid of interference.
In cases where most of the desired stations are in one general direction and
more pick-up is desired, a reflector may
be added. This consists of another halfwave rod located a quarter wave length
behind the other, in a direction away
from the ,desired stations. This is frequently done, in television reception,
but is usually not advisable in F.M. installations, as it reduces the reception
in the other direction. Many of the
~odern F.M. receivers incorporate
built-in folded dipoles in the cabinets.
I.'
II
~
I,
fREQUENCY
MODULATION
FIG. 8
These antennas, or other similar pickups, will be found generally acceptable
in the strong field strength localities,
as, for example, in Metropolitan New
York City. For more remote installations more elaborate dipoles may be
added. Fig. 8 illustrates the construction of dipoles and reflectors as described above.
The R.F. end of an F .M. receiver
has somewhat the. same functions to
perform as in an A.M. receiver, but the
relative importance of the various factors is different. For example, I.F. rejection is of lesser importance, mainly
because of the usual choice of an I.F.
which is generally interference free.
Image rejection in itse)f is not so important, as the current choices of I.F.
place images' of F.M. stations outside
the band; however, the R.F. selectivity,
which would determine the image rejection, is of importance in reducing other
spurious response points. The major
function of the R.F. end of the receiver
is to add as much as possible to .t;lte
stable gain of the set, so that sensitivity
shall be high, with attendant good signal-to-noise ratio. There is a definite
limit to the amount of stable gain
which can be incorporated in an I.F.
amplifier without excessively elaborate
shielding and filtering, consequently
the more gain which can be obtained
from the R.F. amplifier and the converter the better.
The R.F. end of the set has generally
fallen into two categories in current receivers. Most manufacturers use a
more or less conventional type of R.F.
amplifier, wherein the R.F. tube is usually one of the high mutual conductance
types, the amplification is done at the
input frequency (42-50 mc.) ana the
amplified signal is then reduced to the
l.F. in the converter. Converters may
be of types similar to those used in
broadcast practice, with one tube performing the dual function of oscillator
and modulator, or separate tubes may
be used for these functions. In the latter case a high Gm tube is usually used
for the modulator, or "mixer," tube,
and a separate triode for the oscillator.
This has several advantages. For one
thing the resultant sensitivity is excellent, as such a combination has probably the highest transconductance. In
addition good frequency stability is
possible, as the best tube for the oscillator from this standpoint may be
chosen, properly located and properly
compensated.
Where even higher sensitivity is desired a dual superheterodyne is used.
In this system the incoming signal at
42-50 mc. is first heterodyned down to
• Section 7
a moderately high I.F., amplified at
this frequency, then heterodyned again
to the lower or usuall.F. This permits' ,
of higher Qverall gain because relatively few tubes are working at the same
frequency, consequently the problems
of regeneration are not so severe. Receivers of this type have been coqstructed which will give acceptable
noise reduction on inputs of the order
of a tenth of a microvolt.
General Electric has developed a
modification of the dual superheterodyne which employs the same number
of tubes as a conventional R.F. amplifier-single converter combination, yet
permits considerably higher gain. The
basic portion of this circuit is illustrated in Fig. 9. In this arrangement a
variable first, or higher frequency, I.F.
is used, the same oscillator being used
to beat the incoming signal to this frequency and thl(n to beat it down again
to the final I.F. The operation of this
circuit may be understood from the following, together with the equations and
references on Fig. 9:
Let us assume an incoming signal of
46 mc. The input circuit, Ll and Cl, is
tuned to this frequency, and the signal
is then applied to the grid of the first
converter Vl. Tube V3 is a conventional triode oscillator, utilizing the
Hartley circuit, and is tuned to a frequency of 20.85 mc. by L3, C3. L3 is
...-------, 23.15-27.15
MCS.
T
4.3
[f
MCS.
...
SG+
B+
18.8522.85
MCS.
.----~---
C3
1
SOLVING
f;
= t:...:!£
2
£.
o
=f
-F'
2
B+
B+
~-ro
=f,
r,-fo = F'
f =SIGNAL F'REQUENCY
r, = I.F. F'REQUENCY
,n
f;,
= OSC_
F'REQUENCY
F'
= 2""1.F.
F'REQUENCY
FIc. 9
205
THE
Section 7 •
magnetically coupled to Ll, consequently tube VI has impressed on its
grid, oscillator voltage of frequency
20.85 mc., in addition to the 46 mc.
signal. These two frequencies are
mixed in this tube and the difference,
25.15 mc., is produced. Tuned circuit
L2, C2 is resonant to this frequency,
and also passes along the oscillator
voltage, supplying tube V2, the second
converter, two signals of frequency
25.15 mc. and 20.85. These are mixed
in this tube, and the difference, 4.3 me.,
is produced and passed along to the
I.F. amplifier by the first I.F. transformer T. Thus as long as the oscillator
is of frequency equal to one-half the
difference of the incoming signal and
the final I.F., and the intermediate
tuned circuit L2, C2, is resonant to onehalf the sum of these frequencies, this
system will function properly.
This system is capable of greater
gain than a conventional RF. stage for
several reasons. First, the RF. stage
(considering the plate circuit of VI,
the coupling transformer and the grid
circuit of V2 to be an RF. stage) is
working at about half the frequency of
a conventional R.F. amplifier and, since
the maximum theoretical gain with
stability of an RF. stage is proportional to the square root of the reciprocal of frequency this means a very considerable increase in gain. Secondly,
the input impedance of a converter or
RF. tube varies with 'frequency, as
does also the tuned circuit impedance
of the transformer secondary, both im·
pedances in parallel being about twice
as high at the lower operating fre-
I
+15
I
OSCIILLATO~
DRIFT
+10
::: +5
.J
u
>u
o
0
'/~r--
.J
i<
t
5
10
15 -......... 30
60
TIME-MINUTES
I
-5
ii:
<>
-10
-15
JFM90
FIG. 10
206
12o
MY E
TECHNICAL
MANUAL
quency, than they would be at the input
frequency. This permits considerably
greater gain from the coupling transformer. Another factor is overall regeneration. If the R.F. amplifier is operating at the same frequency as input
signal there is considerable coupling in
the supply circuits, in the tuning condensers, between other associated parts,
which further reduces the possible stable gain. All these factors taken together result in a gain of about four to
one due to the use of a dual super in
this circuit over a conventional R.F.
amplifier.
The converters used in these modern
F.M. sets differ from conventional A.M.
practice mainly, as pointed out above,
in the usual use of separate oscillators
and of compensation to reduce frequency drift. This compensation takes
the form of small ceramic capacitors
connected across a portion or all of the
oscillator tank circuit. When properly
located so that they will heat up at
about the same rate as the principal
components of the oscillator tank (coil,
gang, trimmers, etc.), they will cause a
reduction in tank capacity sufficient to
balance the increase in the capacity of
the above-mentioned components, with
the result that the frequency stays very
uniform, and it is not necessary to re·_
tune the set after it heats up. Inciden·
tally, it should be pointt)dout that best
practice dictates that every precaution
be first taken to reduce drift to a minimum without compensation, by proper
choice of insulating materials, location
of parts, coil construction, etc., then
compensation may be added to remove
the remaining drift. In this manner the
departure from fin~l frequency at any
time during the warm-up period will be
held down. Fig. 10 shows how well this
factor may be held down by modern
design.
The design of the I.F. amplifier of a
modern F.M. receiver is one of the
most complicated jobs in it. This is
largely due to the inclusion of the A.M.
band in these receivers. Of course it
would be relatively simple to have two
entirely different receivers for each operation, but today's sets are designed
for economy and maximum result per
dollar, consequently considerable consolidation is required. This makes itself particularly felt in the I.F. design,
as here we must pass both the A.M.
1
~-,--+---~--IOOOX--~--4--'-+~
I
I F SELECTIVITY CURVE
/----1\---1---/00 X
-300
o
-200 -/00
FREQUEN~Y
+/00
DEVIAT/ON
+200 +300
JFM 90
FIG. 11
LF., usually 455 kc., and also the F.M.
I.F., ordinarily 4.3 mc. or higher. The
choice of the F.M. LF. involves many
factors, such as spurious responses,
image responses, sensitivity, stability,
cost, etc. In general the majority of
sets at present use an I.F. of 4.3 mc.,
but there is some tendency to go to considerably higher frequencies than this
on the more elaborate sets.
In practically all ,sets the I.F. transformers comprise units for both I.F.s
connected together, usually with the
various windings in series. This means
that the I.F. system will respond to
either frequency, although in the broadcast band it is customary to short out
the F.M. winding on at least one transformer to prevent the second harmonic
of the oscillator ,from blocking the LF.
tube. High Gm tubes are usually used
in modern sets, permitting a very high
amplification to be obtained. Originally it was thought that the I.F. system
for an F.M. set needed to be flat topped.
Present-day practice relies on the limiters to smooth out any amplitude modulation introduced by the LF. system,
and uses LF. transformers set at about
optimum coupling, with the overall selectivity ddwn 2·1 at about ±75 kc.
This is illustrated in Fig. 11, which
shows the selectivity of the G.E. trans·
'lator, model JFM 90. This receiver ac·
tually has selectivity in excess of current needs, as it was introduced at the
time when local stations were still on
I
I
fREQUENCY
adjacent channels, and current conditions do not require quite as good skirt
selectivity_
Limiters
The limiter is one part of an F .M.
receiver design not found in conventional broadcast receivers, although
noise limiters have been used in deluxe sets and communication receivers.
The limiter forms one of the most important factors in obtaining the great
improvement in performance of F.M.
over A.M. Limiters are largely responsible for the outstanding ability of an
F.M. set to reduce the noise background to practically the vanishing
point, for, though noise reduction is
also contributed by the discriminator
at balance, as will be described later,
when the frequency swings away from
the mid-frequency, any amplitude noise
present can then come through, and
consequently will make itself apparent
as noise distortion on modulation.
Limiters are the reason an F.M. set can
discriminate between two stations on
the same frequency as long as they differ in strength by about 2-1. They
contribute tremendously to the ability
of an F.M. set to reject static, both
natural and man-made. Actually, two
factors which Major Armstrong originally established as essential to proper
operation of an F.M. receiver were
the wide frequency swing and the use
of a limiter_
A limiter is essentially an amplifier
stage which saturates at a certain level.
It may be likened to a dam, which al-
MODUI.ATION
lows the level of the water in a reservoir to rise to the overflow level, then
maintains a constant level regardless of
how much water is poured in. Limiters
in general work on two principles, grid
rectification and current limitation. In
the former type a fairly high resistance
is incorporated in the grid circuit,
shunted by a small capacitor. No fixed
bias is supplied this grid, consequently
it will draw grid current upon the application of a signal. This current
flows through the grid resistor and the
resultant bias reduces the gain of the
tube and maintains a fairly constant
output. This sounds much simpler than
the actual operation of this device really is. To elaborate on the operation of
this apparently simple device let us
consider the circuit of Fig. 12, which
shows two limiters in cascade. Consider, for the time, only one of these
limiters. Let us assume an LF. signal
of several volts is impressed on the
grid of this tube. This strong signal
will charge up the condenser Cl, in the
low side of the grid return, to approximately the peak amplitude of the signal. Condenser 'Cl will in turn discharge through its shunt resistor Rl,
but, since this resistor is usually fairly
high, the discharge rate is slower than
the charge rate through the tube, con:
sequently a steady bias will build up
on the grid. With this bias on the tube
n~arly equal to the peak of t1;te impressed signal, the grid will swing positive only on the peaks, for relatively
short durations. The length of these
durations will depend upon the rate of
discharge of the grid condenser Cl by
the grid leak R1. Thus in the plate circuit there will be a succession of cur-
CASCADE:
LIMITER
SG+
~I
B-tFIG. 12
• Section 7
rent pulses, the height and width of
which depend upon the applied input
signal and the grid circuit time constant (product of Rl and Cl). If this
time constant is properly chosen it will
be found that, over a considerable range
of input signals, the width of these plate
pulses will vary inversely as their
height, i.e., an increase in input signal
causes the plate pulses to become higher but slimmer. The average value of
these pulses remains practically constant over this range, with the result
that any amplitude variation present
on the grid will not appear in the plate
circuit.
This phenomenon may be demonstrated in a very interesting manner by
reconnecting the discriminator circuit
of the F.M. receiver as a conventional
amplitude detector and impressing an
amplitude modulated signal on the grid
of the limiter. For low inputs it will be
noted that the output increases linearly
as the input level is raised, indicating
no limiting. Then the output will start
to level off, then drop, and finally it
will be noted that for certain conditions of grid circuit time constant,
screen and plate potentials and regulation, etc., the amplitude modulation
will practically vanish. Above this input it will usually increase again somewhat, and then once again reduce to a
very low value. Thus when using a tube
such as the 6SH7 in a single limiter
with values for Cl and Rl of about 30
mmf. and 150,000 ohms, respectively,
it will be noted that these points of best
limiting will fall at about 1 volt and 7
volts, respectively, on the grid of the
6SH7. With a single limiter it is possible to get very good reduction in amplitude modulation as indicated by this
test, but not really outstanding reduction except at the above noted points.
Another factor which has an extremely
important effect on the choice of grid
circuit time constant is the susceptibility to impulse noise, such as ignition. If
the time constant is too high, i.e., condenser or resistor too great, the impulse noises will not be sufficiently restricted. This requirement usually dictates that the condenser Cl be of the
order of 20-40 micro-microfarads and
the resistor Rl of about 50,000-150,000
ohms.
This brings us to the use of dual or
cascade limiters_ As was pointed out
207
j
t.
Section 7 •
THE
a .single limiter usually has one or
more input levels at which it is really
effective, one volt or seven volts in
the case given. If two limiters are
used in tandem, and the first adjusted
to limit in such a manner as to put this
critical input, say seven volts, on the
grid of the second limiter for most
values 'of input signal above the limit- .
ing level, it is obvious that well-nigh
perfect limiting is possible, and this is
the case. The value of inductance, of
coil L in the plate circuit of the first
limiter is such as to resonate with the
tube plate capacity and associated
shunt capacities to the LF. frequency,
and its Q is made of such a value (as,
for example, by shunting it with a resistor) as to make the gain from the
grid of the first tube to that of the'second just the correct amount to place
an input of about 7 volts on this second tube over that range of input signals on the first tube for which it is
effectively limiting. The first tube is
therefore working at a range of inputs
over which it has acceptable limiting,
and is holding the second limiter on
that point for which it has very good
limiting. Thus the use of two limiters
doesn't merely double the signal to
noise ratio; it increases it manyfold.
Returning to our original simile a cas·
cade limiter is like the water from our
c9nstant level reservoir supplied
through a small pipe in such manner
that the flow must always be constant.
In the cascade limiter there is more
latitude of time constant, and one limiter may be made to be especially effective to impulse noise, or both may
be, depending, upon how perfect limiting on regular steady noise is desired.
On G.E. model JFM 90, for example,
Cl is 47 mmf., Rl 47,000 ohms, C2 is
22 mmf., R2- 180,000 ohms. Referring
~gain to Fig. 12 it will be noted that
there is considerable gain in the first
limiter, particularly at levels below its
limiting threshold. The RC circuit of
the first limiter may be broken up, with
th·e condenser CIon the high side of
the transformer and the leak Rl between grid and ground .. Occasionally it
is better this way, as it reduces the capacity across the leak by the amount of
strays in the transformer.
In the otherI basic type of limiter,
screens and plates are operated at very
much reduced potentials, so that a
208
MY E
TECHNICAL
small signal will produce current saturation. In general operation it is quite
similar to the grid bias type of limiter,
and the same advantages accrue here
due to the use of two limiters in cascade. In general it will be found that
more sensitivity may be obtained with
the grid bias type of limiter, particularly at low input levels where limiting is
just beginning to take hold, as at thest<
levels the two limiters are acting similar to regular I.F. stages, and while
the reception of signals in this "twilight" zone does not represent good
F.M. operation, it still often gives usable intelligence, particularly in contrast
to A.M. reception.
Incidentally it should be mentioned
that in general, best results in limiters
are obtained with sharp cut-off tubes,
and that high Gm is desirable here, too.
Recently such tubes as the 6SH7 and
the 7T7 have become available, and the
use of these tubes has correspondingly
lowered the requisite input level at
which limiting now takes place.
Discriminators
It will be recalled that the older
A.F.e. systems employed a device
'which translated the variations in frequency into D.C. potentials, which. in
turn were applied back to the reactance
control tube to restore the oscillator to
its proper frequency. This device was
termed a discriminator, in that it discriminated between signals of different
frequency. This same device is now
used in similar manner in F.M. receivers, to transform the F.M. signal which
is being wobbled in frequency, into an
audio variation corresponding to this
wobble.
In general there are three different
types of discriminator circuits. The
simplest works on the principle of resonance, and is illustrated by the circuits
of Figs. 13 and 14. In these circuits we
have a series circuit consisting of inductance, capacity and resistance, with
a rectifier (a triode, in these illustrations, although diodes can also be
used) connected across one of the reactive elements. The mean operating frequency is slightly off the resonant frequimcy of these reactances, consequently the portion of the, applied voltage appearing across the rectifier will be de-
I'.
.'
.j
[I,
~
I'
I'
I
11
I~
FIC. 13
pendent upon the frequency. The circuit of Fig. 13 is not balanced, i.e., only
one rectifier is used, consequently the
output will be dependent upon signal
level as well as upon frequency. As a
result such a. circuit is susceptible to
noise modulation of the carrier which
may succeed in getting through the limiters. The circuit of Fig. 14 is balanced so that at the center frequency
no voltage appears across the output
terminals, and hence noise is balanced
out during quiet passages. Another type
of tuned circuit discriminator uses two
diodes, one across the inductance, the
other across the capacitor, with the two
load resistors in series. This is also
bala:nced to noise. In general it may.
be noted that any type of dual discriminator wherein equal voltages are
impressed on the two rectifiers at the
operating center frequency, will be
noise balanced. These tuned circuit
types of discriminators, while interesting, are comparatively low in audio
sensitivity, and are consequently not
used in current designs.
The next type of discriminator circuit to consider is illustrated in Fig.
15. Here an I.F. transformer is used"
with the secondary split, one side of the
secondary being tuned to resonance
slightly above the center frequency, the
other side slightly below. It is obvious
. that as the frequency is varied either
side of resonance one diode or the
other will get a greater applied signal,
and will create a greater D.e. voltage
than the other. If both signals are
equal, as is the case at the center frequency, the D.C. output is zero, as the
!'
[
I
I
I
I',
I
.I
FREQUENCY
• Section 7
MODULA7'ON
grees out of phase with the secondary
current, which is in phase with the induced voltage. The resultant of these
four relationships is a total shift of 90
degrees between primary and second·
ary voltage at resonance.
Since the top of the primary con·
nects to the center of the secondary,
the primary voltage acts in series with
FIG. 15
FIG. 14
two series voltages are then equal and
opposite. If the upper diode gets the
greater voltage the output will be negative, or positive if the lower diode gets
the higher signal voltage. Thus the
voltage appearing across the series load
resistances will be an audio voltage corresponding to the F.M. signal modulation, and may be applied to an audio
amplifier. This type of discriminator
was extensively used in the earlier days
of A.F.e., but has the disadvantage of
being more difficult to align, and has
been displaced by the phase shift type
to be described next.
In the third basic type of discriminator, and the ~me used almost entirely to. day, the phase shift between primary
and secondary of an I.F. transformer is
utilized. Fig. 16 shows a typical phase
shift discriminator. It will be noted
, that a more or less conventional I.F.
transformer is used, provid,ed with a
center tap, which is connected through
a blocking condenser to the plate of the
preceding tube, and also through an
R.F. impedance (a choke in this illustration) to the center tap of the two
resistors in series. The audio output
is ohtained across these two resistors.
The manner in which this circuit works.
is very interesting and will be described
in detail.
With the applied frequency of a value to which both primary and secondary are resonant, the voltage appearing across the secondary (E1 plus E2)
will be 90 rlegrees out of phase with
the primary voltage Ep. This follows
from the fact that the secondary at resonance reflects only a resistance to the
primary, consequently the current
through the primary inductance will be
90 degrees out of phase with thtt applied voltage. The induced voltage in
the secondary circuit is again 90 degrees out of phase with the primary current, and finally the voltage across the
secondary tuning capacity is 90 de-
one-half of the secondary voltage on one
diode, and in series with the other half
on the other diode. Thus the resultant
voltage on each diode is the vector sum
of two voltages in phase quadrature at
resonance. On one diode the secondary
voltage leads the primary voltage by
90 degrees as viewed from the diode,
on the other it lags. If we assume, for
the purposes of illustration, that the
primary voltage equals the total secondary voltage, the voltage on each
diode at resonance would then be approximately 1.12 times the primary
voltage (square root of the sum of the
squares of Vp and Vp/2).
FIG. 16
209
SectJon 7 •
rH,E
,As the frequency 4eparts from resonance the secondary voltllge also departs from, this 9O-degree ,phase relationship .witit the primary, approach~g '~ither zero or 180-degree phase
shift with the primary applied voltage,
depending upon which way the frequency shifts .. In this event the voltage
in one-half of the secondary will approach nearer to being in phase with
the primary voltage, while the voltage
of the other half approaches nearer to
phase opposition. If carried far enough
one-half of the secondary would ultimately be directly additive to the primary, whereupon the voltage applied
to that diode would be 1.50 Vp, while
the other diode would have .50 Vp applied to it. Another factor enters here,
however, in that the primary voltage is
falling off' as the frequency is varied
from the resonant point. As a result
the voltage applied to the diode will
increase at first as the frequency is
changed due to the phases of the
two component voltages approaching
equality, then will reach a peak value,
and finally decrease as the frequency
is further changed, due to resonance.
Simultaneously the voltage across the
other diode will be decreasing, consequently the D.C. voltage across the
two diode loads connected in series
will vary through zero to plus or
minus as the frequency is varied, thus
developing an audio voltage corresponding to the modulation, which is
passed on to the subsequent amplifier.
This type of discriminator has the highest degree of sensitivity, as the output
is obtained as the difference between
two equal and quite large voltages, so
that relatively small variations in these
voltages result in really considerable
outputs. Also, since the output at bal. ance is zero this system is not responsive to amplitude modulated noise
when no modulation is present. Bear
in mind, however, that when modulation occurs the frequency swings away
from the b~lance point, and then the
output depends upon the amplitude as
well as the frequency of the applied signal. Unless a limiter system is used,
amplitude noise modulation will then
make its presence known in the form of
hash on the program modulation. Thus,
it should be emphasized that complete
noise reduction depends upon a great
many things, signal strength, R.F. sensi-
210
MYE
.
TECHNICAl.
I
I
+20
Dlse~IMINATOR
CURVE
+15
/
+10
...
..I
o
+ 5
>
.;
o
-100
/'
-50
/
/
oL
/.
/
/
I/)
-1 50
MANUAL
+50
FREQUENCY
DEVIATION
+100
+150
-10
-15
JFM90
-20
I
FIG.
sion for better high frequency response
on F.M., where the full audio range
up to 15,000 cycles may be utilized.
This usually takes the form of better
audio amplifiers, more power output,
considerably better acoustic systems,
including many cabinet refinements designed to improve the overall response.
Also, in F.M. the high frequencies are
pre-emphasized at the transmitter in
order to improve the signal-to-noise ratio, consequently the receivers are
equipped with de-emphasis networks
when in the F.M. position, to restore
the fidelity to normal. Some of the
current receivers employ audio degeneration to further smooth out the
overall response curve and reduce harmonics.
I
!
I;
Ii
Ii
I.
I"~
"
i:
I,"
"
17
Alignment
tivity, conversion and I.F. gain, design
of the limiters and the type of discriminator used.
Most of the discriminators used today are of the type described above. In
the General Electric Model LF-1l5,
shown in Fig. 19, a modification of
this circuit is employed which permits
the use of a grounded single cathode in
the associated dual diode. In this arrangement the secondary is opened at
the center, one side going to ground,
the other being effectively bypassed to
ground by a capacitor. The two diode
loads are connected between this point
and ground, and thus are less "hot"
than in the usual arrangement. By tracing the circuit out it will be seen that
it is essentially the same fundamentally,
with the, primary being in series with
one half of the secondary to each diode.
Fig. 17 shows the discriminator
characteristic of a typical modern receiver. It will be noted that this curve
is linear over a plus or minus 100-kc.
region, thus adequately caring for the
maximum permissible swing, together
with a reasonable safety factor for detuning and drift.
Audio Amplifiers
The audio systems of modern F.M.
receivers differ from corresponding
A.M. practice primarily, in the provi-
The alignment of frequency modulated receivers includes several operations similar to those employed in regular A.M. practice, and several peculiar
to F.M. In conventional A.M. alignment the simplest method involves the
use of a signal generator, which is a
source of amplitude modulated waves,
and which may be anything from an
elaborate piece of equipment, complete
with accurate coritrols of output, modulation, etc., to a simple modulated oscillator. Output is usually indicated by
a simple output meter, although the
more elaborate service installations also
have cathode ray oscilloscopes for I.F.
alignment. These oscilloscopes are extremely valuable in A.M. alignment,
but by no means indispensable. In
F.M. alignment a cathode ray oscilloscope is an even more valuable tool, as
it makes the visual effect of the I.F.
and discriminator transformer tuning
adjustments very noticeable. The signal generator employed for F.M. alignment differs from that used on A.M. in
that it must supply a more widely differing range of frequencies than usually
employed on A.M., namely, I.F. frequencies varying from about 2 mc. up to 8
mc., or even higher, plus the signal frequencies of 42-50 megacycles. Also
these signals must be frequency modulated. A conventional A.M. signal generator or test oscillator that covers the
required range of frequ~ncies may be
I~
'"
Ii
FR.EQUENCY
used in aligning F.M. receivers by
using an unmodulated signal and a meter to indicate resonance, as will be described later_ There are not very many
F.M. generators on the market yetBoonton Radio Corporation makes a
very good F.M. signal generator, their
model 150A. In addition Hickok has a
model 188X generator, and General
Electric their type TMV-97-C Test
Oscillator and TMV-128A Frequency
Modulator. Any good oscilloscope may
be used in conjunction with these generators to give visual indication Of
alignment.
To illustrate the usual alignment
process for an F.M. receiver, let us consider G.E. model LF-115 receiver. On
the schematic, Fig. 19, will be noted
two points, "A" where the audio output from the discriminator is connected
to the volume control, and "B," on the
grid of the first limiter. These two
points are the usual alignment points
for connecting meters or oscilloscope in
practically all F.M. sets. Point A is
used for discriminator alignment, B for
I.F. and R.F. alignment.
In aligning this set with one of the
above-mentioned signal generators the
oscilloscope is connected first to point
B through a half-megohm resistor.
6SK7
ell
I" J.F.AMPL.
6SK7
Z"' I.F.AMPL.
• Section 7
With the signal generator set to the LF.
frequency, 4.3 me. in this particular
set, and applied to the grid of the 6SG7
converter tube through a small mica
condenser, the oscilloscope should show
a curve like that of Fig. 22, when the
circuits are properly aligned. In aligning such a set it is customary to align
the last LF. trimmers first, and then
proceed forward.
After the LF. has been properly
aligned the oscilloscope is shifted to
point A, still through the resistor, and a
curve as in Fig. 23 will be obtained
when properly aligned. The effect of
the secondary trimmer of the discriminator transformer is to shift the crossover point of the two straight lines up
and down, while the adjustment of the
primary trimmer affects the straightn~ss of these lines. The proper adjust-
FIG. 22
6AB7
I" CONY.
MODULATION
6SJ7
I" LI MITER
6H6
6SJ7
Z"'LlMITER
C33
T4
DISCRIMINATOR
OUTPUT
C5
PARTS DESCRIPTION LIST-MODEL JFM-90
Symbol
CIa
C1b
C1c
C2
C3
C4
C5
C6
C7
C8
C9
C10
Cll
C12
C23
C24
C25
C26
C27
C28
C29
C30
C3l
C32
Description
Oscillator section of tuning condenser
1st converter section of tuning condenser
2nd converter section of tuning condenser
5-24 mmf. oscillator air trimmer
2-20 mmf. 1st converter trimmer
2-20 mmf. 2nd converter trimmer
40 mmf. t~perature compensating capacitor
470 mmf. mica capacitor
50 mmf. temperature compensating capacitor
470 mmf. mica capacitor
470 mmf. mica capacitor
470 mmf. mica capacitor
470 mmf. miea capacitor
.01 mfd. paper capacitor
.01 mfd. paper capacitor
.01 mfd. paper capacitor
47 mmf. mica capacitor
.01 mfd. paper capacitor
.01 mfd. paper capacitor
47 mmf. mica capacitor
47 mmf. mica capacitor
22 mmf. mica capacitor
47 mmf. mica capacitor
47 mmf. mica capacitor
Symbol
C33
C34
C3S
C36a
C36b
C36c
C37
C38
C39
C40
Ll
L2
L3
PI
R1
R2
R3
R4
R5
R6
R7
R8
R9
RIO
Description
50 mmf. temperature compensating capacitor
47 mmf. mica capacitor
220 mmf. mica capacitor
15 mfd. dry electrolytic
30 mfd. dry electrolytic
1() mfd. dry electrolytic
0.1 mfd. paper capacitor
.02 mfd. paper capacitor
8 mmf. temperature compensating capacitor
.01 mfd. paper capacitor
Antenna coil
Interconverter coil
Oscillator coil
Dial lamp, Mazda No. 44
33,000 ohms carbon resistor
3.3 megohms carbon resistor
6800 ohms carbon resistor
2200 ohms carbon resistor
1000 ohms carbon resistor
3.3 megohms carbon resistor
12,000 ohms carbon resistor
1000 ohms carbon resistor
1000 ohms carbon resistor
47,000 ohms carbon resistor
Symbol
Rll
R12
RI3
R14
R15
RI6
R17
R18
R19
R20
R21
R22
R23
R24
R25
R26
R27
R28
Sla
SIb
T1
T2
T3
T4
T5
T6
Description
15,000 ohms carbon resistor
47,000 ohms carbon resistor
2200 ohms carbon reaistor
2.2 megohms carbon resistor
47,000 ohms carbon resistor
10,000 ohms carbon resistor
180.000 ohms carbon resistor
68,000 ohms carbon resistor
22,000 ohms carbon resistor
100,000 ohms carbon resistor
100,000 ohms carbon resistor
100,000 ohms carbon resistor
1200 ohms 7.4 W, wire wound resistor
3300 ohms 1 W. carbon resistor
47,000 ohms carbon resistor
470,000 ohms carbon resistor
47,000 ohms carbon resistor
47,000 ohms carbon resistor
Power switch
F,M.-Phono switch
1st LF. transformer
2nd LF. transformer
3rd I.F. transformer
Discriminator I.F. transformer
Power transformer for 50-60 cycles
Power transformer for 25 cycles
FIG. IS-Schematic Diagram Model ]FM·90
211
r
Section, 7 •
H I
MY I
.
T'CHNleAL
I
MANUAL
ment is obtained when the two lines are
straight and cross in the middle.
When an oscilloscope is not available,
a high resistance, voltmeter may be
used, preferably one with at least 20,000 ohms per volt. This meter is first
connected to point B through the halfmegohm resistor, and .the signal generatol-" is now unmodulated. All, the trimmers are adjusted for maxinium voltage as indicated by this meter. The
meter and resistor are now shifted to A,
and with the secondary purposely detuned, the primary is tuned for maximum voltage. Then the secondary is
tuned until this voltage drops to zero.
This adjustment is faidy critical, and
the voltage changes polarity as it is
passed through.
..
OJ
..g
FIG.
23
.LW:iJ.r-I.....,.,i\IVI,.........!+--.,.--jl-if!·
The R.F. end is best aligned by the
meter method, and adjustment is made
for maximum output, using as low a
level of signal inpu~ as possible. The
conventional procedure is usually followed, with the signal being nrst
brought in /;\t the correct calibration
point by the oscillator adjustment, then
the ·antenna and R.F. trimmers are adjusted for maximum output voltage at
point B.
When an F.M. receiver hall a built·in
dipole, it is best to couple the signal
generator to it by capacitive pick-up,
using a radiating rod or loop on the
generator. Where external antenna is
required the usual dummy antenna may
be about 50 ohms.
'
Schematics of several samples of current production are shown in Figs. 18
to 21, inclusive. Fig. 18 shows the
G.E. model JFM-90 translator, intended
to be used with any regular A.M. audio
system, Fig. 19 illustrates G.E. model
LF·l J5 and associated models, Fig. 20
illustrates Stromberg-Carlson models
925 and 1025, and Fig. 21 shows Zenith
14Bl chassis.
212
~
on
Ii
o
Ii
I'.
'1
I~
I
~
fREQUENCY
MODU'LATION
• Section 7
- --
, ............... ............... .,
~
:
. i .. i
:'ItI
I' .... '. S :.
II_
I:,
!
~
d
•
...
t-: o~
t
I
6r
~~,
t
0
..
:\
~:
-
:• \" ....~
S/
.
I
~
.11
I
• ~!!
·1
:,
•••••••••• •••••••••••• ..1
III
.
~i
i
~
:t]
iI
I
•
l!
.:
;.
r
....
i
. It-fl
,-- ........ -- .....................................................
................. -........
~
213
en
CD
~
!l.
o·
I-'
>!>o
~
.....
...
:t
III
:t
"<
III
...
III
~.
n
, ..... ~IIW~$S
19C
_
"
. ",..
... E
If1
:t
I'D KtNfI/W.M.
:z:
J'C MTD
1JAS$
~,.
x
4AND SWITt:H $HttWN IN
SHDATWAYE PtlSrr,ON
Dl'NQ7D
•
~
CHA~I$ ~
III ...~
:t
:a.
:z:
c:
:a.
...
AMP. MOD. LF. FRfQUf:NCY 4S5KC.
FREQ MOD. L£ FREQUENcY 8.3MC.
14 TUBE SUPERHETERODYNE
CI-IASSIS N2 14 B I 3 BAND A.c. PHONO
ZENITH RADIO CORPORATION
CHICAGO, ILL.
FIc. 21
e
THE MYE
Section
8
TE£HNI£AL MANUAL
Fundamentals of
Television Engineering
215
Section 8 •
·r
HEM Y E.
r
E C H N I CAL
MAN U A L
I
I
I"
Editor's Note
Commercial television, whose prospects were so brilliant a year or so
ago, has been temporari!y stalemated by the present emergency.
While there is no doubt that advancements comparable to the rapid
strides previously made in the technique of visual transmission and
reception are still being made every day, these developments have
been limited, rightly, to the armed services.
To those interested in this field, we scarcely need to point out
that communications, warning services, etc. of the Army and Navy
have placed great emphasis on high frequency operation. Both Army
and Navy are training large forces for the design, operation, and maintenance of high frequency equipment. With the end of the war the
return of this personnel to civilian life will provide an adequate supply
for the rapid expansion of all the broadcast services employing high
frequency operation. We believe it possible to predict without undue
risk that television will have the nationwide adoption it deserves, as
soon as peacetime and a normal material supply make such an undertaking practicable.
The following article by Mr. Everest gives an excellent portrayal
of the fundamentals of commercial television. The wartime interim
from the publication of this text until the readvent of commercial services, may produce changes or improvements in systems, but the basic
theory of this article provides a sound groundwork for· the future.
216
I.
FUND~"NrALS
OF fELEVISION ENGINEERING
• Section 8
THE FUNDAMENTALS OF TELEVISION ENGINEERING
Reprinted from the Television Engineering Section. COMMUNICATIONS
Part I: 'lte EssentIal Elements of a '.I.vl.lon System
T
HOSE in the communication field
today are witnesses to the addition
of a new phase to this already manifold
field, namely, instantaneous sight at a
distance. Communication over great
distances has been developed through
the perfection of the arbitrary signalsymbol stage, through sound broadcasting, and now the addition of sight to
sour,d promises to open up a multitude
of new opportunities for exploitation
and development. It should be pointed
out here that to the careful student of
these matters, there appears to be no
factual basis for expecting the combined sight and sound type of broadcast
to supplant the common aural broadcast
as an entertainment and educational
medium for many years to come. Even
though the present-day television equipment is in an apparently advanced stage
as compared to the broadcast equipment
at the inception of that service, there are
many problems, both technical and commercial which seem almost insurmountable at this time. Based upon past attainments in technological fields, however, there is no reason to doubt the
ultimate solution of these difficulties.
In the translation of a picture from
light values to electrical currents, some
manner of photo-electric device is
needed. The accidental discovery of the
photo-conductive properties of selenium
by May in 1873 appears to be one of
the important stimuli to the development
By
F. ALTON EVEREST
Au/.tant Profellor of Electrical EngineerillQ,
Oregon State College
of means to transmit sight. At about
the turn of the century, results from
Hertz's discovery in 1887 of the photoemission phenomenon began to appear.
This finally bore fruit in the photoelectric cell which was so prominent in
the early development of television and
which has such widespread application
in other fields today.
There is something else essentially
necessary, however, beside the translation of light to electric current. For
instance, if a photo-sensitive device were
held up before an image to be transmitted, it is obvious that the transmission of the image as such would be
unsuccesSful. A signal would be transmitted which would be proportional to
the average illumination of the subject
only. A comparable occurrence in photography would be snapping a picture
with the lens removed from the camera. True, the film would be exposed,
but absolutely no information would
be revealed because the film would be
uniformly exposed over all of its surface
to a degree depending upon the illumination of the subject and the length
of exposure.
From this fact that any photo-electric
element delivers an electric current proportional to the a'lJerage illumination,
falling upon it, it is evident that to
convey visual information it is nefessary that the photo-electric device does
not look at the whole subject to be transmitted, but rather at one elemental area
of it at a time. In this way, the signal
corresponding to the average light intensity of each elemental area can be
The problem then retransmitted.
solve5 itself into a problem of analyzing
the picture into many of these elemental
areas, allowing the photo-electric device to look at each area in turn transmitting a signal corresponding to the
average light intensity of each small
area, converting this signal back to
light of the correct intensity at the. receiver, and the re-assembling of the picture. While this method is rather complex and unwieldy, at the present stage
of the art it is the only practical one
available"! If, as in the eye, the image
would be thrown upon a mosaic of
photo-electric elenlents each of which
was connected to a similarly located reproducihg element on the receiving
screen, we would have a simple system
in its action but quite impractical. One
reason for this impracticability can be
seen in the fact that the eye has about
A 441·lIne televiflon
Image of L. E. Gulala.
President. Phllco
Radio & Television
Corp. Picture tranl·
mltted over port.
able system ullng
RMA standards.
441 .11 n e tel evil ion
picture tranlmltted
by Philco system
uling RMA stand·
ardl. Jean Muir.
Warner Bros. Star.
217
Section 8 •
THE
MYE
TECHNICAL
MANUAL
TRANSMISSION
SYSTEM
F"i . i a
five million of these discrete elements
(the so-called rods and cones) and a
separate cOllnection between each and
the receiver (the brain). The interconnection of just a few conductors between the ~levision transmitter and
each receiver would be hardly feasible,
to say nothing of five million of them.
The image, then, must be broken
down into many tiny elemental areas,
each of which will be transmitted independently. There have been innumerable systems of scanning proposed such
as, for instance, spiral "canning. radial
scanning, and sine-wave scanning. Most
of these suffer from the effects of a
change in scanning rate on different
parts of the image or some form of nonuniform resolution of detail over the
image surface. The method which has
withstood the test of years of experimentation is a simulation of the form
disc patented by Nipkow in Germany in '
1884. By means of a relatively large
disc with a spiral of small holes arranged near its periphery, the image
was scanned along a narrow line by
one hole and along another line just
below or above the first line by the
next hole in the spiral and so on across
the image in a regular sequence.
Showing scanning strip and
slgnall.
A simple analogy of the form of scanning usually used today is that of reading a page of a book. The eye starts
in the upper left-hand corner of the page
and progresses at a uniform rate along
the first line. At the end of the line,
the eye snaps back to the beginning of
the second line at a much faster rate
and then along the second line at the
original uniform rate. This continues
to the bottom of the page and then is
repeated in an identical manner on following pages. This could be classed as
"uniform speed sequential scanning." If
the book were especially prepared in
(a)
(b)
I
Fig.3
~
Distortions. Scanning spot width
comparable to scanned detail.
such a code that the story was continuous by reading the odd lines first and
then going over it again on the even
lines, the same information could be
imparted with only a little additional
trouble, and it could be classed as an
"interlaced scanning" process.
In
either case, -the image is scanned in a
definite, pre-arranged order, and the
size of each elemental area would be determined mainly by the width of each
~trip. The greater the number of strips
per picture, the smaller each elemental
area and the smaller the picture detailthat can be resolved. We shall discuss
the~e essential qualities of a tele'vision
image in more detail later.
218
ANALYSIS OF TELEVISION SYSTEMS
AI! television systems can be broken
down into a very few essential functions as shown in block diagram form
in Fig. 1. Here we are dealing with
the sight transmission and receiving system alone, because broadcasting the
sound accompanying the image has already reached a high state of perfection and its working is more or less
common knowledge. The scanning dcvice by which the image is to be tom
into the elemental areas can take am'
numher of different forms. Represent;;tive of the mechanical methods arc: (1)
Apall/red disc, sillgle or ml/ltiple
spiml; (2) apertllrcd drllm; (3) apcrIlIrcd clldless balld; (4) mirror drum;
(5) vibratillg mirrors; (6) prismatic
disc: (7) 11Iirror screw.
The optico-electrical device could be
the ordinary photo-electric cell arranged
singly or in banks, possibly even
equipped with electron-multipliers to increase the sensitivity. The radio transmitter section will not be discussed, because no new theories or modes of
operation arc introduced for television
work. The suitable transmission of the
wide frequency bands required, however, and the transmission at the ultrahigh frequencies introduce many new
problems, but they have all been met
by extensiolls of fundamental electrical
theory.
It will be noticed that the scanning
device aud the optico-electrical device
are also connected with broken lines
which indicate that these two functions
can take place within one instrument.
In this series, which will deal mainly
with electronic methods, this is particularly the case. For instance, the
Tmage Dissector and the Iconoscope
which will be taken up in great deta,il
later, utilize electronic methods of scanning in such a way that the photoelectric emission and the scanning take
place within the same evacuated glass
envelope.
Basically, however, these
highly developed devices take their place
in the ,block diagram of Fig. 1 along
I~
!,
fUNDAMENTALS Of TELEVISION ENGINEERING
• Section 8
RECEIVING
SYSTEM
Fi .~ b
with the humble scanning disc and
photo-electric cell.
For these two
devices, we must add electrostatic and
electromagnetic deflection of electron
beams as two other systems of scanning
to follow the list given above.
At the receiver the signals are demodulated and amplified by the customary methods (except for extension
of the pass bands) and the varying
voltage is used to actuate the electrooptical device. In the mechanical svstems this device may take one of the
following forms: (1) flat plate 1leOI1
lamp; (2) Kerr cell; (3) supersonic
light valve. The re-arranging device on
the receiving end of mechanical systems can be anyone of the devices
listed as scanning- (kvices at the transmitter.
For electronic television, in
which \ve are particularly interested, the
electro-optical device and the rearranging device are found in the same
instrument as at the transmitting end.
The cathode-ray tube ordinarily used
contains an electro-optical device in the
variation of fluorescent screen excitation
;ind the resulting emission of light by
the variation of the electron density of
the beam. Hel'e again the re-arranging
,ystem may be electrostatic or the electromagnetic deflection of this electron
beam. This, too, is a special study and
will be dealt with in detail later.
REPETITION RATE
As far as the units in the block diagram of Fig. 1 are concerned, there is
no difference between facsimile and television transmission.
Both demand a
tearing down of the image to be tt'ansmitted into strips and the opticoelectrical analysis of the light and shade
intensities along that strip at' the transmitting end, and the reconstitution of
the image at the receiver by the t\'anslatioll of the ekctrical signab hack to
their corresponding light intensities, and
the arrangement of these picture elements into their proper order. However, the speed with which the process
takes place and whether or not a record
is to be made of the received image determines whether we shall call ours a
television or a facsimile system. A
typical facsimile system might logically
require fifteen minutes to transmit a
photograph eight by ten inches. At the
receiver, at the end of this time, a
permanent record of the image will have
been produced. For television, a C0111plete picture of the subj~ct would be
transmitted and completely reproduced
in, possibly, 1/30 second. Each picture
will differ slightly from the preceding
one due to any motion that has taken
e - About j
]h'
h
~
Min,ute of Arc
t
fk'.
'-+
~------ d ------~
I
~--------- d·----------~
h
h'
ton e - d = (j7'
~O.14
7
-
~ 0.12
~
o
~
o
0.10
o
I
--iV;-/--+-+---+--I
"I-+-+-+--II--+-;--+--I
i!I --."/-+---1--+---1--1
'1-.,"/
--"I/---
--W'!;
--t~"
rrv./
- - h ' r - el/---+--I--l
ru
0
o
i50.06
I
~0.08
...
~
/
I
V
J
~e
/
~~/
~/-+f---'I----- \I'<-:;''/F--t--t--l
r~//
f--~ 17"-
V
y
-tA--+--+---I---t---I
a 0.04 f---lI--l1'-t-I-7"+---+---+--ii--+-+--I
E
about 1/10th second after the stimulus
has been removed. By impressing about
fifteen separate pictures per second
upon the retina, the eye will be unable
to follow the dark spaces between pictures. However, at repetition rates as
low as fifteen per second, the flicker
may be objectionable, and it is standard
motion picture practice to project
twenty-four "frames" per second. Interlaced scanning giving thirty complete
pictures per second, but scanned in such
a way that each picture is traversed
twice with scanning lines which do not
coincide, actually shows sixty pictures
per second, and hence the flicker effect
is practically eliminated.
APERTURE DISTORTION
The number of lines with which a
subject is scanned determines the fineness of the detail which can be resolved.
It is obvious that we cannot expect to
reproduce clearly details that have dimensions comparable to the scanning
spot, or in other words the width of the
scanning strip. An effect which is impOl·tant in this regard is a distortion due
to the finite size of the "aperture" or
scanning spot which is called "aperture
distortion." Fig. 2-a shows in greatly
magnified form a scanning strip having a light detail on it which changes
abruptly fr0111 dark to light at its edges.
As we have seen, the reason we are
iO.021!1~ /
.:,
Ij/
o O":_-'-""fO'--'--:-20'--'-..J30'----'-4..J0-.l.-S..lo---l
/
Viewing Distance
Left: Showing minimum detail eye
can resolve.
Feet
Fig.4
place in that time. Because of a char:lcteristic of the eye which is called
"persistence of vision," it will not be
able to distinguish between the sC{larate
pictures, but will see what appears a
continuous, uninterrupted flow of motion
of the subject. Once the retina of the eye
is stimulated with a single picture focused upon it, the impression remains for
219
Section 8 •
THE
scanning the picture 'at all is because
our photo-electric devices can respond
only to the average illumination and,
therefore, we get the average illumination of the area covered by the spot in
this case. When the spot is in position
(a), the photo-electric current will be
zero because of the black surface. At
(b), half the circl~ is on white and half
on black, and the resulting photo-electric
current would correspond to gray. At
( c), maximum signal corresponding to
white will result. At the right edge
of the white detail, sil!Jilar signals would
be produced in reverse. While the signal for ideal reproduction is that shown
in Fig. 2-c, the actual signal resulting
is shown in Fig. 2-b both for circular
and square scanning spot. Therefore,
when the scanning strip width is com·
parable in size to the detail being
scanned, we must exp~ct distortions
such as shown in Fjg. 3. In (a) is
shown the case of a horizontal detail
unfortunate enough to lie between two
strips, and in (b) is shown the stairstep effect produced in diagonal elements.
It is evident froJ11 this that in order
to analyze the details of, say, the face of
R subject, there mUst be a relatively
great number of lines scanning it. If
the eyes of the subject are about the
MYE
TECHNICAl.
<.
MANUAl.
saJ11e width as the scanning strip, all
one could expect is a blur. If in the
scene peing televised a man is in the
far distance, perhaps a blur is enough,
for the observer's eye has very definite
limits in analyzing fine detail. The
acuity of vision of the normal eye is
between 0,5 alld 2 minutes of arc.
This means that if two details are
separated by an angle greater than this,
the eye can distinguish them as separate
details, but if their angular separation
is less than this amount, the two details
will merge into a blur. This results
from the fact that the rods and cones
on the retina of the eye are spaced a
finite distance apart, and each is capable of responding only to the average
illumination falling upon it. Fig. 4
shows the relation of the minimum size
of the detail that the eye can appreciate
in relation to the viewing distance.
SUMMARY OF PICTURE QUALITIES
The excellence of the television image
is a function of many things, all intimately connected together. The con'rast range, or the relative difference in
.ntensity between "black" and "white" on
the reproduced image is very important.
The brightness of the image is another
factor, and its overall value may be
quite low because the screen is illuminated on only one< elemental area at
a time. For a modern television picture,
the spot brightness may have to be sev:eral hundred thousand times the required overall picture brightness because of this fact. The definition of the
picture, of course, is a function of the
nUl1,lber of scanning strips per picture
which goes hand in hand with the spot
size. With cathode-ray reconstitution,
a doubling of the numbel' of lines in
a picture will increase the definition and
require a spot size of half the .former
value. As the tight flux is proportional
to the square of the spot diameter, the
received picture brightneS5 will be reduced to about one-fourth its original
value.
Picture size, the number of strips per
picture, and the viewing distance are
also closely tied together. For a given
picture size and number of lines, there
is a proper viewing distance at which
the acuity of the eye as expressed in
Fig. 4 and the smallest detail that can
be resolved in the picture are at such
a balance that the eye does not notice
deficiencies in the picture. At a closer
viewing distance, the picture will appear coarse, and at greater distances
some of the definition will be going to
waste.
I
I
I
I
Ii
i
I '~
Part II: The Necessity for Wide Frequency Bands
TRANSMISSION OF INFORMATION
I
T is a well-known fact that the frequency band available and. the time
available for the transmission are two
very important factors which govern
the amount of information that can be
transmitted' . This holds true in a general way for all types of signals such
as telegraphic, voice, music, facsimile,
or television and for all media of transmission, such as air for sound waves,
wires, or the medium in which radio
waves are propagated. The amount of
information that can be transmitted can
be arbitrarily specified in a rather vague
term which we will call "information
units." The frequency band available
extends from some lower frequency, f"
to some higher frequency, f2' and covers
a frequency range of (f2 - f, ) cycles.
The time t available for the transmission
let us' express in seconds. These factors
can be expressed as
Information units
220
= (£2 -
f,) t
'" (1)
Equation (1) can best be explained
by a practical illustration. It has been
found that a certain photograph can be
sent via a facsimile system in 300 secunds and that the band required had a
maximum width of 2000 cycles. By
multiplying 300 by 2000, we get 600,000
information units contained in this picture of practically perfect quality. To
obtain the same quality with a television
image containing 600,000 information
units in a time of 1/30 second to come
within the eye retentive period for
avoiding flicker would require a wider
frequency band< The width of this band
would be found by dividing the number
of information units by the time avail-
able, or 1/30 second. This gives a frequency band width of lR,OOO,OOO cycles
necessary to transmit this nearly perfect
picture in 1/30 second. Actually, however, it has been shown that an information content of about 1/6 of this, or
100,000 information units is ample for
television. This brings the necessary
frequency range down to a m11ch lower
value.
Often it is found that the transmission
of a certain amount of information takes
up a much wider frequency range than
indicated by equation (1). It must be
pointed out that equation (1) is only a
qualitative statement. One of the reasons for this lies in the fact that "information" is such an intangible quan"
tity. It is evident that more actual
information exists in a television image
than in the click of a telegraph sounder,
but how much more? How call one
measure it? A Chinese proverb tells us
that "a picture is worth ten thousand
words", but yet one is forced to question
I
i
.~"
I"
I
FUNDAMENTAlS OF TELEVISION ENGINEERING
• Section 8
the absolute accuracy of the proverb
it probably errs on the conservative
side.
Equation (1) also says nothing about
how efficiently the (f,-f, ) frequency
band is used.' With the ordinary television signal, the energy distribution
throughout this band is simpar to that
shown in Fig. 1. It is seen that there
are: energy concentrations in the region
of the line-scan frequency!HI. ' This fref!ue~cy may be found from
f ..
(f) (n)
.................. (2)
a~
=
(b)
Where
f"
linc scan frequency, cycles per
second
frame repetition rate, or the
number ,of complete pictures
per second
11
total numher of scanning lines
per frame.
=
=
=
For the present standards (see Table I)
f = 30 and n = 441, making f" = 13,230
cycles per second. Concentrations of
energy will then be found in the regions surrounding 13.2 kc, 26.4 kc, 52.8
kc, etc., the amount of energy decreasing greatly as the frequency increases.
Even though the actual shape of these
concentrations change with picture content, it is obvious that the (f, - f,) frequency band is not being used to the
fullest extent. The use of double-sideband transmission is also representative
of inefficient use of the (f, - f,) band".
So even though equation (1) is highly vulnerable from the quantitativc
standpoint, it does rest upon a basic law
TABLE I
SHOW1NG A SUMMARY OF SOME OF TIlE
MAJOR
STANDARDS
PROPOSED
BY
RMA TELEVISION COMMITTEE
Channel Characteristics
Television channel width... 6
me
Separation between sound,
and picture carriers ...... 4.5 mc
(Sound carrier higher frequency than picture carrier)
Guard band between sound
carrier and high-frequency
edge of. channel. . . . . . . .. 0.25 m(;
Pictllre Characteristics
frame frequency.............. 30
Field frequency for interlacing.. 60
. Number of lines per fra~e ...... 441
width .
4
Aspect ratio - - -........... .
height
3
Fig.2
which demapds a payment in the form
of an increased frequency band required
tn exchange for an increase in picture
quality.
FREQUENCY BAND WIDTH
DETERMINATION
A common method of determining
the frequency band required for the
transmission of television images will
be described which, although criticized
by many for its crudeness, does give a
physical picture of the process. This
atlalysis is based upon the scanning of
a checkerboard pattern with squares the
size of the elemental areas. That is,
the squares are the same width as the
scanning spot. The theoretical signal
resulting from scanning across one line
of the pattern of Fig. 2-A" is shown as
the rectangular wave of Fig. 2-B.
Neglecting such things as aperture distortion, etc., the rectangular wave can
he simulated by the sine wave of Fig.
2-C, and its frequency can be determined .fr0111 the speed of the scanning
spot. This, the frequency band representing the scanning of these alternate
black and white squares, which represents the worst possible conditions of
picture resolution, is given by
Approx. frequency band required
1
-n'Rf ............ (3)
2
where
number of lines per frame
n
f
number of frames per second
=
=
=
width
R
= aspect ratio = --- of picture
height
Practical experience has indicated that
the value calculated from equation (3)
is a pessimistic figure and that only
about 70% of this band is actually
needed. Adopting the standard motionpicture aspect ratio of 4/3 and lumping
1/2, the 0.7 factor and the 4/3 aspect
ratio into one constant, equation (3)
becomes
Actual Frequcncy
J>and required
0.47 n' f .............. ; ( 4)
Let us calculate an example using the
present standards of f::= 30 frames per
second and n = 441 lines per frame.
This results in a calculated necessary
frequency range of 2.75 mc, which, with
double-.side-band transmission, ca1Js for
a frequency band of 5.5 me plus enough
for the accompanying sound and the
necessary guard bands. The frequency
band required is directly proportional
to the frame repetition frequency and
proportional to the square of the number
of lines. Doubling the number of lines
gives rise to fJuadrupling' the frequency
band required.
RESULTS OF DeMANDING WIDE
FREQUENCY BAND
Here we see the penalties we must
pay for transmitting lots of information
at a rapid rate as, for instance, a television picture which has high quaiity
221
r
Section 8 •
HEM Y E r E C H N I C'A L
MAN U A L
Televisionl=:lr:;=r=:==i=:'~~F=~=~=;.=!.=JL
Channel'
Number _
._
---..IL..--J
;.
-.
1111
••
...
..
.
.
-----~--
.
Overall Sand
Width __ _
SMe.
- - - -__
-------_ 4
0.25 Me.---_•
•5 Me. ---------~t
_.~
~
°-ry~~~~EJ
Pie"'''r'e
F:requ
eney arr','
esacyc/es
rig. 4
Sound ,/
I
C
uer
M
44
STANDARDS OF TELEVISION
TRANSMISSION
\
I
4'"
y / :
Carrier~
and which shows motion. The penalty,
of course, is the wide frequency band,
and the use of these wide frequency
bands makes the case for television quite
difficult.
First, it is evident that a series of
6-mc transmission channels is not available in the common radio spectrum as
usually used today. The entire broadcast band is only about I-mc wide and
even if this region were unused, it
would not be satisfactory because the
side-bands generated would be such a
large percentage of the carrier. A ratio
of about ten-to-one between the carrier
frequency and the highest modulating
frequency is highly desirable from the
circuit design standpoint. The spectrum
from a few hundred kilocycles to several megacycles is already allotted to a
multitude of different services. The
prior rights of these services on these .
frequencies must be respected. All of
these factors point toward the utilization of the ultra-high-frequency regions,
the propagation characteristics of which
relatively little is known. But considerations taking into account the lack
of sky-wave, the video-frequency band
width, the urban propagation characteristics, and apparatus limitations, have
led to the adoption of the region around
40 t(') 100 mc for television transmission.
One characteristic of these waves 4• 5• 6
from 3 to 6 meters is that they behave
very much like light in that they tend
i:t~:;;!o',cast shadows behind mountains, etc.
".
b,<:y also are not ordinarily reflected
"". ""~22
interconnecting television transmitters
lies in the ~tilizationof highly airec-·
tional beam radio transmitters. Fre-.
quencies of the order of hundreds of
megacycles are ideally suited for the design of highly directional radiating systems. It seems entirely feasible to operate these receiving-transmitting relay
links unattended. The cost of such systems, whether special land lines or radio
links, is very high at the present state
of development.
from the ionized layers except at acute
angles', and thereby do not follow
around the curvature of the earth. This,
of course, limits the service area materially, 30 to 50 miles· being the general
order of maximum distance to which
satisfactory signals can be transmitted.
The absolute distance, however, depends
upon many factors such as height of
transmitting antenna, height of receiving antenna, intervening structures or
hills, and the base noise level of the locality. Interference from automobile
ignition systems is particularly troublesome at tn,ese frequencies causing a
speckled picture (g.iving the appearance
of a snowstorm) and often the tempor.ary loss of synchronization. The signal
strength must be high enough to override such interference of local origin.
In general, a single transmitter of moderate power can cover a metropolitan
area very well at these frequencies.
Television will not have reached the
acme of development until it too has an
interconnected network of stations from
coast to coast. The short transmission
range complicates this problem greatly
for the type of interconnecting links
that can transmit the necessary wide
frequency bands are very expensive.
Coaxial cables have been developed to
the point where they can be used for
such purposes, and the recent progress
in the development of wave-guides,
which are metallic tubes filled with some
dielectric, appears to have merit for this
purpose. Another possible means of
For a successful service, it is necessary ,that any television receiver
manufactured any place in the United
States operates satisfactorily on transmissions from any television broadcast
station in the United States. In order
to accomplish this with such a complex
system, the necessity for some close cooperation between manufacturers and
television broadcasters is obvious. This
cooperation has been realized in this
country through the efforts of the Television Committee of the Radio Manufacturers Association ' •. This committee
to formulate standards was composed of
men representing practically all of the
major television organizations. It is
evident that if this committee mutually
agrees upon television standards, the
television industry which they represent will abide by them for the benefit
of all, including the consumer.
This committee has been working
since 1935, and it was not until the
first of 1939 that the final decisions
were completed. The Federal Communications Commission has made ex·
perimental allocations upon the basis of
these standards. It is fortunate that
such thorough investigation has preceded the formulation of these standards, for once adopted, they will tend
to solidify techniques. The further the
advance before solidification, the greater
the net progress.
THE PROPOSED STANDARDS
Table I gives a sUn1maryof the
standards proposed by the RMA Television Committee which are of the most
interest at the receiving end. Fig. 3
shows graphically the location of the
seven television channel assignments,
each of 6-mc width. In addition to
these ,seven channels between 44 and
108 mc, there are twelve additional 6-mc
channels tentatively set aside for television between 156 and 294 mc. These
are considered more important for relay
and research purposes than for regular
fUNDAMENTALS Of TELEVISION ENGINEERING
television broadcasting at the present
time. To allow room for the increase
in definition and the resulting increase
in frequency bands, vestigial side-band
transmission is contemplated. A typical
channel (Channel I) is portrayed in
Fig. 4 using vestigial transmission. One
side-band (the upper one) is transmitted completely and 0.75 mc of the
Beginning at this
lower side band.
point, the lower side band is attenuated
as rapidly as possible with circuits available for operation at these frequencies.
The overall band width is 6 mc. A
0.25-mc guard band is allowed between
the upper edge of the channel and the
sound carrier. The picture carrier is
placed 4.5 mcbelow the sound carrier.
Because of the relative crowding of
the region within the channel as shown
by Fig. 4, and because television channels are adjacent to each other and to
other services, it will be imperative that
the lower side band transmitted vestigially be cut off entirely within the
channel limit. The need for highly
selective receiver circuits is also evident.
BIBLIOGRAPHY
(1) Hartley, "Transmission of Information," Bell System Technical Journal, Vol.
VII, No.3, July 1928, p. 535.
(2) Mertz and Gray, "A Theory of
Scanning," Bell System Technical Jo_l,
Vol. XIII, No.3, July 1934.
(3) Wilson, "Television Engineering"
(Sir Isaac Pitman and Sons Ltd.), Chapter
I V, "Analysis of Finite Aperture Scanning Methods"; Chapter XII, "Physical
Limitations." (An excellent list of references is included at the end of each
chapter.)
• Section 8
(4) Jones, "Propagation of Wavelengths Between Three and Eight Meters,'·
Proc. Institu,te of Radio EngilU!ers, Vol.
21, No.3, March 1933, .p. 349.
( 5) Trevor and Carter, "N otes on
Propagation of Waves Below Ten Meters
if( Length," Proc. l.R.E., Vol. 21, No.3,
March 1933, p. 387.
(6) Beverage, "Some Notes on UltraHigh-Frequency Propagation," RCA Review, January 1937. (Also giving extensive bibliography.)
(7) Pock and Epstein, "Partial Suppression of One Side Band in Television
Reception," RCA Review, January 1937.
(8) Everest, "Amplification Problems of
Televison," COMMUNICATIONS, January
1938, p. 15.
(9) Goldsmith, "Television Economics,"
COMMUNICATIONS, Feb. 1939, Section A-I,
p. 18.
(10) Murray, "Television Standards,"
COMMUNICATIONS, Dec. 1938, p. 14.
Part III: Television Cameras
I
T makes little difference where one
might go throughout the world examlnmg electronically-operated television pick-up devices, he will probably
find only variations from the two fundamental patents issued originally in
this country, one to V. K. Zworykin
about 19281 and the other to P. T.
Farnsworth about 19312. These two devices pretty much dominate the international television picture at the present
time. In foreign countries, the television cameras may appear under unfamiliar names, but a closer scrutiny will
probably reveal the basic principles of
operation of one of the two cameras to
be described in this installment. For
instance, in England the Emitron camera of the Marconi-E. M. 1. Company
resembles Zworykin's I COlloscope, and
the Baird Electron Camera is similar
to Farnsworth's Image Dissector. Because of this fact, a study of the two
pick-up systems used so extensively in
the United States today will give us an
up-to-date working knowledge of the
television pick-up systems of the world.
In Part I of this series, the necessity
for s~anning and for the translation of
the average light level of each incremental area of the picture into an electric current of corresponding intensity
was pointed out. In both types of television camera tubes widely used today
both of these processes, i.e., the scanning and the optico-electro translation,
occur within the same device. In addi-
tion to this, several models also include
means for amplification of the feeble
signals so that they have a fighting
chance against the circuit noises.
The operation of the I mage Dissector
is made clear by Fig. 1. The image to
be scanned is focused by a conventional
system of lenses onto the cathode surface which has been treated uniformly
for photo-electric emission. It is evident that the bright areas will cause
many electrons to be emitted and that
the darker regions of the image will
cause fewer electrons to be emitted
from this photo-cathode surface. The
anode in the opposite end of the tube is
held at a positive potential with respect
to the cathode so that all of the photoelectrons emitted will be accelerated
toward the anode. Leaving the photoelectric cathode, then, is a beam of electrons about the size of the image whose
electronic density along its cross-section
will vary in a manner similar to the
light variations over the image as it
falls upon the cathode. In other words,
if one could take an imaginary slice
fro111 this electron bundle leaving the
photo-cathode he would find that in the
regions of the slice corresponding to
the light parts of the image, there would
be found many electrons and the areas
corresponding to the dark parts would
be represented by only a relatively few
Sc:hematic:
diagram of
Image
Dinedor
tube.
223
Section 8 •
THE
MYE
TECHN.ICAL
MANUAL
will cO):lfirm this. Let us assume the
electrons. This arises from the fact that
usc of RMA standards of 441 lines per
the photo-electric emission from the
image, 30 complete frames per second,
cathode is a function of the intensity
4
of the impinging light.
and aSpect t:atio of - . The number
Becaus!": aU· of the electrons in a beam
3
possess a negative charge, there will
be mutual repulsion between the various
electrons comprising the electronic
image. This effect is further augmented
by slight initial variations in velocity
and direction as the photo-electrons are
emitted. These effects tend to make the
electronic image bundle to spread apart,
but this spreading is minimized by"
focusing coils A, A' mounted coaxially
with the tube. Its magnetic field is
parallel to the direction of travel of the
Fig. 2. The bosic Iconosc:ope.
electrons, and any electron attempting
Photo courtesy RCA Review.
to travel diagonally to this magnetic
field has a force acting upon it tending
4
to bring it back into line.
of elements per frame is (441)"Above and below the evacuated
3'
cylinder is a pair of coils (B and B')
=
259,000.
As
there
are
30
of
these
connected in series, so situated that their
frames
per
second,
the
time
that
one
axis is perpendicular to that of the tube.
single elemental area will be in front of
The magnetic field resulting from cur1
rent flowing in these two coils will
. the aperture will be - - - , - - - - result in the electronic image bundle
(259,000) (30)
being deflected upward or downward in
seconds
=
0.129
microsecond.
I Now,
the plane of the paper in Fig. 1. Anlet us assume the use of an F-4.5 lens
other pair of coils is arranged one on
in front of our Image Dissector throwthe side of the observer and one on the
ing a brightly illuminated outdoor
back side so that its magnetic field is
scene
upon the photo-electric cathode.
perpendicular both to the axis of the
Under these conditions, the total light
tube and the plane of the paper. By
falling upon the cathode will be In the
means of a current in these coils, the
order of 0.1 lumen. Let us also assume
electronic image bundle may be deflected
that the photo-electr;c surface has a sentoward or away from the observer.
sitivity of 75 microamperes pCI' lumen,
These two sets of coils make it possihle
an extremely sensitive surface which
to deflect the electronic image at will
within the tube by the simple expedient
of sending currents of suitable wave
Schematic drawing of an RCA
Ic:onosc:ope.
form through the coils outside the tube.
As the electronic image approaches
the anode pillar, a few electroris will go
through. the aperture, hit the tiny target
inside the anode pillar structure, and this
constitutes the signal current. The two
sets of deflecting coils are so energized
that each picture element is scanned in
the proper sequence. For RMA standards of operation, the image beam
would be deflected horizontally 441
times per second and vertically 60 times
pe. second to give a 441-line, 30 frames
per second, interlaced image. ~he entire electronic image is moved across
the aperture to accomplish the scanning
process in this Farnsworth Image Dissector, while the scanning point is movable over a stationary image in most
other systems.
The photo-electric current representirig the light intensity of one elemental
area is very feeble. A brief calculation
224
has been obtained by much research
work. The photoelectric current representing a single elemental picture area
(75 x 10-") (0.1)
IS
28.9 X 10-12 am259,000
peres or 28.9 micromicroamperes per
element. This current flowing for the
0.129 microsecond is equivalent to
3.74 x 10-18 coulombs which is equal
to 23.5 electrons. In an extremely generous mood, we will call it an even 24
electrons, which, one must still admit,
is not much of an electric current. This
signal current would undoubtedly be lost
in the noise associated with ordinary
thermionic amplifiers and because of
this inherently feeble signal from the
Farnsworth Dissector, electron multipliers are used. In one of the later models,
this multiplier is built into the anode
pedestal.
An early type of RCA Iconoscope
(Greek: "image observer") television
camera tube is shown in the photograph
of Fig. 2. A schematic drawing of a
commercial model (Type 1849 and
1850) recently put upon the market is
. shown in Fig. 3. The type 1849 Iconoscope is designed for motion-picture
pick-up, while the type 1850 is much
more sensitive and is intended for direct
pick-up at low levels of scene illumina-,
tion.
The heart of the Iconoscope is the
mosaic electrode which has been
especially treated for high photo-electric
emission. The mosaic may be formed
by the deposit of a multitude of tiny
silver globules upon an insulating sheet
such as a thin sheet of mica. These
globules are then photo-sensitized by
caesium and each globule, which is in-
=
fUNDAMENTALS Of TELEVISION ENGINEERING
sulated from all its neighbors, becomes
a minute photo-electric cell. These globules are so small that there may be
dozens of them in one elemental area
of the mosaic or the area of the scanning spot. In general, about 30% to
40% of the area of the mosaic is covered by the globules.
An electron gun and associated beam
deflecting system are mounted in the
neck of the Iconoscope. This gun is
very similar to that found in the usual
cathode-ray tube and consists of a
thd'mionic cathode for emission of the
electrons, means for accelerating the
electrons, and means for focusing them
into a very fine beam. By means of an
electromagnetic or electrostatic system
(the lconoscope uses the former), the
beam may be deflected to any spot on
the mosaic electrode. To meet the RMA
Standards, this beam would be swept
horizontally across the mosaic 441
times per frame, and the beam would
also be deflected slowly in a vertical direction so that each line would fall adjacent to the preceding one, the 441
lines scanning all parts of the mosaic
1
surface every -th second.
30
Let us examine the mechanism by
which the signal currents are generated.
The image is focused upon the mosaic
by means of a suitable external lens
system. The light falling upon the
mosaic $:auses photo-electrons to be
emitted from each element of the mosaic.
The sensitized silver globules lying in
a part of the image which is light will
give off mor~ electrons than the dark
portions. The electrons given off from
each mosaic element photo-electrically
are attracted to the silver coating on the
inner side of the tube which constitutes
the anode and which is held at a positive potential with respect to the mosaic.
It is obvious that the leaving of the
electrons from the mosaic element' will
Filii. 5.
The new Image Ic:ono·
5c:ope. RCA Photo.
leave a deficiency of charges upon it
and, by virtue of the capacitance existing to the metallic backing plate on the
opposite side of the mica sheet, this will
actually result in a charging of this
tiny condenser. The magnitude of the
charge will depend upon the intensity of
the light falling upon it for a given
length of time. Because each of these
mosaic elements is highly insulated
from every other element, it is seen that
a scene focused upon the mosaic will
immediately give rise to a potential distribution over the face of the mosaic
which varies electrically as the light and
shade of the scene itself varies optically.
The function of the electron beam is
to discharge these tiny charged condensers in a certain order. The sweeping of the electron beam across a
Sc:hematlc: drawing of tube shown
in Fig. 5.
• Section 8
charged element will mean the equalization of the charge, or the discharge, of
that condenser element. The charging
current which flowed t6 perform this
equalization is proportional to the
amount of charge on the element, which
is in turn porportional to the intensity
of the light falling upon that element.
The current which flows through resistor R of Fig. 3 produces a voltage
which varies as the light variations
along that particular scanning line, and
this constitutes a feeble· signal voltage
which can be amplified and utilized.
As mentioned before, the area covered by the scanning beam contains
many of the~ mosaic elements. Becaut\e
of this, the signal output of one elemental area of the mosaic will be proportional to the average charge attained
by all the globules in that elemental
area.
The sensitivity of the Iconoscope is
much greater than the fundamental Dissector. This results from the storage
effect that takes 'place by the more or
less continuous process of charging the
minute condensers. While the signal
from a single elementary area of the
Farnsworth Dissector tube might be in
the order of 24 electrons, the signal
from a single elemental area of the storage type would be much greater because
its charging process has been progressing while all the rest of the approximately 259,000 elemental areas were being scanned in turn. In other words, the
Dissector tube has only the time required to scan a single element for the
photo-electric emission of its signal
current (about 0.13 microsecond (while
the Iconoscope merely releases during
this same time a charge that has been
1
accumulated for about - second. The
30
theoretical gain of the Iconoscope over
the Dissector would be about 259,000,
but an advantage of only a few thousand
has actually been realized.
The Improved Fernsworth PiClk·up Tub.
An interesting thing about the improved types of Farnsworth and RCA
tubes is that the new Farnsworth tube
utilizes a photo-mosaic and the new
RCA tube uses electronic images.
The improved Farnsworth· tube is
shown schematically in Fig. 4. The image is focused upon the special "photoisland" grid after passing through the
transparent anode on the end of the
tube. This grid has about 160,000 holes
punched per square inch in a thin nickel
plate. One side is coated with a dielectric material which has deposited upon
225
Section 8 •
THE
MYf
TECHNICAL
MANUAL
Illustrating
the
improved
Farnsworth
tube.
it many photo-sensitive "islands" which
ate so-called because they are insulated
from each other as are the globules on
the Iconoscope mosaic. The image
focused upon this "island" surface
causes an electrical potential image to
be set up over its face. The beam of
electrons from the gun hit the special
surface on the nickel plate liberating
copious quantities of secondary electrons. This cloud of secondary electrons acts as a rapidly moving virtual
cl1-thode source, and these electrons are
drawn through the tiny holes of the
mesh to a degree depending upon the
amount of positive charge built up on
the "photo-islands" on the other side.
In other words, the "photo-islands" act
as the control grid of a triode in that
they control the number of electrons
which shall go to the electron multiplier
to represent that particular area. The
intensity of illumination determines the
amount of positive charge on the islands, and this positive charge determines the number of electrons allowed
to go to the electron multiplier which
constitutes the signa! curnmt.
The main advantage of this tube is
that its sensitivity is increased to about
ten times that of the conventional Iconoscope. Another advantage is that a
peculiar shading signal common to the
Iconoscope and evidently a result of
roving areas of spurious charges over
the mosaic does not appear. A difficulty
at the present time is constructing the
photo-island mosaic so that its charge
.
.
1
leaks off in about - second so that no
30
residual charge remains when the next
frame starts,
Improvlld RCA Icono$coplI
The Image Icot;loscope recently
described has resulted in greatly superi-
226
or performance. A photograph of this
tube is shown in Fig. 5, and a sectioned
schematicdiag-ram is shown in Fig. 6.
Fig. 8. A new RCA Iconoscope
tele"isicllt .camera.
'Referring to Fig. 6, the image to be
televised is focused upon the plane
photo-electric cathode near the end of
e
Fig. 7. Two wen·
known television
res e a, r c h engi.
neers. Dr. Y. K.
Zworykin ('eftl and
E. W. Engstrom.
examine a special
e'ectronh: tub e .
Dr. Zworykln is the
Inventor 0 f th e
Ico!lOlcop.. RCA
photo.
the tube. By virtue of the potential
existing between the anode and this
cathode, an electronic image is released
from the opposite side of the cathode.
With the aid of special focusing arrangements, the electronic image impinges upon the mosaic at the opposite
end of the tube. The only major difference between this mosaic and the one
in the basic Iconoscope is that this one
is not treated for photo-electric emission. The electronic image hitting the
mosaic knocks off secondary electrons
from the globules. In this manner, the
potential distrihution corresponding to
the image di~tributi()n of light and shade
is set up over the face of the mosaic.
The secondary electrons are carried off
by the anode and leave a deficiency of
electrons or a positive charge on each
tiny condenser which each globule
forms with the metallic backing plate.
The value of these charges depend upon
the number of secondary electrons
given off, and this in turn depends upon
the number of photo-electrons representing that particular part of the electronic
image. The electron gun and deflecting
.system scans the mosaic in the usual
way, and the signal is taken off as in
the ordinary Iconoscope.
The advantages of this pick-up tube
lie mainly in the fact that the sensitivity
is increased to about ten times that of
the old Iconoscope due to the fact that
secondary emission is more effective
than photo-emission in building up the
charges on the mosaic. Another advantage is that the photo-cathode is so
close to the end of the tube. This 'allows
the use of short focal length lenses, and,
consequently, a large aperture optical
system can be used. The spurious shading signal generation effect is still present in this tube, though in at least some
cases is slightly less severe.
e
FUNDAMENTALS OF TELEVISION ENGINEERING
BIBLIOGRAPHY
(1) U. S. Pat. No. 1,691,324 (1928).
(2) U. S. Pat. No. 1,773,980 (1931)
(3) "Television by Electron Image Scanning," Farnsworth, Journal of Franklin Institute; Vol. 218, Oct., 1934.
( 4) "Television by Electron Image Scanning," Farnsworth, Electronics, Aug.,
1934.
(5) "Farnsworth's New Tube," Electronics, Dec., 1938, pages 8, 9.
(6) "Theory and Performance of the
Iconoscope," Zworykin, Morton, and
Flory, Proc. IRE, Aug., 1937.
(7) "lconoscopes and Kinescopes in TeleviSIOn," Zworykin, RCA Review,
July, 1936.
(8) "The Iconoscope-A Modern Version of the Electric Eye," Zworykin,
Proc. IRE, Ji.nnuary, 1934.
(9) "Tubes for Television Show Technical Advances," Electronics, July,
1938, p. 12, 13.
(10) "Television Economics," Goldsmith,
Part II, Section E-l (Video Pickup Equipment), COMMUNICATIONS,
March, 1939, page 19.
(11) RCA Rating Pamphlet on 18;9, 1850
lconoscopes.
• Section 8
•
Fig. 9. A typical
scene during the
broadcasting of a
television p la y .
Note the trucks
upon which the
cameras are
mounted and the
powerful lights required. RCA photo.
•
(12) "The Latest Emitron Camera," Television and Short-Wave World, July,
1938, p. 397 (London).
(13) "A New
Farnsworth 'Pick-up'
Tube," Telev. & Short-Wave World,
May, 1938, p. 260.
(14) "A New Emitron Camera," Telev.
& Short-Wave World, January, 1938,
p. 11.
(15) "A New Electron Camera," Tele'll.
& Short-Wave World, August, 1937,
p. 467.
(16) "The Television Camera," Telev.
& Short-Wave World, June, 1937, p.
329.
'
(17) "The Baird Electron Camera," Jones,
Telev. & Short-Wave World, Sept.,
1936, p. 487.
Part IV: The Cathode-Ray Tube as a Television Reproducer
T
HIS installment will deal only with
the cathode-ray tube as a television
reproducer, although there are many
mechanical systems by which the separate picture elements can be reassembled
at the receiving end. This does not
mean that the mechanical systems hold
no promise for the future, but rather
that in the United States at the present
time practically all of the activity is
confined to cathode-ray reproducers.
The major limitation of the cathode-ray
tube, as will be pointed out later, is the
lack of light, and the mechanical systems have advantages in this regard due
to the fact that they control a powerful
local light source such as an intense incandescent lamp, an are, or the recently
introduced high-pressure vapor tube.
The cathode-ray tube is particularly
adapted to the demands of high-definition television, and this fact is largely
responsible for its more or less universal adoption throughout the world at
this stage of television development.
Faraday, observed the effect of application of a high potential between two
electrodes within a crudely evacuated
glass envelope. The Giessler tube giving interesting color effects within its
fancy glass-work was a novel result.
Better exhaust techniques, however,
gave rise to tile discovery of new effects, one of which was the cathode-ray
phenomenon, so named by Plucker
about 1879. The Crookes tube showed
that the "rays" were more properly
discrete particles leaving the cathode at
-right angles to its surface. These particles were later (1890) identified as
electrons suggesting that a better name
for cathode-rays would be electron
beam, and this flas been generally
adopted while speaking of the beam,
but not the tube itself. Many improvements have been introduced, among
them magnetic focussing (1898), the
hot .cathode 'for electron emission by
Wehnelt (1905), and various arrange-
.
Fig, 5·a. Resolution test pattern,
Grid modulated at about 2 me/s_.
Spread vertically to show individual Iconnlng tine.. Photo
court •• y IRE Proc.
HISTORY OF THE CATHODE-RAY TUBE
Many people who have only recently
become acquainted with the cathoderay tube may be somewhat startled to
learn that tubes bearing that very name
have been in existence since 1876. Even
earlier than this, Coulomb, and later
227
Section 8 •
THE
MYE
TEe H N I CAL
'M A N U A L
Fig. 4. An RCA projection type
~athode.ray television tube. Small
Image can be projected on 3 x 4
ft. screen. Photo I:ourtesy IRE
Proc.
become indispensable to the communication engineer.
DESCRIPTION OF THE CATHODE-RAY TUBE
Above: Fig. 6. A 12" tube being
tested with a special test pattern. RCA Photo.
Below: Fig. 8. Removing fluorescent material from a furnace.
RCA photo.
The cathode-ray tube as used today
in television receivers is shown in Fig.
1. This is one of the largest tubes extensively made and has a screen diameter of 12 inches and employs el~ctro
magnetic deflection. In the neck of the
tube the electron emitting and focussing
eleme~ts a:e assembled constituting
what IS qUIte appropriately called the
electr~n gun. The beam originating
~ere IS attracted by the higher potential on the various anodes and then impinges upon the fluorescent screen. The
energy which the electrons have by virture of their mass and velocity is given
up at the screen and some of it is translated to visible light producing a luminous spot.
Fig. 2 shows a partial section view
showing the construction of a typical
electron gun. At the extreme left the
cathode, or the electron emitting device
is shown. The filament within the ca~
thode sleeve is heated by an electric
current which in tllrn heats the cathode
sleeve. The end of this cathode tube
toward the fluorescent screen is coated
with a material which has a high electron emission efficiency when heated.
The first anode, which is held at a very
high potential with respect to the cathode, attracts the emitted electrons
and they are pulled through the hole i~
the cylinder which is usually called the
grid. It is so called, not because of its
structure, but because it performs a
function comparable to the grid in the
ordiriary triode. The intensity of the
luminous spot on the fluorescent sCt:een
is a function of the speed with which
the electrons arrive and the number of
electrons. With fixed electrode voltages,
the speed remains constant, and the light
intensity of the luminous spot is controlled by the variation of the number
of electrons in the beam. This is accomplished by the grid. Because it is
so much closer to the electron source'
a certain low voltage applied to it ha~
the same effect on the electron density
of the beam as a very much greater
voltage on the first anode. Therefore a
relatively small video signaL volt;ge
(say 20 volts) applied between the cathode and grid is sufficient to vary the
beam from full brilliancy to cut-off.
The beam next passes through two
holes in discs within the cylinder which
comprises the first anode. The beam
then passes through the second anode
which may be either a hollow cylinder
with a partially closed end as shown
!n ~ig. 2 or a conducting coating on the
Illslde of the funnel-shaped portion of
the glass envelope. In either case, the
electrostatic equipotential surfaces are
so arranged and adjusted that the electrons in the beam may be brought to a
very fine focus at the fluorescent screen.
The large end of the glass envelope
UP0t; w~ich the fluorescent coating is
appJted IS curved an amount that will
retain the spot focus even though the
beam is bent in any dil'ection by the deflection system.
Because tlie beam is composed of
many individual electrons travelling in
the same direction within a well-defined
space, they should react in the same
Showing approximate spectral
energy distribution compared to
eye sensitivity.
i
\
Re lotive 4-4--I--+--I--+-iH
60 f--- rad iant e n e r g y '
distribution
/
IIJ
40
228
\
I-I--':~ 1~~Ui~~r--t-t/t-t--t-t--1lr-t--f\~+--+-\--L-.l--+~\"+--I
screen
~Relative
\
/
Fig. S·b. Area within white circle
of Fig. S·a enlarged four times to
show detail. Photo from IRE Proc.
ments for focussing the beam electrostatically. Intensive research work during the last few years has resulted in
bringing the cathode-ray tube from a
laboratory curiosity to a tqol which has
\
\
nen~fivity - ' \
\
(
Near
Ultra_ Violet
Violet
Blue
Green
Yellow
Orange
Red
I
I
I,
!
fUNDAMENTALS Of TELEVISION ENGINEERING
manner as· electrons flowing in a conductor occupying the same space. We
know that a c~nductor which has electrons flowing in it is surrounded by a
magnetic field and that it will have a
mechanical force exerted upon it if another magnetic field approaches it. This
is the well-known motor principle uflon
which so many electrical, devices depend.
This electron beam can thus be de
flected to any point on the screen by
suitable currents flowing in suitably arranged coils around the neck of the
tube. Two pairs of coils whose axes
are oriented 90 degrees from each other
are used, the whole assembly being enclosed and mounted around tube's neck.
We also know that each electron has
a small but definite negative electric
charge. Because like charges repel and
unlike charges attract, the electrostatic
deflection system of plates shown on the
right in Fig. 2 will bend the beam. If
the top horizontal plate is made positive
with respect to the lower one, the beam
will be deflected upward an amount
which depends linearly upon the magnitude of the difference of potential applied. If the plate nearer the reader of
the other pair is made positive with respect to the far plate, the beam would
be deflected toward the reader By
means of these two pairs of plates, the
beam may be moved to any part of the
screen. The actual refjuirements and
relative advantages of the tW!) types of
deflection systems will be covered in
some detail in the next installment.
The focussing system is quite effective as demonstrated by the photograph.
of Fig. 5 (a) and (b) which has been
t;tken from Burnett's paper. 4 Regular
scanning methQds were em!Jloyed, and
the grid was modulated at about two
million cycles per second. Each of these
dots is of approximately the same order
of magnitude as an elemental picture
Show in,:! a partial sec:tlon view of
a typic:al elec:+ron ,:!un.
• Section 8
Fig. 1. Comparing 12" television
tube with a small metal tube.
Both tubes are used in same rec:elver. RCA photo.
area, although the lines have been separated for ease in observation. This enlarged area.of Fig. 5 (b) has been taken
from the center of the screen and has
been enlarged four times. A certain
amount of de-focussing, blurring, and
change in spot shape occurs near the
edges of the iluorescent screen, although
this effect is not serious. Fortunately,
also, the center of interest usually lies
in the center of the picture.
LUMINESCENCE
The law of conservation of energy
states that energy may be transformed
from one form to another, but can be
. neither created nor destroyed. Energy
can exist in many invisible forms. For
instance, a small amount of current can
be passed through the filament of an
incandescent lamp causing a radiation
of energy, but the effects of the energy
cannot be seen until enough current is
passed to make the filament become
white-hot and radiate energy within the
visible spectrum.
In nature, there are many substances
which have the power to change invisible ultra-violet radiation energy or cathode-ray ~nergy into visible light. The
study of this phenomenon is in general
known as luminescence. This may be
broken down into two parts, fluorescence and phosphorescence. Flu01'escence is an emission of luminous radiation which stops as soon as ·the exciting
stimulus is removed. Phosphorescence
is that luminous radiation which persists after the excitation has been removed. For example, if a sheet of paper were coated with a certain luminous
coating, it would appear white in daylight and be invisible in the dark. However, let some ultra-violet light fall upon
Above: Fig. 7. A 12" cathode.ray
tube being subiected to factory
t.sts. RCA photo.
B.low: Fig. t. Ma.ufacturlng
pro .... of loiftl09 shaak and tub•.
RCA photo.
Electrostatic
Deflection System
FI':!. 10. A television type c:a·
thode-1liiy tube under,:!oin,:! life
test. RCA photo.
1+----='-- 2000 Volts -.!.-----loi
Approx.
Vertical
Deflection
Voltage
Fig.2
229
Section 8 •
THE
it and it fluoresces with some characteristic color. When the ultra-violet
light is removed, the color continues,
dying away slowly. This latter 'is called
phosphorescence or aiter-glow. Phosphorescence continues for days or even
weeks with certain substances. It is believed that fluorescence is associated
with a change withitjthe molecule itself while phosphoresce1lce is associated
with th~ transit of electrons from one
molecule to another.
The coatings used on television ca·
thode-ray tltbes rely principally upon
the fluorescent effect and, hence, are
usually called fluorescent coatings. The
after-glClw or time lag caused by the
phosphorescent effect is, in fact, usually
very detrimental in television pictures.
For instance, a moving part of the image would leave an eerie trail behind it.
A ball thrown would appear to have' a
tail like a comet. Suitable screen materials should have what is termed short
persistence or medium persistence characteristics. Phosphorescent characteristics of several substances as given by
Levy and West1 are:
Duration of
Material
Phosphorescence
Calcium Tungstate
8 microseconds
Willemite
2-8 milliseconds
Zinc phosphate
About 0.25 second
Zinc sulphide with Fraction of 1 microsecond,
nickel
A scre~n whose relative brightness de~ays to within 10% of "black" in about
15 milliseconds is deemed satisfactory
for television reception, and it would
fall under the medium persistence classification.
COLOR OF EMITTED LIGHT OF
FLUORESCENT COATINGS
The screen that has been used very
extensively for general steady-state oscillographic work is the Willemite
screen. This substance is found in mi.ture ;lnd can also be made synthetically.
This material has been so popular because practically all .of its energy is
developed in a region in which the eye
is very sensitive. Fig. 3 shows the relative eye sensitivity plotted against the
wavelength of light in Angstrom units.
It will be seen that the eye is most
sensitive to yellow-green light. The
spectral energy curve of Willemite is
shown, and it will be seen that almost
all of its energy is concentrated in the
green, where the eye is very sensitive.
230
MY f
TECHNICAL
MANUAL
Although cathode-ray tubes giving
green light were and are used in many
experimental television receivers, the
fact remains that a more sui table and
pleasing color would be white. The approximate spectral energy distribution
of one mixture is shown as a broken
line in Fig. 3. This is an inefficient arrangement because, although the white
screen may have the same efficiency
from the energy standpoint, much of
this energy is expended at wavelengths
at which the eye is relatively insensitive
and, therefore, wasted as far as apparent light intensity is concerned. Even
though the white screen is inefficient,
the public will insist upon something
very close to white because of the comparison to motion pictures which television is always subjected to.
Other difficulties· confront the white
television screen. For instance, the predominating hue shifts to a longer wavelength with higher intensities. The
bright parts of the image may have a
cast that is somewhat different from
the less bright portions. In general,
however, this effect is more pronounced
at the lower intensities as almost any
fluorescent coating tends to appear
white at extremely high intensities.
The extraneous illumination falling
on the screen also influences the apparent color. A screen that appears white
in a totally dark room may appear tinted
if an incandescent lamp is burning in the
room. Added to all this, there appears
to be a wide variety of individual ideas
as to what a "white" screen really is.
In spite ot these difficulties, several
fluorescent coatings have been developed
which give essentially black and white
pictures.u One method of attack is to
mix two or more highly colored substances in such a way that their composite effect is essentially a white. For
instance, substances exhibiting blue and
red-orange fluorescence will produce
white .. Progress is being made in this
direction, and increasing the luminous
efficiency seems to hold real promise.
Because the maximum visible light energy emitted is only in the region of
4% or 5% of the electron energy input,
there is ample room for improvement.
PROJECTION CATHODE-RAY TUBES
Fig. 4, which is taken from Law's
paper,2 shows a cathode-ray tube which
gives a small, intense image so bright
that it can· be projected onto a screen
giving a 3 x 4 foot projected image.
Light may be compared to butter, the
greater the area over which it is spread,
the thinner it lies. This answers the
question often asked as to why a lens
system is not used on an ordinary cathode-ray television image tube. It can
be done, but the picture gets dimmer
the greater the area it is made to cover.
This projection cathode-ray tube is designed for high-voltage operation (10,000 volts), high-electron gun current,
and a small fluorescent screen image
(2.4 x 1.8 inches) which is projected
onto a screen for enlargement. With
such terrific electron bombardment, the
fluorescent screen has a much shorter
life than that of an ordinary directviewing tube. The progress of the projection tube now seems to be bound up
in the development of more durable
fluorescent materials.
BIBLIOGRAPHY
(1) Levy and West, "Fluorescent Screens
for Cathode-Ray Tubes," Journal
lEE, Vol. 79, 1936, pp. 11-19.
(2) Law, "High Current Electron GUll
for Projection Kinescopes," Proc.
IRE, Vol. 25, No.8, August, 1937,
pp. 954-976.
(3) Zworykin and Painter,· "Development
of the Projection Kinescope," Proc.
IRE, Vol. 25, No.8, AugUst, 1937,
pp. 937-953.
(4) Burnett, "A Circuit for Studying
Kinescope Resolution," Proc. IRE,
Vol. 25, No.8, August, 1937, pp.
992-1011.
(5) Zworykin, "Iconoscopes and Kinescopes in Television," RCA Review,
Vol. I, No.1, July, 1936, pp. 60-84.
(6) Maloff, "Direct-Viewing Type Cathode-Ray Tube for Large Television Images," RCA Review, Vol.
II, No.3, January, 1938, pp. 289
(7) Laverenz, "Problems Concerning the
Production of Cathode-Ray Tube
Screens," Journal of the Optical Society of America, January, 1937.
Reprinted in T clevisioll, Vol. II,
RCA Institutes' Teclmical Press.
(8) Wilson, "Television Engineering"
(Pitman), Chapter VIII, Cathode
Rays and Fluorescence.
(9) Randall, "The Theory of Luminescence," Television (London), July,
1937, p. 408. Abstract of paper
appearing in Royal Society oj Art!
Journal, March, 1937, p. 146.
(10) Parr, "The History of the CathodeRay Tube," Television (London),
February, 1937, p. 85.
(11) Schmidling, "Fluorescent Materials
for Television Tubes," COMMUNICATIONS, April, 1939, p. 30.
I
I
jl
<
,
I'
I.
"
fUNDAMENTALS Of TlUVISION INGINffRING
• Section, 8
, Part V: Electron 8eam Deflection Methods
I
N an electronic television system which
uses a'cathode-ray tube as the reproducing element, we have seen that the electronic density of the electron beam is
made to vary with the signal corresponding
to the variations of light and shade of the
image being transmitted. In order that
the visual intelligence be successfully received, it is necessary that the electron
beam of the reproducing tube be made
to traverse the area of the screen which
corresponds exactly to the area being
scanned at that instant at the transmitter.
Exact synchronism must be maintained
between the two extremities of the system,
a subject which will be covered later in
this discussion. In addition to this, means
must be provided whereby the electron
beam can be deflected to any part of the
fluorescen~ screen. As mentioned in Part
IV, the two possible methods of obtaining a deflection of the electron beam are
the electrostatic and the electromagnetic
methods.
tween the deflecting plates, E. is the
accelerating anode potential, and the
other symbols are a's explained in Fig.
1. Equation (1) is derived from the
equation of motion of an electron trayeIling in the y direction, considering
the charge on the electron and the mass
Screen-1+----
Y ---~
ll~
Fig.i
Electron-,'
Beam
lIIustratlllg the prillciple of
electrostatic deftectloll.
Showillg how electromagnetic
deftectloll il accompllslled.
r---+
y
-----.I
x=-
...................... (1)
lEad
where Ed is the potential applied be-
Electromagnetic Deflection
The electron beam can be compared
to a current flow in an extremely flexible conductor. If this beam traverses
a magnetic field, a force will act upon
the beam tending to move it. This
phenomenon is exactly the same one
which causes electric motors to turn,
the well-known "motor action" based
upon Ampere'.s law. Consider an electron beam entering a perfectly uniform
magnetic field whose direction is from
the observer into the paper in Fig. 2.
By means of 'the old familiar left-hand
rule (remembering that electron flow is
opposite to the conventional current
flow) , the direction of the deflection
can be determined. The amount the
beam is deflected is given approximately by:
0.3 Hly
x = - - - . .................. (2)
ylE.""
Electrostlltic Deflection
In the case of electrostatic deflection,
the beam of electrons leaves the gun
and passes between two parallel (at
least considered parallel for this analysis) deflecting plates arranged horizontally. The electric field set up between these two plates causes the beam
to be bent upward and downward in a
vertical plane. The beam next passes
between another similar pair of plates
arranged at right angles to the first
pair. An electric field set up between
these two plates causes the beam to be
deflected in a horizontal direction and
by means of the composite forces acting
upon the beam by the two pairs of
plates, it may be deflected to any part of
the fluorescent screen. These forces
acting upon the beam arise, as pointed
out before, from the fundamental action
of charged bodies: like charges repel,
and unlike charges attract. The beam,
being composed of negative electrons,
will be deflected toward the plate which
is positive at that instant.
The amount of the deflection is gi\ien
by
great anode voltage) requires a relatively large deflecting voltage for a
given deflection.
Electron Beam .;
Fig.2
of it due to its velocity. The trajectory
of the electron is rectilinear before entering the electrostatic field between the
deflection plates and after emerging
from it, but while it is travelling between the plates, its path is cur~ed.
From the mathematical statement of
equation (1) we can see that the deflection x is directly proportional to the
deflecting voltage Ed, the length l of
the electrotatic field traversed by the
electron, and the distance from the
plates to the screen. It is inversely
proportional both to the deflecting plate
separation and the accelerating anode
potential. Of these parameters, all are
fixed quantities for a given cathode-ray
tube except Ed and Ea. The greater
~., the greater the velocity of the electron 'travel and the less time the electrostatic field between the plates has to
act on it. For this reason a "stiff"
beam (one accelerated by a relatively
where H is the field strength in gauss
and the other symbols as explained in
Fig. 2.
It should be emphasized that equations (1) and (2) are only approximate due largely to the fringing effect
and the resulting non-uniformity of
the electric and magnetic fields.
Sawtooth Generating Systems
In order to obtain uniform spot
travel along a line and equally spaced
lines over the whole raster or scanning
pattern, the potentials that must be applied to the deflecting plates -must be of
saw-tooth waveshape.
This shaped
wave can most easily be produced by
a circuit such as that shown in Fig. 3
in simplified form. The condenser C is
charged from th~ d-c source at a rate
determined by the resistor R. When
the voltage across the condenser terminals, and thus across the gas triode
VT" has attained a certain value which
is determined by the grid voltage E c ,
VT, will become conducting and discharge the condenser C very rapidly.
Thus, we have a voltage which increases at an essentially constant rate
up to the firing point of VT, and then
rapidly decreases to zero and again begins a new cycle of ascent producing a
231
Section 8 •
THE
)"
_' .. ,lit
\ ,'{f~.
e2
it
A popular type of .aw-tooth
t •••rator u.ed by RCA.
saw-tooth shaped wave. The frequency
may be varied by varying R or changing the value of C, and the amplitude
may be adjusted by varying E.. To
obtain an essentially linear ascent, the
crest saw-tooth voltage must be only a
relatively small percentage of the applied doc voltage, because the voltage
built up across C is an exponential
function of time. The resistor R may
be replaced by a pentode tube whose
pllite current is essentially independent
of its plate voltage. In this way, the
tube acts as a constant-current device
making the saw-tooth ascent linear over
a greater proportion of the applied voltage. The limitation of this saw-tooth
oscillator utilizing a gas triode is that
the firing point of the tube varies
slightly with aging, temperature, etc.,
causing somewhat erratic operation,
and that there' is a very definite upper
frequency limit due to the finite deionization time. Newer gas triodes
using gases other than' mercury vapor
have overcome. many of these disadvantages; and it is PQssible to use this
type of saw-tooth generator for the line
scan for modern high-definition pictures which is 13,230 cycles per second.
While the mercury-vapor type of'gas
triode only was available, its limitations caused much work to be done
along the line of high-vacuum sawtooth generators. Fig. 4 shows a circuit" '. 8 which, has proved to be very
satisfactory as to stability and highfrequency operation. In fact, highvacuum generators have been made to
operate at frequencies as high as one
megacycle, which gives them a distinct
advantage over the gaseous type even
for oscillographic uses.
In Fig 4, VT. is the high-vacuum
232
MYE
TECHNICAL
MANUAL
triode which acts as the discharger of
the condenser C and VT. has the duty
of aiding this discharge operation. The
acfual discharge and charge circuit is
shown with heavy lines to facilitate an
understanding of the- circuit. U~t us
follow a cycle' of operation through,
starting with the condenser C discharged. At the moment the 300-400
volts ?-c are.. switched on, the full voltage appears across R causing the
cathode of VT. to be highly positive
with respect to ground. The grid of
VT, assumes the potential of the lower
end of R. which depends entirely upon
the plate current flowing through VT.
which in turn is determined by the
screen voltage setting on R.. The grid
of VTl can thus easily be made highly
negative with respect to its cathode.
This results in VT. being non-conducting while C is being charged. As the
F"ig.3
A simplified circuit for producing
saw-tooth voltago.
voltage across the terminals of C increases, the plate voltage of VT. ultimately attains a value which causes
VT. to become conducting in spite of
its high negative bias. As the plate
current of VT1 flows through R" voltage drop appears which is coupled to
the grid of VT. through the C.-R. circuit driving it in a negative direction
which in turn decreases the voltage
drop on R.. The grid of VT. thus becomes less negativ~ allowing more and
more plate current to pass. The grid
of VT. goes positive, and the condenser
C is discharged very quickly through
VT.. When the voltage across C decreases, enough, the VT. grid again
gains control and the' cycle repeats.
The resistor Rl controls the discharge
time Which is aided by the gain of VT,.
Resistor R. controls the amplitude of
the sweep. A pentode can be used as a
constant-current device in place" of R
if the refinement is justified. Synchronization can be obtained by injecting the
pulse on the suppressor grid of VT.
or repla.cing R. by a triode with adjustable cathode resistor and injecting the
pulse on the grid of this tube. The
values of components for 1O,OOO-cycle
operation as suggested by Parr" .are included in Fig. 4.
A simpler single-tube circuit of the
blocking oscillator type is shown in
Fig. 58. The condenser C is charged
in the usual way from a ld-c source
either through a resistor R or a pentode
tube. The discharge tube is connected
across C, the primary of a transformer
being in the plate circuit and the secondary in the grid circuit and the two
windings closely coupled. The tube
is biased beyond cutoff by R. which is
by-passed by C, to provide a smooth
bias voltage for the tube. The method
of action is as follows: the grid is
biased beyond cutoff and the condenser
charges until the plate voltage is great
enough to allow current to pass through
the tube even with the high bias. The
plate current flowing through the
primary of the transformer induces a
voltage on the grid which bucks the
bias from R.. This process rapidly
continues, until the condenser is discharged and the cycle repeats. The
resistor R. is connected across one of
the windings of the transformer and
adjusted so that the tube will not oscillate continuously but will produce es~ential1y a single pulse of current. Synchronization may be realized by inserting the pulses into a third winding.
The resistor R. controls the amplitude,
and R the frequency of the saw-tooth.
Typical values of constants suggested
by Parr" are included in Fig. 5.
There are several other types of sawtooth generators but none as much in
use in this country as that used by
RCA as illustrated in Fig. 6.•.•. 1 Here
Circuit for obtaining balanced sawtooth for el.drostatic d.fI.dlon.
---r--------------~~~-oDf
C2
B+
Fig.S
I.
!
I '~
• Section 8
FUNDAMENTALS OF TELEVISION ENGINEERING
again the ascent of the saw-tooth wave
is obtained by charging the condenser
C. through the resistor R. from a d-c
source. The tube VT. is normally biased beyond cutoff so that it does not
influence the charging cycle. However,
at certain intervals determined by the
selection of constants and the synchronizing signal, the blocking oscillator incorporating VT, delivers a large
positive pulse to the grid of VT., causing it to have a very low impedance
and discharging the condenser C. after
which a new cycle begins. The waveshape of e, is shown in Fig. 6, the
broken portion in the negative region
serving only to drive VT. farther beyond cutoff. The solid positive pulses,
however, are the ones causing VT. to
discharge C.. The phase relationships
between the discharge pulses of e, and
the output saw-tooth wave e. is as
shown in Fig. 6.
contacts for all deflecting plates. The
two types of distortion arising when the
deflection voltages are asymmetric are:
(I) a variation of sensitivity produced
by the deflection voltage which adds or
subtracts from the accelerating anode
voltage, and (2) an inter-modulation of
the two pairs of plates. Both forms of
distortion are avoided if balanced deflecting voltages are used. The effect
of these distortions is the degeneration
of the normal rectangular raster to one
of trapezoidal shape. To avoid this, a
push-pull amplifier stage should be used
to apply the deflecting voltage to the
plates.
Figs. 7, 8, and 9 show three means
of attaining a balanced saw-tooth for
electrostatic deflection. Fig. 7 is a 'conventional circuit, VT, being a straight
amplifier of the unbalanced input, and
VT. is the phase-inverter stage by ob-
A saw-tooth circuit for electrostatic dettec:tlon.
c
'f
Fig.9
B+
orz'." , -
'11("\1
'"
/"?
'.'
,
' I
·~e:l~t~>:)
,.
..
~
Fig.tO
An assembly of horizontal and vertical deftec:ting coils are used in RCA receivers.
voltage appearing across C, divided by
the actual gain of VT,.
Fig. 9" shows a circuit which is inherently balanced to ground. This is
accomplished by dividing the charging
resistor into two equal parts, Rl and
R 2, and placing one on either side of the
S'1.w-tooth genllFating condenser:. To
vary the charging rate (and thus the
frequency) either R, or R2 may be
made adjustable within small limits
without seriously disturbing the balanced conditions.
Electrostatic Deflection
It has been pointed out that in charging a condenser through a resistor (the
case in many of the saw-tooth generators described), the condenser can be
charged only to a small percentage of
the + B voltage if linearity is to be
obtained. There are two ways to get
around this limitation, one to use a
pentode in place or the charging resistor and the other is to amplify the
relatively low saw~tooth generated with
the charging resistor. In either case,
more component parts are required.
One thing that must be met in electrostatic deflection is the distortion
arising when the saw-tooth voltage is
applied to the plates asymmetrically, or
unbalanced to ground. Many of the
small oscillograph cathode-ray tubes
have one horizontal and one vertical
plate bonded within the tube, but the
larger tubes, especially those in television service, always have separate
DIAGRAM
ASSE:M6LE:D YOKE: . /,:>
Electromagnetic Deflection
Fig.7
Circuit fot attaining balanced
saw-tooth for electrostatic deftec:tion.
taining its driving voltage from the
plate circuit of VT 2 • 1~
JllJllfTIlfl
output~
R
Fig .4
Showillg the actloa of the basic
horizontal pulse seleethlCJ circuit.
is actually a simplified version of three
filter sections in cascade as shown in
the plate circuit of the vertical ampli"
fier of Fig. 3.
Pulse Generation
A glance at the complex waveform
of Fig. 1 impresse5 one with the close
tolerances which must be observed for
,.;atisfactory television operation. It is
both interesting and instructive to
understand a method of keeping the
proper relationship between line and
field-pulses. It is also highly desirable
that the 60-cycle output of the vertical
sweep generator be locked into step
with the 60-cycle power frequency.
This results from the disturbing effects
of a-c hum in the vertical or horizontal
deflection circuits or both. The disturbance created is much more discon-
certing to the eye if it is in motion as
would be the case if a slight difference
existed between the field and power
frequencies. Wiggling and creeping
edges and vertically moving horizontal
bands due to uneven line spacing result at the difference frequency. To
avoid this, relatively complex systems
are used. Fig. 6 shows one such possible system. A master oscillator of
some type controllable over a narrow
range operates at 13,230 cycles per second which is the line frequency (441 X
30 = 13,230). This frequency may be
used to control the frequency of the
horizontal synchronizing pulses. This is
fed into a multivibrator circuit which
doubles the frequency and into four successive multi vibrator stages which act
as frequency dividers of 117, 1/7, 1/3,
and 1/3, respectively. The output frequency is 60 cycles. To keep this output frequency the same as the powerline frequency, it can be compared to
the power frequency by means of a suit-
ShowlnCJ action of' the basic: ver·
tic:al pulse seleetlnCJ c:ircuit.
able electrical circuit, and the frequency
of the master ()~cillator ad jllsted to COlllpensate for any differenc~ b~tweell the
two frequencies.
Bibliography
(1) Murray, "Television Standards," COMMUNICATIONS, December, 1938, p. 14.
(2) Murray, "RMA Completes Television
Standards," Electronics, July, 1938,
p. 28.
(3) Goldsmith, "Television Economics,"
Part III, Section E-3, "Synchronizing
and Video Controls," COMMUNICATIONS, April, 1938. p. 26.
( 4) Engstrom and Holmes, "Television
Synchronization," Electronics, November, 1938, p. 18.
(,5) Zaharis, "Synch Impulse Generator
for Television Deflection Circuits,"
Electronics. June, 1939, p. 48.
<.6) "Practical Television by RCA," Service Division, RCA Manufacturing
Company, Inc.
Part VII: Television Receivers
As
far as the basic principles of
operation are concerned, the television receiver does not differ from the
usual broadcast sound receiver. The
television receiver does differ greatly
in several details, however. The carrier
frequencies al'e much higher for the
television receiver (44 to 108 megacycles for seven channels) which alone
demands many refinements for satisfac-
tory operation. The television receiver
must receive and care for two carriers
simultaneously, one for sight and one
for sound. The sound channel must be
very wide (about 2 to 4 megacycles)
SYNCH.
SEPARATOR
FiCJ. 1.
Bloc:k diaCJram of typic:al receiver
58.00 me
FICJ. 6. Rear view of larCJe RCA rec:elver.
237
Section 8 •
THE
inUiiJV\
(a)
a:
F"req.----+
ai~
(b)
TECHNICAL
MANUAl.
TABLE I
P:obable frequency relationships when
:ecelver tuned to television channel I (44,,0 mc)
.
~icture carrier fre.quency ..... . 45.25 mc*
Sou!ld carrier frequency ..... . 49.75 mc*
O~cdlator frequency ........ . 58.00 mc
Picture I F frequency ....... . 12.75 111C*
Sound IF frequency ......... . 8.25 mc*
'Plus sidebands.
F"req. _ _
D~ilo
(c).
MYE
F"req. _ _
Fig. 2. Va rlous response
charaderlstlcs.
to pass the high-frequency components
of the normal video signal. The ex~
istence of this wide pass band introduces problems concerning noise. Although this ultra-high-frequency region is practically immune from natural
static, it is particularly vulnerable from
man-made interference such as that generated by automobile ignition systems,
street cars, diathermy machines, various domestic appliances, etc. The interference generated by many of these
devices is of a random character having its energy distributed more or less
evenly throughout the spectrum. The
Below: Fig. i. Checking frequency
response In RCA plant..
gain of the video channel is thereby
somewhat limited due to the wide pas's
band and the resulting greater noise
level. This means that the sensitivit,·
of the television receiver is less tha;l
the ordinary broadcast receiver. The
necessity for wide video pass bands results in the realizing of only a relatively low gain per stage, more or" less
offsetting the lower sensitivity advantage economically.
The superheterodyne receiver has
been almost universally adopted for
television receivers. The tuned-radiofrequency receiver can be used, but
eco~omi~ cons!derations rule largely
agamst It. Serious variations of sensitivity and pass-band width throughout
the tuning range are also detrimental.
Fig. 1 shows a highly simplified block
diagram of a typical television receiver
for both sight and sound. The degree
of simplification of Fig. 1 can be
realized by counting the number of
tubes in the television receivers now
on the market in this country. The
number varies from 16 tubes for a 5inch receiver designed to use the audio
F19. 3. Front view of
Philco receiver.
power amplifier of a usual broadcast
receiver to 32 tubes· in a receiver having a 12-inch cathode-ray tube which
is complete plus an all-wave receiver.
The usual sight and sound receiver
complete utilizes about 25 vacuum tubes.
Future development and research will
undoubtedly lead to simplification.
The radio-frequencv amplifier if one
is included, amplifie~ both th~ video
carrier and its side-bands and the audio
carrier and its side-bands at the same
I
Fig. 5. Front view of RCA
receiver with 12" tube.
I
,
238
'UNDAMENTALS 0' TELEVISION ENGINEERING
FiC). 4. Rear
view of Phil co reo
ceiver.
time. This is accomplished by designing the tuned circuits to give essentially uniform response over a wide band
and yet provide ample discrimination
against unwanted signals. This usually
entails the use of a coupled circuit
rather than a heavily loaded singletuned circuit, because the selectivity for
a given band width is better for the
former. The new high transconductance
type 1853 tube is almost universally·
used in this position, because it will
give a satisfactory stage gain with relatively low plate load impedance.
As shown in Figs. 3 and 4 of Part
II , there is a constant spacing of 4.5
megacycles between audio and video
carriers in each of the television channels when arranged for single-side-band
transmissions. This paves the way for
simplification of tuning controls, as both
the sound and sight signals may be
tuned by the same operation. This
spacing of 4.5 megacycles has superseded the 3.25-mc spacing which is discussed in the first twelve references in
the bibliography. The process of readjusting a receiver to accommodate the
new sound-sight carrier spacing of 4.5
mc is a minpr one, however.
The output of the radio-frequency
amplifier is fed to the first detector or
converter stage. Here the local oscillator signal is heterodyned with the incoming signal resulting in sum and
difference frequencies as in the conventional superheterodyne receiver. The
oscillator may be adjusted to operate
at a frequency above that of the incoming signal. The sound carrier is always at a higher frequency than the
video carrier by 4.5 mc. This would
cause the video intermediate-frequency
(i-f) channel to lie at a higher frequency than the sound i-f channel,
which is helpful in designing the video
i-f channel circuits to pass the necessary band width. The various frequency relationships when the receiver
is tuned to accept the lowest frequency
television channel (44-50 mc) are
shown in Table 1.
It will be noted that the intermediate
frequencies are selected in the order. of
10 mc. This choice is determined by
the necessity of avoiding strong signals
from local transmitters at the intermediate frequencies. As amateur transmitters are probably the most likely
sources of interference, the 7 and 14-mc
amateur bands must be avoided. A
lower picture i-f is not practical since
with even 12.75 mc, a video-frequency
band of 4 mc represents about 30%
• Section 8
of the intermediate frequency. This
complicates circuit design to achieve
the necessary pass band.
The television receiver is actually
two separate receivers beyond the converter stage. The sound only is accepted in the sound i-f channel for it
is tuned sharply to that frequency. The
picture signals are passed through the
picture i-f channel, as the sound channel is not sensitive to frequencies lying
within this range. It is interesting to
point out that a short-wave broadcast
type receiver tuned to 8.25 mc for channel I could replace the entire sound
channel of the television receiver including i-f amplifier, se.cond detector,
audio amplifier, and loudspeaker. The
broadcast receivers now appearing with
claims that they t
economical and satisfactory combination
at the present time.
D·C Component
In voice transmission the wave "!Jape
is essentially symmetrical with the axis
242
Distortion Requirements
at all times, the axis being defined as the
line which equally divides the area under
the wave. In television transmission this
is usually not the case. The degree of
bymmetry is determined largely hy the
image being scanned at that instant l .
This continuous axis shift may be considered as a varying d-c component. To
improve the transmi tter efficiency hy
reducing the dynamic modulation rallge,
this d-c component may be used to shift
the average carrier to follow the average
illumination of the picture. At the j'eceiver this d-c component is re-inserted
at the cathode-ray tube grid so that a
faithful video reproduction results. The
d-c insertion at the transmitter is only
for more efficient operation of the transmitter, however.
Fig. 3. Diagram of RCA l-kw
television transmitter.
The hum-level requirements of a television transmitter are essentially the
same as those of a high-quality broadcast transmitter. The harmonic distortion requirel!lents for visual broadcasting are much less severe than for ~ound
broadcasting. This arises from the fact
that the detail of the picture wiII not
suffer particularly from a non-linearity
of the system, but only one degree of
l1alftone reproduction at the reproducing
tube. That is, details of the image transmitted through a non-linear system, although appearing in their proper position and size, Illay not have the proper
degree of light and shade as compare.d
to the other parts of the image. ThIS
relative insensiti\'ity to a modest degree
of nonlinearity als~ makes grid modulation more attractive.
Fig. 1 is a photogTaph of a I-hv television transmitter recently placed on the
market bv RCA, Fig. 2 is a rear view
of one un'it of this same transmitter. Fig.
3 is a highly simplified hlock diagram
\7
CRYSTAL
05C.
BUFFER
~ Do8~LER
i·807
I-
t-814
TRIPLER
~
2·808'5
POWER
POWER
AMP.
AMP.
~
2-834'5
2-833's
I-
FINAL
POWER
~
AMP.
2-899'5
SIDEBAND
FILTE:R
t-
~\
"
Vide~~
Input
VIDEO
AMP.
2-S07'5
~
VIDEO
AMP.
4-807's
-{
MODULAT'
ING
AMPLIFIER
m-St3's
Grid
"Modulation
t-
D.C.
INSERTION
i·tV
~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ---
-
- --- - - - - - - - - - - -
I:
!'
FUNDAMENTALS OF TELEVISION ENGINEERING
of the radio-frequency and video-frequency sections showing the tube complement utilized.
Fig. 4 shows video control position in
the National Broadcasting Company's
television studio 5. The operator has
command of the studio floor t~ough
windows before him which are tinted to
minimize glare from the highly lighted
studio. The three knobs at the operator's
left control the electrical focusing of the
iconoscopes in the studio cameras. The
operator is adjusting the brightness and
video gain controls for best contrast and
brightness in the image. The group of
knobs to the right of the operator insert
voltages of various shape and phase into
the video signal to counteract the effect
of spurious "shading" signals generated
in the iconoscope. These spurious signals apparently are due to the fact that
more secondary electrons are generateu
at the iconoscope mosaic than are supplied by the beam and a shower of electrons falls back on the mosaic. These
electrons cause a random charge distribution over the mosaic which has no
relationship to the video signal, but
causes the "dark-spots." These dark
spots are neutralized as well as possible
by the adjustment of the knobs shown
in Fig. 4. These spurious signals cannot be entirely eliminated as shown by
the image of Fig. 5, which is the image
appearing on the monitor tube above the_
operator of Fig. 3. The dark areas and
the white borders on the picture are a
result of these effects and the attempt
to neutralize them. The waveform of the
video signal is constantly monitored by:
means of the oscillograph beside the image tube.
Fi,. 8 (Below). Experimental steps
in determining optimum proportions of antenna in Fig. 7.
l~Ilfft11
°6 4 2 ° 2 4 6
I! Hkl I4~,vl
8
4
0
4
8
f~NfQJJJJ#f1
°12
8
4
0
4
8
Fig. 6 (AboveL Sync:hronizing impulse generator (RCA photoL
Fig. 6 shows a view of the synchronizing pulse generator which generates
the pttlses for' both horizontal and vertical synchronization.
The required
regulated power supplies arid amplifiers
are included within the other cabinets.
Television Transmitting Antennas
The antenna to be used with a television transmitter presents a problem 'in
the relative difficulty in attaining constant characteristics over the necessary
frequency band. Attaining these constant
characteristics over a given band width
becomes easier the higher the frequency
of operation. Therefore, we can expect
considerable simplification of vision antenna structures between the 44-50 mc
channel and the 102-108 mc channel. As
Fig. 9. Optimum proportions of
lingle radiator modified for IUp- .
porting brac:ket.
• Section 8
Fig. 7. Television transmitting antenna atop Empire State Building.
the trend is toward the higher frequencies, the extent of the experimental work
that has been done is highly justified.
Fig. 7 shows a novel approach to the
problem of attaining constant characteristics over a wide frequency band. This
is a photograph of the vision and sound
antennas atop the Empire State Building. The vision antenna is of particular
interest and the neat experimental evolution of the final shapes as reported by
Lindenblad is illll5trated in Fig. 8,
which is taken. from his paper. In general, elliptical shapes of all of the radiator surfaces seemed to give the most
constant impedance characteristics. In
order that the protruding portion of the
ellipsoid and the collar radiate equally,
their relative lengths should be in the
ratio of 7 to 5 as illustrated in Fig. 9,
which is also taken from Lindenblad's
paper. This gives an input impedance
in the order of 110 ohms. The best ratio
between major and minor axes of the
ellipsoid is 15 to 6. The optimum ratio
of mean collar diameter to ellipsoid
diameter was found to be 3 to 2. The
e,llipsoid is bonded to the collar by a
~pecially designed bracket for lightning
protection. For vertically polarized
waves, a single unit could be mounted
vertically. For the desired horizontal
polarization, 4 units were arranged
Fig. 10. Cutaway view of c:oaxlal
transmission line (RCA photo).
12
!Ffli fI° ffl
,8
4
4
8
f~II13{11
°6 4 2 ° 2 4 6
0(0 Frequency Deviation
243
Section 8 •
THE
Fig. 4 (Above). The video e:ontrol
desk of the NBC television studios.
around the tower excited in progressive
phase quadrature as a "turnstile" antenna. It was found upon completion
that this antenna had uniform characteristics over the range of about 30 to
60 mc, or 6 to 10 times that obtainable
with other conventional designs with
complicated correction networks. This
truly represents a real advance in antenna technique.
MYE
TECHNICAL
MANUAL
Fig~ 5 (Below). Monitoring Image
and wave shape of video signal.
See tubes above e:ontrol panel of
Fig. 4.-
mile trial section between N ew York
and Philadelphia. A lead sheathed coaxial cable suitable for such purposes is
shown in Fig. 10.
The second approach to the problem
is that of ultra-high-frequency radio link
transmitters. At high frequencies very
efficient and highly directional antenna
structures can be cheaply constructed.
By the use of such antennas for both the
receiving and ttansmitting functions,
low transmitter power acquirements and
a minimum of interference may be attained. It is conceivable that an extensive network could be built up of many
such units located on strategic geographical points at distances depending
upon the line-of-sight range obtained. Itis also possible that sufficient reliability
could be realized in an unattended station or at least by remote control.
Fig. 11 shows an experimental link
transmitter operating on a frequency
of 177 mc. It is located on the 10th floor
Interconn,ecting Links
In the near future the problem of simultaneous network operation of a multiplicity of local television stations must
be faced. This will be a particularly difficult economic problem in the United
States because of the great distances and
relatively low population density in most
areas. The economic phase is even a
Fig. 11. 117·me: u-h·f transmitter
linking Radio City studios with
Empire State Building transmitter.
limiting factor in bringing to reality the
proposed Birmingham provincial station
outside of London in a relatively highly
populated area.
At the present time there seem to be
two general methods of approach to the
interconnection problem. One is the use
of transmission lines. Over relatively
short distances a selected pair in an
ordinary telephone cable has been used
with correction for remote television program pickups. The coaxial cable is well
adapted to the transmission of video signals ~cause the attenuation is faIrly low
and quite uniform over a wide frequency
range. Unattended amplifying units located in manholes at proper intervals
have been used successfully in a 100-
244
of the RCA building and serves as an
alternate to a coaxial transmission line
between the NBC television studios in
the RCA building and the -television
transmitter located in the Empire State
Building, a distance of somewhat less
than a mi,le. It will be noted that such
transmitters can be made compactly.
Bibliography
(1) Radio Transmission Considerations"
Smith, COMMUNICATIONS, March 1939,
page 30.
(2) "Televison Station W2XAX"-Part 1
-Goldmark, COMMUNICATIONS, No-vember 1938, page 7.
\
(3) "Television Station W2XAX"-Part
2 "- G 0 I d mar k, COMMUNICATIONS,
February 1939, page 27.
H
I
II
i'
I'
,I
fUNDAMENTALS Of TELEVISION ENGINEERING
Transmittet;s,"
(4) "Television
tronics, March 1939, page 27.
RCA Review, April 1939, page 387.
(6) "Television Radio Re1ay"-Trcvor and
Dow, RCA Review, October 1936,
page, 35.
Elec-
)
(5) "Experimental Studio Facilities for
Television"-Hanson, RCA Review
April 1937, page 3.
'
(7) "Television Transmitting Antenna for
Empire State Building"- Lindenblad,
• Section 8
(8) "Equipment Used in the Current
RCA Television Field Tests"-Beal,
RCA Review, January 1937, page 36.
Part IX: foreign Developments
B
ECAUSE of the old American custom of believing that little, if anything worth while is ever done outside
the bounds of these United States, it
would seem appropriate in this series to
pause long enough to take a hurried
glimpse at the development work in
'television in other countries. While
such a study does not fit any too well
into the main title of the series, an
appreciation of foreign television activities is absolutely necessary to view
our domestic developments in their
proper perspective.
Fig. 1. Radiating Iystem of
Rome - Mount Mario television
transmitter.
England
The television acttvittes in England
are perhaps the most intensive of any
foreign country. The British authorities have led the world in providing an
ambitious program service. The radio
listener fee of ten shillings per year
was the source oHhe funds which made
this possible. At the outbreak of the
war there were reported to be about
25,000 television receivers in use with
others being purchased at the rate of
1000 to 1500 per month. The television
broadcasts of one hour each afternoon
and two hours each evening were
abandoned "for national defense purposes" when the war began, and at this
writing have not been reestablished.
The London transmitter is located at
the edge of the city in Alexandra Palace where broadcasts began in August,
1936. The standards adopted are 405
lines, 50 frames interlaced, giving 25
complete picture scans per second. The
equipment in use was provided by the
Marconi-E. M. I. company and is built
around the "Emitron" camera which is
basically a mosaic-storage tube patterned after the iconoscope. The transmitter has a peak output power of 17
kw corresponding to "full picture
white," and is modulated by the conventional grid system. Double-sideband
amplitude modulation, "infra-black"
synchronizing pulses, and positive
modulation are used.
Outside broadcasts are accomplished
by mobile units utilizing radio-link
transmitting special balanced-pair lowcapacitance cables primarily designed
for television signals, and a limited use
of ordinary telephone-cable pairs suitably equalized for short distances. A
line utilizing the special balanced pair
n111S past points from which many
broadcasts emanate, such as Buckingham Palace, Trafalgar Square, and
Piccadilly Circus. The British system
has been covered quite thoroughly in
several recent articles published in the
United States.
Italy
A relatively insignificant amount of
Fig. 4. Rotary converter and
automatic anode voltage regulators of Italian transmitter.
Fig. 2. (Left) Safar standard type
television transmitter for Italian
statlonl.
Fig. 3. (Rlgbt) The
Safar transmitter
with cover plates
removed.
245
Section 8 •
THE
MYE
TECHNICAL
MANUAL
Front (Fig.
5. left)
and rear
(Fig. 6. right)
views of
Safar
c:ontrol desk.
Fig. '.(Above) Sync:hronlzing
opparatus. mixer and c:ontroll
of Safar television c:ameras.
Fig. 10 (Below) Stage in the
Safar television theatre.
_._P4.(".
Fig. 11. (Above) Safar Type B
Telepantosc:ope. a mosaic: devlc:e
used in telec:ameras.
Fig. 14. (Below) A40.1cv Safar
tube for prolec:tion rec:elver•.
246
information on the Italian television
activities has appeared in the Englishlanguage press. A consistent, though
limited, program of research has been
conducted by the Societa Anonima Fabbricazione Apparecchi Radiofonici (the
"Safar") in Milan, the efforts of Mr.
Arturo Cas~ellani being conspicuous.
Outstanding in their list of accomplishments is the Rome station. This station
is built on the top of Mount Mario so
that the transmitting dipoles are at a
height of about 500 feet over the city.
This hilltop location is situated at the
periphery of Rome and, naturally, has
the greatest field strength direct toward
it. A signal of at least 200 microvolts
is delivered to the receiver terminals
by the usual dipole in all parts of the
city. This Mount Mario antenna structure is shown in the photograph of
Fig. 1.
The transmitter's voice carrier is 41
mc and the video carrier is 44.1 mc
arranged for double sideband transmission. The output of the transmitter has
a peak power' of 5 kw for a 6-mc bandwidth. Figs. 2 and 3 are views of the
Safar television transmitter wi~h the
front plates in place and with them removed. Some of the specifications of
this transmitter are:
(a) Frequency distortion ± 1.5 db
for 0-3 mc band ..
(b) Phase distortion .1 microsecond
25-1000 c, 0.5 microseconds 1000 c to
1.5 mc, and 0.2 microseconds between
1.5 and 3 mc.
( c) Harmonic distortion 4% at 90%
modulation.
.( d) Noise level 0.5% at 100% modulation.
(e) Stability of radiated frequency
1 part in 200,000.
An interesting fact is that all tubes in
this transmitter are pentodes. This results from the lower grid currents and
the greater ease of neutralization. The
final amplifier tubes are water cooled.
All anode and bias voltages are supplied by conventional rectifier-filter systems; while the filaments are lit by a
rotary converter. The anode voltages
!
Fig. 12. A stand·
ard type of Safar
television
rec:elver.
If
I
I
I
Fig.
13.
Chassis of a
rec:eiver.
Safar
for the video section and the modulated
r-f stages are equipped with automatic
voltage regulators. Fig. 4 is a view of
this voltage regulator equipment and
the filament rotary converter. The
transmitter is monitored and controlled
from the operating desk shown in Figs.
5 and 6.
The Safar television theatre illustrated in Figs. 7 and 8 is a typical one
shown at the Milan Leonard exhibition,
after which theatres in other parts of
Italy will eventually be ·patterned.
These theatres have modern treatment
in every way as evidenced by the photograph. "Fig. 9 shows the synchronizing
apparatus, mixer, and controls for the
cameras ~rranged so that all operations
fUNDAMENTALS Of TELEVISION ENGINEERING
• Section 8
Entrance
lFlg. 7,
right)
and
Inner hall .
(Fig .•• left)
of Safar
televilion
theatre.
Fig. 15. A tele·
vision receiver
manufactured b y
Allocclilo Bacchlni
Ie Co.
Fig. 16. Rear chassis view of
Allocchlo Bacchini receiver.
Fi,. 18.
Television re.
search laboratorle. at Mont.
rouge, France.
and apparatus is clearly visible through
glass partitions from the main hallway.
The stage, shown in Fig. 10,. is
equipped with adequate lightihg arranged to avoid dazzling, double wall
and inclined glass for acoustic treatment, and a special air-conditioning
system designed for low air velocities
for minimum noise. The heart of the
cameras is the Telepantoscope tube of
Fig. 11, which is of the mosaic type
and very similar to its prototype, the
iconoscope.
One model of Safar television receiver is shown in Figs. 12 and 13. The
cathode-ray tube is of the very short
type having a diameter of 16 inches
which allows pictures of 10 x 12 inches.
Magnetic deflection and focus are used.
Normal sound broadcasts may be received with these instruments as well
as the television programs.
A high voltage projection tube designed for an anode potential of 40 kv
is illustrated in Fig. 14. Persistent development work is being carried on
along these lines.
A receIVer manufactured by the
Italian firm Allocchio Bacchini and
Company is illustrated in Figs. 15, 16.
and 17.
Fi9. 22. Photo of French televl·
slon ImaC)e, 450 lines Interlaced.
50 field •.
Fi9. 20. (Left)
French version
of mosaic type
of electronic
television
camera.
France
France has rather an impressive
series of television experiments dating
back to at least 1929. The greater part
of this work, if not all, has been conducted under government sponsorship,
under the Post Office Department.
At the present time, or at least prior
to the advent of war conditions, an imposing program of experimentation is
being conducted at the television research center located at Montrouge.
This establishment comprises more
than 4000 square meters of laboratory
floor space, a television transmitting
station, 20 technical men, about 20 technicians and draftsmen, as well as an
executive staff of about 40. Through
exchange of patents, the staff has a
minumum of handicap in technical
Fit. 23. (Right)
A 1939 model
of Fernseh A.G.
television
camera
247
Section 8 •
THE
MYE
TECHNICAL
MANUAL
- I;:
, '
~',
,
~":I'
.
'.
,i
1\
l
I""
Fig. 17. Magnetic yoke
for detlectlon and focus
in receiver of Fig. 15.
Fig. 19. (Above) Television studios at the
Montrouge laboratories.
Fig. 24. (Above) A Fernseh cam.
era with associated equipment.
Fig. 25. (Above) A studio scene in
Deutschland Houla (Telefunken).
matters. A photograph of the outside
of this Montrouge laboratory is shown
in Fig. 18.
The Montrouge center has a studio
for television program pickup, part of
which is shown in Fig. 19. An interesting feature is the banks of 100-watt
lamps overhead. By means of a special
glass filter, 80% of the direct heat is
absorbed for wavelengths below 8000
angstroms. The i?3-foot ceiling height
allows the remainder of the heat to be
dissipated above.
The studio is equipped with an electronic camera, one type of which is
shown in Fig. 20. The mosaic type of
248
Fig. 28. Twin arrangement of
mechanical film scanner
(Fernleh A.G.).
Fig. 29. (Below) A 60·80 kv
prolectlon type of reproducer
(Fernseh).
translating device is used in France as
in most other countries. The studio
camera, by means of a wheel mounting,
can be moved into an adjoining garden
for exterior views. An illumination of
200 lux, corresponding to an overcast
sky, is sufficient to provide an acceptable image. Another iconoscope type
of camera is used for film scanning.
Complete synchronizing, amplifying,
and mixing panels are of course provided. The video modulating signal is
amplified without impairment of its
amplitude or phase over a band from
25 cycles to 3 mc until its level is sufficient to modulate two push-pull, 3 kw,
water-cooled tubes. The peak power
output is from 6 to 8 kw.
,
In a reception hall located near the
studio, a projection type of reproducer
is located. An anode potential' of 40
kv is used (Fig. 21), producing a
highly luminous picture 8 x 10 cm
which is ptojected on to a screen by
When full power is used, 30 kw peak
means of a large f 1.4 objective lens.
The overall quality of the television cirwill be fed to the antenna. The antenna
cuits, as well as this reproducer, is
is over 1000 feet above the ground and
illustrated in the unretouched photois fed by a specialS-inch coaxial c~ble
graph image shown in Fig. 22. This
that has a total length of about 1250 feet
picture utilizes 450 lines, interlaced,
weighing over 12 tons. Two studios,
and 50 fields per second.
situated about 10 and 3 miles from the
The Eiffel Tower television station,
transmitter, provide the program main operation since 1937, is one of the , terial. These are connected by special
most powerful transmitters of its type.
lines with the transmitter.
Fig. 21.
(Right)
French
projection
tubes for
20· and 40·
kv anode
potential.
fUNDAMENTALS Of TELEVISION ENGINEERING
• Section 8
Fig. 30. (Above) An amplifier umt
for television signals (Fern.eh).
Fig. 27. (Above) relefunken mechanical film
scanner with storage·type pickup tube.
Fig. 31. A portable amplifier for
television signals lFernsehl.
Fig. 32. A mechanical synchronil:.
ing impulse generator (Fernsehl.
An interesting feature of the final
r-f stage is that its plate is grounded.
causing its filament and grid circuits to
be highly negative. This allows the
plate of the modulator to be connected
directly to the grid of the modulated
stage, eliminating the coupling condenser and grid resistor, and thereby aiding
in . maintaining the necessary band
width.
companies are interested in the commercialization of visual communication,
among them being the Fernseh, Loewe,
Lorenz, TE KA DE, and Telefunken
companies. Recently a group of such
establishments cooperated with the
German Reichspost in the production
of a standard television receiver as
economically as possible in order that
the maximum number of receivers be
placed in the hands of the people.
An idea of the state of the television
art may be obtained from Figs. 23 to
35 inclusive.
Figs. 23 and 24 show two models of
television cameras, while the stuuio
scene of Fig. 25 shows still a tohird. All
are basically oJ the mosaic type. The
image dissector type of scanner is represented in the commercial equipment
by the still-film scanner of Fig. 26.
Film scanning, of course, is very necessary for a sustained service. The need
far dependable scanners is met in the
devices of Figs. 27 and 28. Both are
capable of switching from one film to
another without interruption.
Typical of the theatre projectors for
television reproduction is the Fernseh
Fig. 26. Dlaposltive scanner for 24 x 28 mID transparencies (fernseh).
A G. high-potential cathode-ray unit
of Fig. 29. This unit operates with a
second anode potential of from 60 to 80
kv. The objective lens has an aperture
of f 1.9. A projected image of approximately 10 x 12 feet can be obtained.
German transmitting apparatus of
the transportable type is iJlustrated by
the photographs of Figs. 30, 31, and
32. Fig. 33 shows the amplifier arrangement on the television stage of
Deutschsland Hauses. Two cathoderay tubes allow monitoring of two
channels. The sound and vision control
desks are shown in Fig. 34. Fig. 35
is a view of the television transmitter of
the Reichspost in Berlin. Complete
monitoring facilities are likewise provided.
Fig. 33. (Below) relefunken control panels.
Fig. 34. (Below) Studio sound
and vision control desb ITelefunken) .
Germany
Great television activity has characterized Germany's communication industry for years. Many manufacturing
249
Section 8 •
rHE
MYE
rECHNICAL
MANUAL
Part X: Promising Developments
I
I
i
I
T SEEMS particularly appropriate
to consider, on the very threshold of
commercial television, some of the recent
developments which, at the present time,
appear to hold much promise for the
future. The author claims absolutely no
"crystal ball" powers of prophecy, but
there are several devices which have recently come into existence which would
seem to make their future assured, and
which are bound to influence the development of television. There are scores
of such promising inventions, but only
a few typical ones will be discussed in
this, the concluding instalment of this
series.
rangements using second anode potentials of 40 kilovolts or more, which
p~oduce a small image having an intensity suitable for theatre projection by
means 'of a conventional optical system.
These tubes will probably find a definite
service for presentation of television
images to large audiences. In Germany,
however, they have experimented in the
use of this principle in the production of
modest sized images for home receivers. A photograph of such a tube developed by Fernseh A. G. is shown in
Fig. 2. A polished glass window provides for the external optical system
which enlarges the image and casts
it onto a rear-projection type of screen.
To conserve light, these screens are
usually of the directional type which
throw the bulk of the light perpendicular to the plane of the screen toward
the observers. A folding screen of a size
comparable to a home motion picture
screen could be built into the receiver.
FIg. 1. Italian (Safar) tube for
television reception. Magnetic
deflection and focusing are used.
Attaining Larger Images
Many careful studies have been made
to determine the optimum size of the
image at the receiver. This size is limited on the one hand by the obvious fact
that the image must be large enough to
be viewed co.mfortably by the usual family group without eyestrain or crowding. There is a very definite upper
limit in image size, however, beyond
which it is impractical to go. A tenfoot image in the usual living room
would be ridiculous. In between these
two extremes is an optimum size which,
undoubtedly is larger than the largest
images now available on conventional
cathode-ray tubes in this country. It is
therefore natural that we look for advances in this direction.
Wide-Angle Cathode-Ray Tubes
The first thought in enlarging the
received images would be to make the
cathode-ray tubes larger. Keeping the
usual proportions results in very long,
bulky tubes. Some work on this problem has been done abroad with the
results suc.h as pictured in Fig. 1. The
tubes are made short enough to fit into
table-model cabinets horizontally, yet,
by the use of larger deflection angles.
to obtain an image that is considerably
larger than those obtained previously.
The problem of retaining suitable spot
focus out to the edge of the screen is
no small one, and yet the results reported indicate that even this problem
can be solved. Magnetic focus and magnetic deflection are invariably used in
this type of tube. This type of tube
would apparently hold much promise for
250
i'
I
if
I~
I:
Light Relay Tubes
The ideal large-screen receiver is one
having some device which controls a
local light source, thus eliminating fluorescent screen deterioration and other
similar effects influencing, in an expensive way, the life of the device. The
solution of this problem might be forthcoming in a very interesting form of
crystal light relay.
It has been known for many years
that certain crystals would rotate the
Fig. 2. (Above) Two viewl of 1m all
cathode·ray proleetlon tube •
compare with vacuum tube at
center•. (Fernseh)
the less expensive sets which l11Ust meet
the inevitable demand for larger images.
Small Projection Tubes
Demonstrations have been given in
this country of large cathode-ray ar-
Fig.' 3. Large-screen televilion light relay which depend I upon the
fact that certain crystals rotate the plane of polarllatlon of light
palling through them an amount depending upon the electrostatic
potential existing between the facel of the crystal. Secondary
emlilion from the front face bulldl up the neceSlary chargel.
Polarizer,
"
TransparenT conducti ng
,//
coating
Collector
screen
'~,
i
I
cathode-ray'~~~
beam
I
Crystal plate
i
I.
FUNDAMENTALS OF TELEVISION ENGINEERING
Suspensoid
.; cell
Light
source
Sleek White Gray
";/~~~
~Y},~E'
I}£"'!.}?:;
:','N:I~ I~mt~
1!lt!l:l\l\ l-aIITI!1
++++t+
Slack
j
I::(.'}."':
~.!3'?f~
+++
Fig. 4. Sketch of IUlpenlold cell
utilizing electro-mechanical effect
of colloidal graphite 01 a light
relay.
plane of polarization of light passing
through them when an electric field was
present parallel to the direction of light
travel. Later considerable work was
donel in investigating the magnitude
of electrostatic fields that could be produced between the faces of a crystal
by the bombardment of one face by an
electron beam with the resulting secondary emission from the face. As the
crystal, such as zincblend2 , is an insulator, the high electrostatic charge due
to the loss of secondary electrons remains on the spot that was bombarded
by the beam.
Fig. 3 shows one of several possible
arrangements for utilizing the electrooptical effects of these crystals. The
zincblend plate having a transparent
conducting coating on the rear and a
very fine screen some distance from' the
front face of the crystal is mounted
within an evacuated envelope which also
houses a conventional electron gun and
deflection system trained upon the crystal plate. The high velocity electrons
comprising the electron beam pass
through the meshes of the screen and
strike the crystal with a velocity dependent upon the second anode potential.
This electron energy is imparted to the
crystal surface resulting in a stream of
secondary electrons being knocked off.
These are immediately attracted to the
screen which, with the transparent conducting coating are bonded to the coating within the tube. This loss of electrons from the spot being bombarded
will result in a high charge between
the two faces of the crystal. This effect
is a local one because the charges cannot
leak off due to the high insulating properties of the crystal. The light from the
light source passes through two polarizing discs crossed so that no light
normally passes through. At this spot
under bombardment, however, the potential gradient between the two faces
of the crystal causes the plane of polarization of the light to be rotated, resulting
in light being allowed to pass through
the spot being bombarded, the amount
of light depending upon the density of
the electrons in the beam. The beam
density can be very easily controlled by
th~ control-grid potential' of the electron gun which, of course, would be the
video signal from the television receiver.
In this manner the electron beam .in-
,Electron source
'=
(a)
Heater
Accel~rator
plate
(b)
\
Secondary
cathode No.6
,\r~
Incoming
electrot's
Collector
.. plate
Fig. 5. Sketches of three common type. of electron multipliers.
(a) plate type. (b) screen type.
(cJ tubular type.
tensity would vary from picture element
to picture element along each line and
from line to line, resulting in an electric
potential picture being set up over the
face of the crystal. This picture,
through the medium of polarization, allows the light from the projection lamp
to throw an enlarged image upon the
screen.
The potential distributions over the
face of the crystal at the end of the
frame must be equalized to make ready
for the next frame or field. This process
may be carried out in a number of
ways, one of which would be spraying
the crystal plate with a beam of slow
electrons which would supply electrons
to the face of the crystal, discharging
the picture elements and preparing it
for another frame.
• Section 8
There are many other arrangements
of this particular type of light relay and
there are several other types 3 which
hold out some promise. Onf; other type
that will be mentioned is the colloidal
graphite light relay which has not yet
been developed to the point of the zincblend relay. Colloidal graphite is a suspension of highly purified graphite particles, the flakes of which are relatively
flat and thin. Normally these flakes are
arranged at random rendering the liquid
opaque. If an electric field is applied
between two faces of a vessel containing
colloidal graphite, the flakes tend to line
up with the field, making the liquid
semi-transparent. The greater the potential applied, the more transparent the
liquid becomes. When the potential is
removed, the flakes return to their random positions at a speed dependent upon
the Brownian motion of the liquid. This
can be adjusted to be approximately
1/60 second so that at the expiration of
one field, the relay is ready for the next.
The potential distribution could possibly
be obtained in a manner similar to that
of the zincblend relay arranged as in
Fig. 4.
This resume by no means exhausts
the possibilities of this type of light
relay, but, as intended, it merely introduces the subject to readers interested
in television, as it seems quite probable
that cells similar to these will be common in the future.
Electron Multipliers
Another device that promises great
things in the communication field is the
electron multiplier. Research laboratories throughout the world have been interested in developing this infant of the
electronic family. The basic principle
underlying electron multiplication is
that of secondary emission. A moderately fast moving electron colliding with
a specially treated surface may knock
off one to five other electrons, the exact
number being determined by the electron speed, the type of surface, and
other factors.
Fig. 6. (Below) An RCA electron'
multiplier.
Electron paths made
visible by introduction of gas.
251
Section 8 •
rHE
The multiplier of Fig. 5-a utilizes
both an electromagnetic and electrostatic field to cause the electrons to stay
in the proper path. The successive
treated plates are at progressively
higher potentials, attracting the electrons liberated from the preceding plate.
An electromagnetic field is adjusted until its strength is sufficient to bend the
electron beam so that it hits the plate
in the proper place. The photograph of
Fig. 6 shows a demonstration multiplier
of this type in action. The electron paths
are made visible by the introduction of
a small amount of gas into the tube.
The necessity of a magnetic system
would appear to be a disadvantage.
The screen type muJ&iplier, Fig. S-b
requires an electric potential source for
the acceleration of the electrons, and
sometimes a radial magnetic field is
used to keep tl;1e electrons in the center
of the tube. The screens, some of which
are composed of 10,000 meshes per
square centimeter, are treated for high
secondary emission and it is claimed
that about half the projected area of
this screen is open space. Gains up to
about a million have been attained with
this type of multiplier. Tubes of this
type4 with either a thermionic ora
photo cathode were recently placed upon
252
MYE
rECHNICAL
MANUAL
the market in England. Mutual conductances of the order of 50,000 micromhos
are attainable with these tubes.
The multiplier of Fig. 5-c relies upon
the careful design of the "elbows" for
the proper electrostatic focusing of the
electrons in their travel from one stage
to the other. This is necessary for the
emitted electrons have thore or less
random velocities and a proper electrostatic field is necessary to guide them
to the next stage. The Farnsworth Image Dissector utilizes a multiplier of
this general type to provide sufficient
signal with a satisfactory signal-tonoise ratio.
The limitations of most types of electron multipliers lies in the current carrying capacity of the last stage. Difficulties due to photo-emission from the
treated surfaces exist, making it necessary to shield them from stray illumination, particularly if the light is modulated such as that from an incandescent
lamp operating from alternating current. Voltages from 200 to,300 volts per
stage have produced gains of about five
per stage. A seven-stage multiplier realizing an amplification of five per stage
would result in an overall amplification
of five raised to the seventh power or
78,125.
There are many other devices which,
although perhaps in very crude forms
at the present time, hold great promise
for the future. SU'ih things as frequency
modulation, improved form.s of ultrahigh-frequency generators, television in
colors, and many other things might
either revolutionize the industry or, on
the other hand, leave it l1nscathed. The
impossibility for us to determine in advance which development will amount
to something should influence our interest in these ideas not one whit. For the
future of television, the art of instantaneous sight at a distance, is definitely
assured and its cultural effect on people
will be greater than we now realize.
References
1. Von Ardenne, "Methoden und Anord-
nungen zur Speicherung beim Fernsehemfang," TFT, Bd. 27. November,
1938, pp. 518-524.
2. Schramm, "Uber den electrooptischen
Effekt an Zinkblende," Annalen der
Physik (5) 25. S. 309, 1936.
3. Rosenthal, "The Skiatron," Electronics
and Television and Short Wave
World, February, 1940, pp. 52-55.
4. "The Augetron and Its Application,"
Electronics and Television and Short
Wave World, January, 1940, pp.
17-19.
e Section 9
THE MYE ,(E£DNI£AL MANUAL
I
'I
I
-DC .Dry Electrolytic
•
Capacitors
MALLORY
253
THE
Section 9 •
MY E
TECHNICAL
MANUAL
D.C. DRY ELECTROLYTIC CAPACITORS
• A condenser, or as it is more rightly
termed, a capacitor, consists of two
conducting electrodes separated by a
nonconducting medium called the dielectric.
A condenser is an electrical device
capable of storing a charge of electricity when voltage is applied to its terminals. Applying direct current to the
condenser establishes a static charge
in the dielectric. The static charge
rises until the voltage is equal to the
source voltage. When this point is
.reached the source voltage is opposed
by the voltage of the electro-static
charge in the condenser, and there can
be no further flow of current unless the
source voltage either rises or falls.
If the source voltage rises above
the electro-static voltage, additional
current will flow through the condenser until the electro-static voltage
again equals the applied voltage.
If the source voltage falls below
the voltage of the established electrostatic charge, current will flow from
the condenser into the circuit until the
electro-static voltage again equals the
applied voltage.
Capacity of a Condenser
Capacity is the term applied to a
condenser and indicates the ratio of
the quantity of the electro-static
charge, to the voltage. The quantity
of the charge is expressed in coulombs,
and usually stated: Q=CXV; Where
Q is coulombs, C is capacity in farads,
and V is voltage. This gives us the
fundamentals for stating that the ca. pacity is equal to the quantity divided
by the voltage, or C = Q
V
The capacity of a condenser is dependent upon:
First-Area of the plates.
Second - Thickness of the dielectric.
Third-Dielectric Constant.
The Dielectric Constant of a material is the ratio of the capacity of a
condenser using this material, to the
254 '
capacity of a condenser of equal plate
area, but using air as the dielectric.
The usual formula for Dielectric Constant is K = Cs
Ca
Where Cs is the capacity with the
dielectric in question, Ca is the capacity when using air as the dielectric,
and K is the Constant.
The Dielectric Constant of a material is not constant in value, but varies
with the frequency of the applied current, moisture content, temperature,
voltage applied, and other factors.
Electrolytic Condensers
Condensers are classified according
to the nature of the dielectric medium
employed in their construction. Thus
-an oil condenser is one in which oil
is used as the dielectric; an air condenser is one in which air is used as
the dielectric; a paper condenser is
one in which paper is used as the dielectric.
From the description of the terminology applied to condensers, one
might suppose that the electrolytic
condenser uses an electrolyte as the
dielectric. This supposition, however,
is inaccurate in that the electrolyte
used in the electrolytic condenser is
not the actual dielectric material but
is one of the conducting electrodes.
The dielectric material, or medium,
in the electrolytic condenser consists
of an extremely thin oxide film which
is formed on the surface of the condenser anode or positive plate.
The nature and composition of the
film which forms the dielectric in an
electrolytic condenser is not definitely
known. The formation and action of
this film is understood and can be explained in rather simple terms.
It is a J>'eculiar characteristic of aluminum and a few other metals that
when they are immersed in certain
electrolytic solutions, or electrolytes,
and a current passed through the
metal and electrolyte to another electrode, a non-conducting film will be
formed on the metal, which will oppose the flow of current.
Thus, if we take two pieces of aluminum and immerse them in a suitable electrolyte, and pass a current
from one plate to the other, the current will be very high when first applied, but it will taper off until there is
little, if any, current flowing in the
circuit. This is. termed "forming,"
which means the establishment of a
film upon the surface of one of the
plates. In the case of aluminum, the
film is formed on that plate to which
the positive wire is connected.
The formation of the film on the
plate retards the flow of current. If
the polarity is reversed, i.e., the po. larity of the source voltage, current
will flow. Thus we see that the film
acts as an insulator only as long as we
maintain the same polarity as was
used in forming.
The dielectric constant of the film
in an electrolytic condenser varies
with the formation voltage. Thusfor equal plate area, a condenser
formed at low voltage will have a
higher capacity than one of the same
area formed at high voltage.
Another characteristic of the electrolytic condenser film is that it is
dependent upon the composition of
the electrolyte, inasmuch as this determines the maximum voltage at
which the film can be formed or maintained. If an electrolyte is said to be a
400 volt electrolyte, it means that if
more than 400 volts is applied to a
condenser using this electrolyte, the
film will be punctured though not necessariJy damaged. This is the reason
why, when electrolytic condensers are
rated at 525 volts surge, it means that
525 volts is the maximum momentary
voltage which can be applied to the
plates without puncturing the dielectric film.
A constant D.C. voltage aidsinmaintaining the dielectric film, and because
the film is not perfect, there will be a
small amount of current continuously
flowing through the condenser. This
current is called the leakage current,
D. C.
DRY
and for a good electrolytic condenser,
it is very small. The value of the leakage current is determined by the con-
ELECTROLYTIC
CAPACITORS
• Section 9
dition of the fIlm on the plate and the
length of time it has been without a
polarizing voltage.
Dry Electrolytic Condensers
FIG. 1-,. Typical Dry Electrolytic Capacitors
In general, there are two types of
electrolytic condensers: the wet type,
which uses a liquid electrolyte, and
the dry type, which uses a paste electrolyte.
The dry electrolytic condenser possesses many advantage~. They will not
spill or leak, may be mounted in any
position, and in any type container.
The improved performance, smaller
size, better tone, and lower cost of
modern radio receivers is due in a large
part to the advent of the modern dry
electrolytic capacitors. Prior to their
availability, filtering was accomplished
by the use of paper dielectric capacitors.
Microfarad for microfarad, paper
dielectric condensers are far more
bulky and expensive than dry electrolytic capacitors. In early receivers, filtering was quite generally accomplished by using a two-stage filter consisting of either two iron core chokes,
or one choke and the speaker field.
The capacitors used ranged from one
mfd. to four mfd.
By using large size chokes it is possible to obtain fairly good fIltering in
a two-stage fIlter with small values of
capacity. However, even though the
design achieves a low hum level, the
resonant frequency of the fIlter may
extend up into the useable audio
range. When this occurs, motor-boating and fluttering will occur in the receiver unless certain precautions are
taken, such as1. Restricting the low frequency response of the amplifier. This works
but the reproduction sounds "tinny"
from the lack of bass frequencies.
2. The use of isolating fIlters for the
individual audio stages. This latter
system works and permits extended
low frequency response, but results in
further complexity of design, added
cost and weight.
The availability of modern dry electrolytic filter capacitors revolutionized fIlter circuits. Large values of
capacity-IO mfd., 20 mfd., or even
40 mfd. and more, in small, compact
containers-permitted simplified onesection fIlter systems with a very low
common impedance eliminating hum,
motor-boating, and instability problems, even with a very wide range
audio response. It is little wonder
then, that the use of dry electrolytic
fIlter capacitors has become universal
for the industry.
Electrolytic Capacitor Uses
Dry electrolytic capacitors provide
large values of capacity in relatively
small dimensions, and are the most
economical type for many applications.
At present they are obtainable for
continuous operation on direct current and for use on alternating current
with certain service restrictions.
Typical direct current applications
are:
1. D.C. fIlter networks.
2. Audio frequency by-pass.
3. Voltage doubling.
4. Electrical welding.
5. All polarized circuits with or'
without limited A.C. components.
Alternating current applications are
usually restricted to intermittent duty
as in starting service on capacitor
start induction motors. Discussion of
this form of application will be treated
in subsequent engineering data to be
released.
Internal Mechanical Construction
of Dry Electrolytic Capacitors
General
In general, a dry electrolytic capacitor consists of an anode, a cathode
foil and a separator containing an
electrolyte, all of which are wound into
a roll and provided with means for
electrical connection, housing and
mounting.
The anode, usually of aluminum, is
subjected to a special electro-chemical
forming process which completely
covers it with an extremely thin oxide
FIG. 2-Capacitor Cartridge Co~truction
255
Section 8 •
THE
MYE
TECHNICAL
MANUAL
\
film having the unique characteristic
of uni-directional conductivity. The
nature and thickness of this film
governs ~he voltage characteristics
and '\Capacity per unit area.
The separator is made of some absorbent material, usually gauze, paper, non-fibrous cellulose or various
combinations of these, and serves to
hold the electrolyte in position and
keep the anode and cathode foil from
making physical contact.
The electrolyte consists of a chemical solution essentially similar to a
dry paste and serves as the cathode
electrode. In addition, it tends to
maintain the film on the anode.
The cathode foil, generally aluminum, is usually unformed and acts
'merely as a means of making contact
to the electrolyte, which is the cathode of the capacitor.
Dependable capacitors giving long
and satisfactory service in the field are
easily produced where efficient up-todate equipment is available. Close
attention to design and constructional
details by experienced engineering and
production personnel assures excellent
electrical characteristics, stabilized
moisture content and ability to withstand high surge voltage conditions.
Anode Electrode
satisfactory, and their subsequent replacement arose from th~ ever-present,
requirement for radio t components,
namely, more efficient use of available
space in equipment designs.
As a result, an etching process was
developed for roughening the surface
of the aluminum foil, thereby increasing its effective area. This increased
area produced capacity values ranging
from 2.75 to 1 at high voltages, to
roughly 7 to 1 at low voltag~s, as
compared to the capacity of plain alu1
minum foil units.
In the interests of greater efficiency,
the Mallory Co. developed a new
anode material, neither plain nor
etched foil, in the type FP* capacitor.
The term FP refers to the Fabricated
Plate anode material which is made
by depositing small particles of molten
high purity aluminum on a suitable
carrier. The introduction of this construction in the early part of 1938 provided a further decrease in capacitor
physical size. The FP anode material
has a normal capacity of 10 to 1 as
compared to plain aluminum foil.
Ratios of 20 to 1, or higher, are possible under certain conditions, but are
not in use at present. Fig. 3 illustrates
the representative physical size of a
given capacity value in the three constructions.
Cathode Foil
It, should be understood that the
electrolyte itself is the cathode in an
electrolytic capacitor. The so-called
cathode foil is 'used merely to lower
the equivalent series resistance of the
unit through intimate contact with
the electrolyte.
The cathode foil of plain high purity aluminum originally used, has carried through to recent designs. However, because of improved tab connec-
tions in the FP construction, its cathode foil does not need to be as thick
as previously used.
Internal Connections
III,
I'!
I
The internal connection to the anode and cathode foils, in the case of
the plain or etched plate units, is usually made by cutting and folding a
narrow piece of foil in such a manner
as to form a tab which protrudes from
the finished roll. This tab eventually
connects to the eX,ternallug or lead by
means of a rivet. Great care must be
taken to protect this jUJ).ction from
corrosion. Fig. 4 illustrates the method
of folding the tabs.
, The danger of corrosion at the riveted junction, as mentioned above,
lies in the fact that it must be protected from the electrolyte, since dissimilar metals, i.e. aluminum (plate)
and copper (lead wire), are joined by
the rivet.
Where a number of tabs protrude
from the roll within a small area, as
in some concentrically wound units, it
is frequently difficult to properly insulate these tabs from each other, with a
possibility of future trouble in the field.
A new plethod of making connection to the anode is utilized in the
FP capacitor construction., (See Fig.
4.) The anode tabs are formed as an
integral part of the anode during the
fabrication of the anode material and
are of extremely heavy aluminum
strip rather than foil tabs. The heavy
cross section of the tab strip and its
small surface area will withstand corrosion, if present, far better than the
foil type.
The cathode tabs used in the FP
capacitors are cold welded to the cathode foil by a special piercing and extruding proc~ss. Like the new anode
tabs, they are of heavy strip.
i
ii,
['
i
I
i
I
i
i
I:
FAIRICA1!D
PLATE
FIG.
ETCHED PLATE
The first dry electrolytic capacitors
used plain aluminum foil of high purity for the anode. Their performltllce
in the field was, on the average, highly
256
I~
PLAIN PLATE
1
3-Comparative Size of Plain,
Etched and FP Types
ORDINARY TABS
FIG. 4- Various
'P TAl
Anode Tab Constructions
.Trade Mark Reg. U. S. Pat. 011.
D. C.
DRY
A great advantage of the FP tab
construction is the complete elimination of rivets or joints of any kind
inside of the capacitor container.
The tab protrudes through a special
seal and makes contact with the fmal
terminal outside of the container as
described more fully under the paragraph devoted to "External Mechanical Construction."
Separator
This is the material used to hold the
electrolyte, and mechanically separate
the anode from the cathode foil from
which feature it derives its name. It
must be absorbent and free from any
impurities that might cause corrosion.
Special types of gauze, paper andcellophane have been utilized for this
purpose.
From a surge voltage standpoint,
the separator material also acts as a
barrier retarding the mixture of oxygen and hydrogen gases which might
be generated if the capacitor is subjected to voltage overloads. Naturally,
the density of the separator material
is an important factor and cellophane,
properly processed, has had a decided
advantage in this regard.
Priniarily, gauze was used exclusively as a separator material. However, its open network structure, which
permitted frequent_ gas pressure failures, caused it to lose popularity in
favor of paper separators. Paper also
had the advantage of permitting
smaller physical capacitor size due to
ELECTROLYTIC
CAPACITORS
the difference in thickness of the separator material.
Cellophane separators proved to be
a valuable addition to conventional
separator materials. The use of cellophane, however, has been limited to
certain severe applications due to the
relatively high cost and difficulty in
obtaining the specially processed material. Increased use of cellophane has
lowered the material cost substantially, resulting in a more general
application.
Proportion of Section
A perfectly round section, the length
of which is not less than twice the
diameter has the best electrical characteristics.
Where several anode tabs emerge
from the end of a concentrically wound
section it may be necessary to increase
the diameter and shorten the length
of the unit. This procedure allows
more space between tabs and eliminates the possibility of shorted tabs in
the field.
'
Generally speaking, the manufacturing of flat capacitor sections is not
considered the best practice since-·pressure may damage the anode fIlm during the squeezing process. Where gauze
separators were used, such pressure
often embossed the foil to such an extent that a short circuit occurred. Very
thin sections have an added disadvantage in that future expansion may
cause voids between the electrolyte
and the electrodes, with a resultant
loss of capacity and increase in series
resistance.
'For a given foil area, more turns are
required the narrower the foil width.
N arrow foils in general, therefore,
have a higher value of inductance
which tends to increase the high frequency impedance of the finished capacitor.
COllllllon Cathode Concentrically
Wound (CCCW) Capacitors
A great many capacitor applications
require or permit the cathode connections of the various sections to be
ganged together and connected to one
common point in the circuit.
Since the electrolyte itself is the
cathode in dry electrolytic capacitors,
it is obvious that several anodes could
be included in one common electrolyte, automatically furnishing an internal common cathode connection,
culminating in a single exterior terminal.
In actual production, this type of
unit consists of one long cathode foil
anq the required number of anodes
laid end to end and parallel to it, all
of which together with the proper
separators are rolled into one complete
unit. Each anode is provided with a
terminal and care is taken, -of course,
to see that a sufficient space is allowed
between the adjacent anode ends to
prevent short circuiting at this point.
Capacitors so constructed are entirely satisfactory electrically and mechanically. They may be secured in
different combinations of capacities
and voltages, and require less space
than their equivalent in individual
capacitor units. These capacitors are
marked "CCCW."
COllllllon Anode Concentrically
Wound (CACW) Capacitors
From a general construction standpoint, this type is similar to the commoncathode concentrically wound
type, except that one anode and two
or more separate cathode foils are
used. Its production, however, presents problems affecting its quality
and efficiency.
More than a casual discussion of
Common Anode construction is given
ANODE FILM-....
ANODE
GOOD FOR
QUADS ONLY
GOOD
POOR
.FIG_ 5-Capacitor Cartridge Proportion
I
• Section 9
I
~~
CATHODE FOIL
FIG. 6-Common Cathode Construction
257
THE
Section ljI •
I
MY E
ANODE
ANODE FOIL
UTHODE FOIL
I
FILM
TECHNICAL
I
I
:Ji
CATHODE FOIL
FIG. 7-Common Anode with UnformeiCalhodes
here since the difficulty of manufacture is not generally understood.
Since it is impossible to electrically
form one single anode foil to more
than one voltage, this type of construction is limited to one voltage rating for all included sections. Obviously this would take the value of the
highest section in the group. This is
uneconomical as more foil area is involved than would be required if the
anode were formed for the correct
voltage rating of each section.
Since each cathode foil in this form
of construction is in contact with the
electrolyte common to all, it is obvious
that current would flow between them
and render the unit useless. Some special provision is, therefore, necessary
to rectify this condition.
There are several ways of partially
correcting this condition. The various
methods are:
1. Unformed Cathodes.
This form of construction is the
simplest and does not have any provision whatever to prevent leakage
between the cathodes.
Theoretically, where the potential
difference between cathodes is relatively small, the cathode which is more
positive in relation to the other will
attempt to form to the limit of the
voltage difference between them, when
placed in service. Once formed, this
cathode would to a certain extent become insuillted from the common electrolyte, due to the insulating film produced, and limit the leakage current
to within practical limits.
In service, however, except in rare
" cases not usually encountered in practical applications, heat and internal
gas pressure would be developed that
would more than likely damage the
entire unit. Even though this operation was successfully accomplished,
the particular section involved would
suffer a considerable loss in capacity
due to the new cathode capacity created in series with it.
258
MANUAL
ANODE
CATHODE
I
CATHODE'
FILM
il
I"
,!
FIG. 8-Common Anode with Formed Cathodes
3. Isolated Electrolyte
In this construction a special barrier is made during the winding of the
capacitor roll to separate the electrolyte between the ends of each cathode
foil without breaking the continuity
of the anode foil. A layer or layers of
of the separator free from electrolyte.
This portion of dry separator is usually further protected from electrolyte creepage by coating it with wax
or other substance as nearly impervious to electrolyte absorption as possible.
I
',
"
Separate Section Capacitors
This term applies to capacitors having two or more sections, internally
insulated from each other, and where
each section is provided with its own
pair of terminals.
Separate section construction has
not been widely used on original
equipment since few filter circuits require individual connection to both
positives and negatives of two or more
sections. The major employment of
this construction has been in the replacement field where these units could
be readily adapted to common positive, common negative, or separate
section applications.
The preceding comments regarding
proportion of the individual sections,
connections, etc., apply to the separate section types. Also, there is the
problem of maintaining satisfactory
ANODE
CATHO..
CATHODE
I
2. Formed Cathodes.
This construction is identical to the
"unformed cathode" type, except that
at least one cathode is formed during
the process of manufacture.
This eliminates the possibility of
physical damage to the capacitor due
to internal heat and gas pressure that
otherwise might develop. Additional
foil area must be used to make up for
the capacity loss due to the series
capacity effect.
Constructions of this type, while
obviously more practical, are still undesirable with respect to their ultimate characteristics and stabliity. It
is practically impossible to wholly prevent cross current or feed back which,
in the radio field, would affect the
hum level.
The potential difference between
the cathodes for the application intended must be kept within relatively
low limits.
I
FILM ~
ANODE
~
I
1
CATHODE
FIG. 9-Common Anode with Isolated Electrolyte
material theoretically impervious to
the electrolyte must also be wound
around the roll at each juncture to
completely isolate the electrolyte necessary to each section.
The isolation of the electrolyte between the ends of the cathode foils is
generally accomplished by considerably increasing the gap between them
and attempting to keep that portion
intersection insulation for connection
tabs and electrolyte.
Since separate section units must
be larger in size than an equivalent
common anode or cathode type, and
in view of the consistent trend toward
minimum size common connection
units, the importance of separate section construction has diminished considerably.
I
,"
D. C.
DRY
ELECTROLYTIC
CAPACITORS
External Mechanical Construction
of Dry Electrolytic Capacitors
Dry Electrolytic capacitors have been
housed in cardboard tubes, cardboard
cartons, round and rectangular metal
cans. Various types of mounting features were available, and either soldering lugs, screw terminals or flexible
leads provided for external connections.
In order to give the complete development story of the Dry Electrolytic
capacitor industry, brief descriptions
are given of the constructions which
have been used up to the present time.
Cardboard Cartons
Capacitors of this type were housed
in rectangular cardboard cartons of
various dimensions depending on the
requirement of the application involved, and the space required by the
included sections.
The capacitor itself was generally
wrapped and sealed in varnished paper or equivalent before insertion into
the carton, which had previously been
wax impregnated, as an added protection against moisture absorption.
fied to have mounting flanges made
integral with the carton itself.
Capacity and voltage rating identification in the rectangular carton types
usually took the form of printed or
stamped legend adjacent to the various leads or terminals. Since the wide
variance in capacity and voltage values forbade any standard lead or terminal color codes, this legend was important. Its frequent obliteration
caused by age or abuse, has been a
continual source of annoyance to the
serviceman.
Identification was frequently limited to manufacturers' part number,
and in some cases, differing beliefs as
to rating methods for units incorporating common connections, led to
some confusion during service operations. Fig. 11 illustrates one such system, employing common negative and
common positive connection, wherein
the four terminals were labeled with
the total capacity of the combined
sections. It would be difficult for one
unfamiliar with the internal construction of the capacitor to identify capacity of the individual sections.
+4
+3S
..1-1
4@ISOV.
2SGilISOV.
10GilISOV.
--'-l-T
-29
-10
FIG. 11
Cardboard Tubes
FIG. IO-Typical Carton Types
The carton type of capacitor was
available with either flexible leads or
soldering lugs and generally was speci-
Tubular cardboard housings, as containers for Dry Electrolytic capacitors, were used extensively for individual by-pass sections and later also
became popular for filter capacitors.
These tubes were originally wax impregnated and later improved through
the use of varnish impregnation.
They made possible a general improvement in capacitor quality over
the carton type since effective sealing
• Section 9
MALLORY
FIG. 12- Typical Cardboard
.
Tubular Capacitors
was more easily maintained and sections were always left in their original
round shape.
Almost all tubular capacitor construction has employed lead connections, since the rounded surfaces and
limited end spaces do not lend themselves to terminal anchorage.
. Identification of the tubular has
corresponded to the systems used in
the rectangular types on units of
larger physical size. With the gradual
decrease in capacitor size it has become increasingly difficult to stamp
or print detailed identity in legible
form, and frequent resort has been
made, in the smaller single and dual
units, to the practice of placing a
narrow band or a series of + signs at
the end of the tube from which the
positive leads emerge. In tubular replacement lines, it has been possible
through the use of standardized connections for wide coverage, and logical
progression in capacity and voltage,
to establish a universal system of color
coding for ready identification.
Tubular units have been furnished
with almost every conceivable type
of mounting for either vertical or horizontal use. Such mountings range
from the simplest, that of supporting
the unit by its own leads, through the
tangential strap, fixed metal tab, and
spade bolt, to the rather elaborate
adjustable ring clamp types.
Round Metal Cans
(Inverted Mounting Type)
The first dry electrolytic metal can
units were of the inverted mounting
type, reflecting the mounting required
259
THE
Section 9 •
MY E
TEe H N I C.A L
MANUAL
standardized construction and application, merits a study of the factors
involved.
for a similar wet type. A considerable
m~mber of mounting and connection
variations evolved from this start.
For mounting, we had the metal or
composition threaded neck, the ring
clamps or brackets for grounded or
insulated mounting, and a few spade
bolt types. Connection methods inCluded neck types with lugs or leads,
and the type employing riveted terminals on the composition end piece.
The round metal can provides a pleasing appearance and extra protection
against atmospheric conditions where
this feature is desirable.
Round can replacement units have
also included constructions to cover
the old large upright, multi-section
wet units, employing terminal screw
and nut connection.
General Description
(Mechanical)
FIG. l4-Minimum and Maximum FP
Container Sizes
Type FP Capacitor
FIG. l3-Typical Round Metal Containers
The introduction of the FP capacitor has led to the widespread adoption of its standardized features, such
as mounting, identification, containers, and electrical rating system. The
success of this most comprehensive
program to date, in the interest of
There are but SIX container sizes
ranging from %" diameter by 2" high
to 1%" diameter by 3" high. This
size range covers any single, dual,
triple or quadruple section capacitor
used to date in the radio field and is
designed to take care of any trend
toward the use of increased capacity
ratings likely to occur.
Every FPcapacitor is identical in
construction except for size, rating
and mounting hole dimensions. All
units are of external bead metal can
construction and supplied with soldering lugs of special design clearly identified by a new simplified code character punched into the standard bakelite cover as shown below. The units
are further identified for quick chassis
assembly by the self-contained standard .mounting feature integral with
the container itself.
The standard, self-contained mounting feature, serves the dual purpose of
effectively mounting the capacitor in
a vertical position and providing a
direct means of electrical contact to
the cathode of the capacitor. This
feature is a great advantage where the
unit is to be insulated from the chassis
and also provides low R.F. resistance
contact.
The mounting feature provided re-
STANDARD TERMINAL CODE
_L../-I--
FIG. 15- Type FP Lug
Terminal Identification
260
METAL MOUNTING PLATE
(MAY BE MOUNTED ABOVE
OR BELOW THE CHASSIS)
BLANK cAR AS INDEX
FOR ASSEMBLING
FIG. 16-Simplified Method of Mounting
FP Capacitors
'
FIG. 17-Grounded Mounting with
Metal Plate
D. C.
DRY
quires no accessories of any kind and
is quickly assembled to the chassis by
means of a special tool (similar to a
Spintite wrench) provided by the Mallory Company, or easily made in any
shop. The twisted tongue method
adopted for mounting as shown below
requires a minimum of space.
From a service viewpoint, replacement may be readily accomplished
with long-nose pliers.
Small metal plates are available for
each of the three FP diameters. These
plates, similar to a wafer tube socket,
may be riveted to the chassis where
this seems preferable. The metal plates
lor the popular one-inch diameter can
size may be mounted in any tube
socket hole having one and one-half
inch rivet centers.
Where the unit is to be insulated
from the chassis, bakelite plates similar to the metal plates just mentioned
are provided. Insulating cardboard
EI.ECTROLYTIC
C'APACITORS
tubes may be used over the container
where Underwriters specifications require this practice. The mounting ears
are the cathode terminals as before.
Any FP capacitor may also be
mounted in a horizontal position by
the clamp or bracket method as shown.
Note that provision is made for insulated mounting where required, and
that the mounting ears, integral with
the capacitor, provide the cathode
connection to the unit.
The internal construction of the
FP capacitor has be,en greatly simplified and improved over methods formerly employed. The anode tabs are
an integral part of the anode itself
affording low R.F.'impedance, and are
of heavy rectangular cross section for
rigidity. They are designed to protru4e through the special bakelitepliable rubber combination top for
direct and positive connection to the
anode lug outside of the capacitor
container.
• Section 9
The capacitor cartridge is rigidly
attached to the bakelite cover before
insertion into the container.
By-pass capacitors of the FP type
are made by the identical process used
for the FP filter capacitors and furnished in the standard %:" by 2" container. They may be mounted vertically as previously described or horizontally by the special bracket available. The integral mounting ear, as
before', is the cathode terminal and
the units may be insulated from the
bracket where it is required by circuit
design.
All FP capacitors are identified by
characters die-stamped into the metal
containers. Permanent and always
legible, this form of identification was
adopted after a survey of the various
methods formerly used. The standard
stamping shows the capacity and voltage combination and identifying lug
symbols.
BAKELITE MOUNTING PLATE
(MAY BE MOUNTED ABOVE
OR BELOW THE CHASSIS)
FIG. 2I-By-pass Capacitor with
Horizontal Mounting
FIG. I8-Insulated Mounting
FIG. I9-Horizonlal Mounting
FIG. 20-Type FP Internal COTl.$truclion
FIG. 22-Method of Identification
261
Section 9 •
THE
MY E
TECHNICAL
MANUAL
i
Ele(trical Characteristics
of Dry Electrolytic Capacitors
In this section will be found a brief
discussion ofthe major electrical characteristics pertaining to dry electrolytic capacitors.
Capacity
The capacity of a Dry Electrolytic
capacitor is determined by the surface
area of the anode exposed to the electrolyte and the thickness of the anode
fIlm. As previously discussed, it is possible to increase the surface area exposed to the electrolyte by etching, or
otherwise roughening, the anode surface. In this type' of construction, the
capacity may be increased several
times that for a plain anode of similar
length and breadth.
'
versus temperature is given under the
heading of "Temperature."
Capacitors operated at higher than
their rated voltage may lose capacity
slightly, but do not necessarily gain
any capacity when operated at voltages below their rating. This is true
even though operated at only a fraction of their regular voltage rating.
(See Fig. 25.)
The shelf or idle period (no voltage
applied) does not materially affect the
capacity. Properly made units which
have been out of service over two
years show no appreciable change in
this respect.
The generally accepted reference
temperature for capacity measurements of 21 0 C. was originally adopted
Ii
i.:'
I
ETCHED PLATE
iii
PLAIN PLATE
FIG. 24-Comparative Size Etched
vs. Plain Plate Capacitors
checked against a bridge or standard
capacitor. Measurement of capacity is
described in the "Test Section."
Voltage
The voltage rating of a dry electrolytic capacitor is determined by the
character of the anode fIlm (which is
primarily a function of the forming
solution), the forming voltage and the
electrolyte used in the finished capacitor. This type of capacitor is rated at
its continuous D.C. working voltage.
Its maximum over-all peak voltage,
FIG. 23-Magnified Cross Section Etched Anode Plate
-maximum superimposed A.C. component or ripple voltage and its surge
in order to have a standard of comThe great values of capacity obvoltage are also important characterparison. Correction factors may be
tained by electrolytic capacitors are
istics.
'
applied if measurements of extreme .
due to the close proximity of the
Working
Voltage. This is the
D.C.
accuracy are desired at other than
anode and the electrolyte (which is the
maximum
D.C.
voltage
the capacitor
21/) C.
cathode), these being separated only
will stand satisfactorily under continby the extremely thin oxide fIlm. The
The present trend in capacitor ratuous operating conditions within its
capacity of well made electrolytic
ing is toward the values of 5, 10, 15,
normal temperature range.
units is only slightly affected by tem20 mfd. and multiples thereof, as exPeak Ripple Voltage or A.C. Comperature changes within the normal
emplified by the rating system emponent.
This is the maximum instantaoperating temperature range. At high
ployed in FP capacitors. Capacity
neous value of A.C. across the capacitemperatures, above normal rating,
tolerances popularly used are roughly
tor due to the A.C. component in the
this electrolyte may dry out and
as follows:
capacitor. It also refers to ,a continshrink away from the plate, causing
Under 25 volts ... -10%+200%
uous operating condition and for best
permanent loss of capacity.
25 and 50 volts .. -10%+ 150% '
performance should not exceed the
At low temperatures, below the nor150 volts ........ -10%+100%
limits specified by the manufacturer.
mal rating of the capacitor, a. drop in
250
volts
&
over.
-10%+
50%
.
(See chart of Fig. 27.)
capacity will be noted. This drop in
For
accurate
determination
of
caPeak Voltage. This represents the
capacity is only temporary and repacity, a bridge should be used, but
D.C. voltage plus the peak A.C. ripturns to normal with the return of
for routine testing the impedance . pIe voltage and refers to continuous
normal temperature conditions. Furmethod is satisfactory if periodically
operating conditions. (Peak voltage
ther information regarding capacity
262
I'
THE
should not be confused with surge
voltage.)
Surge Voltage. This is a term used
in reference to acceptance tests for
comparative purposes. It is the maximum voltage the capacitor will stand
without injury for a period of five
minutes when applied to a series combination of the capacitor and a resistance having a value in ohms equal
to 20,000 divided by the rated capacity in microfarads of the capacitor in
question. Momentary surges are sometimes encountered in service and will
not damage the capacitor if they do
not exceed this rating. Continuously
applied, it will generally ruin an ordinary condenser in a short time, because of the development of heat
within the unit.
When first turned on, many radio
receivers and amplifiers develop an
unusually high surge voltage across
the filter circuit, because there is little,
if any, load on the filter. This is especially true where heater type tubes
are used, with a rectifier of the filament type.
An electrolytic condenser is limited
in the amount of voltage which may
be impressed upon it because of the
MY E
TECHNICAL
MANUAL
puncturing of the dielectric fUm on
the plate when the voltage exceeds the
limitations imposed by the electrolyte.
The voltage at which the film of an
electrolytic condenser starts to puncture is called the surge voltage. The
highest value generally obtained is
approximately 525 volts.
Electrolytic condensers are correctly
rated as follows:
Working voltage, 450; surge voltage, 525.
This means that the condenser is
designed to work continuously at a
D.C. potential of 450 volts. Superimposed upon this is, of course, the
ripple voltage. Fig. 27 gives the practical limit for the ripple voltage which
may be applied to different electrolytic condenser ratings.
Measuring Surge Voltages-The best
practical way to make this measurement is to disconnect all filter condensers and install a 1 mfd. paper condenser at the output of the rectifier.
A 1,000 ohm per volt meter applied
at the paper condenser terminals, will
then indicate the voltage applied to
the condensers during the heating
cycle of the tubes. Be sure that the
"
0(
II:
8
tubes are cold and the meter is attached before the set is turned on.
The first steady reading (not maximum swing of the needle) of the meter
may then be taken as the maximum
surge. As the set warms up, the needle
will drop back from the surge voltage
to the operatini voltage. The paper
condenser may be connected to the
terminals of the voltmeter if more
convenient.
It is recommended that this measurement be made where high surges
are suspected, as this initial surge affects all the filter sections.
Surge voltage should always be
measured wherever the line voltage is
high; i.e., above the standard level of
no volts, as in many localities the
line voltage may rise to 125 volts or
more.
Obviously, where the ordinary type
of condenser is used, the speaker plug
should never be removed while the set
is on, as this removes all load and may
damage the first filter condensers. If
there is a possibility of this happening,
as on amplifiers, we suggest the use
of Mallory Type HS Condensers.
Scintillating Voltage. This represents
the critical or sparking voltage char-
8 MFD 450 V. CAPACITOR
OPERATED AT 250 VOLTS PLUS_
20 VOLTS RMS RIPPLE
TEMPERATURE 21 0 C.
10
1ft
• Section 9
'"
~
0
.:
u
-
E
(,
4-
200
400
600
800
1000
1200
1400
HOURS
FIG. 25-Capacitor Operated at Lower Than Rated VoUage
263
MY E
THE
Section 9 •
TECHNICAL
MANUAL
TEMPELTURE IVS
600
,JnLLA1G
V.
8 MFD 450 V. CAPACITOR
(APPROXIMATE)
I
...........
'"
W
"...i$
~
~
~
"=
!SOO
. .
......
i=
I
'(
""
~
"
~
I~
i
~
'"
z
U
eft
400
20
~:
i~
~,
I
"
I
80
60
40
DEGR~ES
I
CENTIGRADE
FIG. 26-Effecl of Temperature on Scintilliliing Voltage
D.C.
Operating
Volts
Maximum
Surge
Voltage
25
50
100
Max. Peak A.C. Ripple Voltage at 120 Cycles
Mfd.
1,2,3
Mfd.
4,5,6
Mfd.
7,8,9
Mfd.
10/12
Mfd.
13/16
Mfd.
17/25
40
75
150
10
15
25
10
15
20
10
15
20
10
15
20
10
10
15
8
8
10
150
200
250
200
250
300
25
30
30
20
27
27
20
25
25
20
20
20
15
15
15
300
350
450
350
400
525
30
30
30
27
27
27
25
25
25
20
20
20
475
500
.525
525
30
30
27
27
25
25
20
20
I
Mfd.
26/35
Mfd.
36/50
8
8
8
5
5
5
10
10
10
8
8
8
5
5
5
15
15
15
10
10
10
5
5
5
5
5
5
15
15
10
10
5
5
5
5
,
FIG. 27-Surge and Ripple Voltage vs. Normal D. O. Rating
I
acteristic of the capacitor. It is determined by the chemical formula of the
final electrolyte, and is only slightly
affected by the original forming solution or voltage used to provide the
oxide film.
Scintillation only occurs when the
capacitor surge voltage or temperature rating is exceeded. If allowed to
persist, it may cause liberation of gas
or actual carbonization of the separator material. This may eventually
264
cause a breakdown and the applied
voltage should not, therefore, be allowed to reach the scintillating point
for obvious reasons. Note paragraphs
on "Gas Pressure," page 271, and
"Separators" on page 257.
Methods of measuring all of these
characteristics are described in the
"Test" Section.
Capacitors should not be continuously subjected to voltages higher
than their working voltage ratings, as
breakdown may occur and a drop in
capacity noted if the unit continues to
function. This latter effect is due to
the increased thickness of the anode
film at higher voltage values. They
may be operated at lower voltages,
however, without any change in characteristics. Operation at, or below,
their voltage ratings will assure long
life. The capacity of the unit is not
affected even though the unit is operated at very low voltages for extended
i'
1\
D. C.
DRY
periods.
A chart is shown giving the surge
voltage and maximum peak A.C. ripple voltage for various working voltage ratings. Note that the capacity
has an effect on the ripple voltage
allowable. This is due to the heat
dissipation being affected somewhat,
by the size of the completed unit.
Polarity
Most Dry Electrolytic capacitors
designed for direct current or inter. mittent direct current (rectified A.C.)
are of the polarized type. In such
cases, only the anode has been formed
or provided with the insulating oxide
film. This film has a peculiar unidirecdirectional conductivity characteristic,
insofar as it allows heavy current to
pass in one direction and very little
in the other direction.
Consequently, D.C. capacitors
should not be subjected to reversed
polarity, as the heavy current passing
through the capacitor under this condition will raise its internal temperature and may cause serious damage to
the unit.
ELECTROLYTIC
CAPACITORS
However, the anode film itself is not
harmed by reversed polarity in any
way except when sufficient heat is
generated. Therefore, short applications on reversed polarity do not necessarily injure the film.
The cathode foil tends to form an
oxide coating when the polarity has
been reversed even for a relatively
short pefiod. Therefore, repeated applications on reversed polarity, even
though removed before too great a
temperature has been reached, will
cause a drop in the capacity of the
unit. This is obvious, as under such
circumstances we now have two capacities in series due to the dielectric
properties of the newly formed cathode film.
• Section 9
plate is formed during manufacture
to exactly the same voltage as the
anode. In such a case, the anode and
cathode lose their identity and simply
become electrodes.
N on-polarized capacitors may be
secured in any single capacity, and in
restricted concentrically wound sections of equal voltage.
The anode area is twice that required for a similar capacity in the
polarized type, and consequently the
unit is considerably larger in physical
size.
N on-polarized capacitors are for applications where the voltage supply
might become reversed and remain so
indefinitely.
Sellli-Polarized
NOll-P~larized Capacitors
This applies to Dry Electrolytic
capacitors so constructea that they
function equally well in either direction, from a polarizing standpoint, on
D.C. lines. They are not designed for,
and should not be used on alternating
current.
In this construction, the cathode
This type is similar to the nonpolarized type, except that the cathode is formed to not more than onehalf the voltage rating of the anode.
This limits the time a reversed voltage
could be applied before damage to the
capacitor would ensue.
The anode area is up to 50% more
than a regular polarized capacitor of
NORMAL LEAKAGE
8 MFD 450 V. CAPACITOR
.7
.6
UI
(!)
.5
CC
lIII:
CC
... .4
UI
ci
~ .3
.2
.1
\
\
"'-....
100
200
300
400
500
600
700
HOURS
FIG. 28-Normal Leakage Current
265
MY E
THE
Section 9 •
TECHNICAL
MANUAL
I
\
-4
INITIAL LEAKAGE
8 MFD 450 V. CAPACITOR
I
"
3
i
I;J
It
1&1
\P
I"~
C
~
:52
...
.
c
€
I
\
\
~
"-
~
I
I
2
3
4-
5
6
7
MINUTES
FIG. 29-Initial Leakage Currepl
sJmilar caphcity, and the size of the
unit falls between the polarized and
non-polarized types.
Semi-polarized capacitors are for
applications where the voltage supply
might become reversed, but for not
more than 15 minutes and at rare
intervals, and provided the regulation
of'the power source is sufficiently high
to protect the capacitor during the
reversed polarity period. They cost
less than non-polarized units, due to
anode area saved.
Auto-radio and D.C. house line
radio where the receiver does not
function properly, or at all, on reversed polarity, represents a field for
this type of capacitor.
Leakage Current
The leakage current characteristic
of a Dry Electrolytic capacitor represents the amount of direct current
flowing through the capacitor other
than its momentary charging current.
It is an indication of the quality of the
anode film and is a direct expression
of the insulation resistance of the capacitor. The leakage current charac266
teristic is affected by temperature.
The leakage current is not affected by
the series resistance representing the
path through the electrolyte, as this
represents a very minute fraction of
the dielectric resistance and is in series
with it. Incofllectly compounded electrolytes have some relation to the
leakage current, due to their tendency
to dissolve the anode film during idle
periods.
Normal Leakage Current. This represents the D.C. leakage current in
actual service and should become
lower with continued use. A wellmade capacitor will have an exceedingly small leakage when in continuous use. On intermittent operation,
the normal value of leakage current
may vary between 50 and 100 microamperes per mfd. depending on the
capacity and voltage rating, except
for the initial periods.
Initial Leakage Current. This represents the amount of current drawn by
the capacitor when first applied to the
voltage source after having been out
of service. It is mainly a function of
the action of the electrolyte on the
anode film, the quality of the anode
film aml. the length of the idle period.
The initial current is relatively high as
compared to the normal leakage current, but should drop quickly at first
and then more gradually until it
reaches the normal leakage value. The
shape of the curve showing this characteristic of the capacitor varies considerably with various manufacturing
processes and electrolyte formulas.
Initial leakage current characteristics
are generally associated with the shelf
life of a capacitor.
Power Factor
The power factor of a capacitor for
all practical purposes is the ratio between the equivalent series resistance
and the capacitative reactance at a
given frequency. It is expressed in percent and indicates mainly the amount
of energy consumed by the capacitor.
Since equivalent series resistance
may be used as a comparative characteristic similar to power factor and is
more generally used for calculating
purposes, this term has been found
preferable to power factor and is described in the following paragraph.
D. C.
DRY
ELECTROLYTIC
CAPACITORS
• Section 9
Equivalent Series Resistance
A------<
This is an important characteristic
and is used repeatedly in mathematical equations relating to electrolytic
capacitors. It is therefore a beiter
term than power factor for most investigations regarding them. The
equivaient series resistance represents'
the total losses (watts divided by 12)
in a capacitor due to:
a-Dielectric loss of the oxide film.
b-Contact resistance.
c-Electrolyte resistance.
d-Insulation resistance.
Due to the nature of an electrolytic
capacitor, it would be difficult, if not
impossible, to accurately ascertain the
values of ::a these losses separately.
They may be satisfactorily controlled,
however, from a production standpoint.
The combined effect of these losses
is expressed as the equivalent resistance value necessary to produce an
12R loss of the same magnitude. The
equivalent series resistance changes
with frequency and temperature.
Stability, rather than the initial
series resistance value (within certain
B----1~~~~~~~~~-~~~
B
-:---)4
---- ---CATHODE
PLATE
A------{
A-RIVET CONTACT RESISTANCE
B-ELECTROLYTE CONTACT RESISTANCE
1-SERIES RESISTANCE OF PLATE AND
LEAD WIRE ASSEMBLIES
i-DIELECTRIC LOSS OF ANODE FILM
3-SERIES RESISTANCE OF ELECTROLYTE
4-PARALLEL LEAKAGE RESISTANCE
FIG. 30-Eqq,ivalent Series Resistance Factors
limits), is the major feature. Initially
excessive, or a continually increasing
series resistance characteristic affects
the filtering, or by-passing efficiency,
temperature rise and life of a capacitor to varying extents.
A low equivalent series resistance
characteristic assures freedom from
"motor-boating" or low frequency oscillation of the circuit. In view of the
foregoing, it is obvious that the lower
the series resistance, the lower the
capacity required.
High Frequency Impedance
The value of a low impedance characteristic at high frequencies is becoming more important with the de-
.
...
A
Z
.,.
10
I0
.
'\
,
.............
12 8
,-
CAPACITY
---
-
~
V
I""""
-
SERIES RESISTANCE
10 6
CAPACITY .AND SERIES RESISTANCE
VS LIFE AT RATED VOLTAGE PLUS 120 en
RIPPLE.
60°C.
84
6
1000
2000
1000
4000
5000
6000
-
8000
HOURS
FIG. 31-Series Resistance liS. Life
267
M YE
THE
Section 9 •
I
2
TECHNICAL
I
I
I I I " I I
34567891
2
I
3
I
4
MANUAL
I I I I I I
5 6 789 1
1 -Ill i
I
2.
'I
I
3
I
I
I I I I I I
i 11
TYPICAL RF IMPEDANCE ICUR-VIE I
(AFFECTED APPRECIABLY ~Y DESIGN)
1--4-
I
4 567891
I
1&1
U-3
z
~
IU
C1.
~
-
-
~
&;100 ~
""
-"
-!
3
~
"
t-.
98
,
~ .............
1\
ii,
,i,I
~
1
...........r--.....
IL
0
-
I',I,
Ij
-~
I:
;
~ 97
I
100
200
HOURS
FIG. 38-Effect of Cathode Formation on Capacity
272
,
I
96
95
',I
3"00
Ii,
1'\
I
D.
8
1
6
au
~
5
lII:
:34-'
.
c(
~
c.
DRY
E·1 E C T R 0 1 Y TIC
1\
\,
CAP A CIT 0 R S
• Section 9
LEAKAGE RECOVERY AFTER 1,000 HOUR
SHELF LIFE AT 60· C.
8 MFD 450 V. CAPACITOR
~
'\
'"
"-
3
2
~
'" '--~
........ ......:.
I
I.
z.
3.
4.
5.
6.
7.
MINUTES
FIG. 39-D. C. Leakage vs. Shelf Life
oration of the water content and, in
severe cases, gas formation.
It is more important, however, to
base life predictions on D.C. applications involving an A.C. component, or
superimposed A.C. ripple voltage, as
this represents the usual and more
severe service. 'l'he introduction of an
4..C. component affects practically
every characteristic to varying degrees, but in reading the following, it
should be borne in mind that properly
processed capacitors, designed with
the full knowledge of the conditions
encountered, function perfectly satisfactorily in such service when kept
within their normal ratings.
Where A.C. components are involved, the cathode tends to form up
and become coated with a film similar
to the anode film. The thickness of
this film, however, is extremely thin
as compared to the anode film since
it is directly dependent on the relatively small value of the ripple voltage.
On life test, the major effect noted
is a slight and gradual loss in capacity
until the cathode has reached its maximum formation, after which it ceases
to directly affect the capacity characteristics. This drop in capacity is due,
of course, to the fact that capacitors
in series produce a final capacity less
than the smallest capacity involved.
Due to the extreme thinness of the
cathode film, the capacity thus developed is of tremendous value as compared to the anode capacity, which
explains the slight overall reduction in
the capacity of the unit itself.
The foregoing action is a normal
characteristic of all capacitors of this
type and does not affect their life
expectancy.
The J2R or watt loss of the capacitor, due to' the ripple current, is of
major importance since it produces
internal heat, which in turn affects
other characteristics.
An increasing series resistance and
an increasing leakage current with age
increases the watt loss. These characteristics should be closely watched on
comparative life tests.
The leakage current, since it increases with temperature, is extremely
important. The quality of the anode
film and the chemical characteristics
of the electrolyte are the major 'controlling factors with respect to the
leakage current.
The controlling factors with respect to the equivalent series resistance characteristic are the contact
resistance between the electrolyte and
the anode film or cathode foil, the
resistance of the electrolyte, and the
leakage current. All of these factors
are affected by temperature, so that
the resultant, the equivalent series
resistance, is also greatly affected by
temperature.
Corrosion, already explained at
length under the paragraph so headed,
is naturally an important feature with
respect to life.
It is obvious from the foregoing,
that abnormal temperatures affect the
life by accelerating detrimental
changes of the major .characteristics.
Accelerated life tests run under severe conditions clearly indicate that
properly manufactured Dry Electro.:
lytic capacitors will give many thousands of hours of satisfactory service.
At this writing actual tests of this sort
have been conducted for well over
20,000 hours.
Naturally, it is difficult to estimate
what these accelerated tests would
represent in normal service, but it is
safe to say that carefully made capaciI
273
THE
Section 9 •
MY E
TECHNICAL
MANUAL
Mallory Standard FP Capacitors
~X:
D.C. Wkg.
Volts
Surge
Volts
Size
Factor
D.C.
Mills
120 V)
OhDlS
- - - - - -- - -
RMS Ripple
Volts
Mills
5
5
5
300
350
400-450
400
450
525
10
12
15
.4
.5
.6
47
47
47
25
25
25
95
95
95
10
10
10
10
10
150
250
300
350
400-450
225
350
400
450
525
11
16
20
23
30
.5
.5
.6
.6
.8
30
24
24
24
24
20
20
20
20
20
150
150
150
150
150
15
15
15
15
15
i50
250
300
350
400-450
225
350
400
450
525
16
24
30
35
45
.6
.6
.6
.7
.9
20
16
16
16
16
15
15
15
15
15
170
170
170
170
170
20
20
20
20
20
20
25
150
250
300
350
400-450
40
225
350
400
450
525
8
21
32
40
46
60
.4
.7
.7
.8
.8
1.0
35
15
12
12
12
12
,3
12
12
12
12
12
45
180
180
180
180
180
30
30
30
30
30
150
250
300
350
400-450
225
350
400
450
525
31
48
60
69
90
.8
.8
.9
.9
1.1
10
8
8
8
8
9
9
9
9
9
200
200
200
200
200
40
40
40
40
40'
25
150
250
300
350
400-450
40
225
350
400
450
525
15
41
64
80
92
120
.6
.9
.9
1.0
1.0
1.2
17
7.5
6
6
6
6
3
7
7
7
7
7
90
210
210
210
210
210
50
50
50
50
50
150
250
300
350
400-450
225
350
400
450
525
52
80
100
115
150
1.0
1.0
1.0
1.1
1.3
6
4.75
4.75
4.75
4.75
6
6
6
6
6
230
230
230
230
230
80
80
150
400-450
225
525
82
240
1.3
1.6
4
3
5
5
300
300
40
Cap. D.C. Wkg.
Mid.
Volts
SUrge
Volts
Size
Factor
250
250
250
250
250
6
10
15
25
150
10
15
20
40
225
20
24
35
70
260
500
500
500
500
500
6
10
15
25
50
10
15
20
40
70
1000
1000
1000
1000
6
10'
15
25
1500
1500
1500
2000
2000
2000
3000
3000
4000
D.C.
Mill..
l20ll)
Oluns
RMSRipple
Volts
Mill..
- - - --- - - -- - .7
.7
.7
.7
3.0
6.4
6.4
4.8
2.8
1.3
.9
1.1
1.7
1.5
2.75
110
135
250
250
500
40
47
70
140
280
.8
.8
.8
.8
.8
3.2
3.2
2.4
1.4
1.4
.5
.75
1.25
1.0
1.5
150
190
350
350
500
10
15
20
40
80
96
140
280
1.1
1.1
1.1
1.1
1.6
1.6
1.2
.7
.4
.55
.9
1.0
210
270
500
750
6
10
15
10
15
20
120
140
210
1.4
1.4
1.4
1.0
1.0
.8
.4
.5
.5
300
370
450
6
10
15
6
10
6
10
15
20
10
15
10
140
190
280
210
280
280
1.6
1.6
1.6
2.1
2.1
2.6
.8
.8
.6
.5
.4
.25
.35
.5
.4
.4
.25
250
350
559
600
700
500
I
II
"
1\
II
"
I
.4
I"
i
I
1\
To determine the proper standard container size for any FP
capacitor, add the size factors, as listed in the above table,
for all of the sections included in a single container. Then using
the proper heading (single, dual, triple, quad), select the
smallest size container which will accommodate the total size
factor. Total container size factors in following table are
mamnum.
EXAMPLE:
5 mfd. 450 volt 15 (size factor)
15 mfd. 400 volt 45 ~size factor~
20 nifd. 25 volt 8 size factor
68 (total size filCtor)
Under column headed "triple," note that the 1" diameter 3"
long container with a 128 total container size factor is the
smallest container which will accommodate 68 total size factor. The 1" diameter 2" long container (size factor 64) is too
small for this combination.
CONTAINER SIZE FACTOR
10
15
25
150
350
250
15
20
40
225
450
350
10
14
28
104
280
240
.7
.7
.7
1.5
2.0
2.,0
16
12
7
3
2
1.6
2.5
3.0
3.25
4.5
4.5
4.0
125
170
225
340
450
450
Container
Size
I"
X
2"
68
66
64
200
200
200
200
6
10
15
25
10
15
20
40
16
19
28
56
.7
.7
.7
.7
8
8
6
3.5
~.O
,90
110
200
200
I"
X
3"
136
132
128
1.1
2.0
2.0
1%" x2"
140
135
128
123
1%"
280
270
255
245
%"x2"
FIG. 40
274
X
3"
Dual
Triple
[,
'Ii
!
11
100
100
100
100
125
150
Single
I
Quad
32
1\
I~
D.
c.
DRY
tors should give many years of satisfactory performance. Many thousands
have been operating satisfactorily for'
over six years in the field.
Shelf Life
The shelf life of a capacitor represents the length of time it can be out
of service, without detrimental change
in its characteristics.
.
The major controlling factor is the
leakage current characteristic which
in turn is dependent on the quality of
the anode fllm, and any tendency of
the electrolyte to dissolve this fllm
when the polarizing voltage is removed.
With proper care and knowledge in
E L E C T R 0 L Y T 'C
CAP A C , T 0' R S
the manufacture of the capacitor,
these characteristics may be easily
controlled.
Well made capacitors may be expected to quickly return to normal
characteristics after several months to
a full two years of idle period.
For those who are interested in
technical ratings covering D.C. working voltage, surge voltage, leakage
current, series resistance at 120 cycles, and A.C. ripple values, as well
as capacitor size requirements in type
FP capacitors; we have included the
characteristic chart of Fig. 40. The
column headed D.C. Mills refers to
normal leakage current while the one
headed 120 ohms, refers to the series
resistance at that frequency.
Dry Electrolytic Capacitors
Test Section
Life tests and production acceptance
tests might be considered unnecessary
effort and expense if it were possible
to have absolute confidence in all suppliers. However, no one can be considered infallible and consequently, it
is accepted practice in industry to
carry on a varying amount of this
work, depending upon the nature of
the product, the prestige of the supplier and the relative importance of
the component part ,to the finished
product.
It is important that the normal
electrical characteristics of Dry Electrolytic capacitors be known and the
tolerances understood in order to insure intelligent application. These
measurements are also necessary to
determine the quality and adaptability of condensers of both conventional
and new types of construction. It is
intended to outline in this text the
various methods of measuring each
characteristic of Dry type electrolytic
condensers so that the engineer can
choose those that are most adaptable
or necessary to his needs.
Leakage
The direct current leakage of an
electrolytic condenser should'be measured at its rated working voltage after
it has been subjected to that potential
for a period of five (5) minutes to
allow the leakage to come down to a
stable value.
Fig. 41 shows a suggested circuit
for measuring leakage. This may be
modified within limits dependent upon
the equipment available or the allowable cost.
• Section 9
Figs. 42 and 43 show two circuits
for measuring capacity by the impedance method. Fig. 43 is an adaptation of Fig. 42 wherein the polarizing
voltage is not used.
The A.C. milliameter should be of
the rectifier type as the relatively high
reactance of a dynamometer, or iron
vane type instrument will affect the
accuracy of the measurements.
Either of the two circuits shown for
the impedance method of measurement, c,an have the A.C. milliameter
scale calibrated directly in microfarads providing the A.C. voltage is constant within the degree of accuracy
desired.
This method is the most adaptable
to large scale rapid production testing.
The values obtained represent impedance rather than capacity reactance. However, any error due to the
difference between these values is
small for capacitors of low power
factor.
Equivalent Series Resistance
Fig. 44 shows a bridge circuit for
measuring both capacity and power
factor, or equivalent series resistance.
Bridge measurements are not as rapid
as can be made with the other method
but are more accurate and split up
the impedance into its two components-capacitive reactance and
equivalent series resistance.
The polarizing voltage is necessary
to obtain correct values of equivalent
series resistance since part of this loss
is made' up of the leakage current
through the capacitot.
Capacity
Radio Frequency Impedance
Capacity measurement 6f electrolytic capacitor!;! should be made with
an A.C. voltage of either 60 or 120
cycle frequency, not in excess of the
maximum rated ripple voltage, plus
a D.C. polarizing voltage equal to the
rated operating voltage. However, if
rapid readings are made, the polarizing voltage may be removed without
resulting in damage to the capacitor
or error in measurement.
Impedance measurements can be
made with fair accuracy throughout
the broadcast and intermediate frequency range using the circuit shown
in Fig. 45.
Thermo-couple errors affect the accuracy at the higher frequency so that
it is difficult to obtain accurate values
at frequencies about five megacycles.
However, comparative readings made
at the higher frequencies by this
275
Section 9 •
rHE
M Y E
rr
MANUAL
E C H N I CAL
. Ix 1000000
c=
SEPARATE FILAMENT 7"RANSflJRNER
MUST BE lISE/)
MAINTAIN CONSTANT
FILAMENT M:>LTA6E WHE<¥ VARYIIItJ
THE Pi..4TE ""-TAGE
ro
Ex 377000
X
I=CURRENT IN MILLIAMPERES
C=CAPACITY IN MICROFARADS
E=VOLTAGE
Fxo.41
~,
.
I
40
36 I - LCAJACI&
\l)32 I -
C!LIBR~ndN JRVE'
CURVE BASED ON MAINTAINING
60 en AC AT 3 VOLTS
Cl
~28
c.
~24
V
o
e:i 20
~
V
/
~4
4
8
12 1620 UZ8 32 36 404448
CURRENT IN MILLIAMPERES
FIG. 42
method are reliable so that it is satisf~ctory for rapid production testing
of the high frequency impedance characteristic.
Accurate laboratory measurements
to obtain actual values at the higher
frequencies should be made with a
Q-meter.
Life Tests
Electrolytic capacitors should be
life tested at elevated temperatures
equivalent to the maximum condition
which they encounter in service and
.at rated :p.C. operating voltage plus
.a peak 120 cycle ripple voltage corresponding to the rating of the capaci~or
under test.
If 120 cycle power is not available,
higher ripple voltages of 60 cycle fre-
FIG. 43
quency should not be used to obtain
the same capacitor current as this
would subject the capacitor to a total
peak voltage in excess of its rating.
Life test ovens should be constructed
with baffles to prevent direct radiation from the heating elements and
capacitors under test should be spaced
from one another, rather thap. grouped
together,. to prevent localized heating.
Measurements of leakage, capacity
and equivalent series resistance tak\'ln
initially, at 100 hours, 500 hours artd
1,000 hours will .suffice to judge the
. quality of any capacitor of standard
design. Capacitors should be cooled to
24 0 C., when recording the values of I
each characteristic.
Continuous life tests at 85 0 C.are
generally unreliable since this temperature is plose to the maximum lill)it
a ·capacitor. can withstand without
appreciable change in characteristics.
There is seldom, an application in field
$ervice that requires the capacitor to
operate continuously at 85 0 C. and at
the maximum voltage rating simultaneously.
Therefore, 85 0 C. life tests should
be altered to more nearly approach
actual operating conditions although
they may be acoelerated.
It is recommended that such life
tests be conducted at 90% of the D.C.
rating plus allowable ripple and that
the temperature be applied intermittently. The temperature. should be
applied for fOll! hours at 85 0 , then
allowed to reduce to 60 0 over a period
of eight hours, and repeat. On this
schedule, the capacitors will be subjected to 85 0 for eight hours and to
60 0 (plus) for sixteen (16) hours for
each 24-hour cycle.
.
I
276
7
./
t::S
\.J
\3 °0/
/
V
~16
~/2
)..
n~
V
./
I~
I'
D. C.
DRY
ELECTROLYTIC
CAPACITORS
• Section 9
r-------=--_,.._ ,/'" THERI1CKOUf'LE
(1\a
~ I~X
~J
:))
0
RF
05C1LATOR
V.l VOLTMETER
X CONNECT CAPACITOR {)IRECTL Y AT THI5 POINT
FIG. 45
FIG. 44
Measurement of Coupling
Common coupling in properly designed multiple section capacitors
should be negligible and eliminate circuit oscillation, or hash interference
difficulties from this source.
If present, this characteristic is
caused by either capacitive or resistive
coupling and it is possible to measure
the coupling as shown in the diagram.
Capacitive coupling is generally
caused by interanode capacitance
where the capacitor cartridge was
rolled carelessly allowing the anodes
to protrude slightly over the cathode
foil.
Resistive coupling is caused by:
1. The IR drop through the long
cathode foil which must act as a
common ground return for all
included sections.
2. Contact resistance between the
cathode foil and the external
cathode terminal.
3. Long lead from cathode to ground
either inside or outside of the
capacitor.
Mallory FP capacitor cartridges are
carefully wound to reduce the possibility of interanode capacity from
poor plate alignment. The entire roll
of cathode plate is short circuited at
the bottom, eliminating inductance
(which also effects the R.F. impedance) and greatly reduces any IR
drop in the cathode foil. An exceedingly short cathode tab, which is
welded to the mounting ring (cathode
-terminal) provides a minimum of resistance in the common lead to ground.
The circuit shown is self explanatory and provides an easy method for
comparison of coupling under given
conditions between various capacitors.
Values of potential and limits of
coupling are not shown, since the
choice of measuring potential, frequency and coupling limits depend on
application conditions.
I' I'
l'li"
....u-
--
II
-0-
-u....
II
el II
£L'
II
e 211
e3
V.T
VOLTMETER
MEASUREMENT OF COUPLING
277
Section 9 •
THE
MY E
TECHNICAL
I
MANUAL
"
ELECTROLYTIC CAPACITOR, APPLICATION
Generally speaking, there are two
main uses for electrolytic capacitors
in radio receivers or similar electronic
equipment. The first, and at this time
most important application, is that of
a filtering agent to help convert pulsating direct current into a smooth,
even supply for vacuum tube plate
potential. The second use is that of
by-pass service in audio frequency circuits. This application usually requires
capacity values slightly larger than
that for high voltage filter service.
However, since the voltage for operation is rather low it is possible to ob- .
tain almost any capacity necessary for
by-pass service in a capacitor of reasonable physical size.
When the electrolytic capacitor is
employed in the high voltage filter
application, the current to be filtered
is obtained by rectifying alternating
current of suitable voltage. There are
a number of different type rectifiers
but the one normally used for high
voltage "B" supply is the thermionic
rectifier tube, employed in either the
half wave or full wave rectifier circuit.
was positive will now be negative, and
the voltage will again rise to a peak
value and fall to zero. This completes
one cycle of the current. The general
frequency of supply current is 60 cycles per second.
FIG. 48
FIG. 46
Figure 47 shows the voltage applied
to the plate during the half-cycle
wherein the plate is positive in respect
to ground.
Half-Wave Rectifier
FIG. 47
Figure 46 illustrates the connections
of a "half wave" rectifier. This circuit
is seen to consist of a transformer and
half wave rectifier tube. The transformer serves to supply the necessary
high voltage alternating current. One
side of the high voltage winding connects to the plate of the tube and the
other side to ground or common.
The filament of the tube is lighted
by the curr~t obtained from the low
voltage winding on the transformer.
The high voltage winding of the transformer, as previously mentioned, supplies an alternating current. Alternating means that the polarity, or direction of current flow, reverses itself
periodically. First one side of the
transformer is positive, then the other.
The voltage will rise to a peak and
then fall to zero, at which point the
polarity reverses; i.e., the side which
278
Fig. 48 shows that during two cycles
the plate will be positive for certain
periods of time and negative for equal
periods.
Notice that the voltage gradually
rises to a peak value and then falls to
zero. If we should connect a voltmeter
across the transformer it would not
indicate the peak value, but rather the
"RMS" value, which means-the root
mean square voltage applied to the
plate of the tube.
When the plate is positive, electrons
are attracted from the filament. The
electrons flowing from the filament to
the plate constitutes a current, the
value of which depends on the voltage
applied to the plate. Therefore the
current is seen to rise and fall with the
voltage applied to the plate. When
the plate of the tube is negative in respect to the filament, there can be no
current flow because the plate must
be positive in order to attract electrons
from the filament.
From our previous explanation of
the action in the tube, and from Fig.
48, we see that during two cycles of
ihe supply voltage, the tube will deliver current for two periods of time,
which is equal to the length of time
during which the plate is positive, and
that there will be a lack of current
during two periods of time in which
the plate is negative. Thus- we see
that for a half-wave rectifier we will
have regular periods of current flow,
each of which is followed by a period
of time during which no, current flows.
This, of course, is far different from
the ste;ldy "Direct Current" plate
supply, which is required to give successful operation of a radio receiver.
A voltmeter connected across points
"A" and "B" of Fig. 46 would show
the average voltage existing across the
load connected to points "A" and
"B." This average voltage would be
far below the RMS voltage supplied
by the transformer, because of the
periods of time during which there is
no current flowing in the circuit.
If by some means we could provide
a reservoir, which would absorb current during the periods of current
flow, and then feed this stored current
into the circuit during the periods
when current is not flowing from the
tube into the circuit, we would be
able to raise our average voltage
across the load. We would, in effect,
have a more continuous flow of current and therefore a higher average
voltage across the load.
A condenser provides just such a
reservoir, and when connected across
the load as in Fig. 46, it will act ex-
D. C.
DRY
actly as the imaginary reservoir action
described.
ELECTROLYTIC
il
TRANSfORME1i
CAPACIT.ORS
• Section 9
current flowing through the plate No.
1), will gradually rise to a peak and
then fall to .zero. This is shown in
Fig. 51.
I
LOAD
FIG. 49
'--------'
Fig. 49 is a graph of the voltage
across the load resistor shown in Fig.
46, as plotted on the basis of time.
The two heavy and dotted curves
show the voltage supplied by the tube,
FIG. 50
and the slanting line shows the voltage which would be supplied to the
Fig. 50 showR the circuit of a full
circuit by a condenser connected from
wave
rectifier. A transformer supplies
points "A" to "R" It will discharge
the
high
voltage, to be rectified, and
current into the circuit during the
the low voltage for lighting the filatime the charging voltage is falling,
ment of the rectifier tube. Note that
and this discharge continues until the
the
high voltage winding is tapped at
condenser is either entirely discharged
its
center.
This center tap of the transor until a charging voltage is again
former
provides
a return path comapplied to the circuit by the rectifier
mon
to
both
sections
of the high volttube.
age
winding.
Inasmuch as the quantity of curThe high voltage winding is arrent is determined by the amount of
to supply a voltage between
ranged
load, it is easy to see that a very large
the
two
ends of the winding, which is
condenser would be required to totally
twice
the
value of the voltage required
"fill in," or supply voltage to the ciracross the load. The reason for this is
cuit during the entire period of time
that only half of the winding is used
in which the rectifier tube plate is
at a time; therefore, each half of the
negative.
winding
has to supply the desired
In order to further smooth out the
output voltage.
current, it will be necessary to provide
The tube shown in Fig. 50 has one
some means whereby we can "hold _
more
plate than the tube shown in
down" the peaks, so that we may take
46,
however, the tube action is
Fig.
full advantage of the action; i.e., the
identical.
Thus-current will flow
"holding up" or maintenance of curfrom
the
filament
to that plate which
rent supplied by the condenser. This
is
positive,
but
not
to the plate which
operation will be covered later in this
is
negative.
text.
For explanation, let us assume that
plate No. 1 is positive. Therefore.
Full-Wave Rectifier
plate No.2, since it is connected to
the other end of the high voltage windThe full wave rectifier operates in
ing, is negative. Current will flow from
exactly the same manner as the half
the filament to plate No.1 (but not
wave rectifier, with the exception that
to plate No.2), and complete the cirthe full wave rectifier enables use of
cuit by leaving the center tap and
both halves of each cycle of current.
going through the chassis and load,
It has been pointed out in the deback to the filament. We will call this
scription of the half wave rectifier,
the "fIrst action."
that current flowed for a certain length
In our previous study of the half
of time and then was absent for an
wave rectifier, it was pointed out that
equal length of time, due to the second
the current and voltage rises, to a
half of the cycle being of reversed
peak, and falls to zero and reverses
polarity. However, the full wave rectipolarity, rises to a peak and again
fier enables us to use the other half
falls to zero, to complete Qne cycle.
of the cycle, to fill in holes which exist
Therefore, in the first action, the voltin the output of the half wave rectifier.
age across the load (because of the
rvv~
FIG. 51
Remember that when the current
supplied by the transformer reaches
zero, the polarity reverses. Therefore,
for the "second action," plate No. 2
of the rectifier tube, in Fig. 50, will be
positive and plate No. 1 will be negative.
As the voltage rises and falls on
plate No.2, there will be a current
flow from the filament of the rectifier.
tube to plate No.2, and from the
center tap of the high voltage winding
through the chassis and load, back to
the filament, thus completing the circuit.
The voltage across the load will
gradu,ally rise and fall. It flows in the
same direction as the current obtained
in the first action. Therefore, the voltage across the load will rise and fall in
the same manner and with the same
polarity as that obtained by the first
action. This is shown in Fig. 51.
By the use of a full wave rectifier,
we have a more continuous current
flow, or in other words, we have filled
in the holes which we found to exist
in the current supplied by the half
wave rectifier. This means that we will
not have to depend upon an extremely
large condenser to maintain the flow
of current in the load.
Refer to Fig. 51 and note that we
have a period of time, between each
half cycle of the supply current, during which the voltage falls to zero. If
a condenser is connected across the
load, it will discharge current tlrrough
the load as soon as the applied voltage
starts to fall, and it will continue this
discharge of current until its voltage
falls to zero, or until the condenser
voltage is opposed by the rising voltage of the second half of the cycle.
Fig. 52 shows the meeting point
between the discharge of the condenser and the increasing charging
voltage of the second half of the cycle
of current supplied by the rectifier.
279
THE
Section 9 •
VOL"'.Ct ACted! 'HE LOAD
$UHUlD IV 1H! DISCH,O.lGf
O. ntE CQNDIHSII
..
_
\
TIMt IDURATION O' I CYCLEI
to DIll
VOLTAQl SUI'JII.IS) TO THE
lOA. ",ND CONDENSUJ
ty '"I .,JUt ACTICHH 01
HMf Of ltfl CYCLE
lOAD 'AND (ONDI"'UIQ
IT TH! "'SECOND ACTIOH"
OR
ltIl(YCLf
YCLTAtH
SUP~D
"""Of
FIG: 52
Compare the shape of the curve,
illustrating the D.C. voltage existing
across the load resistor, in Fig. 51,
with that of Fig. 47. Note that we
have twice the number of peaks of
current per cycle of the supply current. It will require less capacity to
smooth out the current delivered by
the full wave rectifier than is required
by the output of the half wave rectifier. This is due to the fact that there
are more "impulses" of current in the
same length of time. A condenser of
a given capacity will maintain a higher
voltage level,.in the load, with a full
wave circuit, than in the case of the
half wave rectifier circuit, because it
needs supply current for muoh shorter
periods of time between impulses of
current. This is evident in comparing
Fig. 52 with Fig. 49.
The pulsating current obtained from
a rectifier, even with a condenser connected to the circuit, is not suitable
for "B" supply in a radio receiver or
amplifier, because the remaining pulsations or ripple would still give rise
to a very strong and objectionable
hum in the loud speaker.
Increasing the capacity of the condenser connected across the load, at
the output of the rectifier, will not
decrease the hum below a certain
value; inasmuch as the charging voltage applied to the condenser must fall
to a certain extent before the condenser discharges its current into the
circuit. Likewise, the charging voltage
must rise to a certain extent before it
can begin to replenish the charge in
the condenser. Thus-we see that we
can reduce the "amplitude," which
means the height from the lowest to
the highest point of the voltage variation, or ripple, by the use of a condenser, but that above a certain value
of capacity, depending upon the load
and frequency of the supply voltage,
there will be no further reduction in
the amplitude of the ripple in" the
current supply. It will be necessary to
280
MY E
TECHNICAL
MANUAL
use some means, in addition to the
condenser, to entirely eliminate the
ripple from the supply voltage, in
order that there may be a pure direct
current for use in either the receiver
or amplifier. The most convenient
means of doing this is by the use of
an inductance or more commonly
called "choke."
Action of Chokes
The term "choke" has been applied
to the component properly named an
inductor. This inductor or choke, as
preferred, has an electrical property
called inductance, an action of opposing sudden increases or delaying sud-:
den decreases of current through the
inductor.
Any conductor carrying a current
has a magnetic field at right angles to
the longitudinal axis of the inductor.
This magnetic field extends radially
outward from the conductor, a certain
distance, depending upon the intensity or amount of current flowing in
the conductor. If the current through
the conductor is increased, the magnetic field will expand. If the current
is reduced, the magnetic field will contract. Thus, we have a moving mag-"
netic field, the direction and speed of
motion of which is determined by the
rate of increase or decrease of current
in the conductor. NOTE-There is no
motion when the current is flowing at
a steady rate.
A fundamental law of electricity
states that when a moving magnetic
field cuts through a conductor, there
will be a voltage induced in the con~uctor, the polarity of the induced
voltage depending upon the direction
of motion of the magnetic field. If we
take a straight conductor and coil it,
we will have an arrangement whereby
if we increase or decrease a current
flowing through the coiled conductor,
we will have a moving magnetic field,
which, due to the proximity of turns,
will cut through several conductors;
i.e., adjacent turns of the coil. If we
increase or decrease the current flowing through a coil of wire, we will have
a self induced current in the coil in
addition to the applied or driving current. This induced current is of opposite polarity to the applied or driving
current. Therefore, an increase of cur-
rent through an inductor is opposed
by the self-induced current in the coil,
which is usually called the counterelectromotive force.
In line with this explanation of the
action taking place during an increase
of current, it is easy to see that a
decrease in current will generate a
<;lounter-electromotive force which will'
oppose the decreaSe in current.
The amount of inductance in a coil
of wire is dependent upon the number
of turns and the nature of the material
used for the core. Air is the poorest
material, in that it is not a good magnetic conductor. If we use an iron core,
the inductance will be much higher,
because iron is an excellent magnetic
conductor.
In the discussion of rectifier circuits,
it was pointed out that it was necessary to find some means of holding
down the peaks of the ripple in the
current supplied by the rectifier, so as
to obtain a steady flow of current for
use as "B" supply in a receiver or
amplifier; therefore, it appears that an
inductor or choke is ideally suited for
this action.
FiI ter Circuit Action
At this point we are ready to describe the action taking place in a
filter circuit; a circuit composed of
capacity and inductance which will
smooth out the pulsating current delivered" by a rectifier; into the pure
direct current necessary for "B" supply. Fig. 53 shows the connections of
the iron cored inductor choke, and
two condensers which comprise the
simplest and basic type of fIlter circuit.
FIG. 53
The letters "R" and "L" in Fig. 53
indicate respectively, the rectifier and
load. The condenser at the input has
the same action upon the circuit as
the condenser described in the chapter
on rectifiers. This condenser acts as a
reservoir to supply current to the load
during the zero current periods in the
supply from the' rectifier.
D. C.
DRY
The choke in the circuit of Fig. 53
opposes any sudden increase or decrease of current because of its inductance.
At this point, we have a current
supplied to a load ("L" in Fig. 53)
through a choke which opposes and
prevents any sudden increase in the
current, and we have a condenser at
the rectifier output which will supply
current when the rectifier cannot.
Thus, the choke prevents the peak of
the ripple from getting into the load,
and the condenser fills in the hollows
in the supply. Or, we may explain the
action up to this point by saying that
we have reduced the amplitude of the
ripple in the current.
Inasmuch as the choke prevents
any sudden increase in current, or in
other words, maintains a steady current flow, it is necessary to provide a
means of supplying current to meet
any sudden demand for current made
upon the filter. Without such an auxiliary current supply, we would be
forced to wait for an increase of current to come through the choke. We
have in reality, a need for a reservoir,
and a condenser is just such an electrical reservoir. Therefore, we see the
reason for the condenser across the
load side of the filter circuit shown in
Fig. 53.
Before discussing the more elaborate filter systems, the circuit shown
in Fig. 54 should be considered.
I
AL vvvwvv [
I cJ
J
t
I
L
FIG. 54
This circuit is seen to consist of a
resistor and two condensers arranged
in the same manner as the simplest
and the first described filter. circuit.
This type of circuit is not nearly as
efficient as one using a choke. It is
much cheaper, as there is a large difference in cost between the price of a
resistor alld that of a good choke.
The action in this circuit is rather
simple, in that the resistor sets up a
voltage drop in any current passing
through it, the voltage drop being
determined by the current flowing
through the resistor. For use as a filter, there will be a greater voltage drop
in the direct current than there will
ELECTROLYTIC
CAPACITORS
be in the ripple current, because of the
fact that the direct current is greater
than that of the ripple current, or, we
might state that the DC voltage applied to the resistor is much greater
than the ripple voltage. It will require
a rather large resistor to give appreciable drop in the ripple current flowing through the resistor, and for this
reason, such a circuit can not be used
except where the load on the filter is
small.
Resonant EleIllent
Filter Circuits
Our discussion to this point has
been confmed to the filter circuit
known as the brute force type. However, there is another type of filter
circuit wherein use is made of a resonant circuit. Such a resonant circuit
type of filter is shown in Fig. 55.
fill
• Section 9
design, it should be below the lowest
frequency which will be handled by
the audio amplifier receiving "B" supply current from the circuit. In addition, it is very important that the
resonant frequency of the filter circuit
should not be the same as the frequency of the rectified current-i.e.,
60 cycles for half wave rectification,
or 120 cycles for full wave rectification, from a 60 cycle supply frequency.
In addition to ~he low pass type of
filter circuit, there is a high pass filter
circuit; i.e., one which prevents the
passage of all frequencies below the
cut-off point, but allows the passage
of all frequencies above the cut-off
point.
A combination of the high pass and
low pass filter would be most effective
for use as a "B" circuit filter, provided
that the cut-off point of the high pass
filter is above the ripple frequency and
the cut-off point of the low pass filter
is below the ripple frequency. The
most effective arrangement of such a
combination circuit would be to have
the high pass filter between the rectifier and the low pass filter.
An absorption type of filter next to
the rectifier is shown in Fig. 56.
FIG. 55
The capacity of the condenser "C"
is so chosen that it tunes the choke to
resonance with the hum frequency.
The result is that a tuned circuit of
this type offers a very high impedance,
or more simply, opposition to the hum
frequency. The action of this tuned
circuit is often described by saying
that it absorbs the particular alternating current, in this case, the ripple
current, which is applied to it.
The tuned choke type of filter circuit is nearly always used with the
full wave type of rectifier, although it
is possible, but not convenient or advisable, to use it with the half wave
type.
I t is well to point out that all filter
circuits described have been of the
low pass type; i.e., circuits that will
pass all frequencies below a certain
value and prevent all frequencies
above this certain value from passing
through the circuit.
The cut-off point, i.e., the frequency
below which the filter is ineffective,
must be below the frequency of the
hum voltage, or ripple, and in good
I
L
f
FIG. 56
In this circuit the field coil of a
speaker is used as the inductance,
which with the capacity of the series
condenser, resonates at the ripple frequency. Inasmuch as it is a series
resonant circuit, it offers a short circuit for the ripple frequency curr~nt.
This current is not suitable for use as
a field supply. The resistor is shunted
across the condenser in order to provide a path for the necessary D.C.
current.
The resistor is of a much higher
value than the capacitive reactance
of the condenser at the frequency
involved. The resistor does broaden
the peak of resistance of the circuit
and this offsets any slight discrepancy
in capacity value of the condenser.
Fig. 57 is a more practical, although
more expensive, method of using a
resonant circuit in a filter.
281
THE
Section 9 •
MY E
TECHNICAL
11
Fig. 59 shows a circuit wherein
there is no condenser connected across
• the output of the rectifier. This cirR 1'--~ ~ L
cuit is commonly known as the choke
I DT
IT
I
input type of circuit. The choke, which
is connected directly 'to the output of
FIG. 57
the rectifier, is often termed the swingThis circuit shows the use of an
ing choke.
inductance and an electrolytic conInasmuch as there is no reservoir
denser, the sole purpose of which is to
action at the input to the fIlter, there
short circuit the hum frequency. In
will be a lower output voltage from
some instances, the two chokes shown
the filter, because of the hollows in
in Fig. 57 are in reality two windings
the current supply from the rectifier.
on a common core. In other words, a
Because we have an extra choke over
transformer. There is a simpler and
that of the circuit shown in Fig. 53,
less expensive way of obtaining the
we will have a much smoother current.
same action. This method is shown in
The voltage output of the choke
Fig. 58.
input type of fIlter circuit is smoother
for lower values of load, than the corresponding capacity input type of fIl~t
ter. The voltage is lower except for
0
~~ J.
£
£ L
higher loads. This type of circuit is
1]£
useful where there is a large variation
in load.
~~c
,iT
yctMJt{
if
~
FIG. 58
The portion of the circuit in which
we are interested in Fig. 58, is the
tapped choke in the negative lead.
Note the condenser connected between
the chassis and the tap on the choke.
The tapped inductance acts as an autotransformer, the primary of which is
the whole winding, as the secondary
is the circuit formed by a portion of
the winding and the condenser connected from the tap to one end
(through the!chassis) of the winding.
The resonant period of this tuned secondary is equal to the disturbing ripple, and therefore, it appears as a
short circuit to the ripple frequency,
which means that the energy of the
ripple frequency is expended in this
circuit.
Choke Input Filter
In the preceding text we have discussed the actions which take place in
simple fIlter circuits of the capacitor
input type similar to the one shown
in Fig. 53.
t~I'
iC ·.tC~
~
I
18
FIG. 59
282
J;I
I
MANUAL
Voltage Distribution
in Filter Circuits
In addition to a tube requiring a
plate voltage, it also requires a negative bias voltage which is applied to
the grid. If we can obtain both our
plate and bias voltages from the "B"
supply, or, in simpler words, make full
use of the voltage from the "B" supply, we will be effecting an economy.
Inasmuch as the bias voltage must
be negative in respect to the cathode
of the tube, we can easily accomplish
the action of obtaining both our "B"
and "e" bias voltages in the following manner.
Due to the fact that it is convenient
to use the chassis as the negative side
of the circuit, it is possible to insert a
resistance, between the center tap, of
the high voltage winding on the power
transformer, and the chassis. This will
make the center tap of the transformer negative in respect to the cha.ssis. If we connect the cathode, or fIlament center tap of our tubes directly
to the chassis, and connect the grids
to the center tap of the transformer,
the grid will be negative, in respect to
the cathode, by the amount of voltage
drop obtained -across the resistance.
The voltage drop obtained across
the resistance, as outlined in the pre. vious paragraph, is caused by the cur-
.~
rent in the load, which is the sum of
all the plate currents and "bleed"
currents of the receiver. The voltage
drop across the resistance is equal to
the current times the resistance. For
any given current, we can obtain any
desired negative voltage by selecting
the proper value of resistance.
The introduction of the dynamic
speaker enabled designers to work a
dual purpose, in that the dynamic
speaker could be used as the choke.
Inasmuch as the magnetic circuit of
the field in a dynamic speaker must
necessarily include a "gap" (for the
movement of the voice coil), we have
the makings of a choke, as we have a
coil of wire on an iron core, and the
core is provided with an air gap.
The use of the field of a dynamic
speaker as a choke is economical as
the saving in the cost of the choke offsets part of the cost of the speaker.
If the speaker field were placed in
the positive lead, the voltage drop
across the field would be subtracted
from the voltage available from the
rectifier, which voltage, of course,
would have to be raised to offset this.
In addition, if a separate voltage dropping resistor were used, either at the
tube or in the negative lead to the
transformer, to secure the necessary
bias voltage; the rectifier output voltage would of necessity have to be large
enough to include this voltage. Therefore, it is natural to utilize the voltage
drop across the field as the bias voltage, and thereby make a saving in the
power transformer. The result of this
is the use of the field in the negative
lead; i.e., between the chassis and
center tap of the power transformer.
Fig. 60 shows the simplest type of
filter circuit wherein the choke is in
the negative lead.
FIG. 60
Because the same fIltering action
can be obtained with the choke in the
negative lead as is obtained with the
choke in the positive lead, we can
expect to find the same types of circuits as previously described, with the
chokes in the negative side of the cricuit instead of in the positive .
I
D. C.
DRY
Due to the fact that the wattage
required to be expended in the field
coil mayJnot be of such a value as to
give a convenient voltage drop, it is
sometilnes necessary to adopt the expedient shown in Fig. 61.
ELECTROLYTIIC
CAIPAICITORS
greater than approximately 2 mfds, it
was necessary to use a circuit as shown
in Fig. 63.
FIG. 63
FIG. 61
Here we see the same circuit as
shown in Fig. 60, except that there
has been a resistance added in series
with the choke or the field coil; in
order that the voltage drop between
the load and rectifier may be sufficient
for use as bias voltage. It is of no
great importance as to which side of
the choke the resistor is connected,
inasmuch as the resistor offers an impedance to the ripple voltage, the
same as would an inductive reactance
of the same ohmic value. In case the
voltage drop across the field is too
great, a divider network is placed
across the field so as to tap off the
desired voltage.
Multiple Choke Filter Circuits
~t
r;L
~
R..L
~;T
:r
;[l
FIG. 62
The circuit shown in Fig. 62 is seen
to consist of two chokes with condenser input and output, and in addition, a condenser from the point of
connection of the two chokes to the
negative side of the circuit. There is
in reality two of the simple ffiter circuits placed end to end with the advantage of a much better ffitering
action because of two chokes and
three condensers.
Since the introduction of the electrolytic condenser with its advantages
of low cost and small size for an extremely large capacity, it is rare that
one encounters a ffiter circuit of more
than two stages. In older receivers
wherein the designers were forced to
use paper condensers, which were uneconomical to use in capacity values
This three-section ffiter is seen to
consist of three chokes and four condensers. Actually, there are three of
the common, or simple, ffiter circuits
placed end to end.
Even with extremely low values of
capacity, this circuit is capable of
very good ffitering, inasmuch as there
is an over-abundance of inductance to
counteract the usual lack of capacity
with the use of low capacity paper
condensers.
COlnplex Filter Circuits
• Section 9
at this point is to effect an economy
in the ffiter design. The current supplied to the field coil does not need to
be as ripple free as that which is supplied to the plates of the tubes. In
addition, the current drawn by the
field coil is rather large. If the field
coil were connected across the output
of the ffiter, it would increase the voltage drop across the choke, and in
addition, would call for a much larger
choke (in physical size) to obtain the
necessary smoothness in the current
to be applied to the load.
The principal use for such a circuit
is in A.C.-D.C. receivers, wherein a
half wave rectifier is generally used.
Since a half wave rectifier requires the
use of large capacitors, and a good
inductance, any unnecessary increase
in these items would be uneconomical.
There is one point which must be
borne in mind with such a circuit.
The combination of inductance of the
field coil, together with the capacity
of the input condenser, should not be
of such values as to form a tuned circuit resonant at the ripple frequency.
Such a tuned circuit in this position
would cause a high voltage to be developed across it.
Present-day ffiter circuit design is
for the most part simple and direct.
Several years ago, and in occasional
cases even·today, one may encounter
rather complex ffiter circuits. These
circuits often are not as complicated
as they may seem at first glance, as
they are usually combinations of ffiter
circuits and load distribution circuits
with associated by-pass condensers,
arranged in such a manner that the
schematic of the whole circuit with all
the various connections appears rather
FIG. 65
involved.
Study will enable one to disassemble
The circuit in Figure 65 uses a recsuch a complex circuit into its various
tifier tube which has two separate and
functions as to ffiter and load distridistinct half-wave rectifiers within its
bution. These more complex circuits '
envelope, such as the Type 25Z5 tube.
are in reality. made up of combinaWe have a half wave rectifier and
tions of the circuits which we have
ffiter system to supply current to the
previously discussed.
load, and another half-wave rectifier
which supplies current to the field coil.
The condenser connected across the
t
field coil is for the purpose of ffitering
the current flowing through it. Otherwise there would be quite a bit of hum
FIG. 64
due to the ripple current passing
through; whereas, with the condenser
The circuit illustrated in Fig. 64 is
in parallel with the field coil, the peak
seen to consist of the ordinary single
section brute force ffiter with a choke
of the ripple is absorbed and the conconnected across the filter input. The
denser discharges through the field
coil during the period of no current
purpose of. connecting a choke, or in
flow from the rectifier.
reality a field coil, across the circuit
r
283
Section 9 •
THE
One of the main purposes of the
split cathode design is to make the
highest possible voltage available for
the output tube plate. With a given
total capacitor value for both parallel
and individual cathodes, a maximum
increase of approximately 20% is possible with the separate cathode connection.
MY E
TECHNICAL
lytic condensers together negative to
negative, using the remaining positive
terminals for connection to the circuit.
The most general use for non-polarized electrolytic condensers is in receivers to be operated from a D.C.
line, although they are frequently used
in receivers which are to be operated
from batteries.
..
Voltage Doubler Circuits
t
R
Although the principle and action
of the voltage doubling type of rectifier-fIlter circuit was known for many
years, it was not until the introduction of the popular A.C.-D.C. receivers that there was a good commercial
reason for using such a circuit.
Section 3 of this book, entitled Half
Wave and Voltage Doubler Power
Supplies, appearing on pages 48
through 62, gives a complete discussion of all types of voltage doubler
systems. For capacitor characteristics
and service, for the doubler applications, please refer to Section 3.
Non-Polarized Condensers
There are quite a number of applications where it would be dangerous
to use the usual D.C. electrolytic condenser. In cases where the polarity
applied to the condenser may be reversed, the heat generated by the
heavy current flowing through the
condenser would severely damage, if
not totally destroy the unit. This is
due to the unidirectional property of
the dielectric fIlm which retards the
current flow in one direction, but offers no resistance in the other.
There is a simple means of providing an electrolytic condenser which
may be-used in any circuit wher~in
the polarity may be accidentally, or
intentionally reversed. Such a condenser is called a non-polarized type.
A non-polarized condenser is one in
which there is no polarity; i.e., either
one of the terminals· may be connected to the positive side of the potential source.
Such an electrolytic condenser is
easily made by either one of two
methods. The first method is to build
the condenser with two formed plates,
or second-to connect two electro284
MANUAL
~
JiA
Is
I+c
FIG.
L
~
66
Fig. 66 clarifies the method which
is recommended for the replacement
of non-polarized condensers.
Supposing a requirement for a 4
Mfd. non-polarized capacitor, the correct replacement would be a dual 8
Mfd. connected as a common negative unit. To install the replacement
connect the positive leads into the
circuit and disregard the common
negative lead. If replacement unit is
of separate section construction, connect the two negative leads together
and tape to prevent accieJental contact with the circuit. It is obvious
that two single sections could be employed instead of the dual unit if their
connection into the circuit is made as
above.
It should be noted that the capacity
resulting from such an arrangement
of condensers is equal to one-half the
capacity of either section. In addition,
both sections of a condenser so used
should be of the same capacity.
The working voltage of the capacity
resulting from the connections described, and illustrated in Figure 66, is
that of one section, and not twice the
rating of the one section. Thus-two
450 volt condensers so connected will
have a working voltage of 450 volts.
Condenser Action in
AC Circuits
The apparent flow of alternating
current through a non-conducting material i.e., dielectric of a condenser, is
not possible in the strict sense of the
word. However, there is a flow of current in an alternating current circuit
which includes a condenser.
AC GE.NE.RATOR
17
CO"JDEI\JSER
FIG. 67
Fig. 67 shows a condenser connected in a circuit with an alternating
current generator. As the generator
revolves, and starts a cycle, assume
that the upper portion of the:;circuit
is positive, and the lower part of the
circuit is negative. The voltage rises
from zero to a maximum, and then
falls to zero, thus completing one-half
of a cycle. At this point, the polarity
of the circuit reverses; i.e., the top
half of the circuit becomes negative,
and the bottom half positive, and
again the voltage rises to a peak and
falls back to zero, whereupon the polarity again reverses and becomes the
same as at the start. One cycle has
been completed.
When the voltage rises on the first
half of the cycle, the condenser is
charged. After the voltage reaches the
peak, it falls to zero (at the same rate
at which it rose to the peak). We now
have a condition wherein we have a
charged condenser, and a conducting
circuit from one plate of the condenser
to the other through the generator.
A charged condenser will discharge,
if there is a conducting path from one
terminal of the condenser to the other.
Therefore, the condenser will discharge through the circuit. However,
before this discharge is complete, the
voltage from the generator is rising
on the second half of the cycle.
The rising voltage of the second
half cycle of the alternator is of such
a polarity that it aids the completion
of the discharge of the condenser, and
then recharges the condenser (but
with opposite polarity to that of the
first charge). The voltage from the
alternator 'again falls to zero, and
of course, the condenser discharges
through the circuit.
Because the energy required to
ch~ge the condenser during one portion of the cycle is delivered back into
the circuit, the transference of the
charge represents so-called "wattless"
current, since, except for usually negligible circuit losses, no power is consumed.
II
I····
I
I
D. C.
DRY
ELECTROLYTIC
CAPACITORS
By-Pass Condenser Circuits
Many circuits in radio receivers or
amplifiers carry both alternating and
direct current. It is necessary to provide separate paths for the flow of
these two different currents, in order
to accomplish certain actions. A circuit may carry direct current for plate
supply and an A.C. signal current at
the same time. It is necessary to provide a path for the signal voltages so
that they may be applied only to certain portions of the circuit. In other
words, it is necessary to separate the
direct current and the alternating
signal current.
A convenient means of obtaining
this separation is to use a condenser
to provide a path for the alternating
current. Since the direct current does
not flow through a condenser, we can
obtain the desired separation.
This action is perhaps best illustrated by Fig. 68.
SCREEN OR PLATE.
~B+
1
FIG. 68
This circuit shows the use of a condenser to allow the passage of alternating signal current, from the screen
circuit of a tube to ground, the resistor
prohibiting the alternating current
from getting into the "B" supply where
it might cause trouble. In most instances the resistor is necessary to
provide the correct voltage for the
screen, therefore it'readily serves two
purposes.
An additional illustration of the use
of a condenser to provide a path for
alternating current, is shown in
Fig. 69.
In Fig. 69 the resistor shown connected from the cathode of the tube to
ground, is for the purpose of supply:
FIG. 69
ing a bias voltage for the grid of the
tube. This resistor is usually of several
thousand ohms resistance, and would
offer an impedance of this value to the
flo~ of the signal current. Such· an
impedance to signal currents at this
point would introduce regeneration,
and this is usually to be avoided. If
a condenser is connected across the
resistor, it will provide a path for the
alternating current, which will not
affect the required voltage drop across
the resistor necessary for bias supply.
Capacity of By-Pass Condensers
The capacity of a by-pass condenser
is regulated by the frequency of the
current to be handled, and in addition, the resistance of the circuit to be
by-passed. It is a general rule, that the
capacitive reactance of a condenser
should be approximately one-tenth, or
less, the resistance value of the circuit
to be by-passed.
Capacitive reactance is the impedance; or, opposition of a condenser to
the flow of an alternating current.
This reactance is expressed in ohms by
the formula X = _1_, where w is
wFC
6.28, F is the frequency in cycles per
second, and C is the capacity in Farads.
The above formula shows that for
a given value of capacity, the reactance decreases with increasing frequency. For practical illustration, let
us say that a 1 mfd. condenser has a
reactance of 1592 ohms at 100 cycles,
but that for 200 cycles, the reactance
is only 796 ohms.
To find the correct capacity value
to be used for by-pass condensers, it is
• Section 9
only necessary to know the resistance
of the circuit to be by-passed, and the
lowest frequency which will appear in
the circuit. Then find the capacity
value, the reactance of which is approximately one-tenth or less of the
resistance of the circuit to be bypassed, at the lowest frequency which
. appears in the circuit.
Electrolytic By-Pass Condensers
Inasmuch as many circuits to be
by-passed are of very low resistance,
or are carrying a low frequency current, it requires a large capacity to
effect the proper by-passing action.
Previous to the introduction of the
electrolytic condenser, large values of
capacity were extremely expensive.
However, in electrolytic condensers
particularly at low voltages, it is possible to obtain a very large value of
capacity at low cost, and in a small
space. For instance, the usual capacity
required for by-pass in the circuit of
Fig. 69, is in the order of 25 mfds. at a
potential of approximately 25 volts
or less.
An electrolytic condenser suitable
for use in this circuit will occupy a
space of approximately 1}j6" diameter
x lYs" long. Such a capacity value in
a paper condenser would occupy quite
a few cubic inches of space.
Wherever a large capacity is required for a by-pass condenser, and
where there is a D.C. voltage, it is advisable to use an electrolytic condenser. For very high frequencies,
a paper condenser should be used,
inasmuch as electrolytic condensers
are not suitable for use as by-pass condensers at frequencies above several
kilocycles.
Where a circuit to be by-passed carries both audio and R.F. currents it is
often advisable to use both an electrolytic condenser and a paper condenser.
Such arrangements are found in many
receivers. -
..
285
Section 9 •
THE
MY E
TECHNICAL
MANUAL
WARTIME SERVICING
D. C. -ELECTROLYTIC CAPACITORS
• This part of the capacitor section is
3. A greater conservation of copof particular interest to the serviceper thrqugh the decrease of capacitor
men responsible for keeping all kinds
lead lengths.
of electronic equipment in efficient
4. The issuance of suitable cross
working condition.
reference material to provide a means
The wartime demands on various
of rapid substitution for types either
raw materials and manufacturing , temporarily or permanently unavailprocesses are making it increasingly
able.
difficult for radio parts manufacturers
As a fifth and final step we are into procure and fabricate these matecluding cross reference tables ancl cirrials for radio replacement parts. Parts
cuit connection charts for a possible
manufacturers are finding it necessary
replacement of all types of units in the
to standardize, or universalize, their
Mallory line as of this writing, by
products so as to obtain a maximum
what might be termed a "Minimum
replacement coverage with a miniLine." This line is predicated upon
mum usage of critical materials. The
the use of only ten basic capacitors of
Mallory Replacement Condenser Line
the tubular construction as exempliwas originally established as a univerfied by the Mallory BB type.
sal replacement system and has continued in this pattern up to the present time. However, because of the
First Step
scarcity of certain strategic materials,
it was thought that further simplifiUnder the first step, a listing of uncation would be in the interests of
available
wet and dry capacitors using
conservation. This program was inaluminum
cans was provided, tostituted prior to the advent of this
gether
with
the catalog number of the
country as an active belligerent in the
war. It resulted in a number of
Unavailable
Unavailable
changes in the replacement system
Dry Type. Substitute Wet Type. Substitute
Catalog
Catalog
Catalog
Catalog
thought advisable at that time, but
Nutnber
Nutnber
Number
NUlllber
actually a necessity under existing
RS213
FPS142 WE825
FPS142
conditions as this book goes to press.
RS215
FPS143 WE1625 FPS143
The simplification program can be
FPS143 WE2425 FPS144
RS216
RN232
2S567
WE1830 FPS143
considered as occurring in the followRM262 2S567
WE4030 FPS146
ing steps.
RM265 CM175
WE1835 FPS143
1. The recommending of tempo-
rary or in some cases permanent substitutes for wet electrolytic units, the
first to suffer under restricted materhls.
2. The development of replacement
units employing mounting features
similar to that of the wet or threaded
neck-can type dry units, but using a
minim.um of scarce metals.
266
HD684
HD685
HD686
HD683
HS693
SR605
SR644
FPS142
FPS142
2S567
HD682
HS692
2S567
FPS143
WE3035
WE450
WE850
WE851
WE1250
WE1650
WE2050
WE3050
WE4050
WE460
WE860
WE1660
FIG. 70
FPS145
FPS142
FPS142
FPS142
FPS142
FPS143
FPS144
FPS145
FPS146
FPS142
FPS142
FPS143
recommended substitute. This data
appears in Fig. 70. The FP type capacitor, previously discussed, was
specified for replacement since it made
possible a workmanlike job with a
minimum of 'change, employing ca-
CROSS REFERE.NCE
Substitute
Catalog No.
Replaces Unavailable
Catalog Nutnber
FPS142
WE825, WE450, WE850,
WE851, WE1250, WE460,
WE860, RS213, HD684,
HD685
FPS143
WE1625, WE1830, WE1835,
WE1650, WE1660, RS215,
RS216, SR644
FPS144
WE2425, WE2050
FPS145
WE3035, WE3050
FPS146
WE4030, WE4050
2S567
RN232, RM262, HD686,
SR605
CM175
RM265
HD682
HD683
HS692
HS693
FIG. 71
pacitors already widely available.
Five type FP capacitors provided a
complete coverage for 18 wet and 6
aluminum can dry capacitors.
Replacing Wet Electrolytic
Condensers
In replacing a wet electrolytic capacitor with a dry type unit, the following instructions should be considered.
From an electrical characteristic
angle, dry capacitors can be readily
D. C.
·DRY
substituted for all wets except for a
very small minority of applications.
The only limitation is that the surge
voltage should not exceed 525 volts.
In those instances where a high
surge voltage is suspected, check the
surge voltage by temporarily connecting a 1 mfd. 600 Volt Paper Capacitor
in place of the wet and measuring the
surge voltage across this capacitor.
Use a high resistance voltmeter and
take the first steady reading (not maximum swing of the needle). As the set
"warms up" the needle will drop back
from the surge voltage to the operating voltage. Do not forget that if the
set is used on a higher line voltage,
the surge and operating voltages will
be higher by the voltage ratio of the
power transformer.
If the surge is less than 525 volts,
equal or better service will be obtained with the recommended unit.
Should the surge voltage exceed 525
volts, proceed as follows: Connect a
5 to 10 mao bleed~r resistor (Mallory
1HJ or 1AV) across the output of the
filter circuit, and measure the surge
again. If less than 525 volts, connect
the bleeder resistor permanently in
the circuit and replace the wet with
the recommended unit.
If the bleeder resistor does not lower
the surge voltage sufficiently, the current bleed can be increased to the
desired point so long as the current
rating of the rectifier tube or power
transformer are not exceeded; or the
performance of the receiver affected.
Another alternative, should the
surge voltage exceed 525 volts, is to
connect two dry capacitors in series,
each capacitor to have twice the capacity as the one recommended. (When
two capacitors having the same rating
are connected in series, the resultant
capacity is one-half that of either
capacitor.) One unit can be mounted
above the chassis in place of the wet,
and another can be connected in series
under the chassis, using a horizontal
mounting clip. Or if you prefer, you
may use type BB capacitors having
the same rating; under the chassis.
A third alternative, if the surge
voltage exceeds 525 volts and a capacity of 8 mfd. is sufficient, is to use
one Mallory high surge capacitor,
type HS692, which will withstand up
ELECTROLYTIC
CAPACITORS
to 700 volts surge. If a higher capacity
is required, two such capacitors may
be connected in parallel, resulting in
a total of 16 mfd.
The following three mounting procedures are included for convenience
in replacing wet type units with FP
type capacitors.
1. If negative of wet capacitor is
grounded and has %:" diameter screw
neck:
It is unnecessary to use the FP
bakelite mounting plate since the negative terminals of the FP capacitor
will pass freely through the mounting
hole in the chassis. Bend the negative
terminals straight back (do not twist)
and solder these terminals to the chassis. Connect wire or wires to positive
terminal in normal manner. In the
case of the FPS142, the bakelite
mounting plate must be used and
mounted in accordance with No.3
below.
2. If negative of wet capacitor is
grounded but has only a %" diameter
screw neck:
If the hole in the chassis does not
permit the passage of the FP negative
terminals, file small notches around
the periphery of the hole and proceed
as described in No. l.
3. If negative of wet capacitor is
not grounded:
Place the FP bakelite mounting
plate, included with each FP capacitor, over the chassis hole, mark the
location of the two mounting holes,
and drill. Mount the plate on the
capacitor and twist the negative terminals with pliers. Should the negative terminals touch the chassis, notch
out the hole as previously described.
Fig. 71 gives a cross reference of the
recommended substitutes.
• Section 9
policy to continue to supply proven
standardized replacement parts wherever possible, Mallory engineers started working for an adequate substitute.
Critical materials pre-empted by wartime production were passed by and
the less critical materials were thoroughly explored. Knowing that properly seasoned and impregnated hardwood had· been proven practical
throughout the years in the construction of carpenters' tools, such as
screw-threaded clamps, Mallory tested
various treated woods for strength
and ability to withstand splitting and
cracking. Out of this investigation and
research, the recently announced Mallory Wooden Neck Capacitor was developed.
Here is a case proving that necessity is the mother of invention. What
III
I'
CHASSIS
FIG. 72
II
Second Step
The second step was the development of replacements providing
mounting features closely duplicating
those of units discontinued because of
the shortage of critical materials used
in their construction.
The eventual discontinuance of such
capacitors was realized by Mallory
over a year ago and because of their
WASHER
NUT
\
SOLDER
& TAPE
FIG. 73
287
THE
Section 9 •
MY E
TECHNICAL·
could be more practical, during these
critical times, than a container made
of cardboard with a wooden screw
neck and nut~ A wooden nut is used
which grips very securely even when
tightened by hand. In addition it is a
self insulator-simply mount it in the
same manner as the original aluminum screw can and connect the leads
to the desired points in the circuit. If
metal lugs are preferred, they can be
slipped over the self-insulating wooden
neck, as shown in Figures 72 through
75.
MANUAL
The Mallory Wooden Screw Neck
Capacitor replaces original metal can
screw neck capacitors, both dry and
wet type. An insulating washer and
solder lug terminal are packed with
each capacitor for convenience in replacing original capacitors equipped
with lugs.
I
1. To replace a grounded can capacitor. Fig. 72 illustrates the correct
use of the washer and lug. Note that
the washer insulated the lug from the
chassis, and the negative lead (black
or dark color) is soldered to the chassis.
I
FIG. 76
New Wooden
Screw Neck
Dry Type
Cat. No.
Discontinued
AluJrlinum.
Can Wet Type
Cat. No.
INSULATING
WASHER
NUT
INSULATING
WASHER
WE825 .............. RS213
WE1625 ............. RS215
WE2425. . . . . .. . ..... RS207
WE1830 ............. RS217
WE4030. . . . . .. . ..... RS223
WEI835 ............. RS217
WE3035 ............. RS219
WE450 .............. RS213
WE850 .............. RS213
WE851. . . . . . .. . ..... RS212
WE1250. . . . . .. . ..... RS212
WE1650 ............. RS214
WE2050. . . . . .. . ..... RS217
WE3050 ............. RS219
WE4050 ............. RS223
WE460 .............. HS691
WE860. . . . . . .. . ..... HS693
WEI660....... ...... *
FIG. 74
*Use series connection.
Because dry capacitors have lower power
factor, etc., than wets, less dry capacity is required for a replacement. See
table below.
Dry
Capacity
Original Wet
Capacity
4-12
8-16
12-20
16-30
20-40
Mfd.. . . . . . . . . . . . .. 8
Mfd ............... 12
Mfd ............... 16
Mfd ............... 20
Mfd ............... 30
Mfd.
Mfd.
Mfd.
Mfd.
Mfd.
FIG. 77
FIG. 75
288
Immediately following are instructions for correct use of the wooden
neck replacements.
2. To "replace an insulated can capacitor. Fig. 73 illustrates the use of
the washer and lug in the positive
lead with the negative lead spliced to
original negative lead. Fig. 74 illustrates the use of two sets of the
washer and lug. These extra washer
and lug sets, catalog WE-S, may be
obtained separately.
3. To replace a lug type multisection capacitor. Fig. 75 illustrates the
use of three sets of the washer and
lug, with one negative grounded.
4. In applications requiring series
connection of replacement units, the
method shown in Fig. 76 is recommended. Such practice is sometimes
necessary in replacing wet type units
of 600 volt rating, or in applications
where a high surge condition is present. The method of Fig. 76 utilizes
the space occupied by the original
unit, with the small additional space
required by an FP, BB or ST type
mounted below the chassis. It should
be noted that the same considerations
applying to the replacement of wet
electrolytics previously outlined under the first steps (substitution with
FP types) apply equally to substitution with the wooden neck units. Fig.
77 provides a listing of the discontinued types with their correct replacement in the new construction.
N OTE- The catalog numbers of the
original aluminum can type units (RS
types) were carried through into the
wooden neck construction to keep
confusion occurring in substitution,
at a minimum.
D. C.
DRY
Third Step
The cutting down of a capacitor
lead length under step 3 does not work
any great hardship. In most cases the
lead length is still great enough, and
in applications where it isn't, some of
the original lead wires may be easily
salvaged.
Fourth Step
The preparation and issuance of
substitution cross reference material,
outlined under step 4, was quite an
assignment. To be really effective, this
information must cover every D.C.
electrolytic type in the line (as of
December, 1941) , and must also be
provided in two systems, one by capacity rating, and the other by D.C.
voltage rating.
The two cross references appear on
pages 290 through 301. An examination of both cross references discloses
the same general layout. In the center
of the capacity reference pages, is the
capacity rating column with working
volts D.C. to the right and left. Similarly, in the center of the working
ELECTROLYTIC
CAPACITORS
volts D.C. reference pages, is the
working volts column, with capacity
to the right 'and left. Listed on the
right side of the page are the various
horizontal types, with the vertical
mounting types on the left. The columns under the vertical and horizontal mounting headings indicate the
internal connections, and the catalog
number of each capacitor is printed
under the proper column heading.
The capacity or D.C. working volts,
depending on the cross reference used,
is printed in the adjacent column only
when that type of mounting is available for the listed rating.
As an example, let us assume that
an FP type unit having a rating of
10-10-10 mfd. @ 300 volts, such as
Mallory type FPT368, is required but
is temporarily out of stock. Locate the
recommended capacitor in the cross
reference. Keeping in mind that a
higher capacity and/or voltage can be
substituted with satisfactory results
in almost every instance, we look further down the page and find that the
best substitute is the type FPT390
unit, rated at IS-1S-10 mfd. @ 4S0
volts. This rating is equal or higher
for each section. Also note that the
FPT374 having a rating of 20-1S-10
• Section 9
mfd. @ 4S0-300-300 volts would make
a satisfactory substitute.
Now refer to the D.C. working volts
cross reference and assume that a
spade lug capacitor, rated 16-12 mfd.
@ 200 volts, such as Mallory type
UR194 is required, but is temporarily
out of stock. After locating this unit
in the cross reference, look further
down the page, and notice that the
type 2SS62 cardboard tubular with
universal mounting and rated 16-16
mfd. @ 2S0 volts, makes an ideal
substitute.
It is not always necessary to select
a substitute unit from the same column. Sometimes the serviceman knows
that he can mount the condenser under the chassis even though the original mounted in another position. If
this were the case in the example just
given, the Mallory rectangular carton
type CM164, with universal mounting feet, rated 16-16 mfd. @ 2S0 volts,
would make an excellent substitute.
This unit appears under the horizontal mounting classification.
A further possibility in using the
cross reference is the use of paralleled
sections of dual and triples to replace
units of fewer sections, but higher
capacity ratings.
289
t.:I
Cross Reference
g
MA
PRMALLLOLRYO
&CO" R
I"C,
y, DC
UI
Electrolytic Condensers
t""'I"""'NC'I
fr<
....
N
(3.
~
~
t""'It""'INC't
'"(3.'"
.......
...
CI
=
NNN
.... ....N
.!.obc!.J,c!.c!.
Uc!.
........
.... .... N
I I I
J.obc!.obc!.c!.
N"'O
....
'"
.b "I ' 0I J.obc!.obc!.c!.
...........
"'00
'"N '"NI
NI '"N
Ul
0
c!.
0
""z c!.N '"6N
....
:;J 0
N
CI N '"
c!.0 0I
N ...'"
J.,
~~~
~
.....
Ul
...
~
10
Ci
Ul
...
0
10
~
Ul
...
iil:;J
50
150
150
150
250
BB14
BB21
BB25
BB27
BB31
Capac- Volt- Catalog
ity
age
Type
20
8
16
20
30
250
450
450
450
450
BB34
BB61
BB64
BB65
BB68
Replacement recommendations are
listed under the tabulated data pages
302 through 304_ Wiring for the individual universal constructions, as well
as all of the SR (Special Replacement)
types are given in Figs. 78 through
136.
It should be noted that in specifying replacements we have often juggled the capacity values slightly, such
as an original 15-10 mfd. unit to be
replaced by a 16-8 mfd. value, or a
6-10 mfd. type by an 8-8 mfd. rating.
Also as pointed out under Fig. 77, dry
type replacement recommendations
for wet units can be entirely satisfactory if their value is approximately
two thirds the original capacity rating. The precautions regarding replacement of wet condensers, listed
under step 1, also apply to the recommendations of step 5.
In the interests of conserving material, all substitute recommendations
not exactly duplicating the original
rating are made on the basis of minimum total capacity (altering sectional values) which will satisfactorily
do the job. We urge that all servicemen adopt this policy in obtaining
replacements for. unlisted capacitors.
The guiding principles of the service
industry for the near future might well
be those of salvage, conservation, and
improvision, so that our armed forces
are assured of their needs, and the
essential services of radio communications can be maintained for all.
301
MY E
THE
Section 9 •
TECHNICAL
MANUAL
REPLACEMENT RECOMMENDATIONS - SINGLE SECTION UNITS
PRESENT LINE
Capac- Voltity
age
1000
500
1000
2000
1500
500
500
1000
1000
1500
2000
2000
4000
500
1000
2000
10
25
40
50
50
100
100
250
500
500
1000
1000
2000
2000
65
5
10
25
50
100
500
1000
4
8
12
12
16
3
6
6
6
10
12
12
12
12
12
12
12
12
15
15
15
25
25
25
25
25
25
25
25
25
25
25
25
25
25
30
50
50
50
50
50
50
50
150
150
150
150
ISO
Catalog
No.
PRESENT LINE
MINIMUM LINE
capac-I vOlt-1 Catalog I No. Capac- Voltity
age
No.
Req. ity
age
-------
SR646
HC605
HC610
HC620
FPS030
HC1205
• These capacitors not used
HC1205A
for home radio receiver
HCI210
functions. Not subject to
HCI210A
replacement under tbis
HC1215
program.
HC1220
HCI220A
HC1240
FPS037
FPS039
FPS041
BB12
BBl5
FPSI02
BB17
RS200
FPSI05
HC2501
HC25025
FPS057
Not subject' to replaceHC2505
ment under this program.
FPS059
HC2510
HC2520
RC2520
SR608
BBll
25
50
BB14 12
BB13
} 25
50
BB14
I
BB14
50
BBI4
2
25
BB19
HC5001
Not subject to replacement under this program.
HC5005
HC5010
BB20
BB21
8 1150
BB21 11
BB22
20
150
BB25*
1
SR635
BB24
:: I :: I:::: I :
I I
24
30
30
40
50
8
8
8
8
12
12
16
16
16
20
24
15
18
30
30
40
50
ISO
150
150
ISO
150
250
250
250
250
250
250
250
250
250
250
250
300
300
300
300
300
300
BB25
BB26
FPS1l3
40
. BB27
FPS1l5
BB31
ST585
8
RS203
WE825
BB23
,RS205
BB34
ST587
20
WE1625
FPS120
ST589
FPS127
16
WE1830
FPS129
FPS129A
30
WE4030
RS208
30+20
350
350
350
350
350
350
350
350
350
350
350
BB40
BB41
ST590
BB42
ST591
BB44
ST592
WE1835
ST593
WE3035
FPS137
125
350
450
450
450
450
450
450
450
450
450
450
FPS140
CS130
BB60
CS131
BB61
ST595
CS133
18450
RS212
RS213
HD684
2
4
4
8
8
8
8
8
8
tSee "Replacing Wet Electrolytic Condensers, "
page 286
8
MINIMUM LINE
PRESENT LINE
MINIMUM LINE
Capac- Volt- 'Catalog No. -Ca-p-ac-- -V-o-l-t--1--C-a-tal-og-1-C-a-pa-c- -V-o-lt-- -C-a-tal-og- -N-o-.
ity
age
No.
Req. ity
age
No.
ity
age
No.
Req.
,---1----1----------
4
8
8
12
, 12
16
16
18
24
30
50
I
*Revis ed rati ng
Catalog
No.
150
BB27
1
250
BB31
1
250
BB34*
1
450
BB64
1
450
BB68
1
450
BB68 +
BB65 1 ea.
8
450
BB61
I
16
450
BB64
1
20
450
BB65
1
30 +20 450
BB68 + I ea.
BB65
Not su bject to replacement
8
450
BB61
1
8
10
10
10
12
12
12
12
12
15
16
16
16
16
16
20
20
20
20
30
30
40
80
4
8
8
8
8
8
12
16
16
20
30
40
4
4
4
8
8
8
16
-----
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
500
500
500
500
500
500
500
500
500
500
500
500
600
600
600
600
600
600
600
HD685
BB62
8
450
BB61
I
FPS142
SR643
BB63
ST596
RS214
RS215
SR644
FPS143
16
450
BB64
1
BB64
ST597
CS136
RS216
RS217
ST598
FPS144
20
450
BB65
I
FPS144A
RS219
FPS145
30
450
BB68
1
RS223
FPS146 20+20 450
BB65
2
FPS149
Not su bject to replacement
WE450
WE850
WE851
8
450
BB6It
1
HD682
HD683
ST605
WE1250
450
BB6It
1
WE1650
450
ST609
BB64t
I
WE2050
WE3050
450
BB65t
I
WE4050
450
BB68t
I
WE460
HS690
450
BB61
2
8-8
HS691
Use series C onnectio n
WE860
HS692
16-16 450
BB64
2
Use series C onnectio n
HS693
WE1660
30-30 450
BB68
2
Use series C onnectio n
REPLACEMENT RECOMMENDATIONS - DUAL UNITS
. MINIMUM LINE
PRESENT LINE
Capacity
Voltage
--- --- - - Sec. Sec. Section Section
2
2
1
1
- - ----IS
15
1000 1000
10
40
5
10
4
8
8
8
12
12
16
16
16
16
20
20
20
20
20
20
30
30
30
30
30
30
30
40
50
50
50
16
6
8
8
8
8
16
16
20
10
40
.5
10
4
4
8
8
4
4
8
8
16
16
10
20
20
20
20
20
10
10
10
20
30
30
30
20
50
50
50
12
6
8
8
8
8
16
16
20
302
. 25
25
35
50
150
150
150
150
150
150
150
150
150
150
ISO
150
150
150
150
150
150
150
150
150
150
150
ISO
150
150
150
150
200
250
250
250
250
250
250
250
250
25
25
35
50
150
ISO
ISO
150
ISO
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
200
250
- ~~g
250
250
250
250
250
Capacity
Voltage
PRESENT LINE
Catalog No.
Capacity
Voltage
---------- - - - -Section
- -------Sec. Sec. Section Section
2
I
2
2
I
------ - - -- - - -40- -40- 250 250
Not sub ject to r eplacem ent
Cat. No. Sec. Sec. Section Section Section
2
1
1
2
I
FPD200
TNlll
25 25
FPD202 2-25 2-25
25 25
SR619
TN1l3
25 25
2N500
2P541
8
2N502
8
2P542
2P543
SR636
2N504
20
8
2P544
2N506
20 20
2P546
2N507
20
8
2S554
FPD208
20 20
2N509
2P549
URI92
2N512
2P552
20 20
SR620
2P553
40 20
2S556
2N513
40 20
FPD211
2N514
2S558
2N515
40 40
FPD214
UR194
20
8
SR633
8
8
2S56O
2N516
8
8
RM252
RN232
2S562
CM164
20 20
FPD217
50
50
50
50
50
50
50
50
BB14
2-BB14
BBI4
BBI4
BBl4
2-BB14
BBI4
BB14
150
150
BB21
BB21
150
150
BB25
BB21
150
150
BB25
BB25
150
150
BB25
BB21
150
150
BB25
BB25
150
150
BB25
BB25
150
150
BB27
BB25
150
150
BB27
BB25
150
150
BB27
BB27
250
250
250
250
BB34
BB31
BB31
BB31
250
250
BB31
BB31
250
250
BB34
BB34
8
12
8
30
6
8
8
8
12
15
16
20
12
4
15
20
4
8
8
8
8
8
8
8
8
8
8
8
8
10
12
15
16
16
16
20
30
40
80
30
8
8
30
6
8
8
8
12
IS
16
20
8
4
10
30
4
4
4
8
8
'8
8
8
8
8
8
8
8
10
12
5
8
8
16
20
20
40
10
300
300
350
350
350
350
350
350
350
350
350
350
400
450
4S0
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
30
300
300
300
350
350
350
350
350
350
350
350
400
150
250
300
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
MINIMUM LINE
Capacity
Voltage
Catalog No.
-Cat.;No. Sec. Sec. Section Section Section Section
2
1
2
I
I
2 FPD221
SR603
SR601
URI80
FPD228
SR606
2S564
2N517
SR605
2S565
FPD225
2S566
FPD227
SR634
SR627
FPD232
FPD233
CM170
RM261
RN241
SR639
2S567
2N518
CM172
SR645
RM262
MN272
HD686
SR638
SR642
FPD231
2S568
MN273
2S563
2N519
2S569
FPD234
FPD235
FPD238
FPD245
-- -- --- ------------- --- -250
2-20 2-20 250
2-BB34 2-BB34
8
16
8
30
} 8
25
8
8
30
450
450
450
450
50
450
450
450
BB61
BB64
BB61
BB68
BBI4
BB61
BB61
BB68
8
450
450
BB61
BB61
8
)16
20
16
8
16
20
16
16
450
450
450
450
BB61
BB64
BB64
BB64
20
8
8
8
30
450
450
450
450
450
450
450
150
250
450
BB65
BB64
BB61
BB64
BB65
BB65
BB61
BB21
BB31
BB68
8
8
450
450
BB61
BB61
16
8
450
450
BB64
BB61
16
20
30
2-20
Not
450
450
BB64
BB64
16
450 _
20
BB65
450
BB65
BB68
BB65
20
450
450
2-20 450
450
2-BB65 2-BB65
sub ject to r eplacem ent unde rtillil
progra m
D. C.
DRY
ELECTROLYTIC
CAPACITORS
• Section 9
REPLACEMENT RECOMMENDATIONS - TRIPLE UNITS
Capacity
Section 8ection Section
2
3
1
- 20
-20
- -20
20
40
40
4
10
8
10
16
8
16
10
10
16
16
10
16
16
20
24
16
20
10
20
30
20
40
20
20
40
20
20
200
t40
30
100
t50
50
20
50
4
4
4
8
8
8
8
4
16.
8
5
16
4
12
16
20
10
10
20
20
20
5
25
10
30
20
10
40
20
20
40
40
40
20
20
30
16
30
16
50
20
40
20
20
20
15
30
30
50
20
40
20
8
8
15
15
40
16
20
16
20
20
40
30
20
30
8
8
8
8
8
8
16
8
8
15
15
10
8
16
16
30
15
10
40
20
20
5
3
6
4
6
6
4
6
6
8
8
10
15
20
40
10
10
10
20
20
20
4
6
10
25
8
8
6
4
16
12
8
8
8
8
20
8
8
20
12
12
20
15
10
20
15
10
20
16
16
20
20
10
5
30
10
20
8
8
8
15
10
5
20
10
25
8
8
25
8
8
25
20
15
10
15
20
30
20
8
8
20
10
10
12
12
20
15
10
20
20
15
40
20
20
20
20
100
t20
30
10
20
40
40
20
15
10
40
8
8
8
8
8
8
30
30
20
8
8
8
8
8
8
8
8
8
10
5
5
10
10
10
15
10
10
--
tFilter Sections Only
PRE8ENT LINE
Voltage
Section
Section
1
2
25
25
25
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
150
200
200
200
200
250
150
250
150
250
150
250
150
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
250
300
300
300
300
300
300
300
300
300
300
300
300
25
350
350
300
350
300
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
350
400
350
400
400
400
400
450
300
450
350
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
Section
3
25
25
25
25
25
25
25
25
25
25
25
25
25
25
150
150
150
150
150
150
150
150
150
150
150
25
200
25
150
150
150
25
25
25
25
25
250
250
250
250
250
250
250
12
12
25
25
25
300
25
25
25
25
25
25
25
25
25
25
25
250
250
350
350
25
25
25
300
25
25
25
2~
25
25
25
25
25
25
150
350
350
350
450
450
450
450
450
450
Catalog No.
Capacity
Section Section 8ection
1
2
3
-- 25
25
25
40
25
25
8
25
8
20
25
8
FPT351
FPT308
3N520
8R630
3N525
8R617
3N526
20
3N528
3N532
3N534
40
FPT306
FPT304
40
FPT309
40
FPT311
40
UR183
8
TN120
TN124
20
UR193
8R631
TN125
20
FPT354
20
UR182
TN127
40
TN129
40
FPT357
40
FPT313
20+8
8R613
20
FPT322
2-20
FPT360
20
FPT361
20+8
FPT358
2-20
38570
8
FPT316 }
38572
20
FPT316C
FPT319
20+8
RM255
8
38582
RM257
20
20
FPT359
RM259
FPT362
20+8
2-20
FPT363
8R604
8R607
8
8R602
8R628
FPT324
2-20
16
FPT368
FPT329
20
8R629
8R611
8R632
8
8R622
8R637
38575
38577
TN136
16
FPT328
38578
16
FPT369
20
FPT371
30
38583
8
FPT370
16
TN135
20
SR609
8
8R610
20
FPT374
FPT343
30
38579
8
FPT332
38581
16
FPT333
FPT338
20
20
FPT339
FPT340
20
FPT342
20
FPT346
2-20
FPT382
16
8R615
8
8R616
FPT383
30
MN275
38584
8
RM265
FPT388
FPT389
16
FPT390
1
}
}
}
}
}
}
20
25
20
MINIMUM LINE
Voltage
Section
8ection
Section
2
3
1
50
50
50
150
50
50
150
150
50
150
150
50
150
Section
1
BB14
BB27
BB21
BB25
Catalog No.
Section
2
BBI4
BB14
BB21
BB21
Section
3
BB14
BBl4
BB14
BB14
150
50
BB25
BB25
BBI4
25
150
150
50
BB27
BB25
BB14
20
40
40
8
25
8
150
150
150
150
150
150
150
150
50
150
BB27
BB27
BB27
BB21
BB25
BB27
BB27
BB21
BBl4
BB21
8
8
150
150
150
BB25
BB21
BB21
20
20
20
20
40
20
20
40
20
40
40
8
20
8
8
20
40
25
20
25
20
20
20
25
150
150
150
150
150
250
250
250
250
250
250
250
150
150
150
150
150
250
250
150
150
150
150
250
150
150
150
150
150
50
250
25
150
150
150
50
BB25
BB25
BB27
BB27
BB27
BB34+BB31
BB34
2-BB34
BB34
BB34+BB31
2-BB34
BB31
BB25
BB25
BB25
BB25
BB27
BB34
BB34
BB27
BB25
BB27
BB27
BB31
BB25
BB21
BB21
BB25
BB27
BB14
BB34
BB14
BB25
BB25
BB25
BB14
20
25
250
250
50
BB34
BB34
BB14
20+8
8
25
8
250
250
250
250
50
250
8
20
8
8
250
250
250
250
250
250
BB34
BB34
BB31
BB34
BB31
BB31
20
20
8
20
250
250
250
250
250
250
BB31+BB34
2-BB34
BB34
Bj334
BB31
BB34
8
25
450
450
50
BB61
BB61
BBI4
16
8
25
25
8
25
450
450
450
450
50
50
450
50
2-BB65
BB64
BB65
BB64
BB61
BB14
BBI4
BB61
BB14
8
25
450
450
450
50
BB61
BB61
BBU
8
25
450
450
50
BB64
BB61
BB14
16
8
8
8
8
8
8
25
8
20
8
8
25
25
450
450
450
450
450
450
450
450
450
450
450
450
450
450
50
250
250
450
450
50
50
BB64
BB65
BB68
BB61
BB64
BB65
BB61
BB64
BB61
BB61
BB61
BB61
BB61
BB61
BBM
BB31
BB34
BB61
BB61
BB14
BB14
16
16
8
8
25
25
450
450
450
450
450
450
450
50
50
BB65
BB68
BB61
BB64
BB64
BB61
BB61
BB14
BB14
8
25
450
450
50
BB64
BB61
BB14
16
20
20
20
2-20
8
8
25
25
450
450
450
450
450
450
450
50
50
50
50
150
450
BB65
BB65
BB65
BB65
2-BB65
BB64
BB61
BB64
BB65
BB65
BB65
2-BB65
. BB61
BB61
BBl4
BBl4
25
25
40
8
450
450
450
450
450
450
450
30
20
450
450
450
BB68
BB68
BB65
8
8
450
450
450
BB61
BB61
BB61
8
8
450
450
450
BB64
BB61
BB61
BB34+BB31 BB31+BB34
BB31
BB31
BB14
BB31
BB14
BBl4
BB27
BB61
303
MY E
THE
Section 9 •
I
MANUAl.
TECHNICA I.
h
II
I;
I'
i!
REPLACEMENT RECOMMENDATIONS - QUAD UNITS
PRESENT LINE
Capacity
I
MINIM,UM LINE
Voltage
Capacity
- - - - ---- --- ---------
Cat. No.
Sec. Sec. Sec. Sec. Section Section Section Section
3
2
3
1
2
4
1
4
-- -- -- -- ------ --25
8
16
30
t30
5
40
50
16
8
8
16
20
20
20
40
50
8
8
10 10
10 10
10 10
20 200
10
5
30 20
50 20
5
5
8
8
150
150
150
150
ISO
150
ISO
200
250
150
150
150
150
ISO
150
150
200
250
25
25
150
ISO
ISO
ISO
25
250
25
25
25
10
25
25
25
25
250
40
4
30
40
8
20
8
20
8
16
20
8
20
12
16
15
40
3
8
8
10
18
20
20
50
4
20
40
8
20
4
IS
8
8
IS
8
20
8
2
15
30
2
8
8
10
18
20
20
20
10
10
20
16
20
4
IS
10
10
20
5
30
8
2
10
10
I
8
8
10
9
10
20
300
300
350
350
35(1
350
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
250
300
300
300
350
350
300
350
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450'
250
150
250
300
100
ISO
ISO
350
25
25
25
50
300
350
450
450
450
450
450
450
450
450
450
450
25
25
25
25
100
25
25
25
25
25
25
50
300
25
25
25
25
450
450
450
450
450
450
450
20
4
20
20
16
20
12
20
10
10
20
5
30
10
25
20
20
I
8
8
10
9
10
20
!!
Voltage
-- --- -- -------Sec.
Section
Sec.
1
4N701
8
4S715
20
4N708
40
FPQ407 40
SR6I8
8
FPQ409 }40
FPQ410
SR621
20
UR190
8
8+
FPQ412 30
SR624
8
FPQ415 30
FPQ416 2-20
SR612
8
FPQ414 20
SR626
8
FPQ42 I 20
4S718
8
SR640
16
FPQ426 20
SR625
8
FPQ439 20
SR641
16
SR623
16
FPQ424 16
FPQ429 2-20
UR181
Dis
MN277 } 8
UR191
FPQ434 16
MN278
FPQ435
FPQ444 20
yo
Sec. Sec. Section
3
4
1
2
Section Section
3
4
2
--------- --25
8
20
20
20
20
40
150
150
150
ISO
ISO
150
50
50
50
ISO
150
ISO
50
50
50
25
25
150
150
150
ISO
150
ISO
25
8
250
250
250
250
50
250
50
250
20 25
8 25
8 25
20 25
20 20
20 25
8 25
16 25
25 25
25 25
25 25
25 25
30 30
8 25
8 25
8 25
8 25
inned
8
8
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
250
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
450
250
150
250
450
150
150
ISO
450
50
50
50
50
450
450
450
450
450
50
50
50
50
150
50
50
50
50
50
50
50
450
50
50
50
50
25
25
20
8
40
25
8
8
8
2-20
8
20
2-20
8
20
8
16
8
8
16
8
20
8
8
16
30
cont
8
25
25
25
il
Catalog No.
50
50
11
Ii
Section
1
Section
2
Section
3
Section
4
BB21
BB25
BB27
BB27
BB2I
BB27
BB21
BB25
BB25
BB25
BB25
BB27
BBI4
BBI4
BB14
BB25
BB2I
BB27
BBI4
BB14
BBI4
BB34
BB31
BB68 +
BB61
BB6I
BB68
2-BB65
BB61
BB65
BB6I
BB65
BB61
BB64
BB65
BB61
BB65
BB64
BB64
BB64
2-BB65
BB3I
BB3I
BBI4
BB31
BBI4
BB31
2-BB34
BB61
BB65
2-BB65
BB6I
BB65
BB61
BB64
BB61
BB6I
BB64
BB61
'BB65
BB61
BB6I
BB64
BB68
BB34
BB2I
BB3I
BB65
BB25
BB25
BB2I
BB64
BB14
BBI4
BBI4
BB14
BB68
BB61
BB61
BB6I
BB61
BBI4
BBI4
BJV4
BB14
BB25
BBI4
BB14
BB14
BBI4
BBI4
BB14
BB14
BB68
BBI4
BB14
BB14
BB14
BBI4
BBI4
450
450
450
450
BB6I
BB61
BB61
BB61
8
20
8
8
8
8
450
450
450
450
450
450
450
450
BB64
BB65
BB6I
BB65
BB61
BB6I
BB6I
BB61
20
20
20
450
450
450
450
BB65
BB65
BB65
BB65
•
tFilter Sections Only
REP LAC EMEN T RECOM MEN DATION S - FIVE SEC TION UNIT S
PRESENT LINE
MINIMUM LINE
Voltage
Capacity
Sec.
2
Sec.
3
Sec. Sec.
4
5
Capacity
Cat. No. 1 - - - - - Sec. Sec. Sec. Sec. Sec. Sec.
1
2
3
4
5
I
200
250
200
250
25
25
25
URI88
UR189
SR614
------------------Sec. Sec. Sec. Sec. Sec. Sec.
5
2
I
3
4
1
-
8
8
8
- - ----- -- -- -200 200 200
8
8
8
304
8
8
8
5
5
12
5
5
12
200
450
25
25
25
Voltage
Catalog Number
- - - -------- - - - - - - - - - - - - - -
}8
8
8
8
Sec.
2
Sec.
3
Sec. Sec. Section
4
5
I
Section
2
Section
3
Section
4
Section
5
-- -- -- - - - - - --- - - - - - - - -- - - ---'- - - 8
25
25
250
250
250
50
50
BB3I
BB31
BB3I
BB14
BBI4
8
25
25
450
250
250
50
50
BB6I
BB31
BB31
BB14
BBI4
I
I
I
I
DRY
D. C.
ELECTROLYTIC
CAPACITORS
TRIPLE FP UNIT (FPT)
TYPE MN (3SECTION)
DUAL FP UNIT (FPD)
TYP~ MN (2 SECTION)
r-$-$-, ,-t---t-I
I .h.h I :...L!- .J.: I
, --=r
r 4 -, r-l--, r-l-,
..I.t I
1..u11..LJ-1 I
I I~I
L_-t_1
I
L
L_-=&~,:;
FIG. 78
L~
_J
FIG 79
TYPE MN
(4 SECTION)
'i-1
TYPE
£ ___
,t.
ri-I·
t
1
.
RED
RED
RED
ii~ti~l
Ll=-1--1-J
FIG. 81
BLACK BLACK
ri'
ri'
'i1
:f+' IL~~f:::'-J 1+'
I
'
-I
_...J
L..
TYPE RM
(3 SECTION)
(2 S~CTION)
SECTION)
1
L
RED
r
4
BLUE
-i-
1
11:
-I
Lt-t-'
~
IT- T-l
I
Lf--:f=-r~l
- I IT-I
.......
r-1-,
it Il
I
T-'
1- 1-J
1
+I
I
1
I
I
IT-I
Li-.J
BLACK BROWN YELLOW
FIG. 84
FIG. 83
TYPE 2N OR TN
(2 SEC,.'ONS)
ri-
r~--t-±-l
'T' '-t-'
~
BLACK BROWN
LACK
RED BLUE GREEN
,4-, r-1-,
l i t I I ..L+ 1
I
I
+I
+ I
FIG. 82
TYPE 2P
TYPE 25
RED
OR
YELLOW
OR
RED
R~D
RED
+I
IT-I
IT-I
L_~_J
BLACK
TYPE RM
CM (2 OR 3
+I I
I
__ -,
1
FIG. 80
TYPE
r1-' r-i-,
IT:
L __
~_
_
RN
RED
,.£?l-~-C0-i?l.
,1-...,
r- I-...,
.l.t .it it .l.+ I 1 + I I .l.t I 1 + 1 I .1+ I
I
I
T-' I T-! i I
L.. ___
!1 IT
Lt~ L~_ ~J
-:::;;(CAN)
T- ~ : -~l
--_ ....
- I I
QUADRUPLE FP UNIT (FPQ)
1
• Section 9
YELLOW
r-i-:i;-l
it-it:
L-f-:f-J
L__ ~~_J
BLACK
BLUE
FIG. 85
BLUE
OR
BLACK
:--~I
BLACK
FIG. 86
1
,
~
BLUE
OR
BLACK
r=J.t- :1
____ I
FIG. 87
TYPE 3N OR 'TN
(3 S~CTIONS)
REO,
RED
OR
RED
TYPE 3S
YELLOW
OR
YELLOW GRELN
:1-1;-.:[;-1
1
1
l _____ ~_--J
i-E'
it!
-I
'- __ J
RED
Y~LLOW
1
4N
1
1
+
1
1
L~J
I
BLUE
FIG. 89
FIG. 88
TYPE
r-t-·
r~-ti;l
T- --r-L-j----t-- J
BLACK
BLACK
YELLOW
OR
GREEN
TYPE
4S
(4 SECTIONS)
RED
RED
Y~LLOW
OR
OR
YELLOW GREEN
Y~LLOW
OR
GRE~N
:-t--t-:t-.tl ,1-1
:i:
I
L_____ ~----J LJ-J
I
LJ:J
BLACK
FIG. 90
fiG. 91
305
MY E
THE
Section 9 •
TECHNICAL
MANUAL
~EO] [RED]
-£+,
rffl I--i-, r-f-,
+
+
I,
"I
I
rf-li:1 1:-[1
'-f
.--f-.,,
,,
I
,
II
1
I
LrJ
L¥J L+.J I~JJ
1
LJJ
L:[_+-J
(ilLACJ<.]
SR601U;ARTON]
BB64
BB61
B8S1
BBI4
,
ri,
rI~
I
I
I
I
I
'
'
1
IL_ =-'I
=J
I;
L_ .=J L-:...::-J
[BLACJ<.]
LY_J
8B61
I
BB61
SR6OS[CAN]
BBI4
[BLU~
8661
lit, '--f-' ,.--.t~'
rtitii II'
II'
, '
L__J
I
I
,
1
,
,
1·*1
,
L:!-l-!J
,
L
__ ..JI
[BLACJ<.]
I
L~
/i>LAIN]
BB61
SR608[TUBJ;]
BB61
8BI4
+
I
L __ ~_~:~J
6861
SRell ~ARTON]
8BI4
'
I
I
I
I
J
I
L
__JI
B814
I
i
BB61
BB61
1
L ___I
BBI4
B881
_L-
,
I
I,
"
,
I
I
I
I
,
L __ J : __ J
BB25
8B25
8B81
IS.200V.
~f::' .--11h~--,
rf!31 1:rlJJ11
Iii"
L::-"
L¥-l)
,
181'IOOY.
SR613Ii;ARTON]
FIG. 103
BB34
BB34
BB
FIG. 104
,
If,
r11
'
i
±rt'
:T: :r: :1:
L____
~tl
L*-!-!l;:-~j L =JI
I
I
I
I
1
I
I
I
I
I
~_ -=J
L"":.-:"J
BB31
BB31
[YELLOW]
SRSI4[CARTON]
I
30C!'200Y
+
rI~f~r~l~:Cl
,
,
'
FIG. 102
rf-!----i-l if,
'-f,, n=tl I±~l
L__
L__ J
_J
LYE~J I_!. ! '-I'
"LlJI'
[ORANGE]
!jvHITE]
~EtN]
81'45011.
81'250V.
12E'25V.
,
. [RED]
IjILUE]
.J
1-
16E'200Y
SR 112 [CAN]
I
'
B861
'-
[BLUE]
16el001l.
+
L-t
I
I
, - i 'I
[BLACJ<.] -
FIG. 101
[RED]
[REQ)
8IP3S0V 81'350V
I
I
I
,'-_I I.J I.I_I
,
1
L~_I-_~J I
I
LJ-J
BB61
,
,-- -,
rf,
,, ,,
,
+
,1-f-i-1
I
,
,
8B61
[BLUE]
2SE'2SV.
+6IP3~OV.
r-f~'
r£O:L.~t--~t-f-l
B861
FIG. 100
6E'~5011.
SR610[CARTO~
ZSI'2SV.
FIG. 99
+
8B61
BB27
BBZ5
,BE'40011.
2S.2511.
81'40011.
+
_
SR60sIi;AN]
FIG. 98
SR607Ii;ARTON]
I
I
IT~-r.1
L____ ___~~
_J
B8S1
FIG. 105
I
,
L~_J
Il'
I
,
J
II'
1-
8814
BBI4
SR6IS[CAN]
I,:
r-f- ri'
-i'
L1-J
J LlJ
+ +
:i-1-r-1
+
t
FIG. 97
sR60e[cARTo,;j!
[RED] [RED]
181'400V. 81'40011.
SE'12V.
[RED]
41'30011.
,
I
t 1 iL_:.Jl
L.:-J
[BLAC 1\] [BLUE]
FIG. 96
BB61
I'
I
I
L1--i)
J ~ __J
L
'llJll
-
r1' '~l-'
I~-l
li~l :±~l
ri-11I
FIG. 95
SR604[CARTON]
BB27
IjIEO]
I
I
BB61
61' 350V 6 .. 350V.
+ +
I
L__ J
I!,
~UMMY
SR 603[TUBE]
8.35011. 8E' 35011.
rr'
It I ,:r '
L-"T--T:-?:J
306
I
FIG. 94
BB61
~EO] Iit£o]
rf~f~tl
[BLACI\J
L_
FIG. 93
IitEOJ
(ilLU£)
31'300V.
6 .. 12V,
EtELLOW]
+
I
[BLACI\](ilLACI\]
FIG. 92
IYELLOW]
61' 30011.
rrT: '
811P 300V 301lP3011.
12 .. 30011. 8E'300V.
BB81
FIG. 106
BB81
8B81'
DRY
D. C.
[REO]
8-&@450V.
ELECTROLYTIC
CAPACITORS
• Section 9
[YELLOW]
8"'350V.
iA-f~l
L~_~J
[PLA.Nj
-
SR6IS[CAN]
8B61
BB61
SR617[CAN]
BB61
BB25
!yELLOW]
5@'5011.
[RED]
20-101i"50V.
[PLug
5!!'25V.
[RED]
151i'35V.
:±~h-fl
[RED]
5@35V.
:-r-[:
L¥_¥J
!i;REEN]
L¥J
[SLACK]
5R6.8[CARTON]
8B2.
BB25
B1525
[BLACt\]
SR619 ~ARTONJ
B814
FIG. 109
[RED]
'61'20011.
30@ 150V. 10!!' 150V.
fs;REEN]
5@5011.
8!!'20011.
lit, -1'
rf-f-i±f-l IT'
Irf-i :~I'
:r l:r LJ-J
L----i=----J L __ L=-._J
r:.cS:--! :-1-1 r-l-l
1
I
L~J
lL'TTTI
BB25
J
BB34
•
I
I
•
I
I
I
BBl'
I
I
IL ____
L "i" "i"
1= ___ .JI
I
r±-t~ -I~
I
I
III
I
I
Ll'J
&B61
BB61
5R623 [CARDBOARD TUBE]
BBI4
I
I
l _I
'
L-=.-
L2"_~y-_!.J
SI\624[CARTON]
I
I
J._J
L~
1-
BB61
BB6'
•
I
I
&814
FIG. 114
[YELLOW]
10@'50V.
[BLUE]
rf-·
I
I
I
L~_J
BB64
FIG. 113
I
I
BB2.
BB2'
~LACI<]
~LACK]
iii rf-
["-£-1
I
[RED]
[yELLOW]
51!' SOY
B1!'450V.
[BLUE]
[YELLOvil
I
I
I•
I
:rf~fl~1·
I
I
I
I
BB61
BB61
-
[BLACoiJ
BB34
r-I+~I
I
I
i_¥_yJ
ltJ I_l-J 'I'
L~J LJJ
BB61
BB61
I
LJJ
I
[GREEN]
5R 625 [CARTON]
BB2'
FIG. 115
!"!tED]
L-=-:J
rf-,
rti
iI-itrIl
:r
L-JJ
L_ :-.J
rI~f~rt5~.
I
I
[GREEN-BROWN TR]
[REt!]
2 Ii' 450V.
'6@450V.
[YELLOW]
[GREtN]
25P2SV.
21!'450V.
i-f-l rf-I
ri-±t±-t.: !r:
r-f-'
iL_t_J I .
SR622[CAR.TON)
:
I
I
I
FIG. '12
I}yH.TE]
!"!tED]
12@25V.
8P350V
!i>-EO-WH.TE TR]
8!!'350V.
[REt!]
4E'300V.
I
i
I
[BLACK]
SR62' [TUBE]
FIG. 111
L~-f-=--~J
I
I
[YELLOvij [&LACK]
BB27
SB2'
!i;REEN]
5@50V.
~LUE]
L1-IJ L:tJ
BB21
FIG. 110
[RED]
SR620[CAI\TON]
8B.4
BB25
FIG. lOa
FIG. 107
B&2'
BB2'
FIG. 116
[GREEN]
BE'450V.
[PLUE)4@.50VIYELLOW]
4P300V.
41!"50V
12E'25V.
4P150V.
iTT-I-f-! :1-:
ITTTT"I'
L-----k -___ J
[JILACK]
SR626 [CARTON]
--1-- r-I--'
I
FIG. 117
I
I
L-J_J I~J-J
L__ =_J
BB61
1I '
I
I
I
BB61
BB2.
B&14
SR 627 [CARTON]
BB61
BB61
FIG.11a
307
MY E
THE
Section 9 •
TECHNICAL
~LUE]
~LUE}
[flED]
SE>300V
6E>300V
MANUAL
[ORANGE]
IOP2SV.
[REO]
4@300V.
6@350V.
10@25V.
'f~
:±-±-±:
l¥--1)
'1-: 1+:-1 - r±~-:
:~-i+l
1
I
'+:
L_) 'T'
L_ =)
L_.:::J
LJ:-J=l) :t!
1
[GREEN] /.PLAIN]
I
I
:t
I
I
1
I
1l
__ J '--=-'
L _J
1 t 4~
J1
[BLACK] [GREEN]
SR628[CAN]
BB61
BB61
BBI4
B814
BB61
BB61
SR 629!S:ARTON]
FIG. 120
FIG. 119
[REO]
16l"ISOV
·1,
Ir I - 1I
I
I
I
[BLUE]
10l"2SV.
[YELLOW]
B@150V.
[YELLOW}
61!'3S0V.
[RED]
[BLUt;]
4l"ISOV.
161!'150V.
12l"ISOV.
i!lLUE]
161"2SV.
·f,
rf-)i.-i 1r±:=, .i!T:t, :-11-,[-: 1-1-' :fi 1If-I
:±-±--f-l'iii:J rfl
L¥-iJ ___I It! L-¥-1J i~llr l_~+-_IJ i:r : 'f Li-J
I
1
I
I
1
[RED]
4E>l50V.
I
I
I~I
L
__ ~
L_ .=J
I
:
I
I
I
_L __ J L_.:::J
L __ J
BB34
BB34
5R631 [CARTON]
BBI4
I
J i_~~J
[ilLACK]
[GREEtj) [SLACK]
[GREEN] (BLACK]
SR630 [S:ARTON]
BBll
BB34
BBZ5
BB61
SR63Z[TUBE]
FIG. 122
FIG. 121
BB61
BBI4
FIG. 123
[RED]
[fLAIN]
12C!'100V 4@>100V
[RED}
[BLUE]
6@250V 6l"Z50V.
[RED}
r-ff-1 rf-i
1
r~Lt-tJ it! ! +-:
r~-:
'-.[-1
I
L_ )
L:r-_~) It! itl
L ___ J
S831
SR633[TUBE]
1
1
L
[YELLOW] [8LACt\]
611> 400V. IZII>400V.
SR634[TUBE]
(BLAct\I[8ROwtiI
BB31
I
:::.-'
12E>150V.
[RED]
[SLUE]
8i!'350V.
ZOI!OZ5V.
[YELLOYil
B@350V.
:
J.
I
I
~±t,
l~_t-~J
I
L_:J
If
L~_J
L~
it:
1
1
1
I
1 I I1
'- _ _ J
L ___I
1
:__ =J
I
BB61
SR615[CAN)
BB&4
8Bl4
BB34
FIG. 126
[RED]
[GREEN]
B1!'450V.
B@450V
if-:
:tt-t-! It: I-t-: ITI
I
~f'
,-B,::t,
FIG. 125
FIG. 124
i--ftJ±-l
I~I
L_l::._ ::....J
11JJt
r
1
1
J
1.. _ _
[BLAC..;]
:.,.. I :
1
__ -'
~
f!!I..AC~
8IP4S0V.
SR637 [TUBE]
BB61
BB61
BB61
SR63B(CAN]
FIG. 128
BB61
SR639(CAN]
BBSI
FIG ..129
BB61
8B61
FIG. 130
--I'
r-±+I -T-':
I
1
I
1
1.._
SR64 0[TUBE)
BB61
BBI4
BB64
BBI4
SR641 [TUBE]
I·r!
I
1
IL _ _ ...II
_...I
BBS4
FIG. 131
BB61·
BBI4
BB61
FIG. 132
10E> 450V.
,.._±::t_,
,
I
I
L_
I
'+1
ITI
I
LGREENj
8 (II 450V
12 " 4S0V.
r-!:l-,
I
I
1
I
I
L __
__J
::.J
~--
i---ifl±---: -.:'-101-,-t_,
...c:-:L. '
I
I
I
I
I
L__
LI--J~j It:
I
I
.:.._J
itl
I
I
I
I
I
I
,- __
-=J
WLAIN]
8~ 4S0V
BB61
FIG. 133
308
I'
[RED]
8@4S0V.
(1-1±: II-I r-r-I
I¥I
L_-w-=-_J
_J
BB21
FIG. 127
[BLACK]
SR642 [CAN]
1
1
I
L ___
I
I
SRS43 [CAN]
BB61
,
BBS4
FIG. 134
SR644[CA~
BB64
FIG. 135
SR645 [CAN]
BB61
FIG. 136
BB81
1.1
e Section 10
THE
MYE
TECHNICAL MANUAL
Practical Radio Noise
Suppression
MALLORY
Section 10 •
THE
MYE
TECHNICAL
MANUAL
PRACTICAL RADIO NOISE SUPPRESSION
F or years radio listeners have endured
the buzzes, roars, crackles and crashes
of "man-made" static with their music,
under the impression that such annoyances were inevitable. However the public has awakened recently to the fact
that these "man-made static" noises can
be eliminated, or reduced in intensity
to the point where they are no longer
annoying. As a result, numerous municipalities are passing ordinances making it a misdemeanor punishable by fine
and imprisonment, to operate equipment and electrical appliances which
interfere with radio reception. Some
cities and towns are even employing
specialists to locate and suppress radio
interference.
Whether by compulsion of law, or by
the force of public opinion, man-made
static is on the way out. The Serviceman
who understands the simple principles
of noise elimination can profit amply
from his knowledge. It is the purpose of
this chapter to describe in simple, nontechnical language the practical proven
methods of eliminating all types of manmade radio interference.
All noise interfering with radio reception falls'in two general classes. First,
atmospherics, and second, so-called
"man-made" static produced by electrical devices and appliances. Since the
reduction or elimination of the former
is possible only by special methods of
reception and transmission we will give
it no further attention, and the word
noise, as used hereafter, will mean only
interferences caused by electrical apparatus and appliances.
Many kinds of appliances produce
radio frequency impulses which travel
out through the air exactly the same as
the signal from a broadcasting station.
Also some appliances radiate back
through the power line unless stopped
by an impedance or capacity which may
absorb them.
Sources of Radio Interference
Most radio noises' are produced by
one of three sources. First, disturbances
in the power supply and transmission
310
lines, caused by leaks to ground or other
conductors through tree limbs or anything they may be touching, leaky lightning arrestors, cracked insulators, insulated tie wires, loose pieces of wire
hanging on a line, or even defects in the
generator. Second, by commutating devices, such as the commutators on motors and other apparatus. Third, by
appliances which make and break the
circuit such as thermostatic contacts on
heat pads, flashing lights, incubators,
and other similar appliances. Each noise
source requires different treatment.
Remedies for various noise sources will
be given in the order named.
The general location of the noise can
be determined from the following simple observation. If the noise is absent
or greatly attenuated in neighboring
homes, it may be' assumed that the noise
is originating in the building, or in the
lines leading to it. On the other hand, if
the noise is about equally prevalent in
an entire neighborhood, it may be assumed that the noise is originating externally.
Tracing Outside Interference
It is best to always determine whether
a noise is reaching the radio through
the air or through the power line. This
may be done quite easily by using a
good portable radio working on a set of
self-contained batteries. In fact there is
no better noise finder than a sensitive
portable radio. Since portable receivers
use a loop antenna which is quite directional it is often possible to locate the
source of noise by rotating the radio to
the loudest point, then moving in the
direction the loop is pointing. If the
noise increases, you are moving toward
it, and if the noise decreases you are
moving away from it. However, in many
cases, probably most cases, it will lead
you to a point where a group of power
lines converge at a transformer.
Do not make the mistake that most
have made and place the blame on a
supposedly leaky transformer. The odds
are 100 to 1 that the transformer is in
satisfactory condition, and the noise is
being carried by one or more lines lead-
ing to it. True, transformers do leak and
cause noise, but only in less than one
per cent of th~ cases where they are
blamed. The proper procedure in this
case is to follow each of the lines and
compare the noise level under each. This
will genenilly lead to the source of the
noise, or at least give a good idea as to
its location. The loop of a portable radio will point in the direction from
which a noise is being received until
quite close to it, then the loop will pick
it up best at right angles.
If the area blanketed by the interference is so large that tracing with a handcarried portable receiver becomes excessively tim~ consuming, assistance
may be had from your automobile receiver, provided the ignition noise is
well suppressed. In such cases the best
procedure is to circle several blocks to
find the area or areas where the noise is
loudest, then use the portable radio for
tracing. Pulling the main switch of a
building will definitely show whether
the noise maker is in that circuit or not.
If the noise continues, th"at building is
eliminated, but if it stops when the
switch is pulled, the offending apparatus
is on that circuit and should be very
easy to find.
Transmission Line Noise
In every city and town there are numerous places where wires touch tree
limbs or other objects and cause serious disturbance. Even a single leaf has
been known to almost destroy radio reception over an area of several blocks.
In case the leak is on the secondary side,
the disturbance usually does not affect
any but the homes served by that transformer, but when the leak is on a primary line it may travel all over the
system and become a major annoyance
over a large area_
Cracked insulators are hard to locate
but a good portable will usually detect
them as the pole is passed.
Insulated tie wires form high ratio
step down transformers and after a year
or so the insulation becomes defective
resulting in considerable noise. It seems
I
il
it
IiI
I
PRACTICAl. RADIO
at first thought that such a little thing
could not produce noise, but it is a
proven fact that they do.
"Hardware noise" results from the
same effect. Here is a typical example.
In this case, the noise carne on in the
evening in the form of a harsh buzz or
hum with 60 cycle component and was
so strong that radios in two adjacent
houses could not be operated. The usual
checking and pulling of switches showed
that it was not in any of the houses and
the power company was notified. Their
man arrived about noon and the noise
had stopped. As soon as he left it started
again. The noise was on and off at odd
times for several days and then appeared
only at night, remaining all night. The
source.of the interference finally was located on the transformer pole where a
steel bracket carrying an insulator barely touched another bracket supporting
the transformer where they were both
lag screwed to the pole. Clamping the
two brackets firmly together or completely separating them stopped the
noise.
Patrolling the lines many times at
different hours of the day and night
with the cooperation of the power company, and correcting the troubles found,
will make a wonderful improvement.
Care must be taken to consider that
wires loosen in day time and in warm
weather, and tighten at night and in cold
weather, so that a wire which clears a
limb nicely at one time of day may lie
against it at another time.
In this connection we want to warn
very earnestly, never touch or come
within several feet of any wire unless you absolutely know that it
carries low voltage. It would be safer
to allow a power company employee to
handle everything near their power
lines.
Power is usually transmitted at voltages of 13,500, 23,000, 33,000 and
higher. Usually this is stepped down
through a transformer to about 2,300
or 3,600 for distribution about the
streets to other transformers which reduce the voltage to 240 with a grounded
center giving 120 volts on each side,
providing service to the homes. Leaks or
other disturbances on the 240 volt secondary may be just as violent as on the
higher voltages, but generally do not
cover so much territory and are easier
to locate.
NOISE SUPPRESSION
The remedy for power line noises is
obvious-remove the cause. When the
noise-producing condition is located on
the property of the public utility, your
job is only to locate the cause of the
trouble and report it. Public utility companies invariably are glad to correct
any actual defective conditions of lines,
poles, and transformers because not
only does the elimination of radio noise
produce a greater sale of electricity
through the increased use of radio receivers, but also they are safeguarding
their equipment by preventing causes
of breakdowns.
When you find a piece of hay baling
wire hanging ~n a power wire, do not
touch it or attempt to remove it
yourself as you will be risking your
life for nothing and may accidentally
short the line, blowing fuses or damaging expensive machinery. Call the power
company, giving the numbers of the
poles between which the wire is located
and they will send a man equipped to
remove it safely. They will also trim tree
limbs which touch or corne close to their
lines when attention is called to them.
However there is an old feud between
tree owners and power companies, and
in cases where the owner objects to trimming and it is impossible to move the
wires without too much expense, it is a
case of explaining to the owner that he
can have either tree or radio, and m
most cases he will be reasonable.
'
The Elimination of Line Noise
at the Receiver
Conditions will be found where noise
has a multiple origin so that the elimination of the noise at its source becomes
either impractical or unduly expensive.
Also, the owner of an offending appliance may refuse to permit the installation of a noise filter. In such cases, the
only recourse is to eliminate the noise at
the receiver. Mallory builds a filter
especially for this purpose, type Z6 (see
description, page 323), which is easily installed by plugging it into the wall
socket from which the receiver is operated. The attachment plug of the receiver is then plugged into the filter. The
Z6 is provided with a binding post. A
wire should be attached to this post and
run to the nearest good ground. This
may be a water pipe, or even the
screw holding the outlet box cover plate
• Section 10
in place, if the outlet box is grounded,
which will probably be the case if the
house wiring is in pipe conduit. A good
ground is necessary to secure the maximum filtering effect.
It should be understood at the outset
that a line-noise filter can only drain the
noise-producing RF energy from the
power line at the point where it is attached. A line-noise filter will have no
effect on noise that is picked up by the
antenna, since if the antenna is in a
noise field, the noise will be transferred
to the receiver.
The antenna can be tested for quietness by connecting it to a batteryoperated receiver. If the performance of
the battery-operated receiver is satisfactory from the standpoint of noise, it
may be assumed that a noise filter installed at the receiver will eliminate or
greatly reduce the noise.
If the antenna is noisy, the case is by
no means hopeless, sinc~ it is usually
possible to relocate the antenna in a position where it will' be comparatively
interference-free. In most instances, the
best location for the antenna will be at
right angles to the power line carrying
the most interference. In rare instances,
it has been necessary to move the antenna several hundred feet from the
receiver to secure a noise-free installation. Such remotely located antennas require the use of a shielded lead-in,
preferably of the co-axial type, with
suitable coupling transformers.
Lead-in Noise
An ordinary exposed-wire lead-in will
act as a part of the antenna, and may
contribute more noise than the antenna
itself, because a comparatively strong
coupling may exist between the lead-in
and house wiring carrying noise.
There are two ways of attacking noise
that is being picked up by the lead-in.
The most obvious method is to use a
shielded lead-in. A noise filter at the receiver will help lower lead-in noise pickup since.the presence of the filter on the
line will lower the RF potential of all the
associated house wiring in the immediate vicinity.
Further and usually effective help can
be obtained by installing a second filter
in the house wiring near the point
where the service wires enter the build-
311
Section 10 •
THE
ing. This prevents the entire house wiring system from acting as a transmitting
antenna for any incoming noise from
the outside power line. It is often the
radiation from the house wiring that is
picked up by the lead-in or loop of the
receiver, that causes the real trouble. If
the noise can be stopped at the entrance
to the house wiring, the source may
then be so far removed as to be inconsequential.
. The simplest and least expensive installation of this kind consists of mount,ing a capacitor type filter, Mallory Wll
(see page 322 'for description) in the
fuse box of the house. Bolt the mounting
strap of the filter to the fuse box, first
scraping the paint from the box to insure a good, low resistance connection.
For a two-wire installation connect each
lead of the filter, type Wll, to a fuse
holder terminal on the load side. A
three-wire system with grounded neutral is handled the same way except that
the filter leads connect to the two "hot"
wires only. A three-wire installation,
either three-phase, or with an ungrounded neutral, will require the use of
two filters, type Wll, one lead from
each filter connecting to the third wire.
The remaining leads of the two filters
are then connected to the other incoming wires, all connections being made to
the load side of the fuse holders.
For a truly de luxe installation of this
kind, the entire power supply of the
building could be filtered with a combination inductance-capacity filter such as
the Mallory type LB40 (see description,
page 323) providing the maximum
current does not exceed 40 amperes.
Such an installation would provide maximum isolation between the building wiring and the outside service wires. This
arrangement would be especially suit,
able for police radio stations where the
best possible reception of weak highfrequency signals is desired.
Appliance Noise
Noise-Makers in a Typical Town
01 5,000 Population
325 Vacuum Cleaners
70 Fountain Drink Mixers
65 Electric Drills
50 Home Mixers
30 Stationary Motors of various kinds
15 Hand Sanders
312
MYE
TECHNICAL
MANUAL
25 Washing Machines
25 Neon and Flashing Signs
35 Electric Shavers
30 Electric Sewing Machines
10 Electric .Cash Registers
9 Electric Refrigerators
5 Violet Ray Machines
5 Dentist's Drills
2 X-Ray Machines
1 Garage Spark Plug and Coil Tester
I Flat Iron with Automatic Heat
Control
10 Miscellaneous Interferences
The above noise-makers were actually
found in one town and indicates generally what may be expected for each
5,000 population. Among the 10 listed
as miscellaneous are some unusual
things to be dealt with later. The term
"noise-makers" refers to appliances
actually found to be making objectionable noise-the list does not include appliances of similar types found to be
reasonably noise-free.
Commutating Devices
Commritating devices from the largest
motor down to electric razors are responsible for various degrees of interfeFence. Large three-phase motors
seldom produce enough interference to
worry about. In fact few large motors of
FY kind are very bad, and motors havmg no brushes or commutators do not
interfere at all, unless defective.
Brush type motors, either shunt, compound, or series wound produce noise,
the violence of which varies inversely
with their size and directly with their
speed. The little drilling and engraving
tool which is held in the hand is an example of the worst interference to be
found. Brush type barber clippers are
practically the same, and several types
of electric shavers, especially those using a direct make and break commutator are also in the same class.
Thermostats on heat pads, incubators,
electric irons, and various kinds of
. flashing lights are a serious nuisance.
Cases have been found where a heat pad
practically ruined reception all over a·
town of 2,000 for weeks. Flashers on a
single small lamp interfere with radios
in the same house or on the same circuit
but rarely reaCh out far enough to annoy the neighbors.
Ability to identify and locate these
disturbances comes with practice and
after a few months of constant practice,
one can tell quite definitely from the
sound, just what kind of apparatus is
producing it.
I
"
"
Silencing Commutating Appliances
The simplest standard filter for stopping or tuning radio noise out of range
of the radio receiver consists of two
, condensers connected in series across
the electric line, with their center point
grounded, and installed close up to the
apparatus. In this case ground does not
mean earth, but the metal frame of the
machine. True, it is good practice to
ground the frames of all motors and
other electrical apparatus to earth
through a water pipe or other good connection, but such grounds seldom reduce noise very much unless the connection to earth is short.
P. R. Mallory & Co. now is producing,
at reasonable cost, suitable pairs of capacitors scientifically placed in metal
cans with mounting brackets haoving
greater superiority in compactness, ruggedness and ease of application than individual condensers. Since they are designed for continuous service across an
A.C. line, these special twin capacitors
have extra heavy insulation so that they
will be durable and trouble-free. Special
care has been taken in the design of these
units to pr.ovide the lowest possible RF
impedance. Metal cased twin capacitors
for radio noise suppression service may
be purchased as Mallory Noise Filters,
types W7, W7A, W9, and Wll. (See
description, page 322.)
Practically all of the stationary appliances can be silenced by filters containing two capacitors of suitable value.
However we find some appliances, such
as mixers, electric drills and sanders
which must be held in the hands while
using, and for them the twin condenser
filters are unsuitable because when the
operator gets on a damp floor or touches
some grounded object he may be subject
to a small electrical shock.
This makes necessary another type of
filter containing a third condenser connected between ground (the can) and
the common connection of the other two
condensers which are in series across
the line. This third condenser only
slightly reduces the filtering effect.
The shock-proof, three-capacitor types
I
PRACTICAL RADIO NOISE SUPPRESSION
of noise filters are available as Mallory
types W7SP, W9SP, and WHSP.
Since noise or radio interference is
RF energy it can be attenuated by in·
ductance in the circuit. In many applica·
tions, the windings of the appliance may
possess considerable inductance so that
the combination of the appliance windings plus a capacitor-type filter will
provide a complete capacitor-inductance
filter of high efficiency. However, where
the inductance of the appliance is low,
or where a greater filtering effect is required than obtainable from the addition of capacitors alone, combination
inductance-capacity filters are used.
These filters employ RF choke coils in
addition to the usual condensers.
Mallory filters of the combination inductance-capacity type are catalog Nos.
Z2, Z4, Z6, Z8, Z8A, LC5, YClO, and
the heavy-duty box type filters LB5 and
LBlO.
Another noise suppressor of a different type is used on oil burning furnace
igniters, spark plug and coil testers, and
in other places where high frequency
and high voltage are present. These will
be described fully later in this text.
It has been quite customary for filter
manufacturers to recommend that capacitor-type filters be connected to the
brush holders, and for some types of
motors or generators this probably is
the best connection. However, for small
motor-driven appliances equally satisfactory or even better results will usually be obtained by simply connecting the
filter leads to the motor power leads as
close as possible to the point where they
leave the motor. The two most important points to be observed when installing a capacitor-type filter, or a
noise filter of any type, is that the minimum length of wiring be included in the
exposed leads, and second that a really
good ground connection be made to the
motor frame. On some types of filters,
the ground connection is automatically
made when the mounting strap is bolted
to the motor or appliance frame. When
using such filters, the paint or enamel
should be carefully scraped from the appliance or motor frame at the point
where it contacts the filter mounting
strap'to insure a good, low resistance
electrical connection.
We will take up the various appliances in detail, in order, according to
the number in use and give detailed information concerning them.
Vacuum Cleaners
Vacuum cleaners, being more numerous than any other electrical appliance,
cause a very large percentage of the total
radio interference. Each one 'contains a
small, powerful brush type motor which
turns at high speed causing terrific
noise over an area varying with the location, the climate and the condition of
the motor. For example, in Northern
Michigan where reception is not too
good, places were found where a vacuum cleaner could be heard with annoying volume all over a small city. In other
localities where reception is better, the
volume control of the radio would be
run muqh lower, .and the same cleaner
probably would not interfere seriously
at a distance of over one block. However with several cleaners in each block,
each used at least 15 minutes a day, they
become a major problem.
Since vlcuum cleaners are used on
dry floors, the Mallory W7 filter consisting of two condensers in series, with
common grounded to the can may be
employed with very satisfactory results.
The leads are connected across the line
at or near the point where it enters the
case and a screw is raised and tightened
down on the mounting bracket. This
must make good contact to the metal
frame of the machine, and if no screw is
available, a hole must be drilled and the
bracket fastened with a self-tapping
screw. Care must be taken not to drill
into the windings, and to see that the filter does not interfere with the handle
bracket or other moving parts. Many
cleaners have a pair of binding posts on
the case covered with a stamped metal
cover, making the connections easy by
removing the screw that holds the cover.
Others have a spring wire shield around
the cord, extending from the case to the
lower end of the handle. This can be
pulled loose from the handle and slipped
back far enough to splice on the filter
leads.
Little difficulty will be encountered in
silencing most cleaners, and in four
cases out of five a Mallory W7 will do a
satisfactory job. Occasionally a bad
one will require more capacity and
can be taken care of by a W9 or WH.
These two filters are similar to the W7
• Section 1Q
except that the capacities are higher.
Some models of Hoovers are hard to
silence, especially the two-speed type.
Some of these have bakelite cases and
one must be careful to find a ground
that is really grounded to the metal
frame, otherwise the filter will have little or no effect. In the two-speed type
you will find three wires crossing the
front under the outside cover and directly under the lamp. Usually a .25 mfd.
condenser from each of these wires to
ground will make a satisfactory job.
There is little room and it's a tough job,
but can be done.
Use the W7SP shock proof' type on
the little cleaners employed for upholstery as there is more danger of shock
from them.
Plug type filters on the far end of any
long appliance cord, especially cleaners,
are less effective than filters mounted
directly on the appliance. While they
may keep the interference out of the
electric light line, there may be twenty
feet of cord left to radiate the noise and
part of the effect of the filter is lost.
Drink Mixers
The ne;x:t most serious and numerous
radio interference producers are fountain drink mixers, consisting of small
motors mounted on cast-iron pedestals
about fifteen inches high. These devices
may be seen in groups behind almost
every soda fountain. The mixers employ
small, high speed, brush type motors.
With a few of these operating in each
block radio reception is almost impossible.
Since these machines are usually operated by girls standing on a wet or
damp floor who frequently touch the
machines with wet hands, the installation
must be absolutely shock proof. Use a
W7SP or W9SP across the line inside
the metal frame wherever it will provide
sufficient filtering. For the most severe
cases of interference, use a Z8A if the
filter may be bolted to the frame of the
mixer. Otherwise, cut the A.C. cord
close to the motor and install male and
female plugs on the cord ends so that a
Z8A may be inserted in the circuit. In
all cases it is preferable to have the filter
or condensers connected to the load side
of the switch, that is, so that the con·
densers are not across the electric light
line except when the apparatus is in use.
313
Section 10 •
THE
If an A.C. milliammeter is placed in
series with a I mfd. condenser across a
120 volt 60 cycle line, it will show a load
in the order o( 50 milliamperes whictt
might lead us to believe that it was pulling and wasting something like 6 watts.
However this is not the case, for the energy the condenser stores on one·half
cycle is put back the next, wasting only
the power factor loss which in well con·
structed paper dielectric capacitors is
negligible. Therefore the loss through
any good condenser across the line is
negligible. It is preferable to place noise
filters on the load side of the switch,
when an appliance is operated at inter·
vals, merely to prolong their life rather
than to save power.
Electric Drills and Sanders
Electric drills, used mostly at garages
and machine shops, and hand sanders
which are essentially the same thing ex·
cept that instead of turning a drill they
turn a sandpaper disc, cause very bad
interference, quite similar to drink mix·
ers. Sanders are almost always in a
noisy condition, due to grit getting inside and chewing up the commutator,
brushes, brush holders and· bearings.
Drills are usually in a better condition.
These appliances are a serious problem for since they are used on damp
floors and must be held in the hands
they must be shock proof. At the same
time they require a considerable amount
of filter with little space for mounting it.
These devices are handled roughly and a
filter. must be mounted securely in order
to avoid being knocked off within a few
days, also anything on the outside is
likely to be in the way of the operator.
Most electric drills and hand sanders
are factory equipped with a three'conductor cord, the third conductor being
intended for use in grounding the frame
of the appliance. However few garages
make provmion for this ground connection at the socket. Further, when the
cords get old and worn, mechanics al·
most invaril.lbly make replacement with
a standard two·conductor cable. For
these reasons it is imperative that a
shock-proof filter such as the W7SP or
W9SP be employed. In some instances
it will be possible to mO,unt the filter in·
side the handle, or within the end cap of
the motor housing.
314
MYE
TECHNICAL
MANUAL
If a satisfactory location cannot be
found for mounting the filter on the
drill, then recourse can be made to the
Mallory Z8 filter mounted at the far end
of the cord. A three· wire cable should be
used for the drill or sander, the third
wire being employed as the return lead
between the filter and the appliance
frame. The best arrangement is always
the one which uses the shortest return
wire to the appliance frame.
Home Food Mixers
Home mixers are in the same class
with electric drills. However in most
cases there is no room for condensers
inside and little space outside for satis·
factory mounting. Women do not like
to have their appliances look unsightly,
therefore care must be taken about appearance. The neatest and probably the
most effective installation for home mix·
ers is to use the Mallory Z8 noise filter.
Installation is made by cutting the A.C.
cord close to the motor, thc:w. installing
male and female plugs on the cord ends
so that the filter can be inserted in the
circuit. If the design of the mixer is such
that the filter may be bolted directly to
its frame, filter types W7SP, W9SP, or
Z8A may be employed, the choice de·
pending on the severity of the interfer·
ence.
Large Motors and Generators
Large alternating-current motors used
for the operation of heavy machinery
seldom produce much interference;
some types such as three·phase induction motors which have no slip rings or
commutators are inherently noise-free.
Single-phase motors of the shaded-pole
and capacitor types are also noise-free
when not actually defective. Repulsion
start induction motors normally produce interference only during the starting cycle, although if the motor parts
are badly wQrn they can create a terrific
continuous racket. In such cases the wise
thing is to see that the motor is properly
adjusted before attempting to apply
noise filters. In general, however, brush
type, series, shunt and compound wound
A.C. and D.C. motors and generators
are the principal noise-makers.
,The large, box-type Mallory Noise
Filters types LB1O, LB20 and LB40 (see
pages 10-15) , intended for installation in
the power line near the motor, are recommended for permanently connected
motors and generators with loads up to
40 amperes, maximum, and 230 volts
A.C. or D.C. maximum. Larger motors
whose power requirements exceed the
values given require special treatment
described later. The installation of the
appropriate LB filter will probably reduce the noise to a negligible value-if
not, the installation requires the connection of Wll filters to the brush-holders
as shown in Fig. l.
Generator field excitation control
leads will conduct and radiate interfer·
ence. These can be easily dealt with by
by-passing at the point where they leave
the generator housing with a type Wll
filter providing their potential does not
exceed 230 volts. If it does, use two .5
to 2 mfd. metal·cased transmitting condensers of appropriate working voltage
rating, connecting each between one
lead and the motor frame.
For motors and generators having
current above 40 amperes, the connecting wiring may be used in place of
chokes. This calls for two sets of bypasses-one set at the motor '~i: genera·
tor, the second set at the fuse box, or at
a farther distance, the most effective 10'
cation being chosen by experiment. For
three-wire service with a grounded neu·
tral it is usually necessary to by-pass
only the "hot" wires. The filter at the
motor or generator is grounded to its
frame. The filter on the line should be
grounded to the conduit, and the conduit grounded to the earth at the com- .
mon connection.
Mallory Type Wll filters can be used
with potentials up to 230 volts, A.C. or
D.C. For higher potentials use standard
metal·cased transmitting capacitors of
.5 to 2 mfd. size, 1,000 W.V. rating for
330 volts A.C., 2,000 W.V. rating for
440 volt A.C. For D.C. service the working voltage rating of the capacitors
should be approximately 50% or more
than the working voltage of the motor or
generator to give a factor of safety for
voltage surges. .
The usual precautions should be ob·
served regarding the placement of filters
to secure short direct leads, and to se·
cure a location which will afford the
maximum protection against mechani-
I,
I
.1
i
I
I
I
PRACTICAL RADIO NOISE SUPPRESSION
cal injury. The frame of any motor or
generator should be grounded.
Noise in the A.C.leads from an alter·
nator will frequently have its origin in
the small D.C. generator that is used for
field excitation. Consequently when
working on A.C. generating systems it
is well to clean up the interference of the
exciter unit before investigating the
alternator.
BRUSH FILTERS FOR LARGE MOTORS
• Section 10
In the case of gasoline engine driven
generators, the electric ignition sy·stem
of the gasoline engine may create interference in the power line. Such interference can be eliminated by using
automobile spark plug suppressors, and
by applying exactly the same treatment
as would be used in silencing an automobile electric system to permit the installation of an automobile receiver.
Washing Machines
Most washing machines employ electric motors which are inherently noisefree. Probably less than 10% are noisy,
and normally no difficulty is encountered in silencing these because of the
availability of ample mounting space
for any desired type of filter. Washers
are generally used in basements, and
because contact can be made between
the frame of the washer and grounded
metallic objects such as a water faucet,
it is necessary that the filter should be
of the shock.proof type.
Most machines can be silenced with a
filter type W7SP, mounted on the motor
frame with its leads connected to the
A.C. line. For more severe interference
use type Z8A for loads up to three am·
peres, type LC5 for loads up to five
amperes.
If an ironer attachment is used, care
should be taken that the load of the heating element is not carried by the filter.
Before installing noise filters on any
appliance, be sure that it is in a satisfactory operating condition. Excessive Haring or Hashing on the commutator of a
brush-type motor should be taken care
of by replacing brushes, adjusting brush
holder springs, and if necessary by turning the commutator and undercutting
the mica.
Neon Signs
FIG.l
When notified their signs could not be
installed in a certain city unless it was
demonstrated that each sign did not interfere with radio reception, one neon
sign manufacturer said in effect:
''The reasons are obscure why some
neon signs create radio interference. We
do know that when we may make up one
hundred practically identical signs, half
of them will be noiseless while the other
half will be noisy."
315
Section 10 •
THE
The information given in this section
represents the opinions of two practical
radio noise experts who have been outstandingly successful in clearing up all
types of interference. It is recommended
that this section be read with special
care since the procedure is quite different than that used with other appliances.
In checking about 1,000 neon signs it
was found that less than one out of 20
radiated much interference. Practically
all of them could be heard on a portable
radio at a distance of up to ten or twelve
feet with annoying volume, and a o few
for about 100 feet. This applies to signs
in good condition and working properly. However, most all of them fed noise
back through the A.C. power line reaching, in some cases, to every building
served by the same transformer. The
direct radiation through the air of a
properly working sign seldom reaches
far enough to seriously annoy anyone
but its owner, who might have a radio
within a few feet of it.
The procedure with a noisy sign is
first, to listen to it on a portable radio,
then try the electric radios in the buildings surrounding it to gain an idea as to
how much is radiating through the air
and how much through the power line.
Then watch the sign for flicker. If there
is a noticeable flicker it is an indication
that the transformer does not give
enough voltage to light it. There may
have been enough voltage when the sign
was new, but after some use more voltage is required to properly light it, and a
flickering sign is almost impossible to
silence. The remedy is to have the tubing repumped and refilled with new gas.
The next step is to disconnect the
leads from the secondary of the sign
transformer, turn the A.C. supply on
and listen for noise. If there is a frying
sound it indicates that the transformer
is leaking and should be replaced. It is
sometimes possible to silence leaky
transformers, but the transformer will
eventually have to be replaced anyway.
May we remind you that voltages
fro~ neon sign transfor~ers are
deadly and the pri~ary connections to the power supply should
be co~pletely disconnected before
touching the secondary. The voltages
used range from about 6,000 volts up to
25,000 volts or even more for large
signs.
Place a W7 or similar filter across the
316
MYE
TECHNICAL
MANUAL
primary terminals grounding the bracket to the transformer case or frame, turn
the sign on and listen again on both the electric and portable radios. Unless it is
a very bad case the electric radios 25
feet away (antenna included) should
get the noise very faintly or not at all.
While still listening ground the transformer case to earth and if it makes an
improvement, make the ground permanent. Quite often this is all the sign requires, but if the noise still persists
examine the tubing carefully for leaks
at points where the tubing crosses itself.
In large letters or loops where the tubing crosses, high frequency energy may
leak through the glass, partly short circuiting that letter or loop. Such leaks
can be located easily by placing a sheet
of paper between the tubing loop. If
leakage is occurring, a rustling sound
will indicate that the current is breaking
through the paper. Sometimes these
leaks can be cured by fastening a piece
of glass between the turns, but the sign
should be made so that where the tubing
crosses there should be spacing of more
than half an inch, so that leaks cannot
occur.
If tests show that the W7 filter does
not prevent noise from backing up in the
A.C. line, a combination inductancecapacity filter can be installed for greater filtering effect. For loads up to 3
amperes use a type Z8A if the filter may
be bolted directly to the core of the
power transformer, use type Z8 if the
filter must be inserted in a cord. When
using the Z8, cut the A.C. cord close to
the transformer, and attach male and
female plugs to the cord ends. The return lead from the filter should make a
good c~mnection to the transformer
core.
For permanently connected signs having a load in excess of 3 amperes, use
an LB filter of appropriate capacity.
As a last resort try touching the tubing at different points along its entire
length. You will likely find a spot where
the noise is completely eliminated as
long as you hold your finger on that
spot. Wind several turns of fine wire
(about No. 30) around this spot and
try the other end of the wire to other
points on the tube. Hold it with a split
stick about a foot long, so that the capacity of your body does not interfere
and when you find a spot where the
noise is greatly reduced wind several
turns about that spot and stick it fast
with Duco or some similar cement. This
is called balancing out the noise and
sometimes does wonders, but some experts do not consider it a very satisfactory way of getting rid of noise.
Sometimes grounding the wrapped wire
to the frame will silence the sign.
In some cases a sign may have both
terminals at one end so close together
that there is a leak between them. The
remedy is to either increase the spacing
or put glass between them_ Other smail
signs may be suspended by the leads
which may be tied around other things,
such as nails in the window frame.
These leads should not touch anything
except glass and as little of that as possible, even though they have heavy insulation on them. Many are suspended on
chains. A good grade of cord is much
better, but if chains must be used, try
grounding and ungrounding them.
Fluorescent Lights
Fluorescent light interference is comparatively easy to handle by means of a
filter which Mallory has developed especially for this application-type Z8A.
This filter should be bolted directly to
the fixture (see Fig. 2) at a point near
the auxiliary so that the total length of
wire in the by-passed circuit is kept as
short as possible. The ground connection to the frame of the fixture should be
carefully made to insure a good, low resistance connection.
If the design of the fixture is such that
it is impossible to bolt the filter to it, the
type Z8 may be substituted: In this case,
the A.C. cord should be cut close to the
fixture, then male and female plugs are
attached to the cord ends so that the
filter may be plugged into the circuit.
Installation is completed by attaching a
wire to the binding post on the Z8, and
connecting the other end of this wire to
fixture frame.
For installation where economy is of
prime importance, the W7, or W7SP
can be used, but since these filters do not
possess choke coils, their efficiency is
not as great as the ZS, or Z8A. The W7
or W7SP is installed by bolJing it to the
fixture and connecting its leads to the
A.C. wires. The type W7 is to be preferred unless a shock-hazard exists.
I
• Secfion 10
PRACTICAL RADIO NOISE SUPPRESSION
sor should lower the interference level
considerably-possibly no further filtering will be required. If further filtering is indicated, proceed with Stage 2
of Fig. 3.
Stage 2 consists of adding a Mallory
W7 Noise Filter to the load side of the
flasher circuit. The ground indicated
would be the junction box if a thermostatic flasher is used on the line; or the
metal base of a motor driven flasher if
this is used. Try grounding the metal
frame of the flasher motor, or the junction box to a nearby water pipe or
driven ground rod.
Stage 3. If further filtering seems desirable, add a Mallory Wll filter to the
source side of the load, grounding the
filter by bolting its mounting lug to the
junction box or metal base of the flasher
as described in Step 2.
Steps 4 and 5 consist of adding
RF chokes (Mallory types RF581 or
RF583) in the load leads and source
leads respectively.
~c~
FIG. 2
Traffic Signs
Flashing signs, such as are used on
caution signals for street traffic, can
create interference which will disturb an
entire neighborhood. Such interference
is not difficult to eliminate, but owing to
the variety of conditions encountered
and the distribution of the components,
the treatment will vary with different installations. For economic reasons it is of
course desirable to install only such filtering as may be required to actually
reduce the noise level to an acceptable
value.
Therefore, the problem of interference suppressions will be treated stepby-step in five stages. The service engineer should test after each step, carrying
the procedure far enough only to wipe
out the interference. Fig. 3 outlines the
five stages.
Stage one consists of adding a surge
suppressor across the flasher. The surge
suppressor consists of a .25 mfd. 600
W.V. paper dielectric capacitor (Mal-
lory CB314) in series with a 10 watt 100
ohm resistor (Mallory IHJlOO) and
serves the purpose of absorbing the energy when the contact points break. The
use of such a surge suppressor will
greatly increase the life 6f the contacts
of the flasher. The function of the resistor is to limit the discharge current of the
condenser when the points close. Never
place a condenser only across contact
points, which carry voltages approximating those used for commercial lighting services. If the capacitor is large
enough to absorb the spark when the
points break the discharge current will
be high enough so that metal transfer,
welding and sticking may occur when
the points "make."
The values specified are for average
conditions. Higher line current may call
for increasing the size of the capacitor
to a maximum of possibly 2.0 mfd. Possible variations in the value of the series
resistor would run from 30 ohms to 200
ohms, the latter being suitable for 220
volt circuits where the load is low.
The installation of the surge suppres-
'f
..
110-220V.
fj
n
,~
W7
c
~
WIII
3.
..
~
1I0-2~~V.
.
1I0-220V.
~
1I0-220V.
4.
RFC
5.
RFC
FIG.S
317,
Section 10 •
THE
MYE
TECHNICAL
MANUAL
The treatment of large multiple circuit advertising signs is similar to that
outlined except that steps 3, 4, and 5 are
replaced by the installation of a heavyduty LB filter of appropriate capacity.
One W7 filter is required for each load
circuit. If a brush-type motor is used to
drive the flasher it is possible that a W7
filter may be required across its brushes.
The really bad offender in the barber
and beauty shop is the hair dryer, a
small high-speed, brush-type motor
which is easily silenced by connecting a
shock-proof filter, type W7SP, across
the line and grounding it to the dryer
frame. The large hair dryer mounted on
a pedestal in a beauty sho}> is easily silenced by a W7SP filter located under
the end cover, connected across the line
and grounded under one of the motor
screws.
Electric Shavers
Sewing Machines
Electric shavers, particularly types
which make and break the circuit about
100 times per second, have become a serious problem. They can be completely
silenced by bringing out a lead from the
metal frame and using this as a return
lead for a filter such as the X5 or ZS.
However this involves operating on the
shaver, which is likely to bring objections from the owner. The best remedy
seems to be the use of a Mallory Z4 on
the end of the cord. The filter type Z4
consists of two chokes with capacities
across the line and load which prevents
radiation through the power line so that
neighbors are unlikely to hear the racket. Whether or not the use of the Z4 will
eliminate interference in the same house
depends on the type of house wiring,
distance from the receiver, etc. We believe that this interference will gradually be eliminated by the refusal of the
public to buy the noisy type, since there
are many good shavers on the market
which cause no interference.
Electric sewing machines create considerable noise and are quite easily silenced with a twin-capacitor filter, hut
the filter must be mounted directly on
the motor or in some place where it will
not be in the way of the operator or the
cloth going through the machine. Some
motors have a pair of terminal screws
providing easy attachment. In other
cases connection can most easily be
made to the brush-holders. Never mind
the rheostat in the pedal. All that is necessary is to connect the filter across the
line close up to the motor. :The extra
small W7A filter is recommended for
this application.
Multiple Circuit Advertising Signs
Barber Shop Equipment
Many complaints have been received
about the barber's clippers. However a
careful check of several hundred barber
shops reveals the fact that a very large
percentage of the clippers now in use
are of the vibrator type which makes no
noise whatever. There are a few, however, with small brush-type motors
which produce bad interference. It is
impractical to completely silence these
as the condensers would have to be on
the clipper and would be too much in
the way of the operator. A line cord
filter, such as the Z8, will help.
318
Cash Registe,:"s
Electric cash registers make just as
much noise over a nickel as a five dollar
bill hut are easy to silence. Remove the
plate over the motor and find the line
wires. Use a W7SP filter across the line,
grounding the bracket to the register
frame. In case there is not room inside
for the filter, use a Z8A, bolted to the
outside of the register. In some installations it may he easier to use the equally
effective Z8 by cutting the A.C. cord
close to the register, then installing male
and female plugs on the cord ends so
that the ZS may be inserted in the circuit. The return circuit can be made by
connecting a wire from the binding post
on the Z8 to the·metal frame of the register, but the preferred method is to bolt
the Z8 to the register 'housing: Motors
on registers run for only about one second at a time but where there are many
sales they will ruin reception for two or
three hundred feet in every direct,ion.
Electric Refrigerators
The motors of modern electric refrigerators almost never interfere with
radio reception, however some of the
old makes do interfere and .can be silenced the same as any other similar
motor. Usually a W7 is the correct filter. Sometimes a refrigerator will put
out a severe scratching and crackling
noise all the time it is running. This is
caused by making and breaking contact
between the motor frame and the metal
chassis of the refrigerator. The motor is
mounted either on rubber or springs to
absorb vibration, and its frame must be
, grounded to the external frame and supports, with heavy stranded wire. If this
ground becomes loose, much noise will
result. Use very flexible wire and leave
plenty of slack in it so that motion and
vibration of the motor will not break it
off. The large refrigerator systems with
motor and compressor usually located
in the basement are exactly the same as
the home type except for size. Mallory
LB type filters are recommended for
permanently connected motors.
While the following case history deals
with an air compressor, rather than a
refrigerator, the principle illustrated is,
the same. An ~xtremely noisy air pump
motor at a garage was silenced with the
usual filter and the owner brought his
radio down. A few days later he complained that he had a worse noise than
ever. Investigation showed that the motor was mounted on the air tank from
which an iron pipe led through a brick
wall and up the ceiling on the other side,
then across the ceiling and down the
other wall where a rubber hose was
connected. On its way the air pipe barely touched a water pipe and vib~ation
from the motor did the rest. Clamping
together the water pipe and the air pipe
cured the trouble.
Violet Ray Machines
Violet Ray Machines provide serious
annoyance, but fortunately they are seldom used. The old type which uses a
spark gap can be suppressed but is not
valuable enough to make it practical.
Any resistor in the high tension leads
which will stop the noise radiation will
also prevent the machine from working.
I
i
I
I
I.
PRACTICAl. RADIO
The only effective method is to screen
the room in which it is used and place a
filter across the electric light line and
any other wires coming out of it. In
most cases this would cost about as
much as one of the new type machines
which are much better and are also
noiseless.
Diathermy Machines
Diathermy machines used by doctors
are essentially short wave transmitters.
There are two principal types, the self·
rectifying oscillator, and the type em·
ploying a D.C. power supply feeding an
oscillator. Where a rectified power sup·
ply is used, the emission is confined almost entirely to one wave length, with
only low-intensity side-bands existing
from the superimposed ripple of the
D.C. power supply. Since diathermy
machines operate on ultra-short wavelengths, machines having a D.C. power
supply do not cre~te appreciable broadcast interference.
The self-rectifying oscillator type of
diathermy machines can be a real
menace to the radio reception of a
community. In this type of device, the
oscillator, usually push-pull, receives its
plate supply as unrectified A.C. directly
from a power transformer. Consequent.
ly, oscillations start and stop twice each
alternating current cycle, each tube op·
erating only on the positive portion of
its cycle. With the low "C" oscillator
circuit used, the result is not only severe
modulation at twice the supply frequency, but also severe wobbling of the
frequency. The carrier thus generated
splatters all over the. short wave spectrum; and may even be bad on the entire
broadcast band.
It is possible to silence this type by
placing it in a tot~ly screened and
grounded room, and applying line noise
filters to all power supply wires entering
the shielded room. However, probably
the most economical procedure is to install rectifier tubes and a filter in the
machine. This will call for the addition
of two 866 rectifier tubes, a filament
transformer for heating these tubes, a
filter choke of about 4 henries inductance and a filter capacity of about 2
mfd. and of suitable working voltage.
This job of altering a diathermy machine can be easily handled by any servo
NOISE SUPPRESSION
ice man who is also a licensed radio
amateur. If you have not had experience
with high-voltage power supplies we
suggest that you discuss the matter with
a radio operator who will be able to
give you pointers on insulation requirements, selection of components, safety
requirements, etc.
The 115 or 230 volt A.C. supply leads
should be by-passed to the power supply
chassis with a W11 filter to prevent the
A.C. supply line from acting as an antenna. The power supply'chassis should
also be grounded to a nearby water pipe
for reasons of safety. The voltages used
in diathermy equipment are high enough
to be deadly, so use extreme care when
working on any machine.
In addition to the diathermy equipment described above, there is an older
type diathermy machine which obtains
radio frequency energy from a spark
discharge, rather than from an oscillating vacuum tube. These older machines
are extremely difficult to silence, the
only effective remedy being to enclose
the apparatus and the patient in a
shielded room and filtering the A.C.
wires with a suitable LB noise filter, as
described in the paragraph on X-ray
machines.
In closing, radiating diathermy machines of all types create severe interference with television reception when the
emitted wave falls on one of the television channels. For the present, probably
the best remedy is the use of the screened
room. It is the feeling of many engineers
that in the future diathermy' machines
will have to operate on a specified channel, and that some frequency fixing
method such as crystal-control will be
required by law or F.C.C. regulation.
Dental Equipment
Dentists' drills employ small, highspeed, brush-type motors which create
violent interference. They are usually
easy to silence by a standard filter of the
W7 type connected across the line inside
the cast-iron pedestal with the bracket
grounded to the pedestal. This arrange·
ment will be effective unless some of the
pedestal cord (between the point where
the filter is connected and the motor) is
run on the outside of the metal housing;
or if the motor frame is insulated from
the main pedestal and cannot be perma-
• Section 10
nently grounded to it. In such cases the
filter must be mounted in or on the motor itself. In some cases there is room
inside the end cap of the motor for the
installation of the filter. There are a
number of wires in the bottom of the
pedestal. Some go to the foot speed control and others to the switch. Trace the
line wires out and make sure you are
across the A.C. line. The new X-ray machines used by dentists make no noise.
Hospital X-Ray Machines
X-ray machines used in hospitals and
clinics are generally blamed for much
more interference than they actually
create, and experience shows that the
vacuum cleaner used by the doctor's
wife may make more interference than
all the special electrical equipment used
in the doctor's office.
It is true that the older and almost
obsolete X-ray machines employed a
setup similar to that used in an old time
spark-transmitter-high-voltage transformer, spark-gap, etc. However in most
cases where this old equipment is still
employed the tube is only operated for a
few seconds for each patient. The only
practical arrangement for silencing these
older machines is to screen the entire
X-ray room-walls, ceiling, floor, and
doors with wire mesh that is bonnected
to a good ground. Then all power supply wires entering the shielded room
must be by-passed with suitable filtersthe Mallory LB types being excellent for
the purpose. Resistors cannot be incorporated in the X-ray transformer leads
as these will stop the machine from
working.
The more modern types of X-ray machines are not bad interference makers,
and should interference be encountered,
the addition of a line noise filter will
usually be enough to keep the neighbors
satisfied.
We report a typical case of supposed
X-ray interference. In a city having an
ordinance prohibiting the operation of
noise-making appliances, many complaints were registered against the X-ray
machine of a certain hospital.
On checking it was found that the
X-ray machine blamed by everyone was
practically noiseless. One of the fifteen
heating pads used in the hospital was a
bad offender, but the real noise-maker
319
Section 10 •
THE
for the neighborhood was a tree limb
nearby that rubbed the electric power
line.
Spark Plug Testers
Spark plug and coil testers in garages are not numerous but make up in
power what they lack in numbers. The
, treatment is to place a resistor of about
15,000 ohms (the same thing that is
, used on spark plugs in cars having radios) in each high tension lead where it
comes out of the coil, and install a filter
type W7 or better a Z8A in the A.C.
line where it enters the machine,
grounding the bracket to the frame of
the machine.
Thermostat Controlled Devices
Heat pads, electric flat irons and
other appliances with thermostatic heat
control can generate noises which destroy reception over considerable distance. Heat pads are quite hard to filter,
due to the fact that they have no metal
frame. A Mallory filter type Z4 will pro·
vide considerable attenuation of the interference. The Z4 is a combination
inductance.capacity unit which does not
require a return lead to the frame of the
appliance: If absolute freedom from
noise is required, we can only suggest
replacing the thermostatically controlled
pads with pads of the manual heat control type which are inherently noiseless.
Electric irons may be silenced by using a W7SP shock-proof type filter connected across the cord terminals on the
iron and with bracket grounded to the
back of the handle where it will be out of
the way of the operator and as far from
the heat as possible. Other appliances of
this kind can be silenced in the same
manner. If the appliance is held in the
hand use shock-proof filters.
Oil Burners
Most types of oil burning furnaces
use an electric igniter which consists of
a spark coil with one or more ,( usually
two) electrodes hooked over the edge of
the oil trough. When, the thermostat
closes the circuit each electrode throws a
320
MYE
TECHNICAL
MANUAL
shower of sparks into t/le oil. In some
types the spark is shut off as soon as the
oil ignites and in others it remains on
until shut off by the thermostat. The
electrodes usually should be set so that
the spark is about three-eighths of an
inch long. Sometimes these electrodes
get bent, stretching out the spark as long
as an inch and in such cases it is almost
impossible to silence the noise. The remedy is to bend the electrodes so that the
spark will not be too long. Consult the
burner manufacturer's recommendations for the exact adjustment and spac·
ing to be used.
Most oil burners are equipped with
noise suppressor resistors which function similarly to the spark plug suppressors used in automobiles. The
suppressors for oil furnaces are larger,
of course, because of the greater power
to be handled. The usual types have a
resistance of about 20,000 ohms and a
dissipation rating of 25 to 50 watts. If
the furnace on which you are working
is not equipped with these resistors be
sure to secure a set from the manufacturer of the oil burner and install them.
For an "orphan" burner, radio resistors
of the vitreous enamel type can be substituted. A suitable value for trial would
be the Mallory 5H]20000.
The next step is to filter the power
supply leads. The prefer~ed filter for
the application is a Mallory LB, with the
return lead of the filter grounded to the
core of the high-voltage transformer.
Connection to the core can be made by
loosening one of the bolts clamping the
core, fastening the wire under the bolt
head and retightening. If for economic
reasons a customer cannot be persuaded
to use an LB filter, then make the next
best installation by bolting the mounting lug of a Wll filter to the transformer cote, connecting the filter wires to the
primary A.C. leads.
The next step is to bond together the
metal paris of the burner and the furnace so that no potential difference can
exist between these parts. Use heavy
wire for the purpose, and then ground
the system to the nearest water pipe, or
to a driven ground rod.
Clicking from thermostats can be
eliminated by connecting a W7 filter
?cross the thermostat leads at the burner, bolting the mounting lug to the
burner frame.
Railroad Crossing Bells
Railroad crossing bells may be prolific noise· makers for an area having a
breadth extending about a block from
the tracks, and with a length roughly
equal to the distance that the tracks are
bonded for operation of the signal.
Railroad companies consider these
signals to be very important and wiII not
allow anyone to touch them unless their
maintenance engineer is present. The
most used type of signal mechanism employs a "rocking" armature to make and
break six contacts for ringing the bell
and flashing lights. It has been found
that a .1 mfd. condenser across each
contact, plus a W7 across the A.C. line
with bracket grounded to the metal
frame of the machine reduced the noise
about 80%. Apparently the rest of the
noise is caused by surge and could probably be eliminated by installing a second W7 filter from each side of the A.C.
line to the lamp case.
N ow most railroad companies have
their own suppression systems and will
apply them if complaint is made to their
signal engineer located at the nearest
)
division point.
I'
i
Telephone Equipment
Telephone exchanges sometimes produce several kinds of noise which travel
over their system. The older systems use
a 30 cycle ringer which will be heard as
an extremely low pitched buzz 01 hum.
Others have what are called "differep,
tial ringers" which are so arranged that
the operator can ring anyone of four
parties on a line without affecting the
other three bells. Differential ringers
employ a vibrator with circuit very similar to the usual r.ar radio vibrator. The
lengths and weights of the reeds are adjusted so that one will vibrate at 30
cycles per second, the next at 42, the
next at 54 and the fourth at 66. The
noise can be identified by the frequency.
Dial phone systems have many relays
constantly clicking and make a noise
like a typewriter or teletype machine
combined with the dial tone.
Most exchanges use a 24 or 30 volt
storage battery with a Tungar charger
across it which it switches on Ilutomati-
I
i
,
I,
.
• Section 10
PRACTICAL RADIO NOISE SUPPRESSION
cally when the voltage goes below a certain point.
Relays, vibrators, etc., cannot be si·
lenced by the usual methods as capacities interfere with the operation of the
system. The manufacturer of the apparatus will supply the phone company
with special chokes which are very
effective, and the local company will put
them on if complaint is made.
However a W7 should be put on the
Tungar with bracket grounded to the
case and it is good practice to put another at the electric meter, across the
line and grounded to the metal fuse box,
to avoid radiation of clicks through the
power line.
'Street Cars
COLLECTOR
•
BELT
COLLECTOR DETAILS
)~-4gi!l1 ~
SOLD£R
Intermittent noises from street cars
are usually caused by flattened or worn
trolley wheels. Get the number of the
car and report it to the company. They
will be glad to replace bad trolley
wheels.
Noise from generators can travel over
trolley wires. In one case of severe
noise, the trouble was finally located in
a substation, where it was found that the
collector rings on the end of a large
motor-generator were worn a~d "outof-round." This condition produced
considerable vertical motion in the
HJ:ADS
SHARP POINTED
NAILS
FIG. 4
br~shes, and the accompanying poor
contact resulted in severe flashing and
arcing. The company repaired the condition immediately when attention was
called to the severe radio interference
that was being produced.
Belt Static
A high-speed rubber belt can be the
source of considerable noise. If a metal
belt clamp is used a loud popping may
be heard every time the belt clamp
passes over a pulley. In one case like
this, the belt of a linotype machine
spoiled reception in every radio within
200 feet. Connecting the frame of the
motor to the frame of the linotype machine corrected the difficulty. Fig. 4
shows a way of draining a static charge
from a belt when connecting and grounding the machinery does not eliminate the
trouble.
FILTER CLASSIFICATION
.
All radio noise filters may be grouped into two classifications-standard and shock-proof•
SHOCK-PROOF CONSTRUCTION
STANDARD TYPES
The following types of Mallory Noise
Filters do not place an appreciable electric charge on the device with which"
they are used. They are inherently
shock-proof.
Noise filters possessing as an element,
twin capacitors connected across the
line, with return lead to the appliance,
cannot be classed as entirely shockproof. This does not mean that a violent
or dangerous shock will be obtained on
contact with the appliance on which
such filters are used. It does mean that if
the frame of the appliance is ungrounded, and the appliance is used in a
location where bodily contact may be
made with a damp floor or a grounded
conductive object such as a water faucet, a tingling sensation may be experienced.
Xl
X3
Z2
Z4
X5
Z6
Z8
Z8A
W7SP
W9SP
WllSP
LC5
LCIO
The above filters may be used on ungrounded appliances, such as electric
drink mixers, washing machines, electric drills, etc., where the installation of
a ground lead to the frame of the appliance would be inconvenient.
STANDARD TYPES (No' Shock-Proof)
W7
W7A
W9
Wll
LBIO
LB20
LB40
All tendency toward shock when using standard, non-shock-proof type filters will be eliminated if a wire is
connected between the frame of the appliance and a nearby water pipe or
grounded electric conduit. The LB series
filters are automatically grounded in
normal installation by the connecting of
the BX or conduit to the cut-out box.
Fur,thermore, it is very unlikely that any
kind of a shock will ever be experienced
when using the filters listed above on
such devices as vacuum cleaners, sewing machines, etc., which are normally
used on wooden floored or carpeted
rooms.
321
THE
Section 10 •
MYE
TECHNICAL
MANUAL
SPECIIICATIONS
TYPES
TYPES XI,X,]
I
T
Xl, X3
CIRCUIT
:EOJ..
""I
(jROUND
W75P, W9SP,
WllSP
To
CIRCUIT
or appliance cord plug. Size 1% x I%" rated lIO volts, S amps.
Type X3 is a capacitor-type filter having greater efficiency
than Type Xl. Use at radio or appliance cord plug. Size 1% x
2~, rated lIO-220 volts, S amps.
TYPE X5
II
I:!
--z.--=-
COHTAIN(A
DIAGRAM
Type Xl is for relatively slight interference. Use at radio
....
W7Sp, W9Sp, WIISP
..
DIAGRAM
Types W7SP, W9SP, WllSP are triple-capacity shockproof filters for general by-pass service as described in the
previous text. For lIS-230 volts A.C. or D.C.
Type W7SP, for moderate interference. Size 7/8 x 1 15/16.
Type W9SP is similar to Type W7SP, except for medium
interference. Size 1 x 2%.
.
Type WIISP is similar to Type W7SP, except for severe
interference. Size IVs x 31~.
I,
'
TYPE Z2
X5
CIRCUIT DIAGRAM
Type X5 is a triple-capacity filter with provision for return
lead to appliance. Special safety feature prevents possibility of
shock and makes this unit ideal for use with vacuum cleaners,
food mixers, etc. Size 1% x 2Vs, rated lIO-220 volts, S amps.,
and equipped with binding post for connection to appliance or
motor frame. The XS is the equivalent to, and may be substituted for the W7SP when a plug-in type mounting is desired.
TYPES W7.W9,WII
~:I---
CIRCUIT
DIAGRAM
Type Z2 is a capacitor-inductance filter
for medium interference. Use with electric
razor, radio or appliance cord plugs. Most
Z2
effective on grounded line systems where reversal of plug will affect operation. Size 1% x 2%" rated
lIS-230 volts, 3 amps.
lnfC;ROUNO
To
~
v C
W7, W7A,
W9, Wl1
TYPE
CONTAIN£R
CIRCUIT
DIAGRAM
Types W7, W9 and WII are twin-capacity filters with
common connection to container widely ,used for general bypass service as described in this chapter. For lIS-230 volts
A.C.orD.C.
Type W7, for moderate interference. Size 7/8 x 1 15/16.
Type W9 is similar to W7, but for medium interference.
Size 1 x 3.
Type WII is similar to Type W7, but for severe interference. Size 1% x 3.
Type W7A is similar to W7, except smaller physical size.
For lIO-volt A.C. or D.C. service only. Size 1I/16 x 1 1I/16.
Used on sewing machines and similar applications where space
,is at premium.
322
Z4
CIRCUIT
DIAGRAM
I
I
Type Z4 is a dual inductance-capacity
filter for severe interference on appliances
where a return lead from the filter is inconZ4
venient. Ideal for electric razor, vibrators
and household appliances. Use at radio or appliance cord plug.
Size 1% x 3, rated lIO-220 volts, 3 amps.
"
:i
11
\:'
Ii
I,
PRACTICAL RADIO NOISE SUPPRESSION
CIRCUIT DIAGRAM
Type Z6 is a dual inductance-capacity filter with provision
for return lead to ground. Recommended for suppressing severe
interference. Use at radio cord plug. Shock-proof construction.
Size 1% x 3%, rated 115·230 volts, 3 amps., A.C. or D.C.
• Section 10
TYPES Z8,Z8A
Type Z8 is same as Z6
but with provision for rePt~G--"",V'VVVV-\r-, \
\
z
\
u_
<
HIGH
R.
3750.f!:.
LO
R5
700 MEG
R.
2.3 MEG
ONO
R,2
500M
·5
30 M
1600.0..
Vacuum Tube Replacements
Replacement of either the type 955 or
type 6Q7.G tube will, in general, require
readjustment of the movable contacts, A 1,
'------'--------.....---+.-----1
FIG.
r
MFO
~
14
331
Section 11 •
THE
trol is required in order that the pointer
MY E
TECHNICAL
MANUAL
come to the exact center of the scale when
3 section 4 pOSItIOn switch, one section of
which is used to short out the meter during
the meter in opposite directions. One of
these is the voltage delivered by the power
switched to the D.C. position, since the
the time when the contacts of the other sec·
supply and in which case the current flows
switch cuts in the proper balancing network.
tions would normally be open between po·
from B'- through the 3500 ohm'resistor R"
This arrangement permits measuring D.C.
voltages of either polarity from a common
sitions. One of the sections acts on the
voltage dividing input circuit and connects
through the meter from left to right, over
ground point, usually chassis, without both:
the grid to the proper taps to establish the
ering to reverse the lead connections.
proper voltage ranges. The other acts to
the 30,000 ohm resistor R'8 to B+. Current
in the meter as a result of this potential
through P" P2, P., P., and P., then through
One other change, is the voltmeter input
provide the proper bias for the various
circuit which in the case of D.C. measure·
ment comes through the jack on the instru·
ranges so that zero adjustment on the panel
is unnecessary when changing from one
ment panel instead of through the probe.
The probe' may be disconnected and put
range to another. The balance control
the meter in opposite direction flows from
(R·ll) is on the front panel. Other adjust·
B- through the 1600 ohm resistor R2
aside when making D.C. measurements if
ments are preset at the factory so that when
so desired.
There are two separate D.C. range selec·
ranges are changed, the various biases sup·
plied to the grid of the tube, will be
through the meter from right to left on
through to the tube cathode, to the plate
tors, one being from ground to the Low
automatically corrected and always bring
D.C. post, and the other from ground to
the meter back to the zero position.
the High D.C. post. In the Low position
It is well to mention that adjustment of
the ranges are 0 to 1.5·3.0·15 and 150 volts,
any of the 3,000 ohm zero centering controls
in the High position 0·75·150·750 and 7500
in no way eficllcts the calibration or accu·
volts. The input impedance is approximate·
racy of the equipment, but merely shifts
ly 15 megohms on the low range and ap·
the grid to the proper operating point to
proximately 750 megohms on the high
give zero meter reading. As a result of
range. There are four A.C. ranges; 0·1.5·3·15·
recalibration
150 volts.
tubes, it is sometimes necessary to readjust
necessitated
by
varies directly as the output voltage' of the
power supply system.
The other current tending to 1I.ow through
then to B+. The magnitude of this cur·
changing
the center controls. To do this, set the bal·
ance control on the panel to zero and adjust
each of the four A.C. range zero adjustment
The D.C. Voltmeter Amplifier
Circuit
controls found in the rear of the chassis,
so that the pointer rests at zero on each of
the A.C. ranges. Then change over to the
This section consists of a type 6K5G tube
with the meter in the cathode circuit. The
tube acts as a degenerative amplifier and
consequently has a nearly linear plate cur·
rent ~hange with respect to the applied D.C.
grid voltage. The grid voltage is applied
negatively with respect to the cathode and
consequently the limiting current through
the meter is always the bucking voltage
which has been applied, so there is little
possibility of damage to the meter.
The 3500 ohm variable resistor R'6 in
series with the cathode is used as a sensi·
tivity adjustment to compensate for various
tubes. Should recalibration become neces·
sary due to tube changes, this control is
D.C. range and adjust the one D.C. control
P. so that zero comes to the center of
the scale on the D.C. range. The reason it is
necessary to change the grid bias return on
each range of the A.C. section is due to the
emission current of the Type 955 tube, pro·
viding approximately 1.5 volts drop across
the voltage dividing network which feeds
the grid of the 6K5 tube. As the grid is
changed from one range to another, various
potentials are applied to the grid, whereas
in the case of the D.C. section, no emission
potential is applied across the voltage di·
viding, circuit and
th~refore
the grid reo
ceives the same bias regardless of the range
on which it is connected.
FIG. 15-HICKOK MODEL
no
rent is not only a function of the voltage
delivered by the power supply, but also of
the emission current from the cathode of
the 6K5 tube. The circuit is so arranged
that as the line voltage drops from 110 volts
down to 100 or increases from
no
to 130
volts, the cnrrent through the meter can
actually be dropped in proportion, but since
the two currents are bucking each other,
readjusted until proper calibration is ob·
the resultant cnrrent in the meter is held
tained. Adjustment on any range, A.C. or
constant and consequently the sensitivity of
D.C. is sufficient to bring all ranges into
calibration. When using the D.C. voltmeter
Line Voltage Compensation
The extremely high input impedance of
section, the D.C. is applied to the 6K5 grid
in the same manner that the rectified A.C.
was applied. The range change switch is a
332
the amplifier constant.
this instrnment and its stability and ease of
It will be noted, Fig. 14, that there are two
voltages tending to produce current through
operation make it a very valuable and flex.
ible service tool.
I
VACUUM
Meissner Analyst
rUB E
VOLrMErERS
• Section 11
characteristic, but indicating and measur-
lined clearly against the shaded background
ing the new voltage.
of the other sections.
The range of the instrnment is obtained
by means of a voltage dividing network in
Another interesting vacuum tube voltmeter is found as one of the units in the
the grid circuits, providing 0·5·15·150-500
Meissner Analyst, a circuit diag,ram of which
volt steps.
is shown in Figure 16. In this' instrument a
The initial adjustment and calibration is
6E5 magic eye tube is used as an· indicating
set up as follows. Set the voltage scale
device and a direct reading dial calibrated
in terms of volts being used from which to
pointer at zero volts and adjust the zero
read the value of the voltage being meas·
Then connect a high resistance voltmeter
set control near the middle of its range.
(1,000 ohms per volt or so) across the volt.
ured.
A 6F5-G tube is used as a direct coupled
age scale potentiometer and adjnst the
amplifier into the 6E5. The accuracy is in·
dependent of the tube characteristics since
is obtained across the Volts Scale potentiom·
"voltage calibrator" resistor until 9.7 volts
in the circuit used, the readings are made
eter. This adjustment should be made if pos-
when the shadow of the 6E5 tube just closes,
sible at normal line 118 volts approximately.
a condition requiring a given fixed voltage
Then the zero set potentiometer is adjusted
between grid and cathode of the 6F5. When
until the 6E5 shadow angle is just zero.
the input voltage prod is shorted to ground
When measuring voltages of an intermit·
and there is no impressed voltage, the grid
tent nature this method of reading voltages
is biased enough to prevent grid current by
on a dial scale, rather than a meter, is of
the cathode return network, which also is
arranged so as t? cause the 6E5 shadow to
considerable value, since the original setting for zero shadow angle remains un-
FIG.
17
RCA·Rider Chanaly~,t
Vacuum Tube Voltmeter
just close. When a voltage is applied to the
dianged, the shadow angle either opening
grid network, the voltage between grid and
up or overlapping indicating a voltage
Another extremely simple and direct
ground or chassis changes, but the cathode
change and in which direction, whereas a
reading vacnum tube voltmeter is used in
bias is shifted by means of the "Volts Scale"
potentiometer, until the 6E5 shadow angle
meter would have followed the variation
and unless recorded or remembered, would
the RCA·Rider Chanalyst a circuit diagram
of which is shown in Fig. 18.
is again zero, which re·establishes the initial ,
have been forgotten.
This vacuum tube voltmeter uses a type
grid to cathode voltage, thereby maintain-
Fig. 17 illnstrates the Meissner "Analyst."
76 tube as a D.C. Amplifier, the meter being
ing the original operating point on the tube
The vacuum tube voltmeter section is out·
used to indicate the current in the cathode
circuit. A voltage dividing network in the
grid circuit is used to increase the range
of the instrument and a .001 mfd. condenser
from grid to ground is used to bypass any
A.C. voltage, picked up by the test prod.
When measuring A.V.C. voltages etc. at the
grids of R.F. stages, a pro~ with a 1.0 meg·
ohm isolating resistance is provided so as
to allow the D.C. to be picked up and
measured .without interfering with the signal or R.F. voltage.
The meter is arranged so that zero is at
the center of the scale, and either positive
or negative voltages with respect to the
reference point (usually chassis) may be
measured without need for reversing the
leads.
VOLTAGE
CALIBRATOR
210M.
-15V
+B
The ranges provided are plus or minus
5, plus or minus 25, plus or 'minus 100 and
plus or minus 500 volts, D.C., all of these
ranges having a constant impedance of 10
-2 VOLTS
rIG,
16
ZERO SET
-7 VOLTS
megohms or 2.0 megohms per volt on the 5
volt range.
333
THE
Section 11 •
MY E
TECHNICAl.
MANUAl.
B+
zero.setting is required for all ranges. The
ohmmeter accuracy is within 3% at center
scale. A complete circuit diagram of the
instrument is show~ in Fig. 20.
Circuit
The overall accuracy of the instrument is
rated as 5% of full scale deflection on any
range.
scale. Provisions are also made to measure
resistances from .1 ohm to 1,000 megohms in
seven decade ranges," each overlapping the
other with only one scale to read. Only one
RCA Rider Volt Ohmyst
•
A mnlti.range instrument, direct reading,
and employing an unusual circuit design
making its' accuracy essentially independent
of tube or line voltage changes, is shown in
Fig. 19.
With this instrument, one may measure
directly D.C. voltages from .05 to 5,000 volts,
either positive or negative without loading
the circuit under test. Its input impedance
FIG. 19
on all ranges up to 500 volts is 16 'megohms
and on 500 to 5,000 volt ranges is 160 meg·
ohms. Its accuracy is within 2% of full
334
The V ~lt Ohmyst uses a push-pull vacuo
um tube voltmeter of new design. The two
tubes V. and V. are linked by means of a
common high resistance R... Because of
this coupling, any change in the input voltage to the grid of V. changes the cathode
bias of V., and as a result, the change in
the plate current of V. is accompanied by a
simultaneous change in the plate current of
V. in the opposite direction. The differential voltage thus developed across the load
resistors, R..
L, is applied to the
meter which is calibrated in terms of the
voltage applied to the input and in terms
-=
FIG. 18
._-"J
D~sign
:ad
lUI
VI
ti~::::~ ~~//~:
1UR.1R."'A/O~
r'
:
I
I
I
I
I
:
"+:
t
~:
I t )
:
Sf
J
~f$
~ ~'
\
- \,-_____________L_-_-_-_-_-_-_-_..J_'.~-------,
~/
Schematic Nos.
Description
R1, RIO
Resistor, 150 Meg. ± 1%
Rll, R12,
R13, R14
Resistor, 5 Meg. ± 1%
R15, R16
Resistor, 8 Meg. ± 1%
R17, R18
Resistor, 1.5 Meg. ± 1%
R19, R20
Resistor, 300,000 Ohms, ± 1%
R21, R22. R23,
R24, R33, R84 Resistor, 100,000 Ohms, ± 1%
R25, R,26
Resistor, 10 Ohms, ± 1%
R27, R28
Resistor, 100 Ohms, ± 1%
R29, R80
Resistor, 1,000 Ohms, ± 1%
R31, R32
Resistor, 10,000 Ohms, ± 1%
R85, R36
Resistor, 1 Meg. ± 1%
R37, R38
Resistor, 10 Meg. ± 1%
R89
Resistor, 2.5 Meg.
R40
Resistor, 56,000 Ohms
R41, R4~
Resistor, 8,800 Ohms, ± 5% BW 1
R43. R45
Resistor, 20,000 Ohms
R44
Var. Resistor, 3,000 Ohms (Zero
Control)
R46
Resistor, 2,000 Ohms
R47
Var. Resistor, 7,000 Ohms (Calibration Control)
Schematic Nos.
Description
R49
Var. Resistor, 8,000 Ohms (Ohms
Control)
R50
Resistor, 750 Ohms
R51
Resistor, 10,000 Ohms
R52
Resistor, 15,000 Ohms
R53
Resistor, 4,000 Ohms
Cl, C2
Capacitor, 1-1 MFD, 400 Volts
C8
Capacitor, .005 MFD, 1,000 Volts
81
Range Switch
82
Volt-Qhm Switeh
S8
Polarity Switeh
T1
Power Transformer, 105-130 Volts,
25-60 Cycle
Lead-Red Test Lead Co....plete with
Banana' Plug and Probe Sleeve
48" Long
Lead-Black Test Lead Complete
with Banana Plug and Probe
Sleeve 48" Long
Lead-Black Ground Lead with Alligator Clip and Plug
Lead-Voltmeter Cable Complete
with Isolating Resistor
Clip--Clip Attachment Assembly
FIG. 20
i
I
I·
VACUUM
of the resistance being measured when the
instrument is used as an ohmmeter.
In addition to the push.pull action, a
high degree of self regulation is obtained
as a direct result of the high value of
coupling resistance, R.o. This is analogous
to the regulating effect secured through the
use of self-bias but because R.o is approximately 100 times as large as the value of the
cathode resistance which it is possible to
use in conventional circuits, the self-regulating action is correspondingly increased.
At the same time, excessive loss of sensitivity normally experienced when usiug such
a high cathode resistance is eliminated because of the balanced nature of the circuit.
A controlled amount of inverse feedback to
obtain independence of tube characteristics
is secured by means of the two resistors,
R41 and R... A principal factor limiting
the maximum input resistance of D.C. vacuum tube voltmeters has been the problem
of reducing grid current and the so-called
"contact potential" error to a low value.
In this design, the problem has been met
successfully by the choice of a suitable type
tube, the use of a very high cathode resist·
ance, and by operation at a low plate voltage. The ohmmeter circuit utilizes the vacuo
um tube voltmeter described to measure the
ratio between the voltage across the unknown resistance and one of seven stand·
ard resistors. The latter range in value from
10 ohms to 10 megohms so that multiplying
factors of R times 1 to R times 1,000,000 are
provided_
The probe provided for the 0-500 volt input circuit contains a 1.0 megohm isolating
resistance built into the prod to prevent the
capacitance of the cable and the instrument's input circuit from reacting on the
circuit being measured.
This instrument is provided with a calibration adjustment, R .. , which is originally factory set and is used to compensate
for small variations in meter sensitivity or
tube characteristics. Ordinarily, this adjustment requires no attention except when
tubes are replaced_ The meter may be recalibrated by using a known voltage source
of exactly 5.0 volts D.C. and adjusting the
vacuum tube voltmeter calibration control
R'7 so that the meter reads exactly 5.0
volts with the Range switch in the 5.0 volt
position.
T U 8 E
VOLTMETERS
The Volt Ohmyst uses 2-6K6G tubes and
1-6X5G. Because of the low operating
voltages, the tube life will be exceptionally
long. However, when replacement becomes
necessary, care must be taken to see that
the tubes are approximately balanced. If
they are unbalanced, it is not possible to
bring the pointer to zero by means of the
Zero Adj. Control. When the tubes are
matched, the. Zero Adj. Control will bring
the pointer to zero in approximately the
center of its range.
The circuit design is such as to reduce
grid current to a negligible value. When reo
placing tubes, it is advisable to check for
grid current as occasionally a gassy tube
will be found. The presence of gas is indicated by an appreciable change in pointer
position when the Rang~ switch is changed
from the 5 to 25 volt position.
Special Signal Tracing Equipment
The wide variety of measurements, and
therefore usefulness of a vacuum tube voltmeter in radio maintenan~e work is limited
only by the design or capabilities of the instrument available and by its users working knowledge of how the circuits and components being measured should normally
operate.
For obvious reasons, it is necessary to 10·
cate the defect and restore the set to normal
operation in the shortest possible time_ As
a means of rapidly localizing the fault to
some particular section of a receiver, a system of testing, described as Signal Tracing,
or Signal Chasing, has been introduced and
has met with a large approval from the field.
All of the instruments recommended for
use in this method of receiver analysis are
basically vacuum tube voltmeters of some
form or another, mainly because of the
necessity of measuring the" signal voltage
from the antenna to voice coil with a minimum interference to the signal circuits
being measured. With this minimum interference idea in mind, vacuum tube volt·
meters have been designed and introduced
which measure or indicate signal voltages
as low as a few microvolts without appreciably loading the circuits being measured_ This loading is limited to the
• Section 11
extent of a few micro-microfarads probe
capacity, so that the probe may be directly
applied in order to pick up the signal and
indicate its intensity, frequency and quality
through the various stages of the receiver
to the demodulator stage. For this purpose,
a T.R:F. amplifier is usually employed
which will cover the desired frequency
range and is provided with a calibrated input attenuator so that a wide range of voltages may be measured. Usually, the' complete instruments, in order to simplify their
design and increase their usefulness, are
provided with several vacuum tube voltmeters, intended for use in measuring specific types of signal voltages. For example,
the RCA-Rider Chanalyst has 5 separate
vacuum tube voltmeters or channels, namely
the R.F.-I.F. channel, which measures voltages by means of a 3 stage tuned R.F. amplifier over a frequency range of 95 to 1700
K.C.; the Power Consumption Indicator,
which measures line currents in terms of
watts from 25 to 250 watts; the Oscillator
Channel, which measures voltages by means
of a one stage T.R.F. amplifier from 600 to
15,000 K.C.; the Audio Channel, which
consists of a one stage amplifier and is used
to measure A.C_ voltages covering the audio
frequency range; and the D.C. electronic
voltmeter previously described which measures D.C. voltages directly in 4 ranges, 0 to
plus or minus 5, plus or minus 25, plus or
minus 100, and plus or minus 500 volts_ The
manner in which this is done is readily
apparent by examining Fig. 21 in which is
reproduced a complete schematic of the
RCA-Rider Chanalyst. The amplifier o~t
puts are rectified by diodes which in turn
actuate the 6E5 indicator tubes_ The wattage indicator employs a current transformer
in series with the load, the secondary voltage
being rectified by a diode and actuating a
6E5 indicator, which is calibrated in terms
of watts required to just close the eye.
Many other similar instruments are now
available, such as the Hickok Traceometer,
in which meters are used in place of the
Eye Tubes to directly indicate the value of
the voltages being picked up; the Meissner
"Analyst" whose operation is similar to the
description in the preceding paragraph,
the Rimco "Dynalizer," which features
a built-in speaker, so that the signal may
be heard as well as measured, as it is
taken from any stage of the receiver.
Multi-channel instruments are particular-
335
OIl
Section 11 •
THE
ly valuable in serVIcmg a receiver in
which the fault is of an intermittent nature,
since each channel can be used to monitor
or listen in on the signal simultaneously at
several stages of the receiver, so that when
the trouble occurs; it can be isolated down
to a particular stage, at its first occurence.
The vacuum tube voltmeters discussed at
the beginning of this article which were de·
signed for \neasuring A.C. voltages, indio
cate or measure the resultant of all fre·
quencies applied to their input, terminals,
being limited only by the physical design
of their input circuits (probe, tube, lead
capacities, etc.) and in a number of cases as
MY E
TECHNICAl.
MANUAl.
described are kept small enough (6 micro·
microfarads or less) so that their probes may
be directly attached at any of the R.F. or
oscillator grids in the receiver, without ap·
preciably detuning or loading the circuits
being measured. Vacuum tube voltmeters of
this untuned type, having readable sensi·
tivities down 1:0 approximately .1 volt may
usually be employed to directly trace the
signal voltage of an entire receiver from an·
tenna to voice coil providing a source of
signal of .1 volt or more is available. Most
signal generators employed by service men
are capable of this output.
As a means of illustrating the ease with
which a recein~r defect may be located by
using availlum tube voltmeter, the follow·
ing f,scussion is in order.
Servicing Receivers with the
Vacuum Tuhe Voltmeter
Since the tubes themselves are one of the
most probable causes of set failure, it is
customary to check all tubes in the receiver
being repaired as a routine matter, prior to
making any further tests. If the rectifier
tube is found defective, especially in cases
where it shows signs of having been over·
RIZ
el.e:CT~ONIC
VOl.TMeTE~
i
7..
I
IlZ7
J3
AF
CHANNEL,
CZ9
1149
~I
FIG. 21-RCA·RIDER CHANALYST
Description
SYMBOL
Resistors
lH, R45, R46 ......... 250M Ohms
R2 ...•...........•..• 9,000 Ohms
R3, R8, R1L .......•..• 350 Ohms
R4, R7, R9, R12, R18 .. 100M Ohms
R5 ....•............. .4,000 Ohms
R6, R10, R13 .......•.. 1,500 Ohms
R14, R15, R22, R37 .... 500M Ohms
R16, R23, R38, R40, R47, 2 Megohms
R17, R24, R39, R48, R49, R5l>,
1 Megohm
R19 ....•.....•....... 9,000 Ohms
R20 ••....••........... 200 Ohms
R25 ..•.•......•.•.... 8 Megohms
336
Desc~lption
SYMBOL
Resistors
R26 ................ 1.5 Megohms
R27 .................. 400M Ohms
R28 •.............•.•. 100M Ohms
R29, R33 .........•... 6,000 Ohms
R30 .•.......•....•... 2,000 Ohms
R31 •..•............. 27,000 Ohms
R32 ................. 10,000 Ohms
'R34 .................. 1,900 Ohms
R35 .....•.•......•... 500M Ohms
R36 ................. 17,000 Ohms
R41, R44 ............ 20,000 Ohms
R42, R21 .............. 75M Ohms
R48 .................. 2 Megohm.
CONDENSERS
......•.............. 0014MF
..•.............•..••015MF
....................
.15MF
C5, C6, C8, C9, C10,
cn, C12, C13, C20....
.1MF
C7 ................ RF-IF Tuning
C14, C24 ............... .001MF
C15 ..................... 0002MF
C16, C18, C19, C21, C23,
C28, C31, C32, C37....
.OIMF
C17, C36 ................0001MF
C22 ................. Osc. Tuning
C1
C2
C3
C4,
C25, C26, C33 .......... .
.05MF
8-8MF
C27a, C27b ...•......•.•
.01MF
C29 .................. '-'.
C30 ................... .
10MF
C34, C35 .......... RF-IF Coupling
Note: Condenser C·37 and pin
jacks J7, J8 and J9 are used only
on series above No. 199.
VACUUM
loaded, such as burnt off cathode tabs, or
burnt out filaments, it is logical to check
for anything in the B supply system which
might be heavily overloading the rectifier
tube, before placing a new rectifier tube in
operation. This can quickly be done by
checking the D.C. resistance between one
plate and cathode or filament of the rectifier
tube socket with an ohmmeter, or in what·
ever manner the circuit and instruments
available require.
A wattmeter may be used as a rapid
means of determining whether a set's power
supply system is normal. Excessively
high readings from the rated value of
the set indicates some overload condi.
tion and excessively low readings indicate
some open circuit condition of the power
supply. Obviously a fault here must be
corrected before proceeding with any fur·
ther tests. In the case where abnormally
high p~wer is being drawn, there is either a
shorted transformer winding or some short
in the B supply system. When the rectifier
tube is removed and the only load on the
iransformer is the tube filaments and the
high power is still drawn, it is very likely
that the transformer is at fault. Usually
transformer failure occurs in the high volt·
age windings. This may easily be checked
by measuring the secondary voltages, any
decided unbalance between the voltages ap·
pearing across each half of the winding,
indicating a fault. A vacuum tube volt·
meter is not necessary in measuring such
power transformer voltages where appre·
ciable power may be drawn. However, there
is certainly no disadvantage in using one
for this work.
TUB E
VOI.TMETERS
Having eliminated the transformer and
rectifier tube as the cause of power sup·
ply failure, a routine check with the
ohmmeter will readily locate the defec·
tive component; usually a filter or by·
pass condenser in the case of high wattage
readings, or an open speaker field, choke
or faulty connection interrupting the B
voltage supply in the case of low wattage
reading. In locating the cause of an open cir·
cuit failure in the power supply, the vacuum
tube voltmeter is a convenient tool, the volt.
age being traced through the power suppl)
system until the point at which it disappears
is located. The vacuum tube voltmeter also
provides a rapid means of checking the peak
surge voltage applied to the input filter con·
denser before the amplifier tubes warm up,
in case underrated filter condensers are sus·
pected of having been used.
Signal Tracing
After having determined that the power
supply is operating normally, the next step
in locating the fault is to apply a signal
voltage from a test oscillator. Some conven·
ient frequency close to the low frequency
end of the broadcast band and away from any
strong locals present, should be used. Trace
it through all the stages of the receiver until
the point at which it stops or becomes dis·
torted is located. The low frequency end of
the broadcast band is preferred, so that the
slight probe capacity will have minimum
effect in detuning the circuits under test.
In tracing the signal through the audio
stages a steadily modulated signal is needed,
• Section 11
so as to allow stage gains to be measured
and the signal traced up to the voice coil.
In checking for oscillations, hum, or oth.
er' miscellaneous noises present in the reo
ceiver without an input signal being applied,
the vacuum tube voltmeter is used to locate
the source of this voltage which in itself
becomes the signal. ,
Usually testing through with the broad·
cast band signal is sufficient even on an all
wave receiver, if the trouble is present on
all bands. If the trouble is in the short wave
bands only, one would immediately seek it
in the R.F. mixer or oscillator sections,
since all other parts of the receiver operate
the same on either the broadcast or short
wave bands.
Using the signal voltage for testing in the
above manner, it makes little difference as
to the type or complexity of the receiver or
amplifier being tested, the more stages or
the more complex the receiver merely add·
ing more points at which to check for nor·
mal signal and normal gain. For example,
let's take a typical receiver, Fig. 22, and
analyze it, using signal tracing ,methods.
Starting at the antenna, the test oscillator
is set so as to deliver some reference signal,
as measured by the vacuum tube voltmeter
and noted, to the antenna coil or point (I)
on diagram. Failure of the signal to appear
at point (1) would indicate either a shorted
winding or in the case of multi·band sets,
where the primaries are switched, some
connection failure. Having established a
signal at (1) proceed to the R.F. grid or
point (2). A signal here indicates proper
performance of the antenna coil and also
whether the coil is tuning according to the
FIG. 22
337
Section 11 •
THE
dial calibrations. It is common to find the
R.F. coils not tracking with the dial, espe·
cially at the low frequency end of the bands,
advantage being takeit of their broadness
of tuning to allow for production tracking
errors.
Antenna coil gains of 3 to 10 are usual in
household receivers and from 10 to 50 in
autoJeceivers. Failure of the signal to ap·
pear with normal gain at (2) can be caused
by the coil not being tuned to the sig~al
frequency, some failure in the coil wind·
ings, the A.V.C. condenser open, the tun·
ing condenser shorted or the tube drawing
grid current loading the antenna coil sec·
ondary, or leakage between the grid to
ground. The by·passing action of the A.V.C.
condenser can readily be checked by meas·
uring whether any signal appears across it.
Normally the capacity of this condenser is
high enough as to be practically a short
circuit to the signal frequency, and no signal
voltage should appear across it.
The next test point is the R.F. tube plate
or (3) on the diagram. Normal signal volt·
age here would indicate that the tube is
functioning properly as an R.F. amplifier.
Lack of signal or gains appreciably be·
low normal, indicate a tube failure or
failure of the tube to receive its proper
operating voltages. This can be checked in
a routine manner by measuring all its D.C.
voltages including its grid bias directly
with a D.C. type vacuum tube voltmeter.
Should the set have A.V.C., and the input
signal be high, causing the A.V.C. to func·
tion increasing the bias on the R.F. grid,
the stage gain will be lowered and vary
widely, depending on the extent of A.V.C.
bias applied.
Highest gains will be found when the
A.V.C. voltage is at a minimum, correspond·
ing to maximum sensitivity of the tube. In
modern sets utilizing high gain, multi·ele·
ment tubes, usually nearly all the stage gain
is realized in the tube itself, whereas older
sets using triod~ amplifier tubes usually ob·
tained most of their stage gain in the
coupling transformers, the tube seldom
showing a gain of greater than unity. Some·
modern two gang TRF sets have R.F. stage
gains as high as 75, although most 3·gang
multi·band superheterodynes usually have
an R.F. stage gain of approximately 25 or
less, due to thermal noise limitations.
The next check would be for signal volt·
age at the mixer tube grid or point (4) in
Fig. 22. The presence of signal here would
establish normal functioning of the trans·
former coupling the plate circuit of the
33B
M Y E
TECHNICAL
MANUAL
R.F. tube to the mixer grid. Failure of sig.
nal to appear at the mixer grid could be
caused by the transformer not being prop·
erly tuned (or tracking) or by a defect in
the transformer such as shorted or open
windings, or by open plate or grid circuit
by.pass condensers.
The next check would be for signal volt·
age at the mixer plate or (5). Here one
would expect to find several differ.ent fre·
quency voltages, one at the R.F. signal fre·
quency, at the oscillator frequency, and at
the sum and difference frequencies, as well
as harmonics of same. The presence of the
signal frequency at the plate indicates that
the tube is operating as an amplifier and the
presence of the I.F. frequency (hearly all
receivers use the difference beat between
signal and oscillating as the I.F. frequency)
would indicate proper operation of the
oscillator as well. Failure of the proper
I.F. frequency to appear here with a normal
expected conversion gain may be a result of
incorrect alignment, lack of proper tube
element voltages, defective mixer tube, or
low oscillator voltage.
In most modern receivers, conversion
gains between 20·60 are obtained when the
A.V.C. voltage is at a minimum. An untuned
type of vacuum tube voltmeter at (5) will
read the sum of all the various frequency
voltages present, however, the presence of
the proper I.F. voltage is quickly established
by moving over to the I.F. grid, the I.F.
coupling transformer tuning substantially
eliminating the other frequencies. Also, the
set oscillator could be killed by shorting the
oscillator tUlling condenser or removing the
oscillator tube to establish the presence of
the original signal frequency at the mixer
plate.
Absence of oscillator voltage may be
readily checked either by measuring
same at the stator of the oscillator sec·
tion of the gang condenser with the
A.C. vacuum tube voltmeter or by meas·
uring the D.C. developed across the oscil·
lator grid resistor with the D.C. section of
the vacuum tube voltmeter. In this manner,
the uniformity of oscillation over the entire
band may be checked. Should the tube stop
oscillating the negative D.C. voltage devel·
oped across the grid resistor will drop to
zero or become slightly positive with respect
to cathode. Normally this negative voltage
is a minimum of -5 volts. Excessive oscil.
lator voltages are very unlikely since oscil·
lator design is such that with all components
working at maximum efficiency, the proper
oscillator voltages are generated and any
failure tends to reduce rather than increase
the oscillator outputs.
Other oscillator troubles, such as hum
modulation, caused either by cathode to
heater leakage or an improperly filtered
D.C. supply, or to frequency modulation
caused by vibration of some part in the
oscillator circuit may be present. Hum
modulation would show up in the output
only when a station is being received and
can be located by checking the hum level
of the oscillator plate supply with an A.C.
vacuum tube voltmeter.
Assuming that the R.F., oscillator and
mixer stages are functioning properly, the
signal would be traced on through the I.F.
amplifier stages up to the second detect~r
or point (8) on Fig. 22. Obviously, for
rapid isolation of failure of either the
R.F. or audio sections of the receiver, this
test could have been made first; however, in
cases where the set functions but with low
output, it is usually necessary to foll~w
through all the stages, since troubles can
be located in this manner, which would
ordinarily never be located.
I.F. Amplifiers
The receiver shown in Fig. 22 employs
a simple one·stage I.F. amplifier, the output
being coupled into a diode rectifier. The
signal appearing at the I.F. grid point (6)
in the circuit normally should be the same
or slightly less than at point (5), the mixer
plate, since in modern receiver designs, no
gain is obtained in the I.F. transformers, the
gain being obtained i.n the I.F. tube. The
signal appearing at the I.F. tube plate point
(7) in the circuit will vary in gain from ap·
proximately 20 to 100, depending on the
receiver design and amount of A.V.C. volt.
age on the I.F. tube grid. Continuing, the
signal normally appearing at the diode plate
point (8) in the circuit, is usually somewhat
less than at the I.F. tube's plate, due in usual
designs to a step down I.F. transformer ratio
necessitated by the loading effect of the
diode on the transformer secondary. This
step down ratio is usually of the order of
approximately 3 to 1.
I.F. stages and particularly transformer
designs vary widely depending on the type
receiver and perf9rmance desired, although
they all serve the same general purpose,
namely to amplify and select the I.F. signal,
as delivered by the mixer or first detector
tube. The transformers may be untuned,
I
:t
:1
1
VACUUM
single, double or triple tuned. Special pur·
pose transformers, such as band expanding
used for high fidelity purposes or discrimi·
nator type used to develop A.F.C. control
voltages, etc., have been widely used. In
some receivers the coupling between the
primary and secondary coils is varied and
used as a means of controlling the .set's
volume.
Troubles likely to occur in I.F. stages
commonly are mistuned transformers, open
or shorted windings or trimmer condensers,
noisy windings usually dne to lead corro·
sion or loose parts, improper tube voltages,
etc., all of which can be traced to their
source by means of a vacuum tube volt·
meter.
Tracing Signal in Audio Systems
Assuming that normal signal is being ob·
tained at the diode plates, but that ·the set
is still weak or inoperative, the process of
tracing the signal on through the various
audio stages with the vacuum tube volt.
meter until the fault is located, would be_
indicated. In this case, since only the audio
component of the signal should normally
come through the audio stages, a modulated
test signal must be used.
At point (9) Fig. 22, one would expect
to find the audio signal which can be meas·
ured on an A.C. type vacuum tube voltmeter,
and the D.C. component which can be di·
rectly measured with a D.C. type vacuum
tube voltmeter. Since the average value of
the D.C. component varies with the value of
the input signal voltage to the diode plate,
it is widely used to supply the A.V.C. volt·
ages to the R.F. and I.F. grids. To eliminate
the I.F. frequency and its harmonics from
the A.F. signal voltage, the bypass condensers
C and Cl are used from the low side of the
diode winding and filter resistor to ground.
The value of these condensers represents
a compromise between I.F. frequency by·
passing, and not bypassing the high fre·
quency components of the audio signal.
Appearance of the I.F. signal across C or
C1 of any appreciable amount would in.
dicate a failure of this component and may
readily be checked with a tuned type of
vacuum tube voltmq.ter, or with an untune4
type by switching off the modulation from
the test oscillator signal.
The maximum value of A.V.C. voltage
appearing across the diode load resistor
varies widely in different designs, with a
T U 8
E
VOLTMETERS
given signal input, a single stage I.F. reo
~eiver usually having much higher values
than a two stage I.F. set due to the fewer
automatic volume controlled stages.
The presence of a small negative bias
voltage across the diode load resistance
should not be taken for rectified signal volt·
age in inoperative receivers. This voltage is
normal and is due to emission current of
the diode. Its value is normally approxi.
mately 1.0 volt when the diode load resist.
ance is of the order of .5 megohm or better.
Having established the presence of an
A.F. signal at the diode load resistance, the
volume control should be advanced to maxi·
mum and a check made for the signal at
the A.F. amplifier tube plate or point (10)
Fig. 22. If the first A.F. tube is a high mu
triode a normal gain of approximately 30
would be expected here. Usually the cou·
pIing condenser C. is of a value sufficiently
high so as to have negligible impedance
except at very low audio frequencies.
Appearance of the signal at (10) and not
at (11) would immediately indicate a faulty
coupling condenser, either open or partially
or completely shorted. It is extremely im·
portant that the coupling condenser have a
low D.C. leakage, otherwise plate voltage
would be applied to the output grid causing
high grid current and rendering the stage in·
operative. A weak or distorted signal at (11)
could be caused by a defective tube, im·
proper tube bias, overloading of the tube, or
incorrect plate voltage, etc. Here again all
the actual operating voltages may be meas·
ured with a D.C. type vacuum tube volt·
meter without affecting tJae circuit.
Continuing, the signal voltage is checked
at the grid and plate of the' output tube
points (11) and (12) on Fig. 22. Normal
gains of 2 to 5 are obtained using triode
output tubes. Gains of 10 to 20 are normally
obtained with pentode type output tubes
although much depends on the output trans·
former design and the impedance of the
voice coil. Due to the step down ratio of
the output. transformer, the signal appear·
ing across the voice coil point (13) on Fig.
22, will be much lower than at the output
tube plate. This voltage step down depends
on the rated plate resistance of the output
tube and the voice coil resistance. Looking
into the voice coil from the output tube
plate, the load that the transformer presents
to the plate circuit it expressed mathemati·
cally as follows:
.
RLoad =
R (NN: )2
V. Coil
where N p = pri. turns
N. = sec. turns
• Section 11
The actual voltage step down will be di·
. 1 to th e turn ratio
. or N,
rect1y proporUona
Np
'
Other factors effect the operation of output
transformers, however they are primarily
design considerations about which a service
man is ordinarily not concerned.
It might be well to point out here that
carefully made accurate stage gain meas·
urements are usually necessary only in
actual receiver design work, and are unnec·
essary and time consuming in radio servic·
ing. A service man is primarily concerned
with locating, in the shortest possible time,
the defective component which usually
causes a large, easily identified departure
from normal sigual levels. A vacuum tube
voltmeter provides a means of rapidly locat·
ing this point.
Checking Distortion with a
Vacuum Tube Voltmeter
Possibly the most direct and convenient
method of locating the source of distortion
lies in the use of a tuned type vacuum tube
voltmeter provided with an audio output
jack or audio amplifier and speaker so
that the audio component of a broadcast
signal may be listened to as picked up from
any stage of the receiver. In this way the
point at which the signal becomes distorted,
picks up hum, or other noises, may be 10'
cated by a listening test, the stages following
th~s point merely serving to amplify the
distortion.
The subject of distortion is very involved
and is impossible to cover completely in
this article, however, some of the most fre.
quent causes will be mentioned. It may he
caused by improper operating voltages ap·
plied to the tube elements, by overloading
the tube, by rectification where undesired,
by regeneration, by introduction of unde·
sired hum or by excessive selectivity caus·
ing frequency distortion.
Tube operating voltages may be directly
measured with a D.C. type vacuum tube volt·
meter so that distortion due to this cause
. may be easily located. Overloading of an
amplifier stage results in serious distortion
causing the positive peaks of the signal to
be cut off due to the tube drawing grid cur·
rent. Rectification likewise can cause serious
distortion due to the tube being biased high
enough to cause the negative peaks of the
signal to be cut off. This trouble frequently
shows up when attempting to receive strong
399
THE
·Section 11 •
local signals with older type receivers em·
ploying sharp cut·off amplifier tubes such as
tbe type 224 in R.F. and I.F. stages. The
usual remedy for this condition is to substi·
tute a more remote cut·off tube such as the
type 235.
Distortion due to regen,eration is caused
by a part of the amplified signal of a stage
or group of stages feeding back into the
input grid circuit in proper phase so as to
cause
oscillation
or instability tending
towards oscillation. This may be the result
of coupling from B supply systems common
to both plate and grid circuits and frequent·
ly occurs in midget receiver designs which
operate at elevated temperatures causing
M Y E
TECHNICAL
MANUAL
cially on pentodes of the beam type, the
signal decreases, the set becomes more
stage oscillates at a high inaudible fre·
sensitive, and as the input signal increases
quency causing grid current with its at·
tendant distortion and resulting in very
the set is made less sensitive. The gains of
short tube life.
Noise due to some defective component
vary by automatically changing the grid
bias applied to the tubes in accordance with
the various amplifier stages are caused to
in a receiver or amplifier can usually be
the signal output. Since the amplified sig.
traced to its source by considering it as a
signal and locating the first point at which
nal as presented to the second detector stage
it appears.
Noise is frequently caused by worn or
will vary in proportion to the input signal
at the antenna, this amplified signal is used
to control the gain or sensitivity of the
otherwise defective volume or tone controls
receiver by controlling the amount of bias
and is usually most noticeable when turning
applied to the amplifier stages. One of the
the control.
Noise also frequently results from poor
most simple and direct methods of accom·
plishing this is shown in Fig. 23. A diode
contact between the wipers and rotor of
rectifier is used to obtain a D.C. voltage
the electrolyte to dry out of the filter con·
the tuning condenser gang, or from poor
which varies in direct proportion to the
denser thereby decreasing its effective by·
passing action. Regeneration may also be
contact in any of the dial drive parts show·
ing up when the set is being tuned. In
the result of slight capacitive coupling be·
multi·band ~ets noise frequently develops
due to poor contact in the various switch
tween grid and plate circuits resulting from
improper lead placement, shielding, etc.
Distortion due to small capacitive cou·
plings from the second detector stage into
the grid of the first or second A.F. tubes is
frequently found especially at low volume
levels and can usually be eliminated by reo
routing leads and by adequate shielding.
sections.
Occasionally noise develops in an inter.
stage audio coupling transformer usually
amplified I.F. signal voltage E. as applied
to the diode plate and also to obtain the
audio component of the signal voltage.
Since the diode conveniently performs both
functions of detection and supplying A.V.C.
voltage this arrangemellt is widely used in
commercial receiver designs,. The D.C. com·
ponent which appears across the diode load
due to moisture causing electrolysis between
windings ultimately resulting in an open
resistance R, and R. is negative with respect
circuit. Most of these noises can be traced
to their source by using them as a signal
used as a filter in conjunction with the con·
to ground. The resistance R, is commonly
Distortion due to hum is usually caused
and tracing back to the point or stage in
densers C, and C. so as to' eliminate any
by improper filtering of the power supply,
which they first appear since the following
stages only serve to amplify them.
I.F. signal from being passed on to the audio
however it frequently results from cathode
stages. The condenser C. is used to couple
to heater leakage in a tube. Occasionally a
the audio component over to the grid cir.
tube will develop a serious distortion due
to leakage and gas currents causing the grid
cuit of the first A.F. amplifier tube. Resistor
R. and condenser C. are used to filter out
to go positive after having operated for a
Use of Vacuum Tube Voltmeter in
Special Control Circuits
the audio from the D.C. components so that
period of several hours. Such tube failures
a steady D.C. voltage is - obtained which
usually are not found on tube checkers,but
Automatic volume control or A.V.C. is
varies directly as the signal voltage E. into
can be readily traced to their source with
a vacuum tube voltmeter, when the condi.
being used in practically all modern com·
tion appears in the set.
mercial receivers, except possibly the cheap·
est 2 or 3 tube T.R.F. midget types. The
Distortion and extraneous noises due to
purpose of A.V.C. is to cause the volume
loose particles between the spe!lker voice
coil and pole piece or due to the pole piece
output of the receiver to remain constant
rubbing the voice coil frequently occurs.
at any sel~cted level regardless of the varia·
tion of the input signals as received by the
the diode. The values of C. and R. are a
compromise between good filtering action
to the lowest audio frequency encountered
vs. the time constant effect of the series
R.C. filter. Most modern A.V.C. circuits
have ~ time constant of approximately .1
second, the time constant being the prod.
uct of the total resistance in the circuit in
Occasionally, parti?ularly in auto sets, this
set's antenna. Actulilly A.V.C. systems are
condition occurs noticeably only after pro·
longed operation or when the speaker is
not this perfect, however, by their use the
series with the total capacity of the circuit.
variation in audio signal voltage output vs.
input antenna signal voltage is reduced
For example a series resistance of 2.0 meg·
from something like 100,000 to I down to
approximately 7 to 1 for an ordinary A.V.C.
have a time constant of 2 X 106 X 5 X 10-8
circuit. A.V.C. circuits employing a separate
ticularly noticeable during tuning. For ex·
A.V.C. amplifier stage further reduce this
variation. A.V.C. operates by causing the
ample, when tuning from a strong local to
working at its highest temperature.
Oscillation in a receiver
can be traced to
,
its source by considering it as a signal and
tracing it with an A.C. type vacuum tube
voltmeter up to the point at which it origi.
nates. Occasionally as a result of regenera·
tion; sometimes due to an output plate
. circuit bypass condenser being open, espe.
340
ohm and a total capacity of .05 mId. would
or .1 second. Excessive time
~onstant
is par·
a weaker signal, if the circuit time con·
input signal voltage to control the gain of
stant were large, the high bias developed
the amplifier stages, so that as the input
by the local signal would not decrease rap·
VACUUM
VOLTMETERS
T U 8 E
• Section 11.
potential, the operating tube voltages are
obtained by returning the cathode and grid
to points negative with respect to ground.
The grid resistors R. and'R. in conjunction
with condensers C. and C. eomprise a hum
filter arrangement.
In checking this system a slight negative
voltage at the A.V.C. triode plate with reo
spect to ground is normal with no signal,
and should become increasingly negative
with respect to ground as the signal is
increased.
2 ~AUDIO
'--_ _'llvWI/lr_---,=t-_ _ _ _ _ _ _---'W-""I\'(I,f\,_ _ _ _ _ _ _+----\c
+
FIG. 23-TYPICAL DIODE RECTIFIER A.V.C. CIRCUIT
idly enough to allow the reeeiver sensitivity
to inerease suffieiently for the weaker sig.
nal to be heard, unless the set was slowly
dialed. When going from a weaker signal
to a strong one, the bias would not inerease
rapidly enough, so that momentary over·
loading and blasting of the signal would
result. For these reasons replaeement of
resistors or eondensers in the A.V.C. net·
work should have values closely as reeom·
mended.
Referring again to Fig. 23 it will be noted
that the A.V.C. voltage as developed across
the diode load resistor R. is applied to the
grid returns of the R.F. and mixer tubes so
that their grid bias and therefore stage gains
are eontrolled by the signal E. that appears
at the diode plate. Sinee the grids of the
tubes draw no eurrent when they are biased
negatively beyond their so ealled eontaet
potential points, the values of the isolating
resistors R. and R. ean be and usually are
made quite high. For this reason any volt·
meter applied at the R.F. or I.F. grid for
measuring bias requiring more than a few
micro.amperes for its operation will act as
bias will be applied to the A.V.C. grids reo
sulting in blocking and extreme distortion,
_ especially on weaker input signals.
Another simple A.V.C. system commonly
used in the older type receivers is shown in
Fig. 24 and uses a triode as the A.V.C. tube.
A. V.C. Circuit Using Triode with
Plate Operating at Ground
Potential
Delayed A.V.C. Systems
Delayed A.V.C. is used to retard or delay
any A.V.C. action until the signal has
reached a desired level, thereby providing
maximum receiver sensitivity for weak
signals.
Such systems require separation of the
funetion of detection and A.V.C. aetion be·
cause any delay aetion put on a common
detector and A.V.C. tube to eause it not to
produce A.V.C. voltage until a certain sig.
The A.V.C. voltage is developed across R,
in the triode plate cireuit, I.F. signal voltage
being applied to the triode grid by means
of Cl, eausing the plate current of the triode
to vary with the signal strength to establish
a control essentially the same in principle as
previously discussed in connection with the
diode type rectifier.
the other diode being used for detection or
In this system, since it is necessary that
the triode plate circuit operate at ground
audio signal purposes.
In Fig. 25 is shown the delayed A.V.C.
nal level is reached also would bloek the
audio signal until the same releasing level
has been reached.
Most delayed A.V.C. systems make use
of the second diode of a double diode tube
to perform the delay and A.V.C. funetion,
i-_-r---'2o:;ND DET
a load across the A.V.C. circuit and false
readings are obtained. However a vacuum
tube voltmeter whieh draws no current in
making its measurements will indicate the
actual A.V.C. voltag~s in any part of the
system.
Frequent eauses of failure in A.V.C. sys·
tems are the R.F. bypass condensers C. and
C. and the audio bypass condenser C. devel·
oping a leakage resistance low enough to
cause serious reduction of A.V.C. voltage
actually applied to the tube grids. Similar
effects are caused by leakage developing
internally between grid and cathode of the
controlled tubes. Occasionally a gassy tube
will draw enough gas eurrent through the
high resistanee A.V.C. string that a positive
c,
]
40M.
FIG. 24
341
Section 11 •
THE
MY E
circuit of a modern receiver which in addi.
tion provides the no signal fixed grid bias
for the controlled tubes, their cathodes be·
ing grounded.
Following the action of diode D, in Fig.
25 it is exactly the same as has been pre·
viously described for diodes, the A.V.C.
voltage appearing across the diode load reo
sis.tance R. and the audio component also
being taken from the same place, point (1)
on diagram. The second diode D. however
is shunted across the A.V.C. supply as it
comes from the 2.0 megohm audio filter reo
sistor R. at point (2) on diagram. It will
also be noticed that the catho~e of this
shunting diode D. is made negative with
respect to ground or with respect to its plate
by approximately 2.0 volts. In other words
the plate of D. is positive by 2.0 volts with
respect to its cathode, so that it will conduct
and draw current through Ro, It., and R, and
act as a fairly low resistan~ load across the
A.V.C. supply or point (2). The bias due
to the diode current through Ra, R .. and It,
will then appear at point (2) and serves as
initial bias for the R,F., and I.F. tube grids.
For weak signals then that cannot pro·
duce an A.V.C. voltage of more than 2.0
volts across It" the conducting diode D.
eft'ectively shunts the A.V.C. voltage as ap·
pears at point (2). However on stronger
signals when the A.V.C. voltage exceeds 2.0
volts this A.V.C. voltage is applied negative·
ly with respect to ground in the plate circuit
of D. bucking out the eft'ect of the positive
plate voltage from the cathode circuit and
eft'ectively making the D. plate negative so
that it no longer conducts, its shunting effect
342
MANUAL
-'="--..(i'mm5riit---,.--I
J--
AUDIO
FIr.. 26
on the A.V.C. is removed, and the A.V.C.
system operates normally. This type circuit,
due to the use of a 2.0 megohm (or higher
in some cases isolating resistance) R .. is
particularly susceptible to any gas currents
from the controlled tubes, resulting in zero
or positive bias appearing at point (2)
which of course causes mushy or distorted
reception.
Squelch or QAVC Circuits
QAVC circuits are frequently used to
eliminate interstation noise when tuning a
receiver. They operate by blocking the sig·
nal usually in the first audio stage, although
I
FIG.
TECHNICAL
25
AUDIO
some designs block either the I.F. or second
detector and prevent any signal output of
the set until the signal strength of the in·
coming signal has reached a predetermined
level. Thus interstation noise on signals
lower than this "squelch" level "are sup·
pressed. Most designs also provide a eon·
trol for adjusting this "squelch level" to the
particular location requirements or a switch
which eliminates the squelch action com·
pletely.
The actual circuit designs for accomplish.
ing QAVC vary widely, although they all
accomplish the same purpose.
In Fig. 26 is shown the QAVC circuit of
the RCA Model R·78 which operates by
heavily biasing the signal supplying I.F.
amplifier circuit until the input signal is
sufficiently high as amplified by the I.F.·
A.V.C. amplifier stage to cause the triode
section of the 55 tube to drop its plate cur·
rent, thereby removing the blocking bias
from the cathode circuit of the signal I'p:.
amplifier tube.
This circuit can be readily checked in
operation with the vacuum tube voltmeter
by first following the I.F. signal through
from the signal I.F.amplifiergrid,point (1),
over to the plate, point (2), and over to the
grid of the second detector point (3). On
weak signals, approximately 5Q microvolts
or less into the antenna when the switch S.
is closed causing the QAVC to function, very
little signal should appear at points (2) and
(3) due to the high bias developed across
VACUUM
R. by the plate current of the triode section
of the QAVC type 55 tube. On stronger sig.
nals, however, this blocking bias should
drop and normal I.F. signal gains would be
expected at points (2) and (3).
The I.F. signal which appears at point (1)
is taken over to an I.F., A.V.C. and QAVC
amplifier stage to the grid of the type 58 tube
at point (4) and should appear with normal
tube gain at the plate or point (5), also at
the diode plates Dl and D. or points (6)
and (7) on diagram regardless of whether
signal appears at point (3). D. is used also
to rectify this signal for supplying a negative
bias varying with the signal to the control
grid of the triode section of the 55 tube.
This D.C. voltage should appear between
point 9 and the cathode of the type 55 tube.
When this bias voltage i.s small the triode
draws appreciable plate current through the
common cathode resistor R. in the I.F. Slg·
nal amplifier stage, blocking the tube. When
this bias at point (9) becomes high the
triode plate current drops to zero and the
drop across R. becomes normal for proper
amplifier action of this tube. Obviously
opening switc}I S, will open the plate circuit
of the triode making the QAVC inoperative,
the set then bein.g controlled by, normal
A.V.C. action as previously described.
In Fig. 27 is shown a QAVC arrange·
ment as used in the Philco type 16 receiver
and is typical of the blocked audio type.
In this arrangement the type 78 QAVC
T U 8 E
VOLTMETERS
tube i~ used to control the e:lfective screen
voltage applied to the type 77 first audio
tube. When the I.F. signal voltage is low, a
low bias will be applied at the QAVC grid,
point (l), and the tube will tend to draw a
high plate current through the 1.0 megohm
resistor Rl which is also common to the
screen of the 77 first audio tube causing a
high drop across Rl and lowering the e:lfect·
ive voltage available to the first audio
screen, thereby making the, first audio stage
inoperative.
When the I.F. signal voltage is high, a
high biasing voltage is applied to the QAVC
grid, thereby lowering its plate current as
drawn through the resistor Rl (or in other
words lowering its shunting e:lfect) so that
the screen voltage at (2) as applied to the
first audio returns to the proper value for
its normal operation as an audio amplifier.
A switch in the cathode circuit of the QAVC
tube is provided so that the squelch action
may be eliminated if desired. The 10 meg·
ohm control R. is used to adjust the screen
voltage of the QAVC tube, so that the point
at which the "squelch" action releases may
be varied according to local signal require·
ments.
Once the circuit action of these QAVC
arrangements is understood, servicing then
becomes only a problem of measuring the
operating voltage conditions of the com·
ponents involved, which can conveniently
OET
37
500M
AVC_-..---+----1
• Section 11
and without disturbing the circuit's opera·
tion be done with a vacuum tube voltmeter.
Automatic Frequency Control
Circuits
Modern selective broadcast receivers are
frequently mistuned by their users resulting in distortion and poor performance of
the receiver. To overcome this operator
Inistuning error and also to compensate for
slight variations in the adjustment of mechanical push button station selecting arrangements A.F.C. has been developed and
applied to deluxe type receivers.
A.F.C. functions to vary the frequency
of the receiver's oscillator (over a limited
range) so that the frequency di:lference between the local oscillator and the incoming
signal will produce the proper I.F. fre·
quency at which the I.F. stages are designed
to operate.
To accomplish this a means has been devised for translating frequency deviation of
the I.F. signal produced by the local set
oscillator's beat with the incoming signal
into a control voltage deviation, the magnitude and pola~ity of which is determined
by whether the I.F. signal is above or below
the set's resonant I.F. frequency. This is
accomplished by means of what is called a
discriminator. This control voltage supplied
by the discriIninator is used to control the
frequency of the local set oscillator by
means of a frequency control tube caused to
act as a variable inductance in shunt with
the oscillator tuned circuit, the magnitude of
its e:lfective shunting inductance being determined by the control voltage developed
at the discriIninator.
A basic discriminator circuit is shown in
Fig. 28_
-=10 ME:G
cPLA1JF<
'.
"
40ME:G
'-___<"2
I
FIG.
27
FIG_ 28
343
THE
Section 11 •
The I.F.' signal voltage E" appearing
across the tuned primary is coupled mag·
netically to the center tapped secondary
producing the induced voltages .,& and E.
across each half of the secondary winding.
E" is also coupled by C, to .the secondary
midpoint so that the resultant signal voltage
appearing at D, or D. is the vector sum
of the series voltage E" plus E, or Eo. When
the I.F. signal is at the resonant frequency
of the tuned primary and' secondary dis·
criminator transformer circuits the signal
voltages appearing at D, and D. are equal.
Theref~re equal rectified voltages will ap·
pear across AB and BC. However, A will be
positive with respect to Band C will be
positive with respect to B so that the A.F.C.
voltage from A to C or ground will be zero.
In other words when the receiver has been
correctly tuned so as to produce the resonant
I.F. frequency, no A.F.C. voltage is devel·
oped, as expected, since no control is neces·
sary when the receiver is properly tuned.
However, when the set is tuned in such a
manner as to produce an I.F. frequency
above the set's resonant I.F. due to the phase
shift of the series voltage E" and E, and E.
the signal voltage appearing at D, will be
less than that at D. resulting in a negative
A.F.C. voltage across points A-C. Wh.en the
set is tuned such as to produce an I.F_ frequency below the set's resonant I.F. the volt·
age appearing at D, will be greater than that
at D. resulting in a positive A.F.C. voltage
across points A-C: This voltage, varying in
magnitude and polarity dependent on the
incoming I.F. frequency, is applied to the
control tube. Fig. 29 is a reproduction of a
typical resonance curve o( an A.F.C. transformer showing A.F.C. control voltage de·
veloped vs. kc. off resonance.
From the above discussion servicing of
discriminators with a vacuum tube volt-
Fic.29
344
MY E
TECHNICAL
MANUAL
meter becomes obvious C after th~ circuit
action is understood. Most discriminator
troubles arise due to improper adjustment,
and a vacuum tube voltmeter provides a convenient method of correctly adjusting a discriminator transformer after the signal has
been traced to D, and D. and its rectified
D.C. components are established at p,oints
A and B. Alignment is conveni,:ntly accom·
plished by connecting a vacuum tube volt·
meter from B to ground and adjusting the
primary padder C, for maximum voltage
. output when a signal generator supplying
. the resonant I.F. set frequency is connected
back at the 1st .detector. Then the vacuum
tube voltmeter is connected at A and the
ilecondary padder C. is adjusted until the
A.F.C. voltage is exactly' zero. This adjustment is critical and slight misadjustment in
either direction should cause a rapid rise
of A.F.C. voltage, its polarity depending on
the direction of mistuning as indicated in
Fig. 29.
Having established proper discriminator
action we shall next see how this A.F.C.
voltage is used to vary the frequency of the
local set oscillator.
In Fig. 30 is shown a basic oscillator control circuit using a tube as a variable inductance in shunt with the oscillator tuned circuit.
To accomplish its purpose, that is, to provide .some way of increasing or decreasing
the set's oscillator frequency without changing the setting of the oscillator section of
the gang condenser, the control tube is made
to act in effect as an inductance in shJ1nt
with the oscillator coil inductance, the magnitude of this inductance being determined
by the bias on the frequency control tube or
by the A.F.C. voltage from the discriminator.
Referring to Fig. 30 the network R,C,
connected across the oscillator coil has val-
Flc.30
ues such that the resistance of fu is greater
than the capacitive reactance of C" the combination having nearly unity power factor,
so that the current through C, is nearly in
phase with the oscillat,or voltage. Then since
the voltage across a conde~ser lags its current by 90' it follows that the oscillator
voltage as applied to the oscillator cont~ol
tube grid lags the oscillator voltage across
L by 90'. If the tube is properly biased as
an a!Dplifier its plate current will be in
phase with the grid voltage, therefore its
plate current lags the oscillator voltage
across L by 90', causing the tube to act as
an effective inductance across L, the condenser C. having low impedance and used
to isolate the B voltage.
Since the plate current of the control tube
draws a lagging current with respect to the
oscillator voltage across L and since the
plate current can be varied by varying the
bias on the grid, we have in effect a variable
inductance shurlting the oscillator coil,
whose magnitude is controll"d by the discriminator control voltage. Resistor R. and
condenser C. are used to isolate the oscil.
lator voltage across C, from the A.F.C.
network.
Here .again the vacuum tube voltmeter
may be used to measure any of the D.C.
control voltages or A.C. signal voltages
present, and isolating the trouble becomes
a problem of understanding the circuit
action.
In conclusion we would like to point out
this fact. The uses to which a vacuum
tube voltmeter may be applied are limited
only by the design of the instrument itself
as regards sensitivity, frequency characteristics, and circuit -loading due to input capacity, etc. In practice its usefulness also
depends on the user's working knowledge
of the circuits being investigated and so
many short cuts and time saving tests will
suggest themselves, during the process of
locating troubles in radio or allied equipment that it would be impossible to completely cover all the possibilities in many
volumes of writ,ten material. The time spent
on reviewing and keeping up with modern
radio circuits so as to understand their purpose and operating principles will save
many tedious hours formerly spent in attempting to locate the trouble by more
indirect methods.
e
THE
Section
12
MYE TE£HNI£AL MANUAL
Usefnl Servicing
Information
MALLORY
345
Section 12 •
THi
M YE
MANUAL
TECHNICAL
USEFUL SERVICING INFORMATION
To facilitate use of the servicing information in this se,ction, the following table of contents is
, included to provide a faster reference source than the complete book index appearing at
the back of the book.
PAGE
PAGE
1. The application of Ohm's law in power supply.
and divider systems . . . . . .' . . . . . 346,347,348
5. Standard resistor color designations
6. Standard mica condenser color code .
, 2. Methods for calculating voltmeter multipliers
and milliammeter shunts. . . -. . . . .
348, 349, 350
3. Power Transformer-Design and Repair .
360'
. 356
7. Reference tables to simplify commonly
required calculations:
a. Reactance (LC) charts . . .
356, 357, 358,359
b. Inductance of single layer coils
361
353
Copper wire table . . . . .
351, 352, 353
4. RMA approved color coding for
following radio components:
a. Power transformer leads. . .
b. Audio transformer leads. . .
c. Intermediate frequency (LF.) transformer leads
d. Dynamic speaker wiring .
e. Battery cables . . . . . . . . . . . . . . .
.
f'
8. Automobile battery ground chart
354·
354
354
355
356
9. Ballast resistor wiring chart. . .
10. Miscellaneous servicing formulas
363
362
363,364
11. Circuit constant tables for resistance-<:apacity
coupled amplifiers . . . . . . . . . 365, 366, 367, 368
•
I
I
r
I
Application of Ohm's Law
in Power Supply SysteIlls
Ohm's law (and its derivatives) is without
doubt the most widely used formula in radio
service work. It is accepted as the basic
principle for all forms of electrical engineering. In view of this fact it is felt that a
thorough discussion is in order, although a
large portion of those engaged in service
work are already familiar with its use.
Ohm's law may be interpreted as in any
of three expressions that follow:
I. The current flowing in any circuit is
equal to the potential (e.m.f.) applied to the
circuit, divided by the resistance of the circuit, or:
E (potential)
I (current)
R (resistance)
( 0000000'
R=IQO OHMS
R ( .t
) _ E (potential)
reSJ.s ance - I (current)
Fig. 1 shows illustrations for each of the
above formulas~
34.6
In all of the above formulas potential (E)
is expressed in volts. resistance (R) in ohms,
and current (I) in amperes. If the current is
known or measured in terms of milliamperes
it may be converted to amperes by dividing
by 1,000 or by moving the decimal point
three places to the left, i.e., 50 milliamperes
equal .050 amperes.
A
£=250 V
r--0--T
____ J
_l_
I
To summarize, one of the simplest ways
of applying these formulas is by using the
R'=?
300 V
B
1=005 AMPS
2. The amount of potential (e.m.f.) required to maintain a specified current flow
in a circuit in which the resistance is known,
is equal to the product of the current flow
and the resistance.
E (potential) = I (current) X R (resistance)
3. The value of the resistance required to
maintain a given current flow with a known
voltage (potential), is equal to the voltage
divided by the current flow.
The second expression E ... IR is demonstrated by Fig. lC where E = .005 X 2,000
or 10 volts.
FIGURE
I
1 = R
E, IS
. applied In
.
.
The first expressIon,
Fig. IA. 1 =
150~' and solving; I
In the third expression, R =
=
.5 amp.
~' shown in
Fig. lB. we substitute and solye; R =
or 10,000 ohms.
50
.005
expression I : H. To use, simply cover the
unknown or the symbol designating the desired value; thus, to find voltage cover E
and the answer is, multiply current by resistance.
It is often necessary to know the proper
wattage rating for a replacement resistor or
a resistor in experimental construction. The
methods for calculating this requirement are
derived from Ohm's law.
Since Ohm's law gives the relationship
between voltage, current, and resistance, it
is possible to express the dissipated heat in
terms of any two constants of the circuit.
When the voltage across a resistor and the
current passing through it are known, the
power dissipated in the resistor may be computed as follows:
EXI =W
ExaDlple: A resistor having a potential of
20 volts across it, and a current of 2 amperes
I
USEfUL
flowing through it, would be dissipating 40
watts of power.
E (20) X I (2) = W (40)
When the resistance value and the voltage
across the resistance is known, the dissipation is computed in the following manner:
E2
R=W
Example: A resistor of 10 ohms having a
potential of 20 volts across it would dissipate 40 watts of power.
E2 (400) = W (40)
R (10)
When the resistance value and the current
flowing through it is known, the computation is:
I2XR=W
Example: A resistor of 10 ohms having a
current of 2 amperes flowing through it
would be dissipating 40 watts of power.
12 (4) X R (10) = W (40)
One example of the use to which the formulas thus far described may be put, is
illustrated in Fig. 2. In many cases it is
desired to obtain a small current at a constant voltage. This may be accomplished by
connecting a fixed resistor across the output
of a power supply, and circulating enough
current through this resistor so that any
fluctuations in load (either across the whole
resistor, or across a section of it) do not
affect the voltage of the supply source.
CURRENT AT THIS TAP
VARIES FROM I TO 2 MA
TO FlLTEII
j
FIGURE
2
If a current of 10 milliamperes is passed
through a resistor as shown in Fig. 2, and if
the current at a certain tap varies from 1
milliampere to 2 milliamperes, it is obvious
that this small current flowing through the
resistor is not going to change the voltage
appreciably. An additional advantage of a
bleeder is that it connects a steady load
across the power supply at all times and
tends to keep the voltage on the filter condensers at a safe value during the period in
which the tubes are heating up. In usual
bleeder circuit design, the bleeder current is
approximately 10% of the total current
drawn from the power supply. If a: voltage of
250 volts is available at the output of a filter,
and the load of the various circuits is 100
milliamperes, the bleeder resistor should
draw 10 milliaml eres, or 10% of 100. Since
the voltage across it is 250 volts, the value
of resistance is easily calculated by Ohm's
law. That is, dividin~ 250 volts by .01 amperes (10 milliamp~es), gives a value of
SERVICING
INfORMATION
25,000 ohms. The wattage this resistor must
be capable of dissipating is 250 X .01 amperes, or 272 watts. Where greater stability
is required, the bleeder current may be as
high as 25% of the total current.
When several values of voltage are required, the bleeder is tapped at several
points. If the current drawn at anyone of
these taps is greater than a small proportion
of the bleeder current (in this case 10 milliamperes) then the additional current must
be considered in determining the wattage of
the resistor.
, . . - - - - - - { ) l 2 5 0 v.
--iILm~n~m~i
&2+
• Section 12
eral rule for resistors in series is that the
total resistance is equal to the sum of all the
resistors in the circuit. Expressed as a formula:
R (effective) = Rl + R. + R a, etc.
Parallel Resistors
Many circuits have combinations of resistors in parallel, and the current path is
divided through two or more resistors. If the
numerical values of the resistors are equal,
then the effective resistance in the circuit
may be obtained from the formula:
R
R (eff.) = N
_BLEEDER CURRENT
ONLY
~----~~--------~BFIGURE
3
Let us consider a bleeder circuit such as
shown in Fig. 3. The section of the bleeder
resistor between the 250-volt B plus lead and
\ tap 1 must be capable of carrying not only
the current drawn by tap 1 and the current
drawn by tap 2, but also the bleeder current
of 10 milliamperes which circulates through
the entire bleeder resistance. If we desire a
bleeder current of 10 milliamperes, while tap
1 must supply 20 milliamperes and tap 2,
5 milliamperes, then the section between the
B plus 250 volts and tap 1 must carry 35
milliamperes. If the voltage requirtid at
tap 1 is 150 volts, then the voltage drop in
the bleed resistor between B plus and tap 1
must be 250 - 150, or 100 volts.
The resistance value will therefore be 100
divided by .035 amperes (35 milliamperes),
or 2860 ohms. The wattage rating of this
section of the bleeder should be 100 X .035
or 3.5 watts. The section between tap 1 and
tap 2 must carry the bleeder current of 10
milliamperes plus the 5 milliamperes drawn
by tap 2 or 15 milliamperes total. If the
voltage at tap 2 must be 90 volts, there will
have to be a drop of 150 - 90, or 60 volts
in this section of the bleeder. The resistance
of this portion therefore will be 60 divided
by .015 or 4,000 ohms. The wattage required
ofthis section will be 60 X .015 (E X I), or
.9 watts. The remaining portion of the
bleeder resistor will carry only the 10 milliampere bleeder current and will have a resistance of 90 divided by .01 or 9,000 ohms
with a wattage capacity of .9 watts. The
wattage of the total bleeder resistance would
be calculated by assuming that 35 milliamperes flowed through the entire resistance,
that is (2860 + 4000 + 9000) X (.035)2,
or 19.4 watts. The important point in
bleeder design is that the wattage of
the unit should be chosen on the basis
of the maximum current which flows
through any section of it.
Up to this point we have dealt only with
single resistors or resistances in series, although mechanically a single unit. The gen-
Where R is the value of one of- the equal
value resistors and N is the number of resistors in the circuit.
As an example, suppose that a circuit contains three resistors in parallel, as in Fig. 4.
As shown, each of the resistors has a value
of 900 ohms, so, by using the formula and
substituting:
.
R (eff.) =
900
3""
= 300 ohms
R (ErF) 300 OHUS
FIGURE
4
The calculation 9f resistors of equal value
in parallel is very simple as shown above,
but it should be remembered that this formula applies only when the resistors are
equal in value.
In instances where we have resistors of
unequal value in parallel we must use another method to compute the effective resistance in the circuit. In the event that there
are only two resistors in the circuit we can
use the formula:
R (eff.) = Rl X R.
Rl
+ R.
Fig. 5 gives an example of this type calculation. Here we have resistances of 20
ohms and 10 ohms in parallel, and solving
we find that:
R (eff.)
20 X 10 = 200 = 6.6 hms
20 + 10
30
0
20
10
" (£Fr.)
FIGURE
e, OH ...
5
In applications where we have more than
two resistors in the circuit and they are of
347
Section 12 •
M YE
THE
unequal value the solution must be found
by use of the formula:
1
R (eff.)
-
1
1
1
+ - +-etc.
R,
R,
R.
An example of this formula calculation is
illustrated in Fig. 6.
R (EFF')
TECHNICAL
MANUAL
As the above parallel circuits are in series
with resistor R 4, we find the effective value
of resistance by adding 10, 3, 2.2, and 2.2
together. This totals 17.4 ohms.
Resistor RIO is connected a.cross the voltage supply, and the effective value of the
resistance network RI and R9 is, in turn,
connected across RIO' Thus RIO is in parallel
to the 17.4 ohms resistance of the network.
Solving for parallel circuits 50 X 17.4/50
plus 17.4 we have the effective total circuit
resistance of 12.8 ohms.
Knowing that the voltage applied across
this network is 100 volts, and that the effec-
tive resistance is 12.8 ohms, then 100/12.8
is 7.8 amperes, or the total current flowing
in the circuit.
The reader may think that a problem of
this type can hardly occur, but if he will
study the circuit of Fig. 8 he will see the need
for some practical knowledge on the solution
of similar problems. The circuit of Fig. 8 is
a receiver breakdown circuit of the RCA
Radiola 80. Note that there are many small
series circuits,and that they are all in parallel
across the power supply which takes the
place of the Battery E in all the problems
set out above.
22 OHMS
FIGURE
6
The resistances mthe circuit are 20 ohms,
10 ohms, 5 ohms, and 10 ohms. Substituting
in the formula we have:
1
R (efl'.)
1
1
1
1
20 + 10 + '5 + 10
1
1
-------- = = 2.2 ohms
.05 + .1 + .2 + .1
.45
The complete solution of Fig. 6 has been
carried out so that anyone desiring to use
this method of calculation will have a practical example to follow. Although charts have
long been available to simplify the calculation of two resistors of either like or unlike
values in parallel, there has never been,
within our knowledge, any such tables prepared for three or more parallel resistors. As
a result, we recommend that the serviceman
make himself thoroughly familiar with the
procedure for solving such problems.
Resistor Networks
A large number of circuits may be encountered in which resistances are in series
and in parallel. The solution of the effective
value of resistance is obtained by breaking
up the circuit into its local circuits, solving
each portion consisting of parallel circuits,
and then resolving them into simple series
circuits. Fig. 7 is an example along these
lines.
R2 =9 OHMS
RS=
6
E =. 100 V
OHMS
R6=
•
R7=
6
OHMS
OHMS
Ra::40HMS
1=78 AMPS
Rg =5 OHMS
FIGURE
7
The first stcp is to solve all of the branch
circuits. Circuit Rl, R 2 , R a, has an effective
resistance of 3 ohms. Circuit R., R 6, R7 has
a resistance of 2.2 ohms.
Circuit R s, Rg has a resistance of 2.2 ohms.
348
FIGURE
8
Methods for Cal(ulating Voltmeter
Multipliers and Milliameter Shunts
VoltIneter Multipliers
When extending the range of a DC voltmeter, the resistance which must be connected in series with the meter is easily calculated; provided that either the internal
resistance of the voltmeter in ohms, or the
resistance in ohms per volt is known. If the
resistance is given in ohms per volt, the total
resistance of the voltmeter may be found by
multiplying the ohms per volt by the scale
reading of the meter.
If it is desired to extend the range of the
meter by 10 times, the resistance of the
voltmeter is multiplied by 10 - 1, or 9. As
a specific example, let us assume that the
voltmeter in question has a sensitivity of
1000 ohms per volt and a full scale deflection
of 100 volts. It is desired to increase the
range to 500 volts. The range, therefore, is
to be increased by 5 or
(500)
(100)
The resistance of the voltmeter is 1000 X 100,
or 100,000 ohms. It is necessary, therefore,
to multiply 100,000 by one less than 5, or 4.
The resistance necessary in series with the
voltmeter is 400,000 ohms. In terms of a
simple formula:
V.
Rs=RmX---1
V,
where Rm is the resistance of the voltmeter
in ohms, or the number of ohms per volt
times the maximum scale reading of the
voltmeter prior to the change. V I is the original range of the voltmeter; V 2 is the new
maximum range desired and Rs the fixed
external resistor which must be connected
in the circuit. The wattage required of this
resistor is generally less than 1Y2 watts,
which is the rating of the average precision
resistor. In special cases where very large
meters are used, whose sensitivity is very
low, the wattage dissipated in the external
precision resistor may be greater than 1.5
watts. In this case two or more precision
resistors should be connected in series, the
value of each resistor being the resistance
required divided by the number used in
series. The wattage dissipated in the external
resistors is calculated by dividing the maxi-
USEFUL
mum ra~ge of the meter squared (V2)2, by
the sum of the external resistors plus the
resistance of the meter, that is, (Rm - Rs).
FigUre 9 shows a swi tching arrangement
which provides a choice of several extension
ranges. For illustration let us use the voltmeter mentioned in the preceding paragraph. This has a range of 100 volts and a
resistance of 100,000 ohms. In Figure 9 this
range is available at the number 1 position
v
• Section 1:z
INFORMATION
on the milliameter scale is given in milliamperes, then the voltage range desired is
multiplied by 1000 and then divided by the
current range of the milliameter in milliamperes.
Expressed by a simple formula, this is
Rs = V X 1000
1m
where V is the voltage range desired, 1m the
current in milliamperes necessary to give the
meter a full scale deflection before the
change, and Rs the series resistance required
in ohms.
figured using as the meter resistance, the
combined resistances of the meter and the
series resistor. The series resistor serves two
purposes. First, it allows the shunt to be of
more reasonable value, thus decreasing errors
due to contact resistance or to slight miscalculation. Second, in case of momentary
overload, the resistor acts as a ballast slowing down the meter action and in many cases
saving a meter which might otherwise be
ruined.
Extending Milliall1eter Ranges
z
3
RJ == 400,000.1\.
RZ= 500,000
FIGURE
SERVICING
V=O-JOOVOLT
(IOOO.l\.PER Vall)
9
of the switch. If we desire a 500-volt range
at the number 2 position, the multiplier resistance may be calculated by using the
formula:
To extend the range of a DC milliameter
when the resistance of the milliameter is
known, the shunt resistor which must be
connected across the terminals of the meter
is calculated very simply by dividing the resistance of the meter by (K-l) where K is
equal to the ratio of the desired maximum
reading to the original reading of the meter.
This is given as
Rm
Rsh = K
) when
( - 1
Rm = resistance of meter
Rs = R m (100,OOO) X
K
)
V, (500)
( VI
(100) - 1 = 400,000 ohms
Rsh
In a similar manner we arrive at a value
of 900,000 ohms as the correct multiplier for
a lOOO-volt range at position number 3.
However, we already have a resistance of
400,000 ohms for the 500-volt range, so we
merely add 500,000 ohms in series with that
resistor to obtain our second multiplier value.
An accuracy of 1 % is generally satisfactory
for these resistors unless a very high precision meter is used. The general types of
meters encountered in service work are only
accurate to ±2% so that it is useless and
wasteful to use a resistor with an accuracy
of better than ± 1 %.
To Change Over a
DC Milliall1eter to a
DC Voltll1eter
Often it is necessary to convert a DC
milliameter to a voltmeter, either permanently or by means of a switching arrangement, so as to use the same instrument for
the combined purposes of reading current
and voltage. Since the internal resistance of
most,milliameters is very low (in comparison
to the external multiplier which must be
connected when making this change), it can
be neglected without serious error. The resistance which is to be connected in series
with the milliameter is calculated by dividing the voltage range which is desired by the
current range of the milliameter expressed
in amperes. If the maximum current reading
I
12 = range desired in milliamperes
I = original range in milliamperes
=
value of shunt resistor
A prepared table of milliameter shunt and
multiplier resistance values for popularly
used meters is available under Fig. 12;
If the resistance of the meter is unknown,
it may be measured by the half deflection
method. Referring to Figure 10, a variable
high resistance R\ is connected in series with
the meter, and the meter adjusted to exactly
full scale deflection. R2 is then connected in
the circuit and adjusted to make the meter
read half scale. R2 is then equal to the meter
resistance and may be measured by any of
the usual methods. Never attempt to measure the meter itself by either the ohmmeter
or the bridge method.
M
FIGURE
11
Probably the best multi-range milliameter
circuit is a modification of the "Universal
shunt" type. This is shown in Figure 11.
This circuit has several advantages over the
usual circuit. First, contact resistance of the
switch has absolutely no effect on the accuracy of the meter. The usual circuit has the
contact resistance in series with the shunt
and thus makes the total shunt resistance
inaccurate. If the switch contact should
happen to be defective in the usual circuit,
the meter would be ruined. Second, with the
usual circuit the switch can not be operated
while the meter is in the circuit. With the
universal shunt arrangement the switch may
be operated at any time without damage to
the meter.
Though at first glance it would seem to be
more difficult to calculate the resistance
values for a universal shunt, actually it is
quite simple. First we add the series resistor
R4 (Figure 11) to bring the meter plus series
resistance to a value of approximately 200
ohms. The total shunt resistance is now figured by formula I to make the meter read
full scale for the first desired range (5 or 10
milliamperes). The other resistances are figured by the formula as shown in Figure 11 :
X=A+B
K
+
FIGURE
10
It will usually be found advisable, when
making a multi-range milliameter, to increase the meter resistance 5 to 10 times.
This may be done by connecting a series
resistor outside the meter. The shunt is then
II
+
where A = R\
R2
Ra (the total shunt
resistance) and B = Rm (the internal resistance of the meter) + R. (the external
series resistor), and K = the desired range
divided by the fundamental range of the
meter.
As an example, assume that we have a
0-1 rna. meter of 50 ohms resistance, and
that we want a multi-range meter giving
ranges of 0-5, 0-50, and 0-250 milliamperes.
Referring to Fig. II we first add R. (150
ohms) thus bringing total B (Rm
R.)
resistance to 200 ohms. Olii l:'-
200
U
0.02
150
o.OS
0.1
20
100
0.2
10
L&.I
L&.I
L&.I
0
Z
5
.(
Z
°u
Zx
.(
1-0:
0
0
0
a
2
Z
40
a::
I.&.
! :g
30
20
1
50
100
«0:::
Q.5
a
L&.I
10
0
1
;:)4-
5
a.
a::
So
L&.I
.(
L&.I
0
Z
2
.(
0
.(~
;:)
)-
t:U
.(
... ...J
0.5
0
~
::J..
20
200
15
L
500
bE8?
r
Q.2
U
0.002
CI)
0.1
W
~
...J
J:
W
J:
~
CI)
w
0.0 OS
CI)
((
Z
0.05
10
W
U
0
>-
U
5
0.05
o.s
0.02
0.2
4
CI)
0
«
0:::
«u...
0.1
3
Q.2
0.01
0.5
0.1
2
0.005
o.OS
2
1.5
L
0.002
5
0.02
L
10
0.01
L
20
CHART
357
I
L
THE
Section 12 •
MY E
r
2000
TECHNICAL
r
r ':1
1000
~
rOOOf
0.02
~-
0.05
2t
en
500
MANUAL
r
0.1
0.2
500f-
I
~+
0
l:>
0.5
W
~
200
en
2
«
cr:
it
5
~
~
10
0
w
0
en
w
lrOOOOO
100
c:z
0.1
W
!
...J
...J
50
50000
~
en
W
...J
u
>-
...J
~
50
100
20
100
200
10
LaJ
0
Z
r-
W
LaJ
0
z
5
~
2
z
500
100
~
~x
>-
OOI
0
Z
LaJ
0.002
0
0°
~~
0
:)
L
ro.
!:u
0
Zu
t-a:
t--I
0
2001=
U
0
20
~
1
' 'f
~
0.005
~
0.01
a.
LaJ
a::
0
50
:)4-
C1
40
LaJ
a::
LL.
30
0.02
1
1
1
0.05
0.1
Q5
20
0.2
15
en
Q5
0
«
cr:
Q2
it
~
en
W
0.1
~
Z
I
W
I
:J
5
CI)
it:
0.05
U
w
~
CI)
w
2
...I
10
U
U
0
>-
0
20
...J
...J
~
10
5
x:
50
4
0.02
3·
0.01
L
500
0.1
100
r
0.005
CI)
2
o.OOI
0.002
1.5
0
358
LM"f
L
«
cr: 0.005
«
L&.: 0.01
L
0.02
CHART
II
L
USEFUL
SERVICING
2000
INFORMATION
• Section 12
1"0
r
fo.OOO02
lOOO
r
r
5
1000
0.00005
0.0001
2
(f)
500
0.0002
~
:r:
0
~
00005
W
~
().5
200
~
0.001
c::
<{
0.002
<{
u...
(f)
l
100
W
50
:r:
w
...J 200
U
0.01
Z
W
~
(f)
~ 0.005
0.1
rOOOOO
a::
0W
>-
U
50000
~
~
W
~
150
20
100
10
I&J
l&J
0
Z
La.I
0
Z
0
5
<
1--,
-
<
!:u
0
<
Q.
<
0
Zu
30
1
(f)
0
20
<{
c::
as
<{
u...
[
0.2
r
15
100
0.001
8
0.002
(f)
0.1
(f)
(f)
~
:r:
w
zW
:r:
"'(f)
W
~
0.05
...J
u
>-
0
~
~
w
~
~
(f)
0.02
0
<{
c::
~
=t
0.01
2
0.005
~
CHART
L
0.002
L
L
III
L
]359
MY E
THE
Section 12 •
TECHNICAL
MANUAL
STANDARD COLOR CODING FOR RESISTORS
Preferred Values of Resistance
±20%'
±10%
±5%
D=nocoI. D =silver D=gold
56
68
68
82,
100
100
120
150
150
180
220
220
270
330
330
390
Old
Standard
50
51
56
62
68
75
82
91
100
110
120
130
150
160
180
200
220
240
75
lOG
150
200
250
270
300
'330
300
350
360
390
400
430
470
680
470
470
560
510
560
680
820
1000
1000
1200
1500
1500
1800
2200
2200
2700
3300
3300
3900
4700
4700
5600
6800
6800
8200
10,000
10,000
12,000
15,000
15,000
18,000
22,000
22,000
620
680
750
820
910
1000
1100
1200
1300
1500
1600
1800
2000
2200
2400
2700
3000
3300
3600
3900
4300
4700
5100
5600
6200
6800
7500
8200
9100,
10,000
H,OOO
12,000
13,000
15,000
16,000
18,000
20,000
22,000
24,000
Color Coding
Preferred Values of Resistance
Resistance
Values
450
SOO
600
750
1000
1200
1500
2000
2500
3000
3500
4000
5000
7S00
10,000
12,000
15,000
20,000
A
B
C
Green
Green
Green
Blue
Blue
Violet
Gray
White
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Red
Red
Orange
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Yellow
Green
Green
Green
Blue
Blue
Blue
Violet
Gray
White
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Red
Red
Orange
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Green
Green
Green
Blue
Blue
Violet
Gray
White
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Black
Brown
Blue
Red
Gray
Green
Red
Brown
Black
Brown
Red
Orange
Green
Blue
Gray
Black
Red
Yellow
Green
Violet
Black
Orange
Green
Blue
White
Black
Orange
Green
Violet
Black
Brown
Blue
Black
Red
Gray
Green
Red
Brown
Black
Brown
Red
Orange
Green
Blue
Gray
Black
Red
Yellow
Green
Violet
Black
Orange
Green
Blue
White
Black
Orange
Violet
Black
Brown
Blue
Red
Gray
Green
Red
Brown
Black
Brown
Red
Orange
Green
Blue
Gray
Black
Red
Yellow
Black
Black
Black
Black
Black
Black
Black
Black
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Red
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
.
±20%
±l0%
±5%
D=nocol. D =silver D=gold
27,000
33,000
47,000
68,000
39,000
27,000
30,000
33,000
36,000
39,000
47,000
43,000
47,000
56,000
51,000
56,000
33,000
68,000
82,000
100,000
100,000
120,000
150,000
150,000
180,000
220,000
220,000
270,000
330,000
470,000
680,000
390,000
270,000
300,000
330,000
360,000
390,000
470,000
430,000
470,000
560,000
510,000
560,000
330,000
3.9 Meg.
620,000
680,000
750,000
820,000
910,000
1.0 Meg.
1.1 Meg.
1.2 Meg.
1.3 Meg.
1.5 Meg.
1.6 Meg.
1.8 Meg.
2.0 Meg.
2.2 Meg.
2.4 Meg.
2.7 Meg.
3.0 Meg.
3.3 Meg.
3.6 Meg.
3.9 Meg.
4.7 Meg.
4.3 Meg.
4.7 Meg.
5.6 Meg,
5.1 Meg.
5.6 Meg.
6.8 Meg.
6.2 Meg.
6.8 Meg.
680,000
820,000
1.0 Meg.
1.0 Meg.
1.2 Meg.
1.5 Meg.
1.5 Meg.
1.8 Meg.
2.2 Meg.
2.2 Meg.
2.7 Meg.
3.3 Meg.
4.7 Meg.
62,000
68,000
75,000
82,000
91,000
100,000
110,000
120,000
130,000
150,000
160,000
180,000
200,000
220,000
240,000
3.3 Meg.
'Old
Standard
Resist.ance
Values
25,000
30,000
40,000
SO,OOO
60,000
75,000
100,000
120,000
150,000
200,000
250,000
300,000
400,000
500,000
600,000
750,000
1.0 Meg.
1.5 Meg.
2.0 Meg.
3,0 Meg,
4,0 Meg.
5,0 Meg.
6.8 Meg.
6.0 Meg.
7.0 Meg.
7.5 Meg.
8.0 Meg.
8.2 Meg,
8.2 Meg.
10 Meg.
9.1 Meg.
10 Meg.
9.0 Meg.
10 Meg.
10 Meg.
Color Coding
A
B
Red
Red
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Green
Green
Green
Blue
Blue
Blue
Violet
Gray
White
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Red
Red
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Green
Green
Green
Blue
Blue
Blue
Violet
Gray
White
Brown
Brown
Brown
Brown
Brown
Brown
Brown
Red
Red
Red
Red
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Green
Green
Green
Blue
Blue
Blue
Violet
Violet
Gray
Gray
White
White
Brown
Green
Violet
Black
Orange
Blue
White
Black
Orange
Violet
Black
Brown
Blue
Black
Red
Gray
Green
Red
Brown
Black
Brown
Red
Orange
Green
Blue
Gray
Black
Red
Yellow
Green
Violet
Black
Orange
Blue
White
Black
Orange
Violet
Black
Brown
Blue
Black
Red
Gray
Green
Red
Brown
Black
Brown
Red
Orange
Green
Blue
Gray
Black
Red
Yellow
Violet
Black
Orange
Blue
White
Black
Orange
Violet
Black
Brown
Blue
Black
Red
Gray
Black
Green
Black
Red
Black
Brown
Black
C
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Orange
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
YeUnw
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Yellow
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green )
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green
Green '
Green
Green
Green
Green
Green
Blue
Stendardized coding for resistance value
identification i. confined to ten colors
and figures as shown:
Figure
Color
o
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Gray
White
I
2
3
4
5
6
7
8
9
360
The body (A) of the resistor is colored to represent the first
figure of the resistance value. One end (B) of the resistor is
colored to represent the second figure. A hand, or dot (C) of
color, representing the number of ciphers following the first
two figures, is located within the hody color. The two diagrams illnstrate two interpretetions of this standard method
of coding resistance value.
The color "D" appearing on the body of th~ axial lead
resistor and on the end of the radial lead type, is used to indicate tolerance value.
If no color appears in the position shown on the r~tors,
the tolerance is ±20%. If the resistor has a silver dot or band,
the tolerance is ± 10%, while if a gold color is employed, the
resistor is within ± 5 % of the specified value.
USEfUL
SERVICING
• Section 12
INfORMATION
Inductance of Single Layer Coils
T
L
o
R
D
10
8
6
400
S
4
20,000
300
4,000
3,000
2,00,0
3
150
4
- ... --
_-------_-----------
200
5
50
60
40
30
20
80
6
7
to
8
1.5
.6
6
T = Total
4
3
L=
1.0
9
.8
10
.4
.3
.2
10
.8
10
'2
IS
no of turns
Inductance phs
R= Ratio
DIAMETER
.5
.4
LENGTH
D=Diameter (inches)
.3
.0
.1
5
2
600_______ _
400
----------- ____ _
300
-------- ------100
30
_-----
--r,ooo----
60
40
3
6,000
zoo
90
80
70
4
10,000
2
-"Hio---
5
.'l
II
:75
.5
COIL TURNS, INDUCTANCE AND DIAMETER
Knowing the turns of a coil, its length of winding, and the diameter, the ind uctance may be found by using a straight-edge from the turns column to the ratio
(diameter + length) column, intersecting the axis column; then a second line
from the intersection of the axis column to the diameter column. The inductance
in micro henries will be the point where the second line intersects the inductance
column. In the above chart the first line is laid froIll 100 turns to 2.5 ratio,
this .first line intersecting the axis at 3.8 on the scale. The second line is from
3.8 on the axis scale to the 2-inch diameter, intersecting the inductance column
at 600 microhenries.
Knowing the diameter, ratio and the inductance, the number of turns may be
found by reversing the process. As shown in the chart, draw a line from 2 inch
diameter through the 600 microhenries intersecting axis at 3.8 on the scale; then
run line from 3.8 on axis scale to 2.5 on ratio, the extension of this line cutting
the turns scale at 100 which is the number of turns.
.
.
After finding number of turns, consult wire table to determine size of wire
which will permit given number of turns in a given length of winding.
361
Section 12 •
THE
MY E
TECHNICAL
MANUAL
Ballast Tube Circuits
It has been popular in receivers of the
AC-DC type, and in battery-powered receivers, to use plug-in type ballast resistors.
The following information is preSented to
aid in identifying and checking the various
ballast types.
In a large number of instances the type
designation stamped on the tube indicates
the value and circuit'arrangement of the
unit. As an example let us select one of the
commonly used types such as BK55B.
The first letter "B" indicates that a ballast
section for one or more pilot lamps is used.
The second letter, "K" iD ,the above example, indicates that the pilot lamp (or
lamps) is one of the 150 milliampere (0.15
ampere) type. The letter "L" at this position
would indicate use of the 250 milliampere
pIlot lamp while the letter "M" would mean
that a 200 milliampere lamp is employed.
The number 55 (or any number used in
the same location) gives the total voltage
drop across the resistance including the pilot
lamp (or lamps) at the current specified
during normal operation.
The final letter "B" indicates the circuit
arrangement. Reference is made to the popu'lar tYpe base wiring diagrams as shown
below, where circuit B illustrates the wir·
ing diagrams for either octal or UX type
base.
'
Particular attention should be used in any
types bearing the "E" circuit designation
since both circuit "E" and "E," have been
used under the plain "E" classification.
WIRING DIAGRAMS
PLUG-IN RESISTORS WITH OCTAL OR "u X" BASES
UX BASE
UX BASE
OCTAL BASE
OCTAL BASE
A
C
u
362
H
BOTTOM VIEW
OF "u X"BASE
BOTTOM VIEW
OF OCTAL BASE
u
USEfUL
AUTOMO~ILE
SERVICING
INfORMATION
BATTERY GROUND CHART
• Section 12
Power Factor of a Condenser
R
YEAR
1934
1935
1936
1937
1938
1939
1940
1941
Auburn. . . .
.. Pos.... ... POB..
..Pos..... . POB.... .. ......
Buick...
.. . Neg.. . ..Neg... ..Neg...... Neg.. . ..Neg... ..Neg...... Neg ...... Neg..
..Neg.. .
Cadillac....
..POB.... .Pos.
.. Pos... .. Neg ...... Pos.... . Pos.... ..Pos... ..Pos.. .. POB .. ..
Chevrolet ...... Neg. . . . . Neg. . . . . Neg...... Neg ...... Neg: . . . Neg..
..Neg...... Neg. . . . . Neg .. .
Chrysler.... .......... . POB.... ..Pos... ... Pos.. . ... Pos.. . .. Pos.... ... Pos.... ... POB.. . .. Pos .. ..
Cord.... .... . ....... ........ ..Pos....... Pos ................... ..
DeSoto .... , .. Pos.... ... POB... .. POB.... ... Pos.... .. POB..
.. Pos.. . ... Pos.. . .. Pos... ... Pos... .
Dodge.. . . ..
. POB. .. ... Pos... .. POB.... .. Pos.... ... Pos..
.. Pos.... .. Pos.... .. Pos...
.. Pos.. ..
D\leseuberg ..... Neg ...... Neg. . . Neg... .......
........ .. ....
Ford.. ..
. .Pos. .. ... Pos.... .. Pos.... ... Pos.... .. .Pos... . . Pos.. .. ... Pos.... ... POB... ... Pos .. ..
Franklin.. .. .. Pos... .........
.. .. ... ......... .. .....
.. . . .... . ...... .. ..... .
Graham. ... ..POB... ... Pos.... .. Pos.... ... Pos.... ... Pos.... .. Pas.... .......... .... ..
Hudson.
.Pos.... .. Pos... .. Pos.... .. Pos.. . .. Pos... .. Pos.... .. POB.... .. POB... ... Pos ....
Hupmobile . . . . Pos. . . . POB...... Pos.............. POB... . Pos...
.
Lafayette..
.Pos.... Pos.... ..Pos.... .P.os..
Pos.... Pos... .. Pos.. .. .Pos...
LaSalle. .... .. Pos... . .. Pos.... .. Pos.. .. . Neg. .. .. Pos... . Pos....
. Pos.. .. .. .. ..
Lincoln ... ,. . . Neg. .. . . Neg ...... Neg. .. . . Neg. . . . Neg..... Neg..
. . Neg. .. . .... .
Lincoln Zeph.
.. .. . ... ... Pos.. . .. Pos..
. POB... . Pos... ... POB.... .. Pos ... .
Mercury.... ..
....... ........
.. ....... Pos...... Pos...... Pos...
..Pos... .
N ash*.. ... . .Pos.. .. Pos.... .. .Pos.. .. Pos.. . .. Pos.. . Pos....... Pos.... .. Pos.. ... Pos ... .
. Neg... ..Neg..
..Neg... ..Neg... ..Neg..
..Neg...... Neg.. .. .Neg.. .
Oldsmobile . . . . Neg..
Packard..
.Pos.... ..Pos.. . ..Pos... . Pos...... Pos.. . . Pas... . .Pos.... ..Pos.... ..Pos... .
Pierce-Arrow ... Pos...
. POB... ..Pos... .. .Pos... .. .Pos....... Pos.... ... ..... .. ......
Plymouth .. ..Pos.... . Pos...... Pos..... Pos...
Pos.... Pos.. ..POB....... Pos.. ..Pos... .
Pon~iac...
.Neg. . . . . Neg. . . . . Neg. . . . . Neg.
.Neg. . . . . Neg. . . . Neg ..... Neg...... Neg.. .
Studebaker
.Pos.... Pos..
.. Pos... .. .Pos... .. Pos.... .. POB... .. Pos.... .. Pos...
.. Pos .. ..
Terraplane.. ..Pos....... Pos.... ..Pos....... Pos.. . ..Pos.... . Pos.... . Pos..
. Pos........... ..
Willys.. ..
. Neg. . . . . Neg. . . . . Neg..
Neg.
.Neg.. .
Neg..
.Neg. . . . . Neg...
*Some special custom-built models have negative grounded.
Ohms Law for
Direct Current
Where:
E = Voltage
I = Current in Amperes
R = Resistance in Ohms
Resistances in Series
Rt = R. + R. + R •... Rn
Where: Rt is the total value of all resistors
connected in series.
R., R., etc., are the individual resistors.
Resistance in Parallel
The formula for resistances in parallel is:
1
R t = -1--1---1
Rl + R. + R3 etc.
Where: Rt is the effective value of all the
resistors connected in parallel.
Rt, R., R3 are the individual resistors.
This formula may be extended as far as one
has resistances in parallel. For an example
let us say we have four resistances of 5 ohms,
10 ohms, 20 ohms, and 30 ohms. Substituting
in our formula we obtain:
1
R t = ::-1---'1::---1::---::-1
5+
10 + 20 + 30
60
60
=2.60 ohms total resistances.
23
A convenient formula for only two resistances in a parallel circuit is:
R = Rl X R.
t
Rl +R.
By referring back to the formula for resistances in parallel one may readily see how
this equation is derived. As an example for
= -
PC
1942
this formula let us use values of 10 ohms and
35 ohms. Substituting in our formula:
10 X 35
350
R t = 10 + 35 = 45 = 7.7+ ohms
Capacity of Parallel Plates
When two conducting plates are parallel,
close together, and of large area, the capacity is given by
C = 0.0885 times KS
t
Where C = capacity in micromicrofarads
K = dielectric constant
S = area of one plate in square centimeters
t = distance between plates in centimeters
Reactance (Capacitive) of a Condenser
10 6
Xc = - 211.fC
Where: '11' = 3.14
f = frequency
C = capacity in microfarads
Example: What is the reactance of a 2-mf.
condenser at 50 cycles?
106
-:-::---::-,-----,- = 1,590 ohms
6.3 X 50 X 2
hnpedance of a Circuit
=
+
Reactance (Inductive) of a Coil
XL = 2'11'fL
Where '11' = 3.14
f = frequency in cycles per second
L = inductance in henries
Example: What is the reactance of a 20henry choke at 50 cyc)es?
6.3 X 50 X 20 = 6,300 ohms
~R2 + C:C)2
Where: R = the resistance of the condensel'
(0) = 6.28 times the frequency
C = capacity in farads
On a bridge the resistance (R) is determined
by dividing the reading of the series resistance (Rs) by the ratio of AlB (where the
resistance of Cs is negligible).
Dissipation Factor Q
The ratio Q of reactance to resistance is generally used as the factor of merit of a coil or
condenser and is called the dissipation co;:::,stant.
For a coil Q =
WL
It
1
For a condenser Q = wRC
Equivalent IlIlpedance
of a Series Circuit
When an inductance, capacity and a resist·
ance are connected in series, the combined
effect is called the impedance of the circuit.
+
Zo = VR2
(XL - Xc)2
Where: Z = impedance in ohms
R = resistance in ohms
XL = reactance of inductance in
ohms
Xc = reactance,of capacity in ohms
Equivalent IlIlpedance
of a Parallel Circuit
When an inductance, capacity and resistance are connected in parallel the equivalent
impedance
RXLXc
Zo
=
--;;;;=:=:;;~=;::::;;;:::;;;;:".
V(RXL - RXc)2
The impedance of a circuit consisting of a
resistor and capacitor in series is:
Z = VR2
Xc 2
The impedance of a circuit consisting of a
resistor in parallel with a condenser is:
RXc
Z
VR2 + Xc 2
--;====;::=
+
XL 2XC 2
Frequency
Where: f
'11'
L
C
=
=
=
=
frequency in cycles
3.14
inductance in microhenries
capacity in microfarads (mf.)
106
f=-2'11'VLC
Example: To what frequency will a 0.0005
mf. (500 mmf.) condenser, in parallel with a
180-microhenry coil, tune?
106
- - - - - - - = 530,000 cycles = 530
6.3V180 X 0.0005
kilocycles = 565 meters
363
1HE
Section 12 •
Conversion Table
Frequency to Wavelength
300,000
Freque.ncy in Kilocycles
Wav,:length }
In , =
Meters
or
300
Frequencv in Megacycles
Long-Wave
Broadcast Band
Sbprt Waves
Frequency
Kilocycles
Wavelength
Meters
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
545
500
461
429
400
375
353
333
316
300
286
273
261
250
24()
231
222
214
207
200
Frequency Wavelength
Megacycles
Meters
200
150
100
75.0
60.0
50.0
42.9
37.5
33.3
30.0
273
25.0
23.1
21.4
20.0
18.8
17.6
16.7
15.8
15.0
1.5
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
Transformer Ratios
The Voltage across the Secondary
al
.
equ s
The Voltage across the Primary
The Number of Secondary Turns
The Number of Primary Turns
AC Voltage and Power
Where Z is the Impedance in Ohms, E is
Effective Electromotive Force in Volts, and
I i,s Current Intensity in Amperes, then
E
E
I=Z
E=ZXI
Z=T
The Maa:imum Voltage Em is 1.414 X the
Effective Voltage Ee.
The Effective Voltage Ee is 0.707 X the Maximum Voltage Em.
The Average Voltllge Ee is 0.636 X the Maa:imum Voltage Em.
The Power in an AC circuit R
W=IXEX Z
Where the Angle of Lag or lead, and th"
R
.
Sme =
X
Z' and Tangent
X
= R
The Decibel
The number of decibels corresponding to a
given power ratio is 10 times the common
logarithm of the ratio.
P.
N = 10 Log,. - - -
P,
Where: N = decibels.
P.
~
.
= powerrayo
In the case of voltage or current the number of decibels corresponds to 20 times the
common logarithm of the ratio.
Example: What gain in decibels will there
be if the voltage in an amplifier rises to 7
times the normal level at a certain frequency ~
N =20 log,. 7=20XO.845=17 decibels.
At the top of the next column, logarithms
are given of several representative numbers.
Many logarithms not in the table may be
obtained by dividing the number (N) into
its factors as shown under the table and
adding the logarithms of the factors.
364
1ECH.NICAL
N
LOG.
N
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
.3010
.3979
.4771
.5441
.6021
.6532
.6990
.7404
.7782
.8129
7.0
7.5
8.0
8.5
9.0
9.5
10.0
100.0
1000.0
10000.0
MANUAL
Power Output
When Eg expresses the RMS (Root-MeanSquare) Effective Value of the AC Input,
the
LOG.
.8451
.8751
.9031
.9294
.9542
.9777
1.0000
2.0000
3.0000
4.0000
p.2 X Egll X Rp
POWER 0 UTPUT = -'---;----'-=---::---=--.
(1»
Rp)2
JL2 X Eg2
+
The MAXIMUM Power Output is -'--c----'-4rp
The Maximum UNDISTORTED Power Output
is '
2 JL2X Egll
9rp
When Eg is the Maximum (Peak) A. C.
~nput Value
The Maximum Undis~orted Power Output is
Log. XY = Log. X + Log. Y
For example:
8500 = 8.5 X 1000
Log. 8500 = 3.9294
18 = 2 X 9
Log. 18 = 1.2552
JL2X
Egll
,
9rp
Conversion- Factors for conversion-alphabetically arranged.
Multiply
By
To Get
Amperes ......... X· 1,000,000,000,000. micromicroomperes
Amperes ........... X 1,000,000 ....... microamperes
Amperes ........... X 1,000 ............ milliamperes
Cycles ............ X .000,001 .......... megacycles
Cycles ............ X .001. ............ kilocycles
Farads ............ X 1,000,000,000,000 micromirrofarads
Farads ............ X 1,006,000· ........ mierofarads
Farads ............ X 1,000 ............ millifarads
Henrys ............ X 1,000,000 ........ mirrohenrys
Henrys ........... X 1,000 ............ millihenrys
Kilocycles ......... X 1,000 ............ cycles
Kilovolts ......... X 1,000 ............ volts
Kilowatts ........ X 1,000 ............ watts
Megacycles ........ X 1,000,000 ......... cycles
Mhos ............. X 1,000,000 ......... micromhos
Mhos ............. X 1,000 ............ millimhos
Microamperes ..... X .000,001. ......... amperes
Microfarads ...... X .000,001 ......... farads
Microhenrys.. .... X .000,001 ......... henrys
Micromhos......
X .000,001 .... ,.... mhos
Multiply
Micro-ohms ....... X
Microvolts ........ X
Microwatts. . ... X
Mieromicrofarads .. X
Micromiero-ohms .. X
Milliamperes ....... X
Millihenrys ........ X
Millimhos ........ X
Milliohms ......... X
Millivolts ......... X
Milliwatts ......... X
Ohms ............. X
Ohms ............. X
Ohms ............. X
Volts .............. X
Volts .............. X
Watts ............. X
Watts ............. X
Watts ............. X
• By
To Get
.000,001 ......... ohms
.000,001 ......... volts
.000,001 ........ watts
.000,000,000,001 .. farads
.000,000,000,001 .ohms
.001. ............ amperes
.001. ............ henrys
.001. ............ mhos
.001. ............ ohms
.001. ............ volts
.001. ............ watts
1,000,000,000,000 micromicro-ohms
1,000,000 ........ micro-ohms
1,000 ............ milliohms
1,000,000 ........ microvolts
1,000 ............ millivolts ,
1,000,000 ......... microwatts
~,ooo
............ ~liwatts
.001. ............ kilowatts
Greek Alphabet
Letters
Commonly used to designate
Name
Cap.
AlPha...........
Beta............
Power Factor Z = Cosme <1>,
.
MY E'
A
B
Gamma.........
r
Delta...........
Epsilon........
11
E
Small
Angies.
Coefficients.
Angles.
Coefficients.
Specific gravity.
Decrements.
E.m.f.
Conductivity.
Variation.
Z
Impedance.
Eta.............
H
8'
I
K
A
M
N
,...,
Hysteresis coefficient.
Iota..........
Kappa..........
Lambda.........
Mu.............
Nu.............
Xi..............
Omicron .......
Pi.............
Rho............
Co-ordinates.
Efficiency.
Angular phase displacement.
Current in amperes.
Dielectric constant.
Susceptibility.
Permeability.
Kilo.
Visibility.
Amplification factor.
Prefix micro-
Reluctivity.
~
0
II
P
Circumference divided by diameter, 3.1416.
Resistivity.
~
(Cap) Sign of summation.
Tau ..........
T
Y
Time constant.
Phi.............
Chi.............
Psi. ............
Omega...........
Time constant.
(Small) Wave length.
Sigma ..... '.....
Upsilon.........
Density.
Base of hyperbolic logarithms.
Zeta............
Theta ...... ,....
Area.
Time-phase displacement.
..
II.
::>
0
Frequency Characteristic of
Resistance-Coupled TwinTriode Amplifier
w
FIGURE
~
B
~
~
f,
o
w
...
::>
...II.
::J
o
__L-____
EO
~L-
____________
~
__
.20_
,.REQUENCY_
A. Condensers C and Cc have been chosen
to give output voltages equal to 0.8 Eo for It
of 100 cycles. For any other value~ of f"
multiply values of C and Ce by 100/fl.
In the case of condenser Ce, the values
shown are for an amplifier with DC heater
excitation. When AC is used, depending on
the character of the associated circuits, the
gain, and the value ofIt, it may be necessary
to increase the value of Ce to minimize humdisturbances. It may also be desirable to
have a DC potential difference of approximately 10 volts between heater and cathode
B. h = frequency at which high-frequency
response begins to fall off.
C. The voltage output at
stages equals (0.8 E)ofl.
420 ...
,.REQUENCY -
Frequency Characteristic of
Single-Stage ResistanceCoupled Triode AUlplifier
~L-
Twin-Triode DiagraUl
with Legend
Frequency Characteristic of
Single-Stage ResistanceCoupled Pentode AUlpli.fier
.J
t
E,
0.8 Eo
B
STAGE TWO
FIGUBB
..
SEE FIGURE
8m!: FIGUBBA
$TA&E OlE
..~
G. A variation of ±10% in values of resistors and condensers has only slight effect
on performance.
It for n like
D. Decoupling filters are not necessary for
two stages or less.
f... Condensers C, Ce and Dd have been
chosen to give output voltages equal to 0.7
Eo for II of 100 cycles. For any other value
of It, multiply values of ~, Ce, and Cd by
100/1t·
In the case of condenser Ce, the values
shown are for an amplifier with DC heater
excitation. When AC is used, depending on
the character of the associated circuits, the
gain, and the value off1, it may be neCessary
to increase the value of Ce to minimize hum
disturbances. It may also be desirable to
have a DC potential difference of approximately 10 volts between heater and cathode.
B.fl = frequency at which high-frequency
response begins to fall off.
C. The voltage output at
stages equals (0.7 Eo)fI.
It for n like
D. Decoupling filters are not necessary
for two stages or less.
E. For an amplifier of typical construction, approximate values of f2 for different
values of RL are:
RL
0.1 Meg.
0.25 Meg.
0.5 Meg.
h
20000 cps.
10000 cps.
5000 cps.
F. AlwayS use highest permissible value
ofRg.
F"REQUENCY-
The diagram given above is for PhaseInverter Service. The signal input is supplied
to the grid of the left-hand triode unit. The
grid of the right-hand unit obtains its signal
from a tap (P) on the grid resistor (Rg) in
the output circuit of the left-hand triode
unit. The tap (P) is chosen as so to make the
voltage output of the right-hand unit equal
to that of the left-hand unit. Its location is
determined from the voltage gain values
given in the Chart. For example, if the value
of voltage gain is 20 (from the Chart), (P)
is chosen so as to supply 1/20 of the voltage
across (Rg) to the grid of the right-hand
triode.
For phase-inverter service, the cathode
resistor (Rc) should not be by-passed by a
condenser. Omission of the condenser in this
service assists in balancing the output voltages. With twin triodes having a common
cathode terminal, the value of Rc is specified
on the basis that both units are operating
simultaneously at the same values of plate
load and plate voltage.
365
~
n
RESISTANCE COUPLED AMPLIFIER CHART
.
~
g:: Ce=Cathocfe
C =Blockin£ Condenser (Pf)
By-PIlllS Cond~ (}Jf)
Cd =Screen By-pass Cond_ (/Af)
Ebb =Plate-Supply Voltage (Volts)
Eo = Voltage OutJ!ut (Peak Volts)
Re =Cathode ReSIStor (Ohms)
RL =Plate Resistor (Megohms)
V.G. = Voltage Gain
Rd =Screen Resistor (Megohms)
Rg = Grid Resistor (Megohms)
g.
~
....
I'.)
TABLE I-TRIODES
6C5 (Also IC6, 6J7, 6W7, W7, and 57 as Triodes)
180
IAIBee 6N7
Ebb'
RL
Ra'
Re
Ce
C
90
0.05
2800
2
0.05
14
Eo'
V.G.'
9
0.05
0.1
3400
1.62
0.025
17
9
Ebb'
fu
RII'
Re
Ce
C
Eo'
V.G.'
0.1
0.25
3700
1.48
0.0115
17
20
0.25
0.1
3800 4800
1.3 1.12
0.01 0.025
20
16
. 10
10
0.1
0.25
6400
0.84
0.01
22
11
0.5 0.25
7500 11400
0.66 0.52
0.005 0.01
18
23
'12
12
0.25
0.5
14500
0:4
0.006
23
12
1 0.05'
17300 2200
2.2
0.33
0.004 0.055
26
34
13
10
0.05
0.1
2700
2.1
0.03
45
11
0.25
0.1
3100 3900
1.85
1.7
0.015 0.035
54
41
12
11
0.1
0.25
5300
1.25
0.015
54
12
0.25
0.5
1 0.05
12300 14700 2100
0.55' 0.47 3.16
0.008 0.004 0.075
52
57
59
13
13
11
0.5 0.25
6200 9500
1.2 0.74
0.008 0.015
55
44
13
13
180
0.5
1.0
15000
0.43
0.0035
20
24
0.1
0.25
3080
1.84.
0.012
40
22
0.25
5170
1.25
0.012
35
24
0.25
0.5
6560
0.95
0.007
45
25
0.05
0.1
2600
2.3
0.04
70
11
0.25
0.1
3100 3800
2.2
1.7
0.015 0.035
83
65
12
12
"'j . ,
6CBa
90
0.25
0.5
7870
0.81
0.0065
19
23
•
300
1
7550
0.85
0.0035
50
26
1
12500
0.5
0.004
44·
26
0.1
0.25
5300
1.3
0.015
84
13
0.5 0.25
6000 9600
1.17
0.9
0.008 0.015
73
88
13
13
0.25
0.5
12300
0.59
0.008
85
14
1
14000
0.37
0.003
97
14
300
0.25
2840
2.01
.0.013
73
_._. _23_ _ _ _ _.
Ebb'
RL
Rg'
Re
Ce
C
Eo'
V.G.'
0.5
1
11500
0.48
0.004
83
27
0.25
0.5
6100
0.96
0.0065
80
26
Ebb'
RL
R g'
Re
Ce
C
Eo'
V.G.'
90
..,
180
J .."
0.25
0.5
4800
5000
2.1
1.8
0.01 0.005
5
6
34b
35
0.25
0.5
1
0.5
8000
8800
9000 12200
1.33
1.18
0.9 0.76
0.01 0.005 0.003 0.005
6
7
10
8
39b
43c
44
43
0.5
1
13500
0.67
0.003
10
46
2
0.1
14700 1800
0.58
4.4
0.0015 0.025
12
16
48
37
0.1
0.25
2000
3.3
0.015
23
44
0.25
3500
2.3
0.01
21
48
0.5
2200
2.9
0.006
25
46
300
0.25
0.5
1.0
0.5
4100
4500 6100
1.3
1.8·· 1.7
0.006 0.004 0.006
26
32
24
53
57
53
0.5
2 . 0.1
1
6900
7700 1300
0.9
0.83
5
0.003 0.0015 0.025
33
37
33
63
66
42
0.1
0.25
1600
3.7
0.01
43
49
0.5
1700
3.2
0.006
48
52
0.25
2600
2.5
0.01
41
56
0.25
0.5
3200
2.1
0.007
54
63
1
0.5
3500 4500
2
1.5
0.004 0.006
50
63
65
67
0.5
1
5400
1.2
0.004
62
70
2.0
6100
0.93
0.002
70
70
Ebb'
RL
Rg2
Re
Cc
C
Eo'
V.G.'
0.25
0.5
9760
0.55
0.007
18
13
- - - - - - - - _ _------------
0.05
0.1
1490
2.86
0.032
30
17
..
0.1
2330
2.19
0.038
26
14
300
180
0.1
0.25
0.5
2830
3230
1.15
1.35
0.012 0.006
34
38
14
14
0.25
0.5
7000
0.62
0.007
36
14
0.05
0.1
1270
2.96
0.034
51
14
0.1
0.25
2440
1.42
0.0125
56
14
0.25
0.5
1.0 0.05
9290 10950 1740
0.54
0.46 2.91
0.009 0.0055 0.06
52
46
56
12.4 ~,5 10.9
0.05
0.1
2160
2.18
0.032
68
11.6
0.1
0.25
4140
1.1
0.014
79
12.7
0.25
0.5
5770
0.64
0.0075
57
14
Ebb'
RL
Rg'
Re
Ce
C
Eo'
V.G.'
0.25
0.5
1.0
9100 10750
0.4
0.46
0.0075 0.005
80
88
12:8
12.9
Ebb'
RL
Rg'
Re
Ce
C
Eo'
V.G.'
6L5G'
Ebb'
fu
0.05
Rg'
2120
Re
2.3
Ce
0.05
C
14
Eo'
V.G.' 9.3
180
90
0.05
0.1
2500
1.85
0.03
17.8
10.4
0.25
0.1
2900 3510
1.65 1.36
0.014 0.03
21
16
10.9
11
0.1
0.25
4620
1.08
0.015
21.5
11.7
0.5
5200
1
0.0085
23
12
0.25
0.25
0.5
1.0
8050 10300 12100
0.61
0.49
0.42
0.01250.0085 0.0055
17.5
21.5
23.6
12
11.8
11.9
0.05
1810
2.9
0.06
32
10.4
0.05
0.1
0.25
2240
2660
2.2
1.8
0.03 0.014
41
46
11.1
11.5
...
.......
n
0.25
0.1
2600 3070
1.82 1.64
0.015 0.032
79
60
11.9 12.1
2:
....
n
~
po.
i:
300
0.1
0.1
0.25
0.5 0.25
3180
4200
4790 7100
1.46·
1
1.1
0.7
0.03 0.0145 0.009 0.014
36
45.5
50
38
12.1
12.3 12.1
11.6
i:
~
6F8G (One Triode Unit)a. 6JS, WS
90
0.1
0.25
3940
1.29
0.012
17
13 - - - -
Ebb'
0.05
RL
0.1
Ra2
2070
Re
Ce
2.66
C
0.029
14
Eo'
12
V.G.'
6JSsee 6FBG
~
...
-<
IFS. 6SFS. 12FS. 12SFS
Ebb'
RL
Rg2
0.1
Re
' 4400
Ce
2.5
C
0.02
4
Eo'
V.G.' . 28d
....
0.5
4700
0.81
0.0075
89
12.9
0.25
6900
0.57
0.013
64
13
~
2:
c:
~
po.
Ebb'
RL
0.1
Ra"1900
Rc*
0.025
C
13
Eo'
16
V.G.'
6Nn, 6A6t, SU
180
90
0.1
0.25
2250
0.1
19
19
4050
0.01
16
20
0.25
0.5
4950
0.006
20
22
0.1
4500
1.05
0.03
19
8.1
90
0.1
0.25
0.5 0.25
6500
7500 11100
0.82
0.68 0.48
0.015 0.007 0.015
23
25
21
8.9
9.3
9.4
' 1' '
2500
0.006
20
20
1
0.5
5400 7000
0.003 0.006
24
18
22
23
0.5
1
8500
0.003
23
23
0.1
2
9650 1300
0.0015 0.03
26
35
23
19
0.1
0.25
1700
0.015
46
21
0.5 0.25
1950 2950
0.007 0.015
50
40
22
23
0.25
0.5
3800
0.007
50
24
300
1
0.5
4300 5250
0.0035 0.007
57
44
24
24
0.5
2
1
6600
7650
0.0035 0.002
54
61
25 __25
0.1
1150
0.03
60
20
0.1
0.25
1500
0.015
83
22
0.5 0.25
1750 2650
0.007 0.015
86
75
23
23
0.5
0.25
1
0.5
1
0.5
6100
4000 4850
3400
0.0055 0.003 0.0055 0.003
87
100
76
94
24
24
24
23
2
7150
0.0015
104
24
Ebb'
RL
Rg'
Re*
C
Eo·
V.G.'
IPS, 56, 76
Ebb'
RL
Rg2
Re*
Ce
C
0.05
2500
2
0.06
16
Eo'
7
V.G.'
0.05
0.1
3200
1.6
0.03
21
7.7
0.25
3800
1.25
0.015
23
8.1
0.25
0.5
15100
0.36
0.007
24
9.7
1 0.05
18300 2400
0.32
2.5
0.0035 0.06
28
36
7.7
9.8
0.05
0.1
3000
1.9
0.035
48
8.2
7
0.25
0.1
3700 4500
1.65 1.45
0.015 0.035
45
55
9.3
9
180
0.1
0.25
6500
0.97
0.015
55
9.5
300
0.5 0.25
7600 10700
0.8
0.008
57
49
9.8
9.7
0.25
0.5
14700
o.gi~ b~o~~
59
10
1 0.05
17700 2400
0.4
2.8
0.0045 0.08
64
65
10
8.3
0.05
0.1
0.25
3100
3800
2.2
1.8
0.045
0.02
80
95
8._9__ 9.4
0.1
4500
1.6
0.04
74
9.5
0.1
0.25
6400
1.2
0.02
95
10
0.5 0.25
7500 11100
0.98 0.69
0.009 0.02
104
82
10
10
Ebb'
0.25
'RL
0.5
1 Rg'
15200' 18300 Rc*
0.5
0.4 Ce
0.009 0.005 C
96
108 Eo·
10
10 V.G.'
RESISTANCE COUPLED AMPLIFIER CHART
C = Blocking Condenser (ILl)
Cc = Cathode By-pass Condenser (ILf)
Ebb!
0.1
RL
0.25
R II'
1960
Rc*
C
0.012
5.9
Eo'
23
V.G.'
--6SFS 8ee6F5
Eo = Voltage Output (Peak Volts)
Rc = Cathode Resistor (Ohms)
Cd =Screen By-pass Condenser (ILO
Ebb =Plate-Supply Voltage (Volts)
-I_ ___o~g:l ___
90
,~
0.5
90
Ebb!
fu
Rg'
Rc*
Cc
C
0.1
0.25
1070
0.012
24
29
0.5
1
6300
0.003
10
_ _ ~3 ____
0.1
0.25
0.25
0.5
1760
3390
2.02
1.1
0.0115
0.006
11
15
Eo'
.}T.G.- - - - - - - 25 -3012SF5 see 6F5
12J5 see 6F8G
12SC7 8ee 6SC7
0.5
1
6050
0.61
,.""
ffi
==1;
--
0.25
1820
1. 71
,.,m
33
~~" ·
~
3! _ _
~
Ebb!
RL
0.1
RII'
6300
Rc
2.2
Cc
0.02
C
3
Eo'
23d
V.G.'
6B6see 2A6
90
0.25
0.1
0.25
0.5 0.25
0.5
1
0.5
6600
6700 10000 11000 11500 16200
1.7
1.7 1.24 1.07
0.9 0.75
0.01
0.006 0.01 0.006 0.003 0.005
5
5
7
10
7
6
40c
29b
31c
34b
40
39
0.1
0.5
0.1
0.25
4300
4000
4200
ftc
2.07
1.7
1.5
Cc
0.02
0.01 0.005
C
5
8
9
Eo'
23a _ ~llb_22.c
V.G.'
Ebb!
0.05
RL
ltg,
0.1
0.05
2600
2300
Rc
2
1.7
Cc
0.03
0.05
C
14
18
Eo'
8
9
- V.G.'
6SQ7see 2A6
~
2
7500
0.002
15
40
0.1
1050
0.04
21
27
0.1
0.25
1250
0.02
27
31
0.5
0.1
1
2
0.1
0.25
16600 17400 2600
2900
0.7
0.65
3.3
2.9
0.003 0.0015 0.025 0.015
22
10
13
16
44
48
36
29
0.5
1350
0.009
31
34
0.25
0.25
0.5
7200
7600
1.2
1.17
0.01 0.006
8
11
311> __ 32
--
1
0.5
8000 11500
0.9 0.72
0.003 0.006
13
9
31
33
0.5
1
12300
0.6
0.003
13
33
2
0.1
13700 1600
3
0.45
0.0015 0.02
17
19
28
37
0.25
2050
0.02
26
37
0.25
2900
1.27
0.01
20
10
0.1
3500
1.2
0.03
15
10
0.05
1700
2.3
0.05
31
9
90
0.5
0.25
2
0.1
1
0.5
1
0.25
0.5
7500
8300
9000 12500 14200 15500 2420
0.6
0.54 2.55
1.12
1
0.88 0.67
0.012 0.0075 0.005 0.0065 0.0045 0.0035 0.023
12.3
13.2
21
10.2
11.5
7.7
9.4
34.2 23.7
28.2c
30
31.6 30.5
32.9
0.1
0.25
0.5
0.1
4750
5050
4350
ftc
1.5
1.43
1.8
Cc
0.023 0.012 0.007
C
8.5
7.8
5.6
Eo'
24b
25
V.G.' 20.3b
12SQ7 see 2A6
12Q7 see 6Q7
__
Ebb!
RL
R g'
Rc*
C
Eo'
V.G.'
0.5
1
2980
0.003
62
48
-
0.1
0.25
0.5
1900
2100
2.5
2.3
0.01 0.005
26
29
33
35
0.05
0.1
2100
1.9
0.03
40
9
0.1
0.25
300
0.5
1
3890
0.703
0.0035
38
40
1
2400
1.1
,.'" '.00"'
M
:m. __
79t
180
0.25
0.5
2450
0.01
34
41
0
39
1
0.5
2750 3450
0.005 0.009
40
30
42
42
6Q7,12Q7
180
0.25
0.25
0.5
1
0.5
3400
4500 6000
4000
1.05 0.86
1.3
1.6
0.01 0.005 0.003 0.006
30
25
31
37
36
38
40
39
90
0.25
0.1
1
0.25
0.5 0.25
0.5
9800 11300
5000 7600
4400
0.42
0.38
0.77 0.54
0.9
0.01 0.006 0.015 0.007 0.003
21
18
21
15
19
11
10
11
10
11
-
'" 1
300
0.1
0.25
0.5
930
1680
0.006
0.014
55
50
_______34 _ _ _ _ _ _ .12_
0.5
1
3420
0.003
32
43
0.1
0.25
950
2.63
0.012
52
34
0.5
2
0.1
1
4100
4650
800
0.0035 0.002 0.025
44
40
39
44
45
29
TABLE II-DIODE-TRIODES
2A6.6B6.6SQ7.12SQ7.7S
180
0.25
0.5
0.5
1
0.5
1
2
0.5 0.25
3000 4300
5300 7000
4800
8000
8800
2.7
2.1
1.3
1.8
1.5
1.1
0.9
0.007 0.015 0.007 0.004 0.007 0.004 0.002
23
21
28
33
25
33
38
52
37
43
50
53
57
58
90
Ebb!
RL
RgI
Ebb!
fu
Rg'
1
0.5
4650 6150
0.004 0.006
12
8.8
34
35
0.5
1
6850
0.004
12
38
0.25
0.5
211 0
1.38
3li. __
56. 76 8ee 6PS
90
Ebb!
0.1
0.25
fu
0.25
0.5 0.25
0.5
0.1
Rg'
2350 4000
2050
2200
4250
Rc*
0.04 0.015 0.009 0.015 0.006
C
5.8
8.4
7.1
Eo·
9.5
9.7
V.G.- _ 23b _ 290
29
31c __33
-
RL =Plate Resistor (Megohms)
V.G. =Voltage Gain
6Z7Gt
0.1
0.25
II00
2.6
53 8ee 6N7
6SCn.12Scn
180
0.25
0.25
0.5
1
2150
2400
1850
0.011 0.006 0.003
2l.
28
32
35
41
39
-
Rd =Screen Resistor (Megohms)
Rg = Grid Resistor (Megohms)
0.25
2500
1.5
0.01
45
10
0.1
3000
1.3
0.03
35
10
0.5 0.25
3080 4410
~30
2
2.25
1.5
0.0135 0.008 0.012
27
28.5
31.6
28.4
30.6 33.7
6R7
180
0.1
0.25
4100
0.9
0.01
43
10
0.5
1
7100
0.76
0.003
36
40
0.1
0.25
1000
0.01
57
34
0.5
1100
0.006
60
36
0.25
1650
0.01
56
39
0.5
1
3110
0.72
0.0035
70
44
300
0.25
0.5
0.5
0.5
1
1
2050
2350 2850
3600
0.0055 0.003 0.0055 0.003
66
77
61
75
42_ _ ~3
44
46
Ebb!
RL
Rg' ,
Rc"
Cc
C
Eo'
---
2
4450
0.0015
82
46
300
0.1
1900
4
0.03
31
31
0.1
1200
4.4
0.03
35
34
0.1
0.25
1500
3.6
0.015
52
39
1 0.05
10000 1600
0.33
2.6
0.003 0.055
47
50
11
9
0.05
0.1
2000
2
0.03
62
9
0.5 0.25
2300 3300
3
2.7
0.007 0.015
45
42
42
48
0.25
0.5
3900
2
0.007
51
53
0.5
4600
0.8
0.006
46
10
0.25
6700
0.54
0.01
33
10
Ebb!
RL
fit
III
...
..
c:
fit
,.,
Itg.
III
Rc*
C
Eo'
V.G.'
<
0.5 0.25
1700 2600
3.05
2.4
0.007 0.015
53
43
40
42
300
0.25
0.5
3000
1.66
0.007
52
45
1
0.5
4200 5300
1.8
1.6
0.004 0.007
60
47
56
58
0.5
1
2
6100
7000
1.3
1.2
0.004 0.002
62
67
60
63
Ebb!
RL
Rg'
Rc
Cc
C
Eo'
V.G.'
1
0.5
3600 4600
1.45
1.2
0.004 0.007
62
47
45
45
0.5
1
5500
0.9
0.004
60
46
2
6200
0.9
0.002
66
47
Ebb!
RL
Rg'
Rc
Cc
C
Eo'
V.G.-
1
10600
0.44
0.004
74
11
Ebb!
RL
R g'
Rc
Cc
C
Eo·
V.G.'
300
0.25
0.5
8800
0.4
0.006
40
10
V.G.'
c:
-
-...
n
0.1
0.25
2200
3.5
0.015
41
39
2
7900
0.63
0.002
41
41
0.25
0.5
1680
1.46
0.006
59
40
0.25
2400
1.6
0.015
71
10
0.1
0.1
0.25
2900
3800
1.4
1.1
0.03 0.015
52
68
10
10
6T7G
180
0.25
0.5
0.1
0.5
1
2
0.25
0.5
1
0.1
0.5 0.25
5220
9440 10850 1950 2400
2640 3760
5920 7250
1.25
0.74
0.6 2.85
2.55
2.25 1.57
1.11 0.91
0.008 0.005 0.007 0.0045 0.0035 0.0245 0.0135 0.008 0.012
33.8
38.5
31
39
42.6 43.7
58
64
57
36.4
41 26.5
38 38.4 40.5
31.9
33.2 36.6
0.5
4400
1
0.007
71
10
0.25
0.25
0.5
6300
8400
0.7
0.5
0.015 0.007
54
62
10
11
300
0.25
0.5
1
0.5
4580
5220 6570
1.35
1.23 1.02
0.0075 0.005 0.008
80
69
62
40
41 41.5
0.5
1
2
8200
9600
0.82
0.7
0.0055 0.004
76.5
85.5
43.3
44
Ebb!
RL
Rg'
ftc
Cc
C
Eo'
V.G.'
Z
Q
z
,.,o
~
)I.
...
o
z
•
~
n
5-:J
....
~
RESISTANCE COUPLED AMPLIFIER CHART
~--------------------------------------------------------------------------------------------------------------------------~
as
C -Blookina Cond_ <14.)
Cd =Screen By-pass Condenser (pC)
Eo = Voltage Output (Peak Volts)
Rd -Screen Resistor (Megohms)
RL =PJate Resistor (Megohms)
Co-Catboffe By-pass Condenser (pi)
Ebb =PJate-SllPply Voltage (Volts)
Re=Cathode Resistor (Ohms)
0.05
3800
1.4
0.06
16
Eo'
V.G.' 4.5
0.05
0.25
0.1
5400
4600
1.1
0.86
0.03 0.015
23
19
4.9
5.1
75_2A6
85_55
11."
Re
Cc
C
Ebb'
fu
0.1
0.37
1200
0.05
5.2
0.02
17
Eo'
41
V.G.'
R.·
Rd
Re
Cd
Ce
C
0.1
0.25
0.1
0.25
0.5 0.25
0.5
1
6620
9000 10300 15100 20500 24400
0.7
0.55
0.5 0.31
0.25
0.2
0.04 0.015 0.007 0.015 0.007 0.004
17
22
25
23
26
18
5.1
5.5
5.3
5.5 _M
5.4
0.1
0.25
0.5 0.25
0.44
0.44
1.1
1100
1300 2400
0.05
0.05 0.03
5.3
4.8
3.7
0.01 0.006 0.008
22
23
33
55
66
70
-
90
0.25
. 0.5
1 '0.5
1.18
1.4 2.18
2600
3600 4700
0.03 0.025 0.02
3.2
2.5
2.3
0.005 0.003 0.005
32
33
28
85
92
93
0.05
3200
1.8
0.06
33
_4.9
0.05
0.1
4100
1.6
0.045
44
5.2 -
0.25
5000
1.2
0.02
49
5.:1
0.1
0.25
0.5 0.25
0.5
1 0.05
0.1
0.25
6200
8700 10000- 14500 20000 24000 3200
0.7
0.57 0.43
0.29
0.24
0.9
1.9
0.04 0.015 0.008 0.015 0.008 0.004 0.08
50
37
47
40
48
53
50
5.3_
5.5__ ~.5
5.6 - - 5.7 _5.7_ 5.2
0.05
n.l
4100
1.5
0.045
74
5.5
0.25
5100
1.2
0.015
85
5.6
TABLE IIl-PENTODES
6C1.
- - --. 6J7.
-- - -. 57
-180
0.5
1
2
2.6
2.7
5500
55110
0.05
0.02
2
2
0.0025 0.0015
27
29
120
140
0.1
0.44
1000
0.05
6.5
0.02
42
51
0.1
0.25
0.5
750
0.05
6.7
0.01
52
69
0.5 0.25
1.1
0.5
800 1200
0.05 0.04
5.2
6.7
0.006 0.008
41
59
93
83
0.25
0.5
1.18
1600
0.04
4.3
0.005
60
118
V.G.=Voltage Gain
1
1.4
2000
0.04
3.8
0.0035
60
140
0.5
2.45
2600
0.03
3.2
0.005
45
135
0.5
1
2
0.1
2.9
2.7 0.44
3100
3500
500
0.025
0.02 0.07
2.5
2.8
8.5
0.0025 0.0015 0.02
56
60
55
165
165
61
0.1
0.25
0.5
450
0.07
8.3
0.01
81
82
0.5
0.53
600
0.06
8
0.006
96
94
0.1
5900
0.8
0.03
64
5.5
300
0.1
0.25
1
0.25
0.5 0.25
0.5
9600 14300 19400 23600
8300
0.22
0.2
0.54
0.43
0.3
0.015 0.006 0.01 0.006 0.003
84
82
88
94
71
5.7
5.8
5.7
5.8
5.7
380
0.25
0.5
0.25
0.5
1
0.5
1
1.18
1.18
2.9
1.45 2.45
1100
1200
1300 1700 2200
0.04
0.04 0.05 0.04 0.04
5.5
5.4
4.1
5.8
4.2
0.008 0.005 0.005 0.005 0.003
104
75
81
110
97
104
350
161
140
185
Ebb'
RL
Rg'
Re
Cc
C
Eo·
V.G.'
Ebb'
RL
2 Rg'
2.95 Rd
2300 Re 0.04 Cd
4 Ce
0.0025 C
100 Eo'
240 V.G.'
6J7_6C6
Ebb'
0.1
RL
0.1
0.25
R g'
0.59
Rd
0.65
870
900
Re
0.065 0.061
Cd
Ce
5.1
5
0.01
C
0.018
16
20.5
Eo'
46.5
V.G.' 33.3
Ebb'
RL
Rg'
Rd
Re
Cd
Ce
C
Eo'
V.G.'
12SJ7 Bee
Ebb'
RL
Rg'
Rd
Re
Cd
Ce
C
0.5
0.7
910
0.057
4.58
0.007
22.5
53.5
90
0.25
0.5
0.25
1
0.5
0.5
1
2
0.1
1.5
1.6
1.7
3.2
3.5
3.7 0.58
1440
1520
1560 2620
2800
3000
530
0.044 0.044 0.043 0.029
0.03 0.031 0.073
3.38
3.23
3.22 2.04
7.2
1.95
1.92
0.007 0.0055 0.004 0.004 0.0026 0.0024 0.017
12
13.7
18
19
15.4
16.4
33
55.5
66.5
77 69.5
84
93.5 47.4
0.1
0.25
0.29
880
0.085
7.4
0.016
23
68
6SJ7
57 __ 6C6
0.1
0.37
2000
0.07
3
0.02
19
Eo
24
V.G.'
0.1
0.25
0.5
2200
0.07
3
0.01
28
33
0.5
0.6
2000
0.06
2.8
0.006
29
37
90
0.25
0.5
0.92
1700
0.045
4.5
0.005
18
93
90
0.25
0.25
0.5
1
0.5
1.18
1.35
2.6
1.1
3500
3500
3500 5000
0.04
0.04
0.04 0.04
1.9
2.1
1.5
1.9
0.008 0.007 0.003 0.004
26
22
33
32
43
55
65
63
0.5
1
1.7
3800
0.03
2.4
0.002
22
119
657
180
0.1
0.25
0.5
0.25
0.5 0.25
1.8
0.68
0.71
1.6
540
540
850
890
0.07 0.065 0.05 0.044
4.6
4.7
6.9
6.6
0.01 0.0063 0.0071 0.005
43
48 32.5
39.5
66
75
79
104
300
0.5
0.1
2
1
0.5
1
0.1
0.25
3.3
1.9
3.6
3.8 0.59
0.67
1520
950 1410
1600
430
440
0.046 0.041 0.037 0.031 0.077 0.071
4.4
3.5
3
2.9
8.5
8
0.0037 0.0041 0.003 0.0024 0.0167 0.01
44
30
37.5
41.5
57
75
118
134
147
57
109
78
0.5
1
2.2
2180
0.04
3.8
0.002
44
192
0.25
0.5 0.25
0.5
0.71
1.7
1.95
440
620
650
0.071 0.058 0.057
8
6
5.8
0.0066 0.0071 0.005
82
54
66
89
98
122
2
2.9
6200
0.04
1.5
0.003
27
100
0.1
0.44
1000
0.08
4.4
0.02
30
30
0.1
0.25
0.5
0.5
0.6
1200
1200
0.08
0.07
4.4
4
0.015 0.008
52
53
41
46
0.25
0.25
0.5
1.2
1.18
2100
1900
0.05
0.06
2.7
3.2
0.01 0.007
·39
55
55
69
1
1.5
2200
0.0s.
3
0.003
53
83
0.5
0.5
1
2
0.1
2.6
2.8
3
0.5
3300
3500
3500
950
0.04 0.04
0.4 0.09
2.1
2
2.2
4.6
0.005 0.003 0.002 0.025
47
55
53
60
81
115
116
36
0.5
2
1
0.5
1
4.1
2.1
3.6
3.9
1120
1080
700 1000
0.055 0.04 0.041 0.043
3.8
5.2
4.1
3.9
0.0036 0.0037 0.0029 0.002
73
52
66
76
174
162
136
136
300
0.25
0.5
1.10
860
0.06
7.4
0.004
8jl
167
0.1
0.25
0.37
530
0.09
10.9
0.016
96
98
...
:t
11'1
~
-<
0.5 '
1
2.2
1410
0.05
5.8
0.002
79
238
Ebb'
fu
Rg'
Rd
Re
Cd
Ce
C
Eo·
V.G.'
Ebb'
RL
RgI
Rd
Re
Cd
Ce
C
Eo"
V.G.'
...
11'1
n
:t
...n2:
:..
....
~
:..
2:
TABLE IV-DIODE PENTODES
2B7.6B7.6B8.12C8
180
0.5
1
2.8
6000
0.04
1.55
0.003
29
85
•
11'1
-
6SJ7.12SJ7
- - - - -. --- - - 180
0.25
0.25
1
0.5
0.83
0.94
0.94
1100
1050
1060
0,06- 0.07
0,06
6.8
6.6
6.1
0.001 0.004 0.003
47
54
38
161
131
109
0.1
0.25
0.31
800
0.09
8
0.005
60
82
~
:;,
....
"'.
55.85
-,
180
91
Ebb'
RL
Rg=Grid Resistor (Megohms)
fr
300
0.1
0.25
0.55
1100
0.09
5
0.015
89
47
0.5
0.6
900
0.08
4.8
0.009
86
54 -
0.25
0.25
0.5
1
0.5
1.2
1.2
2.7
1.5
1500
1600
1800 2400
0.06
0.08 0.05
0.06
3.2
3.5
2.5
4
0.015 0.008 0.004 0.006
70
100
80
95
64
79
100
96
c:
Ebb'
0.5
RL
2 Rs'
1
3.4 Rd
2.9
2500
2800 Re
0.05 Cd
0.05
2.3
2.8 Ce
0.003 0.0025 C
120
90 Eo'
15.11_ 1~ V.G.'
PENTODES AS TRIODES-6C6. 6J7. 6M. W7. and 57 __ 6CS under TRIODES
a At 2 volts (RMS) output.
, Voltage at plate equals P1ate-SllPply Voltage minus voltage in RL and Re. For other supply voltages
differing as much as 50 % from these listed, the values of resistors, condensers, ~d gain are approximately
bAt 3 volts (RMS) output.
OOITIlCt. The value of voltage output, however, for any of these other supply voltages equala the listed
e At 4 volts (RMS) output.
voltage output multiplied by the new pJate-supply voltage, divided by the plate-supply voltage corred At 2.2 volts (RMS) output.
spondiug to the listed voltage output.
* See NOTES under TWIN-TRIODE DIAGRAM on page 365.
• For following stage (see Circuit Diagrams page 365).
: The cathodes of these twin units have a common terminal, and the cathode resistor values' listed are·
, 'Voltage acr088 Rg at grid-cun",nt point.
based on both tube sections operating under similar conditions.
, Voltage Gain at 5 volts (RMS) output unless index letter indicates otherwise.
UThe cathodes of these twin units have separate t.erminsIs.
:..
....
e
THE MYE
Section
13
TE~HNI~AL
MANUAL
Receiving Tube
Characteristics
MALLORY
369
Section 13 •
THE
MY E
TECHNICAL
MANUAL
R'ECEIVING TUBE CHARACTERISTICS
• This chapter represents a complete revision and modernization of the original Supplement 1 to the 3rd Edition ,MYE, issued
in October, 1939. Important revisions of the
ratings of older tubes have been incorporated,
and listings of 9S new tubes have been added.
The fact that less than 100 new types can
be added to our listings after over two years
of radio progress is indeed remarkable in
view of the progress of the vacuum tube art.
A common sense viewpoint by the tube
manufacturers has kept the tube types from
multiplying endlessly and aimlessly. There
will always be new tube types, but the important point now seems to be that new tube
types are added only when good and definite
reasons justify their existence.
To the reader there are advantages in
technical literature prepared by organizations not directly connected with an industry, because the viewpoint can be more objective and dispassionate. Furthermore, the
disinterested observer can frequently discern
trends which may not be so apparent to
those more intimately associated with the
art. It is difficult for anputsider however to
assign credit where credit is due when policies for the improvement of an industry are
promulgated.
Great credit is due to the various tube
manufacturers for their tube standardization programs which by united' action have
prevented or eliminated many duplicating or
overlapping tube types. This policy, originated during peace times, has been expanded
during the war, and there is every reason to
anticipate that many of the little used or
obsolete tube types will be discontinued,
The restriction of tube types provides great
benefits to the distributor, dealer, and serviceman by limiting inventory; but may provide a headache to many servicemen since
tube replacements in some sets may involve
the installation of new tube sockets, the use
of different cathode bias resistors. and realigning.
converter. This type is a much stronger oscillator than the lA7GT and will operate at
frequencies well above what can be done
with the lA7GT. Because of this fact this
type has been used in a number of all-wave
household battery sets.
Since the previous supplement "Lock-In"
line shave been increased in scope so that tubes
of this construction are available to duplicate the metal or "GT" functions. Likewise
the introduction of single-end metal tubes
was followed by the introduction of interchangeable single-end GT types. Receiver
manufacturers have been urged to design.
sets so as to use either metal or GT and in
most cases this is possible. In view of present
conditions on materials such practice seems
even more desirable at this time.
Other trends in the past year and a half
are the increased use of 12-volt ISO-milliampere types for A.C.-D.C. receivers, and
the addition of 1l7-volt types to facilitate
A.C. operation of battery receivers. Recently, the 4SZ3, a tube of miniature size,
was introduced to make possible this conversion of small-sized portable receivers. To
a large extent, tube manufacturers have
concentrated in the past year and a half on
improving existing tube designs rather than
bringing out new variations. This effort has
resulted in improved overall quality, and in
many cases, improved performance.
Metal tubes have been further. improved
and are now recognized to be of first line
quality. Some of this has resulted from actual design changes and some of it from
increased production on fewer types. The
trend seems to be to use metal types in RF,
IF, Detector and Audio Amplifier applications and' to use "GT" rectifier and power
output types.
An interesting development has been the
designing of the high GM amplifier tubes
with two-watt cathodes taking either 300
mils at 6.3 volts or ISO mils at 12.6 volts.
The previous high GM tubes used three-watt
cathodes taking 4S0 milliamperes at 6.3 volts.
The most noteworthy advancement of the
art, ,and the only complete new "line" of
tubes to report since the issuance of our
previous tube supplement is the new miniature battery tube line-ultra small tubes
only %;" in diameter with an envelope
height of lYs". These tubes have a glass
button 7-pin base.
The first of the high GM tubes was the
7H7 rated at approximately 4000 micromhos
against 2000 for the SK7GT type. The
6SD7GT followed soon with slightly different characteristics than those of the 7H7
type. A metal tube with two cathode leads,
the 6SG7, was recently announced, and is
an example of a design having very low grid
plate capacitances and high transconductance, features all beneficial to improved
high-frequency performance.
These tubes represent a new achievement
so far as size is concerned and have made
possible the extremely compact "personal"
sets now in every radio manufacturer's line.
The performance of these tubes is somewhat
improved over that of the regular 1.4 volt
tubes particularly in the case of the IRS
The new high GM tubes are used as radio
frequency amplifiers with untuned circuits
and mixer tubes with a separate oscillator.
The increase in gain with new high GM
pentodes as amplifiers is about directly proportional to the increase in GM over the
older tubes.
Advancelllent of the Art
370
The high GM tubes as mixers though,
have only about >i the tube noise of the
pentagrid type. The gain realizable with the
new high GM tubes as a mixer is about three
times that of the pentagrid type, thus. the
high GM type tube as a mixer will have
three times the sensitivity of the pentagrid
mixer tube for the same apparent noise.
The reduction of the number of metal
types in mass production referred to previously was achieved by sales promotion and
work with set engineers. Both RCA and
Ken-Rad launched a program of so-called
"Preferred" or "Recommended" Types in
1940 and this promotion has been highly
successful. It has benefited everyone all
along the line. The tube manufacturer has
been able to obtain lower costs and better
quality on the higher production of these
types, the set manufacturer has fewer types
to stock and can use more uniform chassis
design and even the dealers and servicemen
appreciate the reduction in tube types.
A further step in this same direction has
been the recent elimination of a number of
"G" type tubes by changing to a "GT"
construction entirely and double-marking it
. GT /G. This could not be .done on types
where shield cans were used as in RF or IF
types with top caps.
A list of the combination types follows:
G/TG Double Etched Types
The following types have been listed by
RMA as being double-etched and are of the
r -9 or GT construction.
lASGT/G 6PSGT/G
2SA7GT/G
lC5GT /G 6N7GT /G 2SL6GT /G
IG4GT /G 6V6GT /G
2SZ6GT /G
IG6GT /G 6X5GT /G 2SACSGT /G
lQSGT /G 6ACSGT /G 3SL6GT /G
3QSGT /G 6AESGT /G 3SZSGT /G
SW4GT/G 6SQ7GT/G SOY6GT/G
6H6GT /G 12SQ7GT /G 117Z6GT /G
6K6GT /G 2SA6GT /G
Additionally the following types have been
officially released through RMA but may
not be made by all tube manufacturers:
SY3GT/G
SZ4GT/G
117L7GT /1l7M7GT
Bias Resistor Calculations
The serviceman often finds it necessary to
replace the grid bias resistor in receivers
employing a self-biasing arrangement for
• obtaining the proper grid voltage. When the
resistance value is not known, it may be
calculated by dividing the grid voltage required (at the plate voltage at which the
tube is operating), by the plate ~urrent in
amperes, plus the screen current in amperes,
times the number of tubes passing current
through the resistor.
RECEIVING
Under this rule, the grid bias resistor
value is given by the following formula:
R = ECl X 1,000
(IB + Ic.)n
where: R = Grid bias resistor value in ohms.
Ee 1 = The grid bias required in volts.
IB·= The plate current of a single
tube in milliamperes.
Ie. = The soreen grid current of a
single tube in milliamperes.
n = The number of tubes passing
current through the resistor.
ExaDlple--1t is desired to determine the
value of bias resistor used to obtain the
proper value of grid bias on three type '35
tubes working in the radio frequency stages
of a receiver. First, determine the plate and
soreen voltages employed in this set. Suppose, in this case, it is found that the plate
supply voltage is 250 and the screen voltage
is 90. Looking in the characteristics chart
on page 374, it is found that the proper grid
bias for the '35 under these conditions is
-3.0 volts. In addition, the plate current is
6.5 milliamperes. The screen current is 2.5
milliamperes. Substituting in the formula,
R = 3.0 X 1,000 = 111 hms
(6.5 + 2.5)3
0
The value of grid bias resistors can be calculated in this manner for any type and any
number of tubes. I,n the case of triodes, the
screen current term drops out entirely.
Be sure to determine the plate voltage at
which the tubes are working, the number of
tubes being supplied from the bias resistor,
the screen voltage (if a tetrode or pentode),
the correct value of grid bias voltage required (whether the tube cathode is operated from A.C. or D.C. will affect the value
of bias voltage), and the plate and screen
current for the given plate voltage.
In the case of resistance-conpled amplifiers which employ high resistance in the
plate circuit, it must be remembered that the
plate voltage is equal to the plate supply
voltage minus the voltage drop in the plate
load resistance caused by the plate current.
The net plate voltage alone determines the
correct value of grid bias.
The foregoing methods of calculations
apply to self bias only.
Size of Bias Resistors--In addition to having the proper resistance, a resistor should
have sufficient size and heat dissipating
ability to carry the current. The actual
wattage dissipated in a resistor can easily
be calculated from the following application
of Ohms law:
E2
Watts = R
where
E
voltage across resistors
R = resistance in ohms
When selecting the proper resistor for a
given application, the actual wattage given
by the formula should be multiplied from
two to ten times, depending upon such factors as air circulation, mounting position,
and amount of heat which may be developed
without injury to other parts. For a given
T U 8 E
CHARACTERISTICS
dissipation, the larger the resistor, the lower
the operating temperature per unit of area.
Cut-Off Bias--Every serviceman should be
familiar with the formula for calculating
"cut-off." This is the point where plate current ceases to flow as the grid voltage is
made increasingly negative. In volume control circuits, the control ,range should never
be extended into the "cut-off" region, otherwise serious distortion will result. The formula for triodes is
"Cut -0ff" voItage = Plate
voltage
----"M-u-The "cut-otf" voltage for tetrodes, pentodes
and variable mu tubes cannot be calculated
from this simple formula, and should be obtained from the tube manufacturers' tables.
Mutual Conductance
The term "Mutual Conductance" has
been retained in this compilation since it is
in general usage by servicemen and engineers. Actually, this term is a misnomer;
and for the purpose of more exact definition
it has been superseded in rigorous engineering terminology by the term "Grid-Plate
Transconductance." Numerically, the figures expressing "Mutual Conductance" and
"Grid-Plate Transconductance" are identical.
These figures are of value to the serviceman in comparing the relative merits of
tubes. When used in this manner, comparison should be made only with tubes designed
for the same service; because, for example.
a comparison of the mutual conductance of
an output tube with a pentagrid converter
would have no practical value. However.
generally, the value of mutual conductance
has been accepted as the best single figure
of merit for vacuum tube performance.
Mutual Conductance (GM) is an expression which combines in one term amplification factor and plate resistance and is the
ratio of the first to the second. Mutual conductance may be more strictly defined as
the ratio of a small change in plate current
(amperes) to the small change in the control
grid voltage which produces it, under conditions that all other voltages remain constant
If a grid potential change of 1 volt causes a
plate current change of 1 rna. with all other
voltages constant, the mutual conductance
is .001 divided by 1 or 0.001 mho. A "mho"
is the unit of conductance and was created
by spelling ohm backwards. For convenience
a millionth of a mho, or a micromho, is used
to express mutual conductance. In our example, 0.001 mho X 1,000,000 = micromhos.
The main reason for dropping the expression "mutual conductance" in precise definition is the fact that the term "mutual"
implies a reciprocal effect. This is not the
case in a vacuum tube, because a plate
voltage change will not cause a grid current
change of the same ratio.
For the precise definition of the term
"Grid-Plate Transconductance" refer to the
Table of Definitions, lE56.
• Section 13
Definition of Terllls
Through the special courtesy of the Institute of Radio Engineers, the following glossary is reproduced from the "Standards of
Electronics." These definitions are accepted
as standard by the Radio Industry.
lEI. Vacuum Tube. A vacuum tube is a device con-
~~':,f ~:~;:'d~~Ut~~~:~~~;~e ;;,n!,a~~~n~t;~~
conduction of electricity through the vacuum or
contained gas may take place.
tE2. Hlah-Vacuum Tube. A high-vacuum tube is
a vacuum tube evacuated to such a degree that its
electrical characteristics are essentially unaffected
by gaseous ionization.
lE3. Gas Tube. A gas tube is a vacuum tube in
which the pressure of the contained gas or vapor is
such as to affect substantially the electrical characteristics of the tube.
tE4. Mercury-Vapor Tube. A mercury-vapor tube
is a gas tube in which the active contained gas is
mercury vapor.
'
lE5. Thermionic Tube. A thermionic tube i. a
vacuum tube in which one of the electrodes is heated
for the purpose of causing electron or ion emission
from that electrode.
lE6. Phototube_ A phototube is a vacuum tube in
which one of the electrodes is irradiated for the
purpose of causing electron emission.
lE7_ Cathode-Ray OsclllOWSph Tube. A cathoderay oscillograph tu\;e is a vacuum tube in which the
deflection of an electron beam, effected by applied
electric and/or magnetic fields, indicates the instantaneous values of the actuating voltages and/or
currents.
lE8. Diode. A diode is a two-electrode vacuum tube
containing an anode and a cathode.
lE9. Triode. A triode is a three-electrode vacuum
tube containing an anode. a cathode. and a control
electrode.
tEIO. Tetrode. A tetrode is a four-electrode vacuum
tube containing an anode. a cathode. a control
electrode, and one additional electrode ordinarily
in the nature of a grid.
lEll. Pentode. A pentode is a five-electrode vacuum
tube containing an anode. a cathode, a control
electrode, and two addi tional electrodes ordinarily
in the nature of grids.
lEU. Hexode. A hexode is> a six-electrode vacuum
tube containing an anode, a cathode, a control electrode, and three additional electrodes ordinarily in
the nature of grids.
lEl3. Heptode. A heptode is a seven-electrode vacuum tube ~ontaining an anode, a cathode, a control
electrode. and four additional electrodes ordinarily
in the nature of grids.
lE14. Octode. An octode is an eight-electrode vacuum tube containing an anode, a cathode, a control
electrode. and five additional electrodes ordinarily
in the nature of grids.
lEIS. Multie1ectrode Tube. A multielectrode tube
is a vacuum tube containing more than three electrodes associated with a single electT(,~ .cream.
lEt6. Multiple-Unit Tube_ A multiple-unit tube is
a vacuum tube containing within one envelope two
or more groups of electrodes associated with independent electron stream •.
Note-A mUltiple-unit tube may be 80 indicated;
for example, duodiode, duotriode, diode-pentode.
duodiode-triode, duodiode-pentode, and triode-pentode.
lEU. Cathode. A cathode is an electrode which is
the primary source of an electron stream.
lEIS. Filament. A filament is a cathode of a thermionic tube, usually in the form of a wire or ribbon.
to which heat may be supplied by passing current
through it.
lE19. Indirectly Heated Cathode. (Equipotential
Cathode. Unipotential Cathode.) An indirectly
heated cathode is a cathode of a thermionic tube to
which heat is supplied by an independent heater
element.
tE20. Heater. A heater is an electric heating element
for supplying heat to an indirectly heated cathode.
lE21. Control Electrode. A control electrode is an
electrode on which a voltage is impressed to vary
the current flowing between two or more other
electrodes.
lE22. Grid. A grid is an electrode having one or
more openings for the passage of electrons or ions.
lE23. Space-Charge Grid. A space-charge grid is a
grid which is placed adi acent to the cathode and
positively biased 80 as to reduce the limiting effect
of space charge on the current through the tube.
371
MY E
Section 13 •
lEU. Control grid. A control grid is a grid, ordinarily placed between the cathode and an anode,
for use as a control electrode.
lE25. Screen Grid. A screen grid is a grid placed
between a control grid and an anode, and usually
maintained at a fixed positive potential, for the
purpose of reducing the electrostatic influence of tije
anode in the space between the screen grid and the
cathode.
lEU. Suppressor Grid. A suppressor grid is a grid
which is interposed between two electrodes (usually
the screen grid and plate), both positive with respect to the cathode, in order to prevent the passing
of secondary electrons from one to the other.
lE27. Anode. An anode is an electrode to which a
principal electron stream flows.
lE28. Plate. Plate is a common name for ijle principal anode in a vacuum tube.
lE29. Electron Emission. Electron emission is the
liberation of electrons from an electrode into the
surrounding space. Quantitatively, it is the rate at
which electrons are emitted from an electrode.
lE30. Thermionic Emission. Thermionic emission
is electron or ion emission due directly to the temperature of the emitter.
lEal. Secondary Emission. Secondary emission is
~~~~~~~ emission due directly to Impact by electrons
lEll. Grid Emission. Grid emission is electron or
ion emission from a grid.
lE33. Emission Characteristic. An emission characteristic is a relation, usually shown by a graph
between the emission and a factor controlling the
emission (as temperature, voltage, or current of the
filament or heater).
'
IBM. Cathode Current. C~thode curreut is the
total current passing to or from the cathode through
the vacuous space.
lE35. Filament Current. Filament current is the
current supplied to a filament to heat it.
lE36. Filament Volta~e. Filament voltage is the
voltage between the terminals of a filament.
lE37. Heater Current. Heater current is the current
flowing through a heater.
lEa8. Heater Vol~e. Heater voltage is the voltage
between the terminals of a heater.
lE39. Electrode Current. Electrode current is the
current passing to or from an electrode through the
vacuous space.
Note,The terms grid current. anode current
plate current, etc., are used to designate currents
passing to or from these specific electrodes.
lE40. Electrode V.ol~e. Electrode voltage is the
voltage between an electrode and a specified point
of the cathode.
Note-The terms grid voltage, anode voltage,
plate voltage, etc., are used to designate the voltage
between these specific electrodes and the cathode.
lE41. Direct Grid Bias. Direct grid bias is the direct
component of grid voltage.
Note-This is commonly called grid bias.
1M2. Grid Drl~ Power. Grid driving power Is
the average product of,the instantaneous value of
the grid current and of the alternating component
of the grid voltage over a complete cycle.
Note-This comprises the power supplied to the
biasing device and to the grid.
lE43. Peak Forward Anode Vol~e. Peak forward
anode voltage Is the maximum instantaneous anode
'voltage in the direction in which the tube is designed
to pass current.
lE44. Peak Inverse Anode Volta~e. Peak inverse
anode voltage is the maximum instantaneous anode
voltage in the direction opposite to that in which
the tube is designed to pass current.
, IE45. Tube Vo1t~e Drop. Tube voltage drop in a
gas or vapor-filled tube is the anode voltage during
the conducting period.
lE46. Electrode Dissipation. Electrode dissipation
is the power dissipated in the form of heat by an
electrode as a resnlt of electron and/or ion bombardment.
lE47. Ionization Current. Ionization current is the
electric current resulting from the movement of
electric charges in an ionizing medium under the
influence of an applied electric field.
0
l
TECHNICAL
MANUAL
lE48. Gas Current. Gas current is a current flowing
to an electrode and composed of positive ions which
have been produced as a result of gas ionization by
an electron current flowing between other electrodes.
lE49. Leaka~e Current. Leakage current is a con, ductive current which flows between two or more
electrodes by any path other than across the vacuous space.
lESO. Electrode Admittance. Electrode admittance
is the quotient of the alternating component of the
electrode current by the alternating component of
the electrode voltage, all other electrode voltages
being maintained constant.
Note-As most precisely used, the term refers to
infinitesimal amplitudes.
lESI. Electrode Impedance. Electrode impedance
is the reciprocal of the electrode admittance.
lE52. Electrode Conductance. Electrode conductance is the quotient of the in-phase component of
the electrode alternating current by the electrode
alternating voltage, all other electrode voltages
being maintained constant.
Note-This is a variational and not a total conductance. As most precisely used, the term refers
to infinitesimal amplitudes.
lE53. Electrode Resistance. Electrode resistance Is
the reciprocal of, the electrode conductance.
Note-This is the effective parallel resistance and
is not the real component of the electrode imped.
ance.
lEM. Transadmlttance. Transadmittance from one
electrode to another is the quotient of the alternating component of the current of the second electrode
by the alternating component of the voltage of the
first electrode. all other electrode voltages being
maintalned constant.
Note-As most precisely used, the term refers to
Infinitesimal amplitudes.
lE55. Transconductance. Transconductance from
one electrode to another is the quotient of the inphase component of the alternating current of the
second electrode by the alternating voltage of the
first electrode, all other electrode voltages being
maintained constant.
Note-As most precisely used, the term refers to
infinitesimal amplitudes.
lE56. Control ~ Grid - Plate Transconductance.
Control-grid-plate transconductance Is the name
for the plate-current-to-control-grid voltage transconductance.
Note-This is ordinarily the most important
transconductance and Is commonly understood
when the term "transconductance" is used.
lES7. Rectiflcation Factor. Rectification factor is
the quotient of the change in average current of an
electrode by the change in amplitude of the alternating Sinusoidal voltage applied to' the same electrode, the direct voltages of this and other electrodes
bellig maintained constant.
lESS. Conductance for Rectification. Conductance for rectification is the quotient of the electrode
alternatiJ;lg current of low frequency by the In-phase
component of the electrode alternating voltage of
low frequency, a high-frequency sinusoidal voltage
being applied to the same or another electrode and all
other electrode voltages being maintained constant.
IE59. Transrectiflcation Factor. Transrectification factor is the quotient of the change in average
current of an electrode by the change in the amplitude of the alternating sinusoidal voltage applied to
another electrode, the direct voltages of this and
other electrodes being maintained constant.
Note-As most precisely used, the term refers
to infinitesimal changes.
lE60. Conversion Transconductance. Conversion
transconductance is the quotient of the magnitude
of a single beat-frequency component (ft +1.) or
(ft -/0) of the output-electrode current by the magnitude of the control-e1ectrode voltage of frequency
I., under the conditions that all direct electrode
voltages and the magnitude of the electrode alternating voltage I. remain constant and that no impedances at the frequencies /t or /0 are present in
the output circnit.
Note-As most precisely used, the term refers til
an infinitesimal magnitude of the voltage of frequency /to
lE61 . p, Factor. p, factor is the ratio of the change
in one electrode voltage to the change in another
electrode voltage, under the conditions that a specified current remains unchanged and that all other
electrode voltages are maintained constant. It is a
measure of the relative effect of the voltages on two
electrodes upon the current in the circuit of any
specifi~ electrode.
Note-As most precisely used, the term refers to
infinitesimal changes.
lE62. AmplIfication Factor. Amplification factor is
the ratio of the change in plate voltage to a change
in control-electrod ,voltage under the conditions
that the plate current remains unchanged and that
all other electrode voltages are malntained constant.
It la a measure of the effectiveness of the controlelectrode voltage relative to that of the plate voltage
upon the plate current. The sense is usually taken
as positive when the voltages are changed in opposite directions.
Note-As most precisely used, the term refers to
infinitesimal changes. Amplification factor is a special 'case of J.l-factor.
lE63. Electrode Characteristic. An electrode characteristic Is a relation, usually shown by a graph,
between an electrode voltage and current, other
electrode voltages being maintained constant.
lE64. Transfer Characteristic. A transfer characteristic is a relation, usually shown by a graph,
between the voltage of one electrode and the current to another electrode, all other voltages being
.
maintained constant.
lE65. Intere1ectrode Capacitance. Interelectrode
capacitance is the direct capacitance between two
electrodes.
lE66. Electrode Capacitance. Electrode capacitance is the capacitance of one electrode to all other
electrodes -connected together.
lE67. Input Capacitance. The input capacitance
of a vacuum tube Is the sum of the direct capacitances between the control grid and the cathode
and such other electrodes as are operated at the
alternating potential of the cathode.
Note-This is not the effective input capacitance,
which is a function of the impedances of the ass0ciated circuits.
lE68. Output Capacitance. The output capacitance of a vacuum tube is the sum of the direct
capacitances between the output electrode (usually
the plate) and the cathode and such other electrodes
as are operated at the alternating potential of the
cathode.
'
Note-This is not the effective output capacitance, which is a function of the impedances of the
associated circuits.
lE69. Class A Amplifier•• A class A amplifier is an
amplifier in which the grid bias and alternating grid
voltages art!' such that plate current in a specific
tube flows at all times.
lE70. Class AB Amplifler.* A class AB amplifier
is an amplifier in which the grid bias and alternating
grid voltages are such that plate current in a specific tube flows for appreciably more than half but
less than the entire electrical cycle.
lE7l. Class B Amplifler.* A class B amplifier is an
amplifier in which the grid bias is approximately
equal to the cutoff value so that the plate current
is approximately zero when no exciting grid voltage
is applied and so that plate current in a specific tube
flows for approximately one-half of each cycle when
an alternating grid voltage is applied.
lEn. Class C Amplifler.* A class C amplifier is an
amplifier in which the grid bias is appreciably greater
than the cutoff value so that the plate current in
each tube Is zero when no alternating grid voltage
is applied, and so that plate current in a specific
tube flows for appreciably less than one half of each
cycle when an alternating grid voltage is applied.
*NQte-To denote that grid current does not
flow during any part of the input cycle, the suffix
1 may be added to the letter or letters of the class
identification. The suffix 2 may be used to denote
that grid current flows during some part of the cycle.
The Characteristics Charts by type numbers, appearing on
pages 373 through 401, are arranged in the following manner:
1. The numerically numbered types (OlA, 10, 56, 76, etc.)
3.- Rectifier tube types (80, 5Z3, 6W5, etc.) pages 391-393.
pages 373-377.
4. Special tubes as used by a single manufacturer (Sparton's
2. The' R M A standard numbered types (lA5, 2B7, 6A8,
485, Majestic's 2Z2, etc.) page 401.
12B8G, etc.) pages 377-391.
372
r-
COMPLETE TUBE CHART
Basing
CAPACITANCES
See
Fil.
Micra-Microfarads
Socket
Curro
Connection Amps.
Cathode
Chart on
Grid Input Outpu
Plate
Pages 394·401
DESCRIPTION
~
Type
Triode
01A
Triode
10
WD11
Triode
WX12
Fit.
5.0V
Fil.
7.fiV
Fit.
l.lV
Fil.
5.0V
0.25
1.25
7.0
0.25
3.3
0.25
8••
0.220 0.01
18
Pentode
Heater
14V
6B
Small 6 Pin
0.3
19
Twin Triode
Fil.
2.0V
6C
Small 6 Pin
0.260
Triode
Fit.
3.3V
4D
Small 4 Pin
22
Screen Grid
Fil.
3.3V
4K
Medium 4 Pin
24A
Screen Grid
Tetrode
Heater
2.5V
5E
Medium. Pin
Triode
Grid Leak
Detector
4.0
2.0
2.35
-------
7.80
1.7.
0.007 5.3
10.5
80
Triode
Triode
Heater
2.5V
Fit.
2.0V
SA
SmallS Pin
m
Sma1l4 Pin
81
Triode
Fit.
2.0V
4D
Small 4 Pin
82
Screen Grid
Tetrode
Fil.
2.0V
4K.
Medium 4 Pin
88
Pentade
Fit.
2.0V
5K
Medium 5 Pin
1.05
8.1
2.8
2.5
1.75
3.3
3.1
3.0
3.5
2.8
2.1
2.7
0.015
6.0
8.0
-1
~
84
VariableMu
Pentade
Fit.
2.0V
4M
Medium 4 Pin
0.060 O.ot5
6.0
2.5
8.0
11,000
725
0.015
25,000
:III
3.0
8.0
10,000
800
0.05.
20,000
III
-
350
32
16
8.0
.,1.0
1550
0.9
11,000
42.
40
18
8.0
5,000
1600
1.6
10,200
+A
90
4.•
2.5
6.6
1.,.00
425
0.007
15,000
135
10.•
3.0
6.6
1.,000
440
0.040
15,000
135
9.0
6.2
8.5
.,100
1650
0.130
9,000
180
13.5
7.7
8.5
4,700
1800
0.285
10,700
1.8.
,0.30
600
800,000
7.0
7.•
18.
79,000
23.0
0
13.
3.0
Power Amplifier
13.
22.5
6.0
RF Amplifier
13.
67.5
1.5
3.7
180
90
3.0
250
90
3.0
RF Amplifier
12.0
Amplifier
1st Detector
12.6
c:
3.0
7,000
5 (Zero signal plate c urrent per pI ate)
2.1
10,000
2 (Zero signal plate c urrent per pi ate)
1.9
10,000
0.130
6,500
34
3.•
.,850
600
1.3
12.
250,000
500
4.0
1.7
400
400,000
1000
4.0
1.7
Z
Q
....
•
III
n
::t
~
I.
15
630
600,000
1050
10
•• 5
8.3
7,600
1100
0.080
8,800
180
14.5
6.2
8.3
7,300
1150
0.180
10,500
250
30
135
n
III
<
45
13.
- -- - - 0.260 1.0
4.5
Complete
ClassB
Amplifier
I
Cut-Off
Bias
Volts
9.0
135
9.0
4.7
9
9,000
1000
0.080
13,000
180
13.5
5.0
9
9,000
1000
0.165
19,000
13.
9.0
3.0
9.3
10,300
900
0.070
20,000
180
13.5
3.1
9.3
10,300
900
0.130
20,000
135
22.5
8.0
3.8
4,100
925
0.185
7,000
0.375
5,700
30.0
12.3
3.8
3,600
1050
13.
67.5 '
3.0
1.7
0.4
610
950,000
640
180
67.5
3.0
1.7
0.4
780
1,200,000
650
135
135
13.5
14••
3.0,
70
50,000
1450
0.700
7,000
180
180
18.{)
22.0
5.0
90
55,000
1700
1.400
6,000
180
12.0
670
Reeomm.!
Load
Resist.
Ohms
13.
16••
Amplifier
~Mh08.
Max.
Undist.
Output
Watts
90
250
Amplifier
Mut.
Condo
Plate
Resist.
Ohms
12,000
25Q
Amplifier
Ampl.
Factor
8.0
Power Amplifier
Amplifier
Screen
Current
Ma.
1.8
1.5
-0.06
+A
Plate
Current
Ma.
67.5
---0.130 5.7
1
45
Grid
Bias
Volts
(Neg.)
135
-0.060 6.0
Sv::~
Screen
Grid
Volts
Detector·
Oacillator
Detector
-~
Amplifier
- -- --
2'2'
Amplifier
Plate
2.5
---2.4
0.132 3.7
2.3
- -- 0.132 0.02 4.0 12.0
- -- -
m
Medium 4 Pin
2.5
----
.F
SmallS Pin
26
3.0
----
4D
Heater
2.0V
Fil.
1.5V
4.0
Amplifier
Pentode
.
2.2
Amplifier
1&
20
3.1
----
4F
Special 4 Pin
Medium 4 Pin
8.1
----
4D
Medium 4 Pin
When
Used A.
Grid Leak Det.
4D
Medium 4 Pin
4D
Medium 4 Pin
Triode
12A
I I
I
OPERATING CONDITIONS CHARACTERISTICS
~
-n
....
III
:III
CIt
-....
n
CIt
9.0
9.0
•
VI
CD
67.5 to 180
67.5
5.0
135
67.5
3.0
2.8
1.0
360
600,000
6!Y.l
22.5
180
67.5
3.0
2.8
1.0
620
1,000,000
620
22.5
Amplifier
:III
n
a::J
-'
W
~
CAPACITANCES
Basing
Micr().Microfarads
Fil.
See
Curro
Socket
Amps.
Connection
Cathode
Grid
Chart on
Plate Input Output
Pages 394-401
DESCRIPTION
~
.
Type
I
I
Grid
When
Used As
1st Detector
VariableMu Heater
Tetrode
2.5V
30/01
.
Screen Grid
Tetrode
38
.
Heater
6.3V
5E
MediumS Pin
1.75
0.007 5.0
10.5
-5E
SmallS Pin
0.30
0.007 3.7
-Triode
3'2'
Heater
6.3V
5A
SmallS Pin
0.30
2.0
3.5
88
Pentode
•
89/44
40
41
SF
SmallS Pin
0.30
0.30
3.5
7.5
---VariableMu Heater
6.3V
Pentode
Fi!.
5.V
Triode
Pentode
Heater
6.3V
SF
Small 5 Pin
4D
Medium 4 Pin
6B
Small 6 Pin
0.30
.007 4.0
8.0
2.8
Amplifier
1st Detector
4,8
Pentode
Pentode
Heater
6.3V
Heater
25.0V
6B
Medium 6 Pin
6B
Medium 6 Pin
Fi!.
2.5V
Triode
4'2'
48
49
00
Double Grid
Triode
Pentod.
Tetrode
Fil.
2.5V
Heater
30V
5C
Medium SPin
5B
Medium 5 Pin
6A
Medium 6 Pin
Double Grid
Triode
Fi!.
2.0V
5C
Medium 5 Pin
Triode
Fil.
7.5V
4D
Medium 4 Pin
Recomm.,
Load
±
3.0
6.3
2.5
305
300,000
1020
3.0
6.5
2.5
420
400.000
1050
180
67.;;
6.0
100
55
1.5
1.8
470
5S0,OOO
850
6.0
250
90
3.0
3.2
595
550,000
1080
8.0
180
40
20
9.2
11,500
800
0.030
17,500
10
:z:
250
18.0
7.5
9.2
8,430
1100
0.340
20,000
30
III
15,000
100
100
9.0
7.0
1.2
120
140,000
875
0.270
135
135
13.5
9.0
1.5
120
130,000
925
0.550
13,500
250
250
25
3.8
120
100,000
1200
2.5
10,000
90 to 250
90
7. approx.
90
90
3.0
5.6
1.6
360
375,000
960
250
90
1.4
1050
1,000,000
1050
22
•-<
III
42.5
5.8
4.5
0.1
Amplifier
180
3.0
0.2
42.5
30
30
150,000
200
n
250,000
3.0
150
81,000
18;;0
1.5
9,000
150
7,600
180
180
13.5
18.5
250
250
18.0
32.0
5.5
68,000
2200
3.4
250
250
16.5
34.0
'6.5
80,000
2500
3.2
7,000
285
285
20.0
38.0
7.0
78,000
2550
4.8
7,000
375
250
26.0
17.0
2.5
18.5
10,000
95
95
15.0
20.0
4.0
160
120
6.5
.
45,000
2000
0.9
4,500
18.0
33.0
42,000
2375
2.2
5,000
180
31.5
31.0
3.5
1,650
2125
083
:z:
:z
n
~
(P. to P.)
2,700
275
56.0
36.0
3.5
1,700
20;;0
2.00
4,600
6.5
3.6
3.0
18.00
3,200
5.6
2,380
2350
1.25
6,400
~
1.75
AB. P.P.
275
68.0
250
33
300
0
4 (Zero signal plate current per tu be)
16.00
5,200
(P. toP.)
400
0
6 (Zero signal plate current per tu be)
20.00
5,800
(P. to P.)
1.2
8.6
--
13.0
Amplifier
250
16.5
31.0
6.0
95
95
20.0
52.0
12.0
15.6
125
100
22.5
56.0
12.0
43
250
150
60,000
2500
2.7
7,000
4,000
3900
2.0
1,500
11,000
3930
2.5
1,500
4,175
1125
Amplifier
0.40
-0.12
1.25
22.0
(P. to P.)
7.1
4.2
3.4
Class A
135
20.0
Class B
180
0
6.0
350
63.0
45.0
3.8
1,900
450
84.0
55.0
3.8
1,800
4.7
0.170
11,000
3.0
9,000 mi n.
2000
2.4
4,100
2100
4.6
4,350
2 (Zero sigllat plate c urrent per tu be)
Amplifier
.
c:
~
Class B
---1.75
:z
Class A
14 to 69 per tube
po
•
Amplifier
1.50
...
III
250,000
Amplifier
0.30
...
2.5
Amplifier
--
i
6.0
3.0
All. P.P.
I
90
180
0.70
.....
W
•
Bias
Volts
Resist:
Ohms
90 max.
1.7
~
Cut-Off
Amplifier
-Fi!.
2.5V
I
Max.
Undist.
Output
Watts
~
0.40
.
48
I
Mut.
Condo
pMhos.
2.2
--
4D
Medium 4 Pin
90
Plate
Resist.
Ohms
250
Detector
-40
7.0
Amp!.
Factor
Amplifier
- -- 42
90 max.
Screen
Current
Ma.
Amplifier
10.0
-0.25
250
Volts
(Neg.)
Plate
Current
Ma.
Amplifier
---Heater
6.3V
Screen
Grid
Volts
180
Detector
2.9
Bias
Plate
Supply
Volts
Amplifier
Detector
9.2
f.
OPERATING CONDITIONS CHARACTERISTICS
po
Twin Triode
53
&&
&8
&7
Heater
2.iV
Duplex
Diode
Triode
Heater
2.5V
Triode
Heater
2.5V
Pentode
Heater
2.5V
VariableMu Heater
Pentode
2.5V
&8
Class A
7B
Medium 7 Pin 2.0
Large Pin Circle
6G
Small 6 Pin
5A
Small 5 Pin
6F
Smoll6 Pin
6F
Smoll 6 Pin
Cia•• B
-1.0
1.5
1.5
4.3
(Trio de Sile tion)
1.0
3.2
3.~
2.2
-1.0
.007
1.0
.007
5.0
6.5
4.7
6.3
-&9
Triple Grid
71A
7&
7A
Medium 7 Pin 2.0
Large Pin Circle
Triode
Fil.
5.0V
4D
Medium 4 Pin
Bl'J:l:x
Heater
6.3V
6G
Smoll 6 Pin
Triode
78
Heater
2.5V
Triode
Heater
6.3V
SmallS Pin
Pentode
Heater
6.3V
6F
Small 6 Pin
78
VariableMu Heater
Pentode
6.3V
6F
Small 6 Pin
Twin
Triode
Duplex
Diode
Triode
8&
Heater
6.3V
Heater
6.3V
6H
Small 6 Pin
6G
Small 6 Pin
7.5
, 3.2
2.9
---0.30
1.7
1.7
3.8
( Triode Sectio n)
--
5A
77
79
---0.25
0.30
2.8
3.5 . 2.5
---0.30
.007
4.7
-0.30
.007
4.5
0.30
-1.5
1.5
4.3
( Triode Sectio n)
-89
Triple Grid
V99
Triode
X99
Heater
6.3V
Fil.
3.3V
Voltage
Regulator
.
VR101iSO
, Voltage
Regulator
so
-.l
til
Non.Microphonic
Triode
88;1,
-
-.063 3.6
2.5
2.2
Cold
4W
Octal
(Gas D ischarg e)
Cold
4W
Octal
(Gas
m
30,000
8,000
10.0
10,000
13.5
6.0
8.3
8,500
975
0.160
20,000
20.0
8.0
8.3
7,500
1100
0.350
20,000
Detector
250
20.0
Amplifier
250
Detector
250
100
4.3
Amplifier
250
100
3.0
1st Detector
250
100
10.0
Amplifier
250
100
Triode
250
(Plate curren t-Adjust to 0.2 mo. with no AC input signal)
13.5
5
9,500
1450
1,500,000
1225
13.8
0.5
1500
3.0
8.2
28.0
26.0
18.0
35.0
2.0
1280
800,000
1600
6
2,300
2600
100
40,000
2500
250
400
0
135
27.0
17.3
3
1,820
180
40.5
20.0
3
250
2.0
0.8
100
S.O
250
Amplifier
Diode Detector,
Triode
Amplifier
Amplifier
9.0
13 (Zero signal plate c urrent per tu be)
5,000
3.00
6,000
III
...<
(P. toP.)
20.0
6,000
1650
0.4
3,000
1,750
1700
0.79
4,800
100
91,000
1100
2.5
13.8
12,000
1150
c:
13.5
5.0
13.8
9,500
1450
III
4.3
0.43
III
500,000
Amplifier
250
100
3.0
1.t Detector
2&0
100
10.0
Amplifier
250
100
3.0
Complete
ClassB
250
0
10.5
135
10.5
3.7
8.3
11,000
750
.075
25,000
180
13.5
6.0
83
8,500
975
0.160
20,000
20,000
2.3
~
Ci)
...
100
Diode Detector,
Triode
Amplifier
n
50
1".25
250
.
'"
...
7
III
Pentode
250
0.260
500,000
2.0
ClassB
0.5
1500
1,500,000
1250
7.5
1160
800,000
1450
42.5
(Suppressor ti ed to cathode)
7.0
1.7
n
:t
,
-
250
20.0
Triode
250
31.0
32
Pentode
250
25.0
32
Class B
180
Amplifier
250
0
90 max.
4.5
Regulator
MinimumStarting Voltage,'125 Volts.
Operating Voltage, 90 Volta.
Operating Current 10 Ma. Min., 30 Ma. Max.
Regulator
Minimum Starting Voltage, 137 Volta.
Operating Voltage, lOS Volts.
Qperating Current 5 Ma. Min., 30 Ma. Max.
Regulator
Minimum Starting Voltage, 180 Volts
Operating Voltage, 150 Volt.
Operating Current, 5 Ma. Min., 30 Ma. Max.
-D ischarg e)
-4.0
17.5 (Ze ro signal curr ent per plate)
0.37
8.0
180
--
0.25
0
3200
(Zero signal current, per p late)
8.0
5.5
8.0
14,000
8.3
7,500
1100
0.350
4.7
2,600
1800
0.9
5,500
125
70,000
1800
3.4
6,750
3.5
9,400
6 (Zero .ignal current per plate)
~
'"
...
...'"
~
n
III
(P. toP.)
2.5
6.6
15,500
425
......
.007
n
(Ga. D ischarg e)
Small 4 Pin
300
11,000
35
250
--
Cold
Fil.
l.lV
14 (Zero signal curren t per plate)
CIt
4W
Octal
Voltage
VR1&o- Regulator
0.40
4E
Small 4 Nub
4D
Small 4 Pin
VR9oSO
~
6F
Small 6 Pin
7.0
O'
11.0
-0.60
6.0
250
Diode Detector,
Triode
Amplifier
Detector
11.0
294 (Pa rallel Conn.)
CIt
•
VI
CD
n
2.6
2.1
Amplifier
135
9.0
3.5
8.2
12,700
645
15,000
go
:::l
w
~
CAPACITANCES
Basing
Micr()oMicrofarads
Fil.
See
Curr.
Becket
Amps.
Cathode Connection
Chart on
P~te
G hl Input Output
Pages 394-401
Type
No.
8'1'4
.--
Type
_I
Voltage
Regulator
I I
Cold
Medium 4 Pin
Cathode No.1
Anode No.3
884
Gas
Triode
Heater
6.3V
6Q
Octal
886
Gas
Triode
Heater
2.5V
5A
SmallS Pin
FiI.
2.0V
5K
SmallS Pin
960
964
Pentode
Heater
6.3V
Acorn
Pentode
(Gas D ischarg e)
-.06 )
.012
--
966
Heater
6.3V
Special
0.150
.007 3.0
968
12~U
Pentode
Heater
6.3V
6F
8mall6 Pin
Pentode
Heater
6.3V
7R
Octal
1281
Heater
7.0Vt
Pentode
0.150 1.4
1.0
Special
8V
Lock-In
0.150
0.3
0.3
0.48
.007 2.7
-.010
---
5'
.015 8.5 '
:1802
I
Ampl.
Factor
Plate
Resist.
Ohms
I
Max.
Undist.
Output
Watts
I
5-
Recorom'l
Load
Resist.
Ohms
:::I
Cut..Off
.....
Bias
Volts
W
•
I
3 Mao-below 200 cycles
2 Ma.- above 200 cycles
300 (ins t.)
Grid Controlled
Rectifier
350
Power
Amplifier
135
135
16.5
7.0
1.8
125
125,000
1000
90
90
3.0
1.2
0.5
1100
1,000,000
1100
2.0
0.7
2000
1,500,000
1400
75 Max.
16 volt max. drop
250
100
3.0
Detector
2:;0
100
6.0
Class A
'Amplifier
90
2.5
2.5
25
14,700
1700
135
3.75
3.5
25
13,200
1900
25
12,500
2000
5.0
4.5
35
7.0
3.5
Amplifier
250
3.0
5.5
605
Detector,ynplifier
} SpeciaI Non -microphpnic Tube. Charsc teriaties same as Type 6C6.
DetectorAmplifier
} Special Non -microphonic Tube. Charac teristics same ao Type 6C6 except octal b ase.
100
0.45
...
13,500
:t
III
250,000
180
6:5
I
Mut.
Condo
I'Mhos.
Sweep
Circuit
Oscillator
180
Fil.
7.5V
4D
Medium 4 Pin
Bayonet
--
1.25
7
4
3
- -P entode
--6F
Small 6 Pin
Non-MiCf()o
phonic
Pentode
Heater
6.3V
Heptode
Heater
6.3Y
7T
Octal
0.30
1881
Tetrode
Heater
12.6V
7AC
Octal
0.45
1882
Tetrode
Heater
12.6V
7AC
Octal
0.6
1888
Twin
Triode
Heater
25V
8BD
Octal
0.15
1884
Twin
Triode
Heater
12.6V
8S
Octal
0.15
1861
Pentode
He\ter
6.3V
7R
Octal
I 0.4/f
0.30
.007 5.0
- - Triode
2.0
-1812
I
Screen
Current
Ma.
Cl.... C Amplifier
(For merly de signsted as 10 8 pecia!)
1808
Plate
Current
Ma.
n
.135
=t
-<
20,000
III
0.5
1.8
1440
800,000
...
1800
III
n
:t
~.
Pentode
300
150
2.5
10.0
2.5
3850
700,000
5500
(Suppressor to Cathode)
Tetrode
300
150
2.5
12.0
0.5
3500
540,000
6500
(Suppressor to Seroen)
Triode
250
2.0
13.0
33
5,200
6300
(Suppressor to Plate)
Class A
425
40
18
8.0
5,000
1600
Class B
(Two Tubes)
425
50
Class C
450
200
n
..
~
(See Ty pe7G7 /1232
Pentode
Triode
Grid
Bias
Volts
(Neg.)
J
0.6
--
1282
Screen
Grid
Volts
Minimum Starting Voltage, 125 Volts
Operating Voltage, 90 Volts
Operating Current, 10 Ma. Min. 50 Ma. Max.
3.0
--
VariableMu Heater
6.3V
Acorn
Pentode
1228
Regulator
Plate
Supply
Volts
Amplifier
Special
-Acorn
Triode
When
Used As
1
1.4
~
OPERATING CONDITIONS CHARACTERISTICS
DESCRIPTION
~
3.0
6.5
10.5
250
Triode
Connection
250
Mixer, or
Amplifier
--
~
100
2
8.0
6.5
25.0
8,000
=t
~
(P. toP.)
~
13.0
60
3.0
10,200
1500
1,500,000
1225
20
10,500
1900
c:
.
7
250
150
6.0
3.3
8.3
1,000,000
350
(G3=Neg.1 5.0V Approxi mately)
250
100
3.0
5.5
5.5
800,000
1100
(G3=Neg. 3.0V Approxi mately)
10.0
2.5
750,000
9000
~
Other characteria tics identical with6L6
--
Other characteris tics identical with 25L6
--
For applications critical as to the matching of the two triode units.
Other ratings, characteristics and dimensions same as 12SN7GT.
--
For applications critical as to matching of the two triode units.
Ratings, characteristics and dimensions identical with 128C7.
-0.02
Amplifier
Pentode
8 (Zero signal current per plate)
1.6
11.5
5.2
Amplifier
300
150
160o~
I
/
6750
I
-
~-
'2'000
Pentode
Heater
6.3V
7R
Octal
0.30
'2''2'00
Pentode
Hester
6.3V
6F
Small. 6 Pin
.3
9001
Midget
R.F.
Pentode
Hester
6.3V
But~~ype
.06
5.6
14
.06
5.6
14.
--
Vol~
Ampldier
~b!r!~:. =h~:C6.
RF Amplifier
0.15
.01
3.6
3.0
Mixer
9002
Mi
!l
,
I
O·
:::I
w
w
00
o
CAPACITANCES
FiI.l Micro-Microfarads
Socket
Curro Grid
Connection Amps.
Cathode
Chart on
Plate Input jOutput
Pages 394-401
DESCRIPTION
Type
No.
Type
Basing
See
I
I
1SIi
Diode
Pentode
Fi!.
1.4V
1T4
R.F.
Pentode
FiI.
1.4V
OPERA TI NG CON DIT I ON SCHARA C TE RI S TIC S
When
Ueed AB
Vol+~-
6AU
.•05 I 0.3
7 Pin
2.2
2.4
AJllPilfier
Button Base
1--1--1
I
Besm
1 T IiGT
Tetrode
I
Triode
2A4G
2AIi
I
Argon
Thyratron
1.4V
0.05
FiI.
2.5V
4D
Medium 4 Pin
2.5
~~~er Mediu~ 4 Pin
2.8
I
FiI.
2.5V
Hester
2.5V
Pentode
.05 I .01 I 3.6 , 7.5
6X
Oetal
2A3
2A3H
F.il.
6AR
7 Pin
Button Base
r Amplifier
I
----
6Q
Oetal
2.5
IMedium6B 6 Pin'
Power
-Amplifier
---I
1_-_1__1 I
Screee
Grid
Volts
Grid
Bias
Volts
(Neg.)
Plate
Current
Ma.
Screen
Current
Ma.
Amp!.
Factor
Plate
Resist.
Ohms
90
90
o
Plate load resistor 1. meg.
Sereen series resistor 3. meg.
45
45
o
Plate load resistor 1. meg.
}
Sereen series resistor 3. meg. Voltage gain 30.
90
67.5
0
90
45
0
2.0
45
45
0
1.9
0.7
6
6.5
1.4
-90-M-ax-.-
90 Max.
I
3.7
I
1.25
Pentagrid
Converter
I
Hester
2.5V
I Small
7C
7 Pin
Mut.
Condo
pMhos.
I
Max.
Undist.
Output
Watts
Reeomm.
Load
Resist.
Ohms
Cut-Off
Bias
'foIts
I
. I
.65'
,
....
(.)
•
l
IVoltage gain 50.
5QO,OOOr
900
18
I
750
10
800,000
350,000
250
45.0
60.0
Class ABI
300
62.0
40.0
Contro: :--:.-
,---
4.2
700
I (Zero signal,
800
10
1150
0.170
5250
3.5
2,500
15.0'
3,000
Ipsr tube)
14,000
...
11'1
(P. toP.)
,.-.-.~,'-' :::: :.:-. :",'_":':"_:_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _I
250
250
16.5
34.0·
6.5
285
285
20.0
38.0
7.0
185
Triode
250
20.0
31.0
6.8
Triode P.P.
Cla&q AR
350
38.0
24.0
(Zero signal, 'per tube)
1.0 I 7.0 , ~I Oscillator
0.8 , - - , - 0.3 , 8.5 , 9.0
Mixer Section
80,000
2500
3.2
7,000
79,000
2550
- 4.8
7,000
2,600
2600
0.85
13.0
91,000
100
2M'
I
:z:
Class A
Single Tube
Pentode
Amplifier
1.75
Plate
Supply
Volts
~
n
'1 6:l
11'1
...
4,000
6,000
it
-<-
(P. toP.)
11'1
n
:z:
:z:
....
1100
n
I
2
360.000
45
(Conv. Trans.l)
286
~
...
!:
~
287
:z:
c:
~
Fi!.
2.8 or
Power
Pentode
FiI.
2.8 or
1.4V
Tetrode
Fil.
2.8 or
1.4V
Power
Pentode
Fil.
2.8 or
7 Pin
1.4V
Button Base
Twin
Fil.
2.00r
4.0V.
8L
Octal
3Q4
301i-
Gf/G
3S4
4A6G 'Triode
90
o
o
0.15
90
1.2
0.3
600,000
750
Parallel Filament
90
90
4.5
9.5
2.1
100,000
2150
.270
10,000
Series Filament
90
90
4.5
7.7
1.7
120,000
2000
.240
10,000
Parallel Filament
90
90
4.5
9.5
1.6
100,000
2100
.270
8,000
Series Filament
90
90
4.5
7.5
1.0
100,000
1800
.250
8,000
7
7.2
1.5
100,000
1550
.180
5,000
1.2
100,000
1400
.160
5.000
90
8AS
Octal
Diode
3ASGT , Triode
Pentode
1.4y
7BA
.05
7 Pin
or
Button Base
.1
7AP
Octal
.05
or
.1
7BA
.0.5
or
.1
I· ;12
.06
...
Parallel Filament
67.5
67.5
Series Filament
67.5
67.5
Class A
(One Section)
Class B
90
90
1.5
1.5
1.1
1.1
240,000
65
I
20
26,600
(Plate currenltr-max. signa 1-10.8 Ma.
per plate)
275
I
750
1.0
8,000
6A3
Triode
6A4
--LA
Pentode
Fil.
6.3V
Fil.
6.3V
4D
Medium 4 Pin
5B
Medium 5 Pin
1.0
7.0
0.30
Heater
6.3V
6T
OctalS Pin
1.25
250
45.0
60
Class AB1
325
6S.0
40 (per tube)
4.2
sao
5250
3.2
2,500
15.0
3,OJO
135
135
9
13
2.S
100
52,600
1900
0.700
9,500
ISO
ISO
12
22
4.5
100
45,500
2200
1.4
s,Q1n
45.0
60
4.2
SOO
5250
Amplifier
---Triode
Amplifier
One Tube
3.5
----
----
6AsG
16.0
16.0
7
Amplifier
One Tube
250
325
5
6S.0
3.75
325
8A6
Twin
Triode
Heater
6.3V
~
Class A
Parallel Conn.
40 (per tube)
3,OOJ
(P.ta P.)
40 (per tube)
10.0
5,00)
(P. to P.)
6A7
Converter
Heater
6.3V
O.SO
7C
Small 7 Pin
Class B
1.0
-0.30
6AS
---8ASG
----
Pentagrid
Converter
Heater
6.3V
SA
Octal 8 Pin
0.3
6AsGT
6ABS/
6NS
Tuning
Indicator
Heater
6.3V
6R
Small 6 Pin
6AB6G
Direct
Heater
Coupled
6.3V
Twin Triode
7AU
Octal 7 Pin
.50
8AB7/
1SS3
Video
Pentode
SN
Octal
.45
8ACsG
- - - - Triode
GACsGT
Heater
6.3V
Heater
6.3V
6Q
Octal 6 Pin
6AC7/
1SS2
Video
Pentode
Heater
6.3V
SN
Octal
8AD6G
Tuning
Indicator
Heater
6.3V
7AG
Octal
0.150
7.0
5.5
---0.30
S.5
9.0
---MO.S
6.5
5.0
-----G 1.0
7.0
5.5
---M.03 12.5
12.5
-----G.03
S.5
9.0
-------
---.015
8
5
------
6AD7G
Power
Pentode
6AESGT/G
Triode
8AE6G
Twin Plate
Triode
Heater
6.3V
SAY
Octal
Heater
.6.3V
6Q
Octal
Heater
6.3V
---.45
.015 11
----
Combination Heater
6.3V
Triode
(Twin
Cathode)
w
co
I-'
8AF6G
Tuning
Indicator
Heater
6.3V
7.0
250
0
14 (Zero signal, per pia tel
300
0
17.5 (Ze ro signal, per plate)
11,000
0.400
3200
7AH
Octal
7AX
Octal
7AG
Octal
Oscillator
250
Mixer Section
250
10J
I
S.O
8,000
(P. to P.)
10.0
10,000
(P. to P.)
3.0
3.5
250
Mixer Section
250
dropping resistor)
300,000
2.2
550
(Conv. Trans. )
45
I
300.000
2.2
550
45
(Conv. Trans. )
Dynamic
Coupled
Amplifier
250
each
Amplifier
300
Dynamic
Coupled
250
+13
Class B
250
0
0
Input 5
Output 34
3
12.5
3.2
32
72
40,000
lS00
3,500
700,000
5000
125
36,700
3400
-
Triode
---0.30
-0.15
.50
(Per S ection)
------
---0.15
300
150
ode resistor
2.5 (Ze ro signal curf ent, per tube)
10
4
Pentode
250
250
(Pentode section equivalent to 6F6)
16.5
34
Amplifier
15
95
2.5
6,750
750,000
S,OOO
IrI
15
3.7
7,000
S.O
10,000
(P. to P.)
lao
...
IrI
6
6.5
7.0
4.2
19,000
325
SO,OOO
2500
3500
1200
1.5
25
1000
Driver
250
1.5
33
95
Characteristics
250
13.5
lao
n
250
I
n
:z:
9000
Dual Tuning
Indicator
1.8
...
;Ia
25.
250
:z:
atII
3.5
Dual
Tuning Indicator Target Voltage 150 Max. Control Electrode +75 Volts~Shadow Closed.
- +S Volts~900 Shadow.
-50 Volts~135° Shadow.
0.15
-2.5- -3.0-
Amplifier
c:
Eg ~ 0, Shadow Angle ~ 90°.
135V through .25 Meg., Ip~.5 Ma.
Eg ~ - lOV Shadow Angle ~ 00.
200
3.5
Q
4.0
3.0
100
n
IrI
<
4.0
(Through 20,000 ohm
Oscillator
Section
Tnning
Indicator
(Through 20,000 ohm
dropping resistor)
IrI
1600 cath5
---
GAE7GT Driver
6.0
0.4
---Triode
;Ia
35
294
7B
Medium 7 Pin
Large Pin Circle
---Pentagrid
(Self bias S50 Ohms)
2,500
15.0
Class AB1
--
(P. to P.)
5.0
Typical Driver Operation-Dynamic Coupled to two 6AC5G tubes in push-pull.
250
0
10-19
(Driver)
64·76
(Output)
Dual
Tuning Indicator Target Voltage 135 Max. Control Electrode, 0 Volts~100° Shadow.
+Sl Volts~ 00 Shadow.
14
9300
3.2
7,000
-...
;Ia
-
en
(Cathode dri ver for 25AC5 G)
35
n
en
9.5
1500
9.5
10,000
(P. to Pl.
•
(II
CD
!l
O·
::l
eN
(II
0:>
t-:l
Basing
See
Socket
Connection
DESCRIPTION
~
Type
No.
Type
ICathode
Chart on
Fil.
f:;~.
Pages 394-401
I
CAPACITANCES
Micro-Microfarads
CD
OPERATING CONDITIONS CHARACTERISTICS
I -I
Grid
Plate Input Output
When
Used As
I
Plate
Supply
Volts
Screen
. Grid
Volts
300
300
I Volts
gf!~ I
(Neg.)
Plate
Current
Ma.
Screen
Current
Ma.
300
10.5
25.0
6.5
125
2.0
2S.0
7.0
Amp!.
Factor
Plate
Resist.
. Ohms
I
Mut.
Condo
pMhos.
n
I U~Ji~t.
Output
Watts
----.!----.!!------------
Heater
6.3V
Video
6AG7
I Power
Pentode
Twin
6AH 7GT
6AL6G
I
---,
6B 4G
I Triode
.65
.3
.06 112.5
7.5 1 Amplifier
I
Heater
6.3V
Twin-
6AS
Medium 6 Pin
3.0
180
6.5
7.6
16
8400
1900
2.9
2.6
100
3.6
3.7
16
10,300
1550
Dynamic
Coupled
Amplifier
I O.SO
Duplex
Diode
Pentode
6B7
.
1---1
6BS
6BSG
I~I
6CSG
Duplex
Diode
Pentode
I Triode
I 6CsGT I
I-I
Heater
6.3V
Heater
6.3V
Heater
6.3V
Variable Mul Heater
6.3V
Pentode
I
I
6F
Small 6 Pin I 0.3
SG
Octal SPin
6000
6.5
2500
Input
8
I Output
100
0.0071 5.0
58
24,100
2400
4.0
9 I 51
.9
51
7,000
5.2
7,000
13.5
10,000
~
(P. to P.)
I 0.3
6.5 1 Triode Amplifier
250
Detector
250
Class A
One Triod~
250
Phase
Inverter
100
3.0
5.S
I
Tuning
Indicator
Heater
6.3V
Twin
Healer
6.3V
1
5.5
4.6
Oscillator
0.150-----------0.2
S.O 11.0
Mixer
1.1
Tuning
Indicator
6R
Small 6 Pin I~
IMedium7B 7 Pin I 0.60
100
3.0
2.0
S.O
6.5
100
4.3
1.7
285
300,000
950
17
...
1.5
800
800,000
1000
17
1"11
4.5
n
:t
~
n
lao
1500
1,500,000
1225
20
10,000
1900
~
3.2
22,500
36
lao
~
1600
c:
3.0
1.0 (Colmmon Catholde Resistor 15100 ohms)
100
100
3.0
S.O
2.2
375
250,000
1500
40
250
100
3.0
8.2
2.0
12S0
SOO,OOO
1600
40
(Through 20,000 ohm)
(dropping resistor)
4.3
250
250
250
100
3.5
I
I
250
20.0
27.5
Per Section
11.5
Per Section
18
I
_ _2_.6__
250V through 1 Meg. Ip=.25 rna. Target current 4.0 rna.
Eg=S.OV. Shadow Angle=Oo.
180
100,000
lao
1---1
3.0
-'-'-1
Class A
Pnsh-Pull
0.5
250,000
6.5 1 Amplifier
---SA
Octal 8 Pin
-<
1"11
~
250
I I I
I I I
0.0071 4.7
...
1"11
45
I See Data on 175
Amplifier
- 2.4
2.5
3.9
Top c ap sec tion
0.3 , - - , - 2.5
3.4
3.5
Base pin sec tioD
I
Triode
I
RF Amp!.
0.3
8.5
1_ _ 1_ _ 1_ _ 1
1Small6F6 Pin
Pentagrid
Heater
60SG
Converter
6.3V
1_ _ _ _ _ _ _ _ _ 1
6E6
1. 7
2.7
4.5
(Trio de Sec tion)
16
1--1
1_ _ 1
1---1
6ES
0.3
3500
0.00713.5 19.5
250
100
3.0
6.0
(Pent ode Se ction)
AF AmpL
250
50
4.5
0.65
250,000
1--1
1--1-----,
RF AmpL
250
125 Max.
3.0
10.0
0.0051 6.0 I 9.0
2.3
SOD
600,000
1325
Heater
8E
21
6.3V
Octal 8 Pin
0.3 - - , - - , - - 1 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - See characte Iristics of 6B 7.
0.0071 ~I~
1-11:81 4.0 113.0
6Q
Heater
Amplifier
250
S.O
20
10,000
Octal 6 Pin
1.9 I 4.4 110.4
8.0
2000
6.3V
0.3
I Triode
606
1-1-1-1-1
Diode Detector
Triode
Amplifier
325 ea.
w
•
--- ---- --------
I~.
6'
:::I
:t
o
o
o
325 ea.
Pnsh-Pnll
-----------
7D
Small 7 Pin
Heater
6.3V
Twin
6C SG
Octal 7 Pin
I~-
Pentode
6C6
7V
300
each
22,500
72
Bias
Volts
Ohms
140V
Voltage
Output
3.2
14
Cut~Off
7700
2.2
Triode
Duplex
I6B6G
- II Diode
Triode
1--1
100,000
3.0
, - - , - - , - - Amplifier
Heater
6AM
Amplifier
250
250
6.3V
Octal
.9
1--1
1--1--1--1--1-----1---1
5S
Fi!.
Amplifier
Identical to 16A3.
OctalS Pin
I 7
6.3V
1.0 16
Direct
Coupled
6BS
8BE
Octal
Heater
6.3V
I Triode
Beam
Tetrode
8Y
Octal
R"L~::d'
Resist.
I
400,000
550
I
I
-----
(Conv. Trans. )
40
Eg=O, Shadow Angle=90o.
I
Per
Se~tion
4,300
Per Section
3,500
I
1400
0.750
15,000
(P. to P.)
1700
1.600
14,000
(P. to P.)
~
oF5
--OF5G
---
Hi¢'-Mu
Triode
Heater
6.3V
5M
Octal 5 Pin
oF5GT
2.0
0.30
6.0
12.0
-2.0- -3.5- 11.0
250
2.0
250
1.3
Amplifier
----
OFO
oFoG
Pentode
Heater
6.3V
7S
Octal 7 Pin
Single Triode
oFsG
OG5
6H5
oGoG
Triode
Pentode
Twin
Triode
Heater
6.3V
Heater
6.3V
7E
Small 7 Pin
8G
Octal 8 Pin
250
16.5
34
6.5
80,000
2500
3.2
285
285
20
38
7.0
78,000
2550
4.8
7,000
20
31
2,600
2600 .
0.85
4,000
-2.00.30
0.60
2.5
3.0
.008 3.2
12.5
----
-4.0-
3.2
3.2
3.6
3.0
3.8
- - - -I -
--
Tuning Indicator
Hester
6.3V
6R
8ma1l6 Pin
0.30
Pentode
Heater
6.3V
7S
Octal 7 Pin
0.15
Single
Diode
Hester
6.3V
5AF
Octal
285
6.~
7,000
AB Triode
350
38
24
(Zero signal c urrent, per tu be)
13.0
6,000
(p. to P.)
AB Pentode
375
2.i0
26
17
(Zero signal c urrent, per tu be)
19.0
10,000
(P. to P.)
AB Pentode
375
250 .
3000
27
(Zero signal c urrent, per tu be)
19.0
10,000
(P. to P.)
Triode
3.0
3.5
Pentode
250
100
3.0
6.5
1.5
Converter
250
100
10.0
2.8,
0.6
8.0
9.0
Phase
Inverter
Tuning
Indicator
----
100 Max.
8.5
16,200
525
900
850,000
1100
2000,000
300
7,700
2600
Diode
Detector
0.15
lID
III
-n
3;
Individual sections of this tuhe are identical with 6J5G.
...
...<
250V. Through 1 Meg. Ip~0.24 rna.
Eg~22 Shadow Ang\e~Oo.
Q
250
Eg~O,
20
III
(Conv. Trans. )
Z
Shadow Angle~90o.
135
135
6.0
11.5
2.0
360
170,000
2100
0.600
12,010
180
180
9.0
15
2.5
400
175,000
2300
1.100
1O,OOJ
Amplifier
-6H4GT
250,000
0.70
OFOGT
OF'2'
1500
250
Single Pentode
---
66,000
100
0.9
.2 to.4
.
....
c:
100 Max.
III
• 1,000 (At .2 5 Ma.)
4 Max.
---Twin
OHO
- - - Diode
OH6-
Heater
6.3V
7Q
Octal 7 Pin
OJ5
Diode
Detector
0.30
GTjG
---
III
Hester
6.3V
6Q '
Octal 7 Pin
3.4
0.30
W5-
3.6
- - - -I 3.4
GTjG
3.4
3.8
4.0
Max.
per plate'
n
,
---Triode
100 Max.
AO'
Amplifier
::a:
8.0
250
9.0
7,700
20
:..
2600
\
3.3
--
100
100
3.0
2.0
0.5
1185
1,000,000
1185
7
7.0
12.0
250
100
3.0
2.2
0.5
1500
1,500,000
1225
7
.007 4.7
11.0
100
36
2.0
0.1
250
50
2.0
0.1
250
100
4.3
0.1
Amplifier
OJ '2'
--OJ'2'G
---
Pentode
Hester
6.3V
7R
Octal 7 Pin
.005
0.30
----
OJ'2'GT
oJSG
Bias Detector
Triode
Heptode
OK5G
oK5GT
OK6-
Triode
Pentode
Hester
6.3V
Heater
6.3V
8H
Octal 8 Pin
5U
Octal 7 Pin
Hester
78
6.3V . Octal 7 Pin
---0.30
0.30
---2.4
3.6
2.0
- - - -I --
Triode
250
Heptod.
250
w
00
w
-OK'2'G
----6K'2'GT
Hester
6.3V
7R
Octal 7 Pin
0.005
0.30
III
250,000
...
tn
.......
lID
250,000
1.3
4,000,000
290
(Conv. Trans. )
100
1.5
0.35
70
78,000
900
(Rating value s, not operati ng conditions)
n
250
3.0
1.1
70
50,000
1400
(Ratiug value s, not operati ng conditions)
tn
2.9
20
125
125
10.0
11.0
2.0
150
100,000
1525
0.650
11,000
167.5
167.5
12.5
17.0
3.0
150
85,000
1800
1.250
9,500
180
180
13.5
18.5
3.0
150
81,000
1850
1.500
9,000
250
250
18.5
32.0
5.5
1bO
68,000
2200
3.400
7,600
90
90
3.0
5.4
1.3
400
315,000
1275
38.5
10.5
2.6
990
600,000
1650
52.5
Amplifier
0.40
-Pentode
....
250,000
5.0
-
n
3.0
100
Amplifier
GTjG
OK'2' .
(Through 20 000 ohms)
"
lID
:..
7.0
12.0
-.007
--5.0- 12.0
•
Amplifier
Converter
250
125
3.0
250
100
10.0
(Oscillator p eak 7.0 volts)
fr
n
6-
:::J
.....
W
CAPACITANCES
FiI. / Micro-Microfarads
Curro
Basing
DESCRIPTION
~
See
(Xl
-,...
Socket
Type
. No.
Type
eKS
Triode
Hexode
eKsG
I
Connection ~~
Chart on
Plate Input 100tput
Pages 394-401
Cathode
Heater
6.3V
8K
Oetal
0.3
1 3.2
G 1.8 1 6.5
1 3.4
~
Used As
Triode Oacillator
M .03 1 6 6 1 3 5 I Hexode Mixer
eKsGT
elsG
M 1.1 1 6.0
~
Triode
Heater
6.3V
I
6Q
Octal 7 Pin 1 0.15 I 2.7
1---1
I 3.0 I 5.0 I Amplifier
1--1--1--1
Heater
7AC
Octal 7 Pin
6.3V
Tetroile
Grid
Volts
~
Volts
(Neg.)
100
2.5
I
I
~
3.0
9.0
[
~
Factor
--
~
Resist.
Ohms
Condo
J'Mh08.
1j
72-79
135
250
250
1 13.5 (Self)
1
75-78
300
200
1
12.5 (Fixed) 1
48-55
300
203
1
11.8 (Self)
350
2:;0
Class Al
Push-Pull
250
2~0
16 (Fixed)
Class ABI
Push-Pull
360
270
22.5 (Fixed)
Class AB2
Push-Pull
360
270
250
100
250
2:;~
1
18.0
_22.~
(Fixed)
1
600,000
6.0
4.0
8.0
14 (Fixed)
0.9
~
Current
Ma.
~
CHARACTERISTICS
n
Max.
Reconnn.
Output
Watts
Resist.
Ohms
~
~
----
5-
Cut-Off
Bias
Volts
Pentagrid
Mixer
el7'
7T
Oetal7Pin
Heater
6.3V
G,
11 I Mixer
.001
7.5
G,
0.
10.0
.10_ 1_'_-1-1
1_
0.3
G.
Gt
el7'G
I Amplifier
250
135
0.150
Tuning
Indicator
0.8
Amplifier
.005
5.8
.25
11.1i
Heater
I Small6R6 Pin
Heater
Direct
Coupled
6.3V
Twin Triode
Octal 7 Pin
Tuning
Indicator
eNs
eNe
eNeG
6.3V
1
10.0
G,
G,
17'
I
350
Twin
eN7'G
8B
Oetal8 Pin
Heater
2.5-4.7
51-54
3-4,6
54-66
2.5--7
30
6•..5
2,500
35,000
5300
6.1i
.4,500
III
'6.5
4,500
33,000
5200
10.8
4,000
22,500
1500
1900
---t---------I
6000
6.5
2,500
J:
120-140
10-16
14.5
5,000
(P. to P.)
88-132
5--15
26.5
6,600
(P.to P.)
88-205
5--16
47.0
3,800
(P. toP.)
6.3V
Triode
0.8
eN7'GT
Heater
1
eQ7'G
I eQ7'GT
::G
eR7'GT
0.3
1
Amplifier
'2.8 1 3.5 1 2.1i
\.
~ex I~~~r I OetaI~
Pin
t- 0.3
1_~·3
2.3
4.4
" 2.0 " 3.1
2.5
4.5
1100
o
Amplifier
n
:t
...nZ
po
9. Input
58
24,00)
33
l1,Oy')
240)
7,on
4.~
J:
42. Output
3201
17.5 (Zelro signal, per Iplate)
10.0
10,000
(P. toP.)
I
250
I
13.5
(Electrical c,bsracteristics Mentical withl Type 76.)
13.8
9,503
100
1.5
0.35
70
88,000
800
250
3.0
1.1
70
58,000
1200
9.0
9.5
8,500
1900
250
-I
16
0.400
Z
c:
)0
-po
1450
11"";"--
I
...
III
)0'
Through 0.25 Meg. Ip=.5ma. Eg=O,Shadow Angle=90o.
Eg=12, Shadow Angle=Oo. Target Current=2.0 Ma.
o
1-1-1-1
1
803,000
300
0.3
5.0
5.5
(P. to P.)
7V
Octal 7 Pin
1
5.3
15
(Both Grids)
8,000
Heater
6.3V,
-2.1
43
8.0
Duplex
~
!(Conv. Trans.!)
14 (Zolro signal, per /plate)
2.2 1 2.5 I 3.0
C.3 [ - - , - - , - - , See Cbsracteristilcs of 6F7
.0081 ~112.5
I
350
o
Oetal8 Pin
1.5' - 5.5-1 5.0
Amplifier
1.7
2.2
(Rating
- - - - ~ Value Only)
1 1,000,000 miln.
30
250
6.3V
1
8.3
(Conv. Trans.l)
-
Gt -3.0
Class A
eN 7'
ep sGT
.1
300 ea.
7W
.....
•
G. -3.0
G,
:::l
3.8
100
250
eleG
~
Current
Ma.
100
250
250
Class Al
One Tube
ele
Grid
~
Supply
Volts
G .08 1 4.6 1 3.1i
1
-
____ . _____ . ____
. ____ _
OPRRA'I'TlIT~
r.ollTnT'I'ToNS
.(}5
to.1 Meg.
.1 to .25 Meg.
U'
6S6GT
6S'2'
65'2'G
6SA'2'
---
5AK
Octal
Variable Mu Heater
Pentode
6.3V
7R
Octal 7 Pin
Pentagrid
Converter
6SA'2'GT/G
65C'2'
6SD'2'GT
6SFIS
6SFoGT
65F'2'
6SG'2'
65H'2'
6SJ'2'
6SK'2'-
Heater
6.3V
.45
BR
Octal
Twin
Triode
Semi
VariableMu
Pentode
Heater
6.3V
Heater
6.3V
0.30
Diode
Heater
VariableMu 6.3V
Pentode
7AZ
Octal
VariableMu Heater
Pentode
6.3V
BBC
Octal
R.F:
Pentode
Heater
6.3V
0.30
BN
Octal
BP
Octal
6AB
-.005
-
7•
6.4
6.5
10.5
---7.
---.13 9.5
--
12.0
Amplifier
.3
2.6
4.2
.004 5.5
.003 B.5
0.3
.003 B.5
4000
30
3.0
B.O
2.2
375
250,000
1500
40
250
100
3.0
B.5
2.0
1100
630,000
1750
40
13
B
0
7.5
250
Amplifier
3.B
Amplifier
3
(Grids 2 & 4)
4500
3.4
BOO,OOO
450
6.5
7.
7.0
2
2
53,000
1325
(Each Seetio n)
125
2
9.5
3
70
700,000
4250
-
250
100
2
6.0
1.9
1 meg.
3600
11
100
100
2
5.7
2.0
250,000
3350
11
66,000
1500
Amplifier
Amplifier
Amplifier
--
100
27
250
100
1
12.4
3.3
700,000
2050
35
100
100
1
12
3.4.
200,000
1975
35
250
150
2.5
9.2
3.4
1 meg.
4000
17
250
125
1
11.B
4.4
900,000
4700
14
100
100
1
8.2
3.2
250,000
4100
11.5
250
150
1
10.B
4.1
900,000
4900
5.5
100
100
1
5.3
2.1
350,000
4000
4.0
BN
Octal
M.005 6.0
7.0
0.30 - - - - - - Amplifier
G .005 6.5 10.0
250
100
3
3.0
O.B
2500
1,500,000
1650
VariableMu Heater
Pentode
6.3V
(Single end)
BN
Octal
M.OO5 6.0
1.0
0.30 - - - - - - Amplifier
G.OO5 6.5 10.0
250
100
3
9.2
2.4
1600
BOO,OOO
2000
--
35
GTIG
Twin
Triode
Heater
6.3V
BBD
Octal
.3
6SN'2'GT
Twin
Triode
Heater
6.3V
BBD
Octal
.6
4.
,
4.
I.B
Duplex
Diode
Triode
(Single end)
Heater
6.3V
BQ
Octal
Duplex
Diode
Triode
Heater
6.BV
BQ
Octal
.3
6S5'2'
VariableMu Heater
Pentode
6.3V
8N
0cta1
.15
6TIS
Tuning
Indicator
Hestet
6.3V
6R
Small 6 Pin
0.30
6T~
Heater
6.3V
7V
Octal 7 Pin
0.150 1.7
6Q
Duplex
Diode
Triode
6UG/
6Go'
Tuning
Indicator
Heater
6.3V
6R
Small 6 Pin
65Q'2'
6SQ'2'GT/G
6SR'2'
.
3.2
-----
3.4
3.B
2.6
4.2
3.4
--
0.30 - - - - - -
2.
3.4
2.B
.004 5.5
7.0
--
.3
I.B
~~lt;tion
250
2
2.3
70
44,000
1600
Class A
250
B
9
20
7,700
2600
90
a
10
20
6,700
3000
250
2
91,000
1100
8,500
1900
~:~lit'tion
Diode Detector
Triode
Amplifier
3.7
250
250
Amplifier
100
Amplifier
(Rating
Values Only)
Tuning
Indicator
n
III
...<
z
o
...
.
c:
n
:z:
-......
O.B
100
~
n
...
III
(Similar to Type 75)
(Rating values-not operating con dition.)
Amplifier
TUJ!ing
Indicator
I II
~
Class A
6SL'2'
-...
III
Heater
6.3V
Pentode
(Single end)
(Conv. Trans. )
250
250
2
0.9
(Rating valueS-Dot operating con ditions)
----
BBK
Octal
350,000
100
250
---.3
1400
100
Mixer Section
---.3
2
100
---0.30
100
Oscillator
AmplifierPhase-Inverter
---.0035 9.
,
250 -
(Characteristic•• ame 8. 6SA7 except capaci tances)
_.-
8S
Octal
High-Mu
Heater
Triode
6.3V
(Single end)
•01
0.150 - - - - - - Amplifier
.OOB 4.4
B.O
BAD
6SJ'2'GT
6SK'2'
.
VariableMu Heater
Pentode
6.3V
.
250
9.5
100
3
9
2
1. meg.
IB50
35
100
1
12.2
3.1
120,000
1930
35
16
.3
...
n
'fA
Through 1 Meg. 11'=.24 Max.
Eg=O, Illumination i. Max.
Eg=22, IlluminatIOn is Min.
(Discontinued type-replace with 6U5/6G5)
100
250
fA
9
1.5
I
3.0
0.3
I
1.2
I
Eg=O Illumination is Max.
Throug!p. 1. meg., Ip=.24 Ma. Max.
Eg=22.0V Shadow angle zero degrees.
I
65
95,000
680
.05 to .1 Meg.
65
65,000
1000
.1 to .25 Meg.
.
•
rr
n
~
00
~
'Note-This combined type may be need to replace types 6U5, 6Ho, 6T5 and 605.
::r.
o
:::J
---'
t.)
UI
~
J
HESCRIPTION
00
C\
Tge
6U6GT
Type
I
Cathooe
Basing
co~~Jon ~~~.
P C~4.401
ages
Heater
6.3V
TetrOOe
7AC
Octal
CAPACITANCES
OPE RA TI N G CON D IT I ON B C HA RA C TE RISTIC S
::rO-Microf1arads
Plate Input Output
When
Used As
I
.75
I
Amplifier
•
Variable Mu Heater
PentOOe
6.3V
7R
Octal 7 Pin
0.30
Tetrooe
Heater
6.3V
7AC
Octal 7 Pin
0.45
Duplex
Diooe
Triooe
Heater
6.3V
7V
Octal 7 Pin
0.3
Pentooe
Heater
6.3V
7R
Octal
0.15
6Y6G
Tetrooe
Heater
6.3V
7AC
Octal 7 Pin
1.25
6Y 'tG
Twin
Triooe
Heater
6.3V
8B
Octal 8 Pin
0.60
6U7'G
.007 5.0
6V6
---6V 6GTIG
6V'tG
1.5
1.5
9.0
-
Plate
Supply
Volts
I
Sereen
Grid
Volts
I ~~~ I
Volts
(Neg.)
Plate
Current
Ma.
14
55-62
200
135
135
135
13.5
110
110
10.5
1
I
I
Sereen
Current
Ma.
Amp\.
Factor
I
Plate
Resist.
Ohms
I
Mut.
Condo
/LMhos.
6200
(J)
I u~di.t. I~":i'1
Output
Watts,
Resist.
Ohms
5.5
3000
3-13
20,000
55-60
5-15
10,000
6200
3.3
2000
44--47
4-11
10,000
5600
2.0
2000
n -
5:::J
Cut-Off
',Bias
Volts
.....
'(..)
•
Bee Charact eristics of 6D 6.
---r--~----I-------I------I------I-------II-------I------I------I---~--I-------I------------
Amplifier
250
250
12.5
45-47
4.5-6.5
Class AB,
250
250
15.0
70-79
5-12
4.3
218
52,000
4100
60,000
3750
4.25
10
•
5,000
-t
10,000
:z:
See Charact eristics of 85
III
-----I-------I----·I-------I------------I~-------I------I-------I-------I~'~---1------1-------1-------1------1------1-------1------
6W7'G
.,()()7
5.0
8.0
Blas Detector
250
100
4.3
Amplifier
250
100
3.0
2.0
250,000
Amplifier,
135
135 Max.
13.5
5~60
0.5
1850
1,500,000
1225
9,300
7000
3.5-11
11:
7
3.6
-<
2,000
III
Bee Charact eristics of 79
----!I-~l-----·I----I-----I----I-----I----I,----I,----I-----1-----1-----1-----
6Z7'G
Twin
Triooe
Heater
6.3V
8B
Octal 8 Pin
0.3
Cl.... B
Triads
Heater
7.0Vt
SAC
Lock-In
7'A5
Tetrooe
Heater
7.0Vt
6AA
Lock-In
7'A6
Duplex
'Diooe
Heater
7.0Vt
7AJ
Lock-In
0.16
Variable Mu Heater
Pentode
7.0Vt
8V
Lock-In
0.32
Pentagrid
Converter
8U
Lock-In
0.15 7.5
9.0
0.16 - - - - - 0.50 3.6
4.4
7'A4o
7'A7'
1------1------1
7'AS
7'B 4
High Mu
Triooe
Heater
7.0n
Heater
7.OV t
5AC
Lock-In
0.32
4.0
.80
.32
1.6
3.6
7.0
3.4
0
3 (Zero signal current, per plate)
1.5
135
0
3 (Zero signal current, per plate)
2.5
180
0
4.2 (Ze ro signal curr ent, per plate)
2.2
20,000
180
0
4.2 (Ze ro signal curr ent, per plate)
4.2
12,000
Amplifier
250
Power
Amplifier
125
125
9 '
110
110
7
Diode Detector
AVC Rectifier
.005 6.0
135
150 Max.
(Similar to Type 6H6G)
7'B6
Hester
7.0Vt
Pentads
Duplex
Diode
Triooe
6AE
Lock-In
Heater _ 8W
7.0Vt
Lock-In
1------1------1
'tB't
Va lable Mu Heater
Pentode
7.0yt
8V
Lock-In
7'BS
Pentagrid
Converter
8X
Lock-In
Heater
.. 7.0Vt
-
-- - - - -
2.2
2700
41
3-7.5
13,800
5800
1.5
2500
3.0
9.2
2.4
3.0
3.5
3.2
Oscillator
Section
250
(Through 20 000 ohms)
250
1600
7
9.5
1.6
180
180
13.5
18.5
3.0
250
250
18.0
32.0
5.5
315
250
21.0
25-28
4-9
250
(Similar to Type 75)
2.0
1.0
3.0
8.5
1.7
3.0
3.5
2.7
7.0
Amplifier
250
100
0.32
0:2 ~
--
9.0
Mixer Section
250
100
3.4
Oscillator
Section
250
I
(Through 20, 000 ohms)
'I'
800,000
2000
700,000
550
66,000
1500
100
85,000
1175
150
104,000
1450
68,000
75,000
2100
91,000
1100
750,000
1700
360,000
550
100
1.5
100
:z:
:z
n
:..
...
11:
35
(Conv. Trans. )
'
:..
30
:z
3.6
2.9
100
n
,
100
Amplifier
20
10 Max.
100
.005 5.0
5.0
6000
250
0.16
0.9
2600
16,800
250
Diooe Detector
Triode
Amplifier
0.32
7,700
3.3-9.5
Amplifier
Power '
Amplifier
0.43
I
9.0
III
9,000-
45
Mixer Section
100
7'B5
8.0
-t
15,000
40
I
150
150
100
1200
,
c:
:..
...
0.35
12,000
1850
1.5
.9,000
2300
3.4
7.600
,
4.5
9000
I
,
(Conv. Trans. )
40
!
35
I
'
•
~
Beam
Tetrode
7'CI>
7'CU
7'C7'
Heater
7.0Vt
6AA
Lock-In
Duplex
Diode
Triode
Heater
7.0Vt
8W
Lock-In
Pentade
Heater
7.0Vt
8V
Lock-In
0.16
.007 5.5
180
8.5
29
3
210
58,000
3700
2.0
250
12.5
45
4.5
218
52,000
4100
4.25
Claas AB1
(Push Pull)
250
Diode Detector
Triode
Amplifier
1.4
---0.16
180
250
6.5
Amplifier
3.4
Diode Detector
Triode
Amplifier
4.6
Amplifier
----
Duplex
Diode
Triode
7'E7'
Duplex
Diode
Pentode
Heater
7.0Vt
8AE
Lock-In
7'F7'
Twin
Triode
Heater
1.0Vt
8AC
Lock-In
7'G7'/
:1282
R.F.
Pentade
Heater
7.0Vt
8V
Lock-In
0,48
.007 9.
7.
Amplifier
7'H7'
SemiHeater
VariableMu 7.0Vt
Pentode
SV
Lock-In
0.32
.007 S.
7.
Amplifier
Triode
Hexode
SAR
Lock-In
5.5
7.5
Mixer
S.5
2.0
Oscillator
7'J7'
R.F.
Pentade
7'L'1']
7'N7'
Twin
Triode
7'Q7'
Pentagrid
Converter
7'R7'
7'V7'
:l2A5
Heater
7.0Vt
8W
Lock-In
Heater
7.OVt
Heater
7.OVt
.
SV
Lock-In
Heater
. 7.0Vt
SAC
Lock-In
Heater
7.OVt
SAL
Lock-In
0.64
0.32
Pentode
0.60
or
0.30
Heater
12.6V
8A
Oetal
Twin
Triode
Heater
12.6V
SBE
Oetal
.01
.01
3.0
S.O
-3,4
6.5
2.0
0.32
Amplific.
Mixer
.004 5.6
5.3
Amplifier
--
.004 9.5
6.5
Amplifier
-Amplifier
-- -- -
0.30
--
M 1.1 6.0
0.15 - M .26 9.5
-2.2- -3.2-
4.6
12.0
3.0
--
0.15 - - - 3.0
2.9
2.6
100 000
1000
0.4
1,200,000
1225
0.5
2,000,000
1300
8,500
1900
700,000
1300
42.5
36
9.5
7
~
250
100
100
100
3.0
16
1.6
7.5
10
150,000
1600
2
2.3
70
44,000
1600
100
1
0.65
7Q
62,000
1125
6
2
800,000
4500
6
19
1.0
2.7
, III
250
250
100
2
250
150
2.5
9.5
3.5
SOO,OOO
3800
100
100
1
S.2
3.3
250,000
3800
250
100
3
1.3
2.9
1.5 meg.
300
50,0000
Grid Leak
5.4
250
Through
20,0000
n
-<
III
Z
12
(Conv. Trans. )
20
Q
...
c:
DI
III
250
100
100
100
1.5
4.5
1.5
2.4
1 meg.
3100
5
5
1
5.5
100,000
3000
250
S
9
20
7,700
2600
90
0
10
20
6,700
3000
1 meg.
550
S.5
0
3.5
n
:z:
~
(GridsU4)
(Conv. Tmns. )
35
~
~
250
100
1
5.7
2.1
1 meg.
3~00
20
100
100
1
5.5
2.2
350,000
3000
16
...
300
150
1600
(Cathode)
9.6
3.9
300,000
5800
6
III
100
100
15.0
180
180
25.0
250
12.5
Amplifier
250
Reetifier
125 Max.
Amplifier
135
Oscillator
250
Mixer Section
250
Amplifier
(P.to P.)
1.8
9.0
(Similar to Type 6R7G)
100
5000
10,000
1.3
250
250
9.0
10.0
1.0
2.0
100
9.0
5-12
5,500
3.0
100
3.0
(Similar to Type6W7G)
Oscillator
0.2
100
7(}-79
250
7.0
--
0.15
100
Amplifier
----
250
15.0
(Thi. tube i. similar to 6V 6)
250
-3.0- -2.9- -2.4--
7F
Small 7 Pin
Pentagrld
Converter
GT
0.32
Heater
6.3Vor
12.6V
:l2A7
Volta~
Amplifier
- - -I.-
0.4S
7K
Small 7 Pin
:I 2AH 7'-
0.32
Pentode
Heater
!2.6V
.005 4.6
0.32
SV
Lock-In
Reelifier
Pentode
3.0
----
Heater
7.0Vt
7AC
Oetal
:l2ASGT
0.32
8AE
Lock-In
Heater
12.6V
1.5
------
Heater
7.0Vt
Tetrade
:l2AsG
0.32
Duplex
Diode
Pentade
:l2AU
---
1:,1.:>
----
Cia•• Al
(One tube)
7'EU-
~
00
-l
0.48
,
17
3.0
70
liO,OOO
1700
0.8
4,500
45
8.0
80
35,000
2300
3.4
3,300
30
3.5
50,000
3000
2.5
7500
13.5
102,000
975
0.550
13,500
(Through 20 ,000 ohms)
100
(Conv. Tran•. )
9.0
-...
~
t it
n
30 Max.
135
n
tit
2.5
100
4.0
3.0
3.5
360,000
550
ISO
6.5
7.6
16
8,400
1900
100
3.6
3.7
16
10,300
1550
I
tImportant Note: Lock-In Tubes carry 8 nominal heater rating of 7.0 volt•• Actual recommended heater voltage for household receiver ..mce is 6.3 volte.
2.7
45
16
S.5
•
ff
n
:::T.
o:::J
......
W
CAPACiTANCES
B.."mg
Micro-Microfarads
Fil.
See
Socket
Curro
Cathode Connection Amp". Grid
Chart on
Plate Input Output
Pages 394-401
Type
No.
Type
Heater
12.6V
8T
Octal
Duplex
Diode
Pentode
Heater
12.6V
BE
HighMu
Triod.
Heater
12.6V
5M
Octal
Twin
Diode
Heater
12.6V
7Q
Octal
0.15
Heater
12.6V
6Q
Octal
0.15
Heater
12.6V
7R
Octal
Triod.
12<:S
12FSGT
12H6
12JSGT Triode
12J7G
---
Pentad.
0.30
0.15
Octal
0.15
12J7GT
12K7G
9.6
.00'; 6.0
9.0
VariableMu Heater
12.6V
Pentade
2.3
2.2
------3.4
3.8
---.007 4.7
0.15
.007 4.5
M.03
12KS
Triode
Hexode
Heater
12.6V
BK
Octal
.015
12KsGT
6.6
.
G 1.8
Duplex
Diode
12Q7GT Triode
12Q7G
Heater
12.6V
3.3
11.0
12SA7GT/G
Pentagrid
Converter
(Single end)
128C7 'Twin
Triode
128FS
H~Mu
TrIode
Heater
12.6V
7V
Octal
0.15
1.3
12SG7
128J7
0.15
BAD
BS
Octal
0.15
Heater
12.6V
8P
Octal
6AB
0.30
Heater
Diode
VariableMu 12.6V
Pentode
VariableMu Heater
12.6V
Pentode
Pentade
(Bingle eod)
--
Heater
12.6V
12SFSGT
12SF7
BR
Octal
Heater
12.6V
7AZ
Octal
VariableMu Heater
12.6V
Pentode
12SK7- .(Single end)
Pentode
100
100
8.0
Diode Detector
Amplifier
250
125
6.5
2.7
.13
7.
9.5
- -- ---4.2
0.15
.004 5.5
250
2.0
0.9
250
1.3
.2 to .4
8N
Octal
0.15
8N
Octal
.003 8.5
M.OO5 6.0
0.15
5.7
12.
3.8
6.5
0.15
7.0
7.0
6.0
7.0
G.OO5 6.5
10.0
M.005
Amp!.
Factor
Plate
Resist.
Ohms
Mut.
Condo
~Mho••
73,000
1500
2.5
170,000
2100
42.5
800
600,000
1325
100
66,000
1500
110
2.0
2.3
Load
5'
:::s
....
Cut:OiI
Bia.
Volls
Resist.
Ohm.
,
(,)
I
•
21
...
( Plate resistor %to1meg.)
:z:
III
Amplifier
250
8.0
9.0
250
100-
4.3
0.43
Amplifier
250
100
3.0
2.0
20
7,700
2600
0.5
1500
1,500,000
1225
------
!II:
"<
500,000
7.0
90
90
3.0
5.4
1.3
400
315,000
1275
38.5
III
250
125
- 3.0
10.5
2.6
990
600,000
1650
52.5
250
100
1,0.0
...
Mixer
250
100
3
2.5
600,000
350
Oscillator
100
0
3.B
,
III
6.0
3000
3.4
-- -- G .005 6.5 10.0
----
Sereen
Current
Ma.
Recomm.
Characterist ics same as 6 H6•
Detector
250
3.0
1.1
Resistance
Coupled
250
2.0
0.5
Oscillator
100
Mixer Section
250
Amplifier
Phase-inverter
Amplifier
Amplifier
AmpIilier
Amplifier
(Conv. TranB. )
30
':z:"
:z
....
~N ot OBcillat ing with triode grid =0 volls
riode plate = 100 vol~B)
_
n
Diode Detector
Amplifier,
Transformer
Coupled
- -- 8BC
Octal
10
Resistance
Coupled Amp.
Mixer
3.5
---2.6
3.0
TransformerCoupled Amp.
--
12SJ7GT
128K7
0.6
11.0
-,
12SA7
1
- 3
Diode
. Detector
-----G .OB 4.6
4.B
---Ml.l 6.0
3.2
------
- -- -
Plate
Current
Ma.
n
Max.
Undist.
Output
Watt.
2.9
12K7GT
- -- -
Sv~ft~
Sereen
Grid
Volls
100
Amplifier
7R
Octal
Plate
Grid
Bias
Volls
(Neg.)
-
----
~
---
---P .015 5.2
-------
0.15
When
Used A.
Triode Amplifier
T 2.3
12BSGT Pentode
g'
OPERATING CONDITIONS CHARACTERISTICS
DESCRIPTION
~
00
00
70
58,000
~
....
1200
-
200,000
!II:-
B.O (Gr idB 2 and 4)
0
3:4
250
2
2.0
, 250
2
.9
100
BOO,OOO
450
70
53,000
1325
100
66,000
1500
700,000
2050
35
(Conv. Trans. )
~
35.0
:z
c:
(Each Seetio n)
~
po
-
250
100
r
12.4
3.3
100
100
1
12
3.4
200,000
1975
35
250
150
2.5
9.2
3.4
Over 1 meg.
4000
17Jl
250
125
1
11.8
4.4
900,000
4700
14
100
100
1
B.2
3.2
250,000 -
4100
II.5
100
100
3.0
2.9
0.9
1100
700,000
1575
250
100
3.0
3.0
0.8
2500
1,500,000
- 1650
100
100
3.0
B.9
2.6
475
250,000
1900
250
100
3.0
9.2
2.4
1000
800,000
2000
Amplifier
I
35
GT/G
i
12SL'fGT Triode
Twin
Heater
12.6V
BBD
Octal
Twin
12SN'f- Triode
Heater
12.6V
BBD
Octal
GT
Duplex
Diode
Triode
12SQ'f(Single end)
GT/G
12SQ'f
12SR'f
14-'4
0.3
4.
4.
-Heater
12.6V
BQ
Octal
0.15
-3.2
3.4
3.B
2.6
1.8
Amplifier .
(Each SectIOn)
250
2
2.3
70
44,000
1600
Amplifier
(Each Seetion)
250
B
9
20
7,700
2600
90
0
10
20
6,700
3000
91,000
1100
Diode Detector
Amplifier
250
2.0
Diode
Detector
Amplifier
250
9
9.5
16
S,500
1900
250
8
9
20
7,700
2600
90
0
10
20
6,700
3000
BQ
Octal
Heater
14V#
5AC
Lock-In
0.15
0.16
2.
4.
3.4
3.4
2.8
3.0
Amplifier
14-'5
14-''1/
1~B'f
14B8
14B8
Beam
Tetrode
Heater
14V#
6AA
Lock-In
VariableMu Heater
Pentade
14V#
8V
Lock-In
&"J:i:x
Triode
Pentagrid
Converter
Heater
14V#
SW
Lock-In
Heater
14V#
BX
Lock-In"
0.16
0.16
.
14C5
14C'f
14E8
14FT
14H'f
R.F.
Pentade
Heater
14V#
6AA
Lock-In
Heater
14V#
Duplex
Diode
Triode
Heater
14V#
Twin
Triode
Heater
14V#
SV
Lock-In
Amplifier
7•
--
Amplifier
Diode
Detector
Amplifier
0.16
0.9
5.
3.4
0.16 - - - 0.2 10.
9.
BW
Lock-In
0.24
Oscillator
Seetion
Mixer
Section
VariableMu Heater
Pentode
14V#
SV
Lock-In
6.5
- -- 0.16
- -- -
BAC
Lock-In
.007 6.
0.16
.007 S.
7.
1-iJ'f
Heater
14V#
Twin
Triode
Heater
14V#
SAC
Lock-In
Heater
14V#
SAL
Lock-In
SAR
Lock-In
.01
14Q'f
""
co
\0
Pentagrid
Converter
7.5
0.16 - - - 1.
8.5
2.0
.
14N'f
5.5
0.32
---3.0
3.4
2.0
-----3.0
2.9
"2.4
7.
0.16 - .02 9.0
3000
2.6
800,000
2000
35
100
100
2.6
35
30
1
S.9
250,000
1900
250
2
0.9
100
91,000
1100
100
1
0.4
100
110,000
900
250 (Th rough 20,000 0)
4
100
2.0
250
100
3
-<
3.5
360,000
550
(Conv. Trans. )
600,000
360
(Conv. Trans.)
77,000
3750
5.5
B500
12.5
45
4.5-7
52,000
4100
4.5
5000
8.5
29
3-4
58,000
3700
2.0
5500
19
71Hl2
4-13.5
65,000
14.0
BOOO
(P. toP.)
250
15
7(}-79
5-13
60,000
10.0
10,000
(P. toP.)
100
3
2.2
0.7
1 meg.
1575
:Ill!
100
1
5.7
1.B
325,000-
2275
:..-
B,5OO
1900
250
1BO
AB,
2S5
2B5
250
250
100
1.5
1.1
Diode
Detector
Amplifier
250
9
9.5
16
100
3
3.9
16.5
11,000
1500
Amplifier
(Each Section)
250
2
2.3
70
44,000
1600
100
1
70
62,000
1125
III
n
III
150
2.5
9.5
3Ji
SOO,OOO
3BOO
19
100
1
B.2
3.3
250,000
3800
12
250 (a)
100
3
1.3
2.9
1.5 meg.
300
(Conv. Trans. )
20
100 (b)
100
3
1.1
3.1
300,000
260
(Conv. Trans. )
20
250 (a)
(Through 20 ,000 0)
100 (b)
50,0000
5.4
50,0000
3.7
8.0
Amplifier
90
0
20
7,700
2600
20
6,700
3000
100
0
3.5
3.3
100
100
#Important Kote: These lock-in tu!>es carry a nominal heater rating of 14.0 volts. Actual recommended heater voltage for hoysehold receiver service i. 12.6 volt••
f it
-
n
fit
•
8.5 (Gr ids2&4)
100 Max.
250
9.0
10.0
-...
:Ill!
100
,
:z:
:..
...n
250
" 250
Mixer
.65
20
...
c:
•
1.3
ISO
Oscillator
35
2.2-6
250
Mixer
z:
Q
.
2.7
-
34
Amplifier
Sinr.e
En ed
Oscillator
9.0
70,000
9.2
13
---Triode
Hexode
3.5
3
50
Amplifier
7500
12.5
100
~25
Amplifier
2.8
250
250
100
- -- 0.16
n
250
315
Push-Pull
(Both Tubes)
---0.16
III
III
-•005 6.
:Ill!
- -- -
Beam
Tetrod.
100
--
Duplex
Diode
Heater
Triode
12.6V
(Single End)
Triode
0.15
1 meg.
550
(Conv. Trans. )
35
500,000
525
(Conv. Trans. )
35
fr
n
g:
:::I
.....
W
o
Basing
CAPACITANCES
Fi!.
Micro-Microfarads
See
Socket
Curro
Connection Amps.
Cathooe
Chart on
Grid Input Output
Plate
Pages 394-401
OPERATING
DESCRIPTION
W
\0
Type
No.
14R7
Type
Duplex
Diooe
Pentooe
I
I I
Heater
14V#
8AE
Lock-In
0.16
.004
Pentooe
Heater
25.0V
7S
Octal 7 Pin
Power
25AC5GT Triode
Heater
25.0V
Heater
. 25.0V
8F
Octal 8 Pin
6Q
Octal
0.30
------
25B5
Heater
25V
6AS
Small 6 Pin
Heater
25.0V
7S
Octal 7 Pin
Triode
25BsGT Pentooe
Heater
25.0V
8T
Octal
Beam
25C6G Tetrode
Heater
25.0V
7AC
Octal
0.30
-2.2
-.02
5.5
0.15
--
25N6
----
7AC
Octal 7 Pin
---7W
Octal 7 Pin
0.3
Heater
32.5V
Beam
Tetrode
Heater
35.0V
6AA
Lock-In
0.16
Beam
Tetrode
Heater
35.0V
7AC
Octal
0.15
Tetrooe
Heater
50.0V
6AA
Lock-In
0.15
35L6-
GT/G
50A5
8Z
Octal
50C6G
Tetrode
7AC
Octal
Diode
7oA7GT Rectifier
Heater
50.0V
Heater
70.0V
7AC
Octal
8AB
Octal
Heater
70.0V
8AA
Octal
5.5
2.2
100
100
1
95
95
15
20
4
90
85
Plate
Resist.
Ohms
I
Max.
Undist.
Output
Watts
Mut.
Condo
/LMhos.
Recomm.
I
Load
Resist.
Ohms
1 meg.
3200
350,000
3000
45,000
2000
0.900
135
135 Max.
20
37
8
160
120
18
33
6.5
35,000
2450
2.000
4,000
42,000
2375
2.200
5,000
100
15
180
37
110
45
Cut-Off
Bias
"' Volts
'
i
'"
-","
20
Dynamic
-
0
Input
7
Output
45
16
48-55
110
(each)
105
20.5
Amplifier
105
Triooe Amp.
100
Pentode Amp.
100
135
200
135
110
110
7.5
110
110
7.5
4.0
-------
0.15
...
80
50,000
1800
0.770
4,500
58
15,200
3800
2.0
5,000
:t
2.7
2.000
"'
25
11,400
2200
2.0
2,000
15,500
4800
2.4
1,700
112.5
75,000
1500
370
2-10
:I
"<
100
3.0
7.6
2.0
185,000
2000
135
13.5
58
3.5-11
9,300
7000
3.6
2,000
14.0
61-66
2.2- 9
18,300
7100
6.0
2,600
49
4-9
10,000
8200
2.100
1,500
49
4-11
10,000
1>200
2.200
2,000
11,400
2200
2.0
2,000
...
15,000
6000
1.5
2,500
I:
Power Amp.
7.5
110
35
2.8
110
25,000
Note: Nominal h eater rating= 35 volts, .16 Amp. Actual recommended working volt age=32 volts, .15 Amp.
5500
1.4
2,500
~
Power Amplifier
5800
1.5
2,500
c:
2.5
10.0
41
Dynamic
Coupled
Amplifier
110
(each)
Rectifier
125
Amplifier
110
0
-
Input
7
Output
45
25
110
"'
:t
Z
n
~
60
7.5
7.5
40
3
I
Z
40
3-7
8
50-55
1.5-6
35,000
8250
4.7.
3,000
7.5
49-50
4-11
10,000
8200
2.2
2,000
61-66
2.2-9
18,300
7100
6
2,600
58-60
3.5-11.5
9,300
7000
3.6
2,000
3.5-10.5
10,00D
8000
2.2
2,000
5800
1.5
2,500
7500
1.8
2,000
110
110
200
110
110
110
200
135
14
135
135
13.5
Power Amplifier
110
110
8
45--48
110
7.5
40
110
7.5
40--43
Rectifier
125
Power
Amplifier
110
Rectifier
125
Power Amplifier
110
...
n
80
~
...
60 Max.
'0.15
0.15
"'
.0.6
Amplifier
--
•
16
Amplifier
--
W
1.0
----
0.15
.....
4,500
75 Max.
0.30
Power
Tekode
Rectifier
70L7GT Beam
Tetrode
~2.1
I
I
100
DynamicCoupled .
Amplifier
-Beam
50L6GT Tetrode
5.7
I
250
100 Max.
----
Heater
50.0V
Ma.
Amp!.
Factor
Amplifier
0.30
Single
32L7GT Diode,
Tetrode
35A5
1
Screen
- Current
Amplifier
0.30
Direct
Heater
25.0V
I
Plate
Current
Ma.
125 Max.
Coupled
Amplifier
0.3
GT/G
Coupled
Twin
Triode
Volts
(Neg.)
Amplifier
.25L6
Heater
25.0V
Bias
Grid
Volts
Rectifier
------Tetrode
25L&-
I
Screen
--
Pentooe
25B6G
Grid
PJate
Supply
Volts
~
o
::l
n
:t.
Amplifier
Amplifier
----
CHARACTERISTICS
0.30
Direct
Coupled
Twin
Triode
.
0.30
25A6GT
25A7G Rectifier
- - - - Pentode
25A7GT
5.3
--
25A6
---25A6G
----
5.6
'When
Used As
CONDITIONS
3
80
70
#Important Note: These lock-in tubes carry a nomioal heater rating of 14.0 volts. Actual recommended hetter voltage for household receiver service is 12.6 volts.
3-6
15,000
-
-
I
117L7GT
Diode
Rectifier
Power
Heater
117.0V
8AO
Octal
.09
Tetrode
117M7GT
117N7GT
Diode
Rectifier
Power
Tetrode
Heater
117.0V
Diode
Rectifier
Heater
117.0V
Power
----
8AO
Octal
17P7GT
Heater
117.0V
117
Power
Amplifier
105
Rectifier
117
Power
Amplifier
100
Rectifier
117
Power
Amplifier
100
Rectifier
117
Power
Amplifier
105
I
75 Max.
105
5.5
100
5.5
45
4
20,000
4
15,000
0.6
4,000
1.0
2,000
75 Max.
.09
--
8AV
Octal
45
6500
I
~
I
75 Max.
I
.09
Tetrode
Diode
Rectifier
Power
Tetrode
Rectifier
8AV
Octal
100
6
51
16,000
5
7000
i
I
3,000
1.2
I
75 Max.
'"n
.09
105
5.2
43
4-5.5
17,000
5300
4,000
0.85
III
III
....
<
....
RECTIFIER TUBES
DESCRIPTION
Base
Pages 394-401
}ro.e
Circuit
I
Class
I
Full Wave
Ga.
Cold
4J-Medium 4 Piu
--
BH
Full Wave
Ga.
Cold
4J-Medium 4 Pin
-
BR
Half Wave
Ga.
Cold
4H-Medium 4 Pin
--
Half Wave
High Vacuum
Heater
4G-Small 4 Pin
6.3
0.3
Choke
Condenser
I
Wt~!
Max. D.C.
Output
Current
Ma.
Max.
Peak
Inverse
Volts
Max.
Peak
Plate§
Current
Ma.
350
350
1000
1000
350
125
1000
400
200
Input
Choke
Value
(Min.)
Plate
SupJ:c
Im~in.
Ohm.
aD
300
50
850
117
45
1000
200
0
150
45
1000
200
30
325
45
1000
200
75
:z:
5hy
10
~
Full Wave
High Vacuum
Heater
4C-Medium 4 Pin
5.0
2.0
350
500
125
1400
375
Half Wave
High Vacuum
Heater
4B-Medium 4 Pin
7.5
1.25
700
700
85
2000
300
8=
Full Wave
Mercury Vapor
Filament
4C-Medium 4 Fin
2.5
3.0
450
550 -
115
1550
500
6 hy
50
83
Full Wave
~ercury
Filament
4C-Medium 4 Pin
5.0
3.0
450
550
225
1550
1000
3 hy
50
83V
Full Wave
High Vacuum
Heater
4L or 4AD
Medium 4 Pin
5.0
2.0
375
500
175
1400
525
4 hy
100
84/62.4
Full Wave
High Vacuum
Heater
5D---Small 5 Pin
6.3
0.5
325
450
60
1250
180
10 hy
150
OZ3
Full Wave
Ga.
Cold
5N-Bmall 5 Pin
-
-
350
350
75 Max.
30 Min.
1250
200
Full Wave
Ga.
Cold
4R-Octal 4 Pin
--
-
300
300
75 Max.
30 Min.
Half Wave
High Vacuum
Filament
4P-Small 4 Pin
2.5
1.75
4500
Half Wave
High Vacuum
Filament
4X-Octal
2.5'
1.5
350
5T4
Full Wave
High Vacuum
Filament
5T-Octal 5 Pin
5.0
2.0
450
550
5U4G
Full Wave
High Vacuum
Filament
5T-Ortal 5 Pin
5.0
3.0
450
550
5V4G
Full Wave
High Vacuum
Heater
5~ctal5Pjn
5.0
2.0
375
500
OZ4G
=X=/879
=W3
5W4
Full Wave
High Vacuum
5W4GT/G
Filament
5T-Ort".! 5 Pin
5.0
1.5
....
III
81
Vapor
e
c:
80
OZ4
350
1000
(Peak plate-to-pla tel
n
'"
~
n
....
III
'"
....
CIt
....
....
200
n
CIt
12,500
100
225
1550
675
3 hy
225
1550
675
3 hy
75
175
1400
525
4hy
100
•
25
UI
CD
n
:::!".
7.5
55
500
100
1400
300
6hy
75
o
:::s
\0
~
Fil.
Amp•.
~r~!
BA
1V
c..:>
Fil.
Volts
Cathode
:z:
Q
Max. A.C. Volts
Per Anode
§Note-Value per plate on double rectifiers.
.....
W
(J)
C;.:)
DESCRIPTION
~
Base
Pages 394-401
Type
No.
Circuit
Class
Cathode
5X4G
Full Wave
H4d> Vacuum
Filament
5YsGT/G
Full Wave
High Vacuum
5Y4G
Full Wave
mgh Vacuum
5ZS
Full Wave
High Vacuum
Full Wave
Full Wave
5Z4
It
Max. A.C. Volts
Per Anode
Fil.
Volts
Fil.
Amps.
Condenser
Input
Filter
I
Choke
Input
Filter
Max. D.C. Output
Current
Ma.
Max.
Peak
Inverse
Volts
Max.
Peak
Plate§
Current
Ma.
Input
Choke
Value
(Min.)
n
go
Plate
Supply
Impedance
Min.
Ohms
5Q-Octal 8 Pin
5.0
3.0
450
550
225
1550
675
3 hy
75
Filament
5T-Octal 5 Pin
5.0
2.0
350
500
125
1400
375
5hy
10
Filament
5Q-Octal 8 Pin
5.0
20
350
500
125
1400
375
5 hy
10
Filament
4C-Medium 4 Pin
5.0
3.0
450
550
225
1550
675
3 hy
75
High Vacuum
Filament
5L-Octal 5 Pin
5.0
2.0
350
500
125
1400
375
5 hy
30
High Vacuum
Heater
68--0ctal 6 Pin
6.3
0.9
325
450
90
1250
270
6 hy
::J
.....
W
•
"
5Z4GT/G
JJW5
-t
::t:
6W5G
6X5
11'1
Full Wave
mgh Vacuum
Heater
68--Small Oct"l 6 Pin
6.3
0.6
325
450
70
1250
210
10 hy
150
6X5GT/G
6ZY5G
Full Wave
High Vacuum
Heater
68--Small Octal 6 Pin
6.3
0.3
325
450
40
1250
120
13ihy
225
~
/fY4
Full Wave
mgh Vacuum
Heater
5AB Lock-In
6.3
0.5
325
450
60
1250
180
10 hy
150
"<
/fZ4'
Full Wave
High Vacuum
Heater
5AB Lock-In
6.3
0.9
325
450
100
1250
300
6 hy
75
11'1
117
55
700
330
0
150
55
700
330
30
235
55
700
330
75
70
1250
210
:l2ZS
:l4Y4
Half Wave
Full Wave
High Vacuum
21iZ4
S5Y4
S5ZS
0.3
5AB Lock-In
12.6
0.3
325
mgh Vacuum
Heater
6E-Small 6 Pin
25.
0.3
235
450
Half Wave
8hy
-t
11'1
n
150
I
Doubler
High Vacuum
High Vacuum
Heater
Heater
5AA Octal
6E-S1!lI'~6Pin
'25.
25.
0.3
0.3.
125
75
(per plate)
700
0i
125
::t:
...Z
I n
750
235
75
(per plate)
700
100
150
75
(per plate)
700
40
117
75
(per plate)
700
15
Doubler
).
...
~
).
2 liZ 6
25Z6GT/G
12.6
Heater
Rectifier
21iZ5
4G---Sniall 4 Pin
mgh Vacuum
Rectifier
25Y5
Heater
High Vacuum
H~ater
7Q-Octal 7 Pin
25.
0.3
Characteristics s ame as 25Z5
Doubler
Z
Half Wave
c:
HaJfWave
High Vacuum
High Vacuum
Heater
Heater
5AL-Lock-In
4Z--Lock-In
32.
32.
0.15
. 0.15
.
sliZ4GT
Half Wave
High Vacuum
Heater
5AA--OCtaJ
35.
. SliZ5GT/G
Half Wave
High Vacuum
Heater
6AD-Octal
35.
(Note-He ater tapped for pa nellamp)
§Note--Value per plate on double rectifiers.
0.15
0.15
.
235
100
(Note-He ater tapped for pa nellamp)
700
600
100
).
235
100
700
600
100
150
100
700
600
40
117
100
700
600
15
235
100
700
600
15 ohms (117V)
100 ohms (235V)
235
100
(without pilot)
60 •
(with pilot)
90
(pilot and shunt)
700
600
15 ohms (117V)
100 ohms (235V)
...
-,
~
Base
Pages 394-401
Circuit
Class
I
I
40Z5
Fil.
Volts
Fil.
Amps.
Cathode
I
Half Wave
6AD-Octal
Heater
High Vacuum
(Note-He ater tapped for pa nellamp)
45.
0.15
Half Wave
High Vacuum
45.
.075
45Z5GT
45Za
Max. A.C. Volts
Per Anode
DESCRIPTION
~
Heater
5AM Button 7 Pin
Condenser
Input
Filter
I
Max. D.C.
Output
Current
Ma.
Choke
Input
Filter
For other ratings , see 35Z5
High Vacuum
Heater
7Q Octal 7 Pin
50
0.15
117
350
390
15
75 (per plate)
700
450
100
150
75 (per plate)
700
450
40
65
75 (per plate)
700
450
235
65 (per plate)
700
400
235
60 (per plate)
700
360
100
150
60 (per plate)
700
360
60
117·
60 (per plate)
700
360
15
117
;Ig
II'!
15
n
-
,
Rectifier
Doubler
Plate
Supply
Impedance
Min.
Ohms
235
Doubler
50Z7G
Input
Choke
Value
(Min.)
iI'
Rectifier
50Y6GT/G
Max.
Peak
Plate!
Current
Ma.
Max.
Peak
Inverse
Volts
Hig\! Vacuum
Heater
BAN Octal
(Note-He ater tapped for pa nellamp)
50.
0.15
II'!
15 ohms (117V)
100 ohms (235V)
<
Rectifier
117Z6GT/G
High Vacuum
Doubler
Heater
7Q-Octal 7 Pin
(Originally based 7AR)
117.
.075
2:
Q
§Note-Value per plate on double rectifiers.
,>
....
'.
c:
DI
II'!
n
:t
SPECIAL ANNOUNCEMENT
~
;Ig
• As this book goes to press, the War Production Board has
issued Limitation Order L-76 prohibiting the manufacture of
349 types of tubes.
6/10 of 1% of current production, and that present stocks will
~
last for approximately two years.
n
The Technical Information Section, Wholesale Division, of
In general, this order simply marks a continuation of the
....
I
I
P. R. Mallory & Company, Inc., will be glad to assist any user
I
tube standardization program, in that the discontinued tubes
in selecting suitable substitute tubes on receipt of information
represent the duplicate, small demand, or obsolete types. In
as to the make, model number, and tube complement of the
fact, estimates on these types show that they represent only
radio receiver.
!;oo.
II'!
;Ig
en
I
....
n
en
I
•
,
~
\C
~
(J)
__ J
CD
n
5-
:::I
-'
w
Section 13 ..
THE
MY E
TECHNICAL
MANUAL
4B
4C
4E
4F
4G
4J
4K
4L
4AA
4AO
40
4H
OCTAL
BASE
4M
394
4P
4Q.
4R
RECEIVING
T U 8 E
CHARACTERISTICS
• Section 13
5A
5AD
5AL
5AF
5AG
5AM
58
5C
5E
5F
·5K
5AK
5Q
395
Section 13 •
THE
TECHNI'CAI.
MANUAl.
OCTAL BASE
5T
6A
6AB
6AM
6AR
6AS
6AU
I
OUTPUT SECTION I INPUT SECTION
I
I
I
6AX
396
6B
6C
RECEIVING
TUBE
C H
~
R ACT E R 1ST I C S,
• Section 13
6E
6J
6K
65
OCTAL BASE
397
THE
Section 13 •
MY E
TECHNICAL
MANUAL
7AK
7AO
7AP
7AU
7AV
7BA
398
7AT
7AX
7AZ
T U 8 E
RECEIVING
.. Section 13
CHARACTERISTICS
7Q
8AB
8AC
8AD
8AE
8AL
8AN
8AO
8AR
~99
Section 13 •
THE
8AS
MY E
TECHNICAL
MANUAL
8AV
8AW
8AY
8BC
8BD
8BE
8BK
8L
400
RECEIVING
TUBE
CHARACTERISTICS
• Section 13
8Y
8Z
SPECIAL TUBES
FILAMENT
BASING
CHARACT "RISTICS
T~
Volts
Amps.
View
Shield Conn. to
28/48
2.5
1.35
5D
Cathode Pin
Approximately 40 Ma. on each Diode Plate at 50 volts DC.: Duplex
Diode Detector.
USE AND DIMENSIONS
248
2.5
1.75
5E
Cathode Pin
Same as 24A
21'8
2.5
1.75
5A
Cathode Pin
Same as 27
358/518
2.5
1.75
5E
Cathode Pin
Same as 35
558
2.5
1.0
6G
Cathode Pin
Same as 55
508
2.5
1.0
5A
Cathode Pin
Same as 56
50A8
6.3
0.4
5A
Cathode Pin
Same as 76 except Heater Amps.
51'S
2.5
1.0
6F
Cathode Pin
Same as 57
51'A8
6.3
0.4
6F
Cathode Pin
Same as 6C6 except Heater Amps.
588
2.5
1.0
6F
Cathode Pin
Same as 58
58A8
6.3
0.4
6F
Cathode Pin
Same as 6D6 except Heater Amps.
'2'58
6.3
0.3
6G
Cathode Pin
85A8
6.3
0.3
6G
Heater pin Adjacent
to Cathode Pin
Similar to 85 except Amp. Factor =20; Mutual Condo =1250; Plate Curro =
4.5 Ma.;PI. Volts=250V;Gr. Bias=-9V.
182B/482B
5.0
1.25
4D
No Shield
Similar to 45 except Fil. Volts; Amp. Fact. =5.0; Mutual Condo =1500; Plate
Curro = 18 Ma.; PI. Vdtl =>-50 V; Gr. Bias = -35V.
183/483
5.0
1.25
4D
No Shield
Silllilar to 45 exc~t Fil. Volts; Amp. Fact =3.0; Mut. Condo =1500; PI.
Curro =20 Ma.; I. Volt, =250V; Gr. Bias = -58V.
485
3.0
1.25
5A
No Shield
Similar to 27 except Heater Volts; Amp. Fact. =12.8; Mut. Condo =1300; PI.
Curro =5.2 Ma.; PI. Volts =180V; Gr. Bias = -lOY.
950
2.0
0.12
5K
No Shield
Similar to 33 except Fil. Amps; PI. Curro =7 Ma.; Power Output =0.45
Watts; PI. and Scr. Volts=135V; Max. Cont. Gr. Bias = -16.5V.
2A'2'8
2Z2
G84
OA1'8
2.5
1.0
7C
Cathode Pin
2.5
1.5
4B
No Shield
6.3
0.3
7C
Cathode Pin
Same as 6A7
/
Same as 75
Same as 2A7
Half Wave Rectifier, Filament Type Cathode
OB'2'8
6.3
0.3
7D
Cathode Pin
Same as 6B7
oC'2'
6.3
0.3
7G
Separate Pin
Similar to 85AS
00'2'
6.3
0.3
7H
Separate Pin
Similar to 6C6
0E'2'
6.3
0.3
7H
Separate Pin
Similar to 6D6
of'2'8
6.3
0.3
7E
Cathode Pin
Same as 6F7
OY5
6.3
12.6
6.3
0.8
0.4
0.8
6J
Separate Pin
Similar to 6Z4/84
6K
No Shield
Similar to 6Z4/84
OZ5
,
401
I
A
N D E
Pages
Acoustic Loading Networks, Loudspeakers. . . . . .
9
Alignment, Frequency Modulation Receivers .... 210-212
Audio Amplifiers, Frequency Modulation. . . . . . .
210
Audio Transformer, RMA Color Code. . . . . . . . . .
354 .
Autodyne, Detector-Oscillator. . . . . . . . . . . . . . . . . 32-35
Automatic Tuning
Audio Silencing During the Automatic Tuning
Cycle .................................. 179-181
Cam and Lever Mechanisms ................. 147-149
Condenser Tuned System. . . . . . . . . . . . . . . . . . .
156
Emerson Miracle Tuner. . . . . . . . . . . . . . . . . . . .
158
Permeahility Tuned System ................. 156-158
Ratchet Switch Mechanisms ................. 158, 159
Rocker Bar Mechanism ..................... 149, 150
Mechanical Station Button or Indexing Adjustment' .................................. 150-156
Mechanically Operated Manual Types ........ 147-156
Motor Operated Types ..................... 159-161
Reference Table hy Make and Model. ....... 139-146
Station Selecting Commutator Devices ....... 181-183
Station Selector Switches ................... 165-172
Transfer Devices and Circuits from Manual to
Automatic Tuning. . . . . . . . . . . . . . . . . . . . . . . 172-177
Tuned Circuit Substitution Types ............ 156-159
Tuning Motors ................ , ........... 162-165
Zenith Permeability and Mica. . . . . . . . . . . . . . .
159
Automobile Battery Ground Chart.. . . ... . . . .. .
363
B
Baffles, Loudspeaker .... '" '" .............. .
8
Ballast Tube Circuits ........................ .
362
356
Battery Cable, RMA Color Code .............. .
Bias Resistor Calculation ..................... 370, 371
c
Capacitor Application
284
Action in A.C. Circuits .................... .
Action of Chokes ......................... .
280
By-Pass Circuits .......................... .
285
Capacity of By-Pass Units .................. .
285
Choke Input Filter ........................ .
282
Complex Filter Circuits .................... 283, 284
Electrolytic By-Pass Units. .. . .. . . . . . . .. . . . .
285
Filter Circuit Action ....................... 280-284
Full Wave Rectifier ........................ 279, 280
x
Pages
Half Wave Rectifier ....... : ................ 278,279
No~-Polarized Units . . . . . . . . . . . . . . . . . . . . . . .
284
Multiple Choke Filter Circuits ... '.' . . . . . . . . . .
283
Resonant Element Filter Circuit ............. 281, 282
Voltage Distribution in Filter Circuits ........ 282, 283
Charts
Automohile Battery Ground. . . . . . . . . . .. . . . .
363
Ballast Tube Circuits. . .. . . . . . . . . . . . . . . . . . . .
362
Inductance of Single Layer Coils. . . . . . . . . . . . .
361
Milliammeter Extension Range. . . . . . . . . . . . . .
3S0
Reactance (LC) .......................... 356-359
Receiving Tube Characteristics by Type Number .................................... 373-401
Resistance Coupled Amplifier ............... 365-368
,Transformer Design
Core Loss Curves-Kilo lines Per Square Inch
vs. Watts Per Pound. . . . . . . . . . . . . . . . . . . .
352
352
Core Loss vs. Frequency ................. .
Flux Density-Core Area-Turns Per Volt ..
352
Small Power Transformer, Core Area vs.
Watts ............................... .
352
Voltmeter Multiplier ..................... .
350
Color Code
Mica Condenser .......................... .
356
Resistor .......................... , .. , ... .
360
RMA Audio Transformer .................. .
354
RMA Battery Cable ....................... .
356
RMA Dynamic Speaker Wiring ............. .
355
RMA IF Transformer ..................... .
354
RMA Power Transformer ................. .
3S4
Condensers
Capacity of .............................. .
254
Dry Electrolytic General Theory ............ .
255
Conversion Table
Electrical Factors ........................ .
364
Frequency to Wavelength .................. .
364
Converters, Superheterodyne (see Superheterodyne First Detector and Oscillators)
Copper Wire Table ..................... , .. . .
353
Coupling
Superheterodyne First Detector and Oscillator 29-37
Coupling Transformers, Loudspeaker. . . . . . . . . .
15
Crystal Pickup
Equalization ............................. 99, 100
Installation .............................. 94-100
Representative Connection ................ . 95,96
Terminal Impedance ..•................. , . 94,95
403
INDEX
D
Pages
D.C. Dry Electrolytic Capacitors ............... 254-308
Cross Reference by Type Number ............ 290-301
Replacement Chart by Minimum Line ....... 302-308
Detector, Superheterodyne First. . . . . . . . . . . . . . .
23
Discriminators, Frequency Modulation ......... 208-210
Dry Electrolytic Capacitors
Electrical Characteristics
Capacity ............................ , ..
Corrosion ...................... ' ....... .
D.C. Working Voltage ................... .
Equivalent Series Resistance ............. .
262
271
262
267
Gas Pressure. . . .. . . . .. . . . . . . . . . . . . .. . .. .
271
High Frequency Impedance ............... 267,268
Humidity ........ :.....................
Leakage Current . '. . . . . . . . . . . . . . . . . . . . . . .
271
266
Normal Life .... , ....................... 271-275
Peak Ripple Voltage. . . . . . . . . . . . . . . . . . . . .
262
Peak Voltage .. . . . . . . . . . . . . . . . . . . . . . . . . .
262
Power Factor. . . . . . . . . . . . . . . . . . . . . . . . . . .
266
Scintillating Voltage ..................... 263, 264
Shelf Life. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
275
Surge Voltage. . . . . . . . . . . . .. . . . . . . . . . . . . . 2 6 3
Temperature ................... : ....... 268-271
External Construction
Cardboard Cartons and Tubes ............. 259, 260
Type FP ............................... 260, 261
Round Metal Cans. . . . . . . . . . . . . . . . . . . . . . .
260
Internal Construction
Anode Electrode ....................... .
256
256
Cathode Foil .......................... .
Common Anode Concentrically Wound
(CACW) ............................ 257,258
Common Cathode Concentrically Wound
(CCCW) .............................
257
Connections ............................ 256, 257
Proportion of Section. . . . . . . . . . . . . . . . . .. .
Separate Section Units ............. '. . . . . . .
257
258
Separators .............................
Non-Polarized. . . . . . . . . . . . . . . . . . . . . . . . . . . .
257
265
Polari\y . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
265
Semi-Polarized ........................... 265, 266
Test Section .............................. 275-277
Wartime Servicing ........................ 286-308
Dynamic Speaker Wiring, RMA Color Code. . . . .
404
355
(Continued)
.E
Electrolytic Condensers, General ........ .
Pages
254
F
Field Coils, Loudspeaker .................... .
'Formula
8
A.C. Voltage and Power ................... .
Capacity of Parallel Plates ...... , ............
364
363
364
363
363
363
Decibel .. : .............................. .
Dissipation Factor Q ...................... .
Equivalent Impedance of a Parallel Circuit .. .
Equivalent Impedance of a Series Circuit .... .
Frequency .............................. .
Impedance of a Circuit .................... .
Ohm's Law .............................. .
Power Factor of a Condenser ............... .
363
363
363
363
364
363
363
Resistances in Parallel. . . . . . . . . . . . . . . . . . . . . .
363
Transformer Ratio ..... . . . . . . . . . . . . . . . . . . .
364
Frequency Characteristics, Loudspeakers ...... 13, 14, 19
Frequency Modulation
Audio Amplifiers. . . . . . . . . . . . . . . . . . . . . . . . . .
210
Discriminators ................... : ........ 208-210
General Theory ........................... 200-202
Limiters ................................. 207, 208
. Receiver Alignment ....................... 210-212
Receiver Design ........................... 204-214
Transmitters ............................. 202-204
Full Wave Voltage Doublers, Description. . . . . . .
53
Power Output ........................... .
Reactance (Capacitive) of a Condenser ...... .
Reactance (Inductive) of a Coil. ........... .
G
Greek Alphabet, Designations. . . . . .. . . . . . . . . . .
364
H
Half Wave Rectifier
Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Peak Ripple Current Through the Rectifier. . .
Peak Ripple Voltage Across Input Filter Condenser. . ... ......... .... ... ............
RMS Ripple Current in the Initial Filter Condenser.. .... ..... ...... ..... ..... . .....
49
51
52
50
Heterodyne, Between Stations. . . . . . . . . . . . . . . . .
26
Home Recorder, Description and Service Instructions .................................. 105-108
INDEX
(Continued)
I
IF Transformer, RMA Color Code ............. .
Image, Superheterodyne .................... .
Impedance Matching, Loudspeakers ........... .
Inductance of Single Layer Coils .............. .
Pages
354
24
14
361
L
Limiters, Frequency Modulation .............. 207, 208
Loudspeakers
Acoustic Loading Networks .. '" . .. .. . ..... .
9
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
Audio.Frequency Transformers. . . . . . . . . . . . .
15
Audio.Frequency Transmission Lines. . . . . . .. 15, 16
Baffles ...................................
9
Cahinets .................................
9
Design and Application .................. " " 8·20
Field Coils ...............................
8
Frequency Characteristics ................. 13, 14, 19
General Description ........ '" ... ... . .. . . .
8
Horn Types ..............................
11
Impedance Matching ......................
14
P. A. Systems..............................
17
Permanent Magnets .......................
8
Phasing ............. " . . . . . . . . . . . . . . . . . . . .
16
Physical Characteristics ................... .
8
Power· Handling Capacity ................. .
12
17
Replacements ............................ .
M
Mica Condenser Color Code. . . . . . . . . . . . . . . . . . .
356
Milliammeter Shunts, Calculation of ........... 348·350
Mutual Conductance, Definition..... ..........
371
o
Ohm's Law, Application in Power Supply Systems 346·348
Oscillator, Grid Leak and Condenser Operation,. 28,39
Oscillator Circuit
Colpitts ................................. . 27,28
Hartley ................................. .
27
Oscillator Systems, Superheterodyne.. .. ... .... 27,28
p
Permanent Magnets, Loudspeaker ............ .
8
16
Phasing, Loudspeaker
Phono. Radio, Typical Switching Circuits ..... . 96·99
Power Supplies, Transformerless, Component
Failures ............................... . 61,62
Power Transformer
Design ................................... 351·353
Rehuilding ........... " ... , ............. : 351·353
RMA Color Coding. . . . . . . . . . . . . . . . . . . . . . .
354
~ractical Radio Noise Suppression ............. 310·323
R
Radio Noise Suppression
Appliance Noise .......................... 312·321
Barber Shop Equipment ..... " . .. ... . .. . .. .
318
321
Belt Static ............................... .
Cash Registers ........................... .
318
Commutating Devices ...................... 312, 313
Dental Equipment ........................
319
Diathermy Machines. . . . . . . . . . . . . . . . . . . . . . .
319
Drink Mixers ............................. 313, 314
Electric Drills and Sanders. . . . . . . . . . . . . . . . . .
314
Electric Refrigerators . . . . . . . . . . . . . . . . . . . . . .
318
Electric Shavers. . . . . . . . . . . . . . . . . . . . . . . . . . .
318
Elimination of Line Noise at the Receiver .... .
311
316
Fluorescent Lights ....................... .
Home Food Mixers .................... '.....
314
Hospital X.Ray Machines ................... 319, 320
Large Motors and Generators ............... 314, 315
Lead·in Noise ............................. 311, ~12
Multiple Circuit Advertising Signs. . . . . . . . . . .
318
Neon Signs .................. ','" ... '" .... 315, 316
Oil Burners ..............................
320
Sewing Machines . . . . . . . . . . . . . . . . . . . . . . . . . .
318
Sources of Interference. . . . . . . . . . . . . . . . . . . . .
310
Spark Plug Testers. . . . . . . . . . . . . . . . .. . . . . . . .
320
Street Cars .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
321
Telephone Equipment ..................... 320, 321
Thermostat Controlled Devices. . . . . . . . . . . . . .
320
Tracing Outside Interference... . . . . . . . . . . . . . .
310
Traffic Signs .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
317
Transmission Line Noise .................... 310, 311
Vacuum Cleaners.........................
313
Violet Ray Machines ................ '" .... 318, 319
405
INDEX
(Continued)
Pages
Pagel
Washing Machines ........................
315 '
Radio Noise Suppression Equipment-Repre.'
sentative Types ......................... 321·323
, Reactallce (LC) Charts.,. . . . . . . . . . . . . . . . . . . . . . 356·359
Reactance Control, Frequency Modulation ...... 202·204
Receiving'Tube- Characteristics ................ 370·401
Bias Resistor Calculation .................. 370, 371
, .Chart hy Type Number ..................... 373·401
Definition of Terms .•...................... 371, 372
Mutual Conductance. . . . . . . . . . . . . . . . . . . . . . .
371
New Developments........................
370
Record Changers, Service Data
Capehart 16·E ..•...•..................... 109·119
Farnsworth S30 .. . . . . . . . . . . . . . . . . . . . . . . . .. 120·123
Garrard........ ............ .. ......... .. .
121
Ma~avox Gl, RC5, RC8, RCI0, RC11, RC50,
RC51 ....••...........•................ 124·130
RCA RPI39A, RP145, VI09 ................. 131·133
Wehster.Chicago 11, W1270. . . . . . . . . . . . . . . .. 134·136
Record Player~, Wireless Type. . . . . . .. . . . . . . .. 100·104
Resistance Coupled Amplifi.er Charts .......... 365·368
Resistivity Table of Popular Metals. . . . . . . • . . . .
350
Resistor Color Code. • . . . . . . . . • . . . . . . . . . . . . . . .
360
, Resisto~s, Parallel Calculation of .............. 347, 348
Ripple Current, HaH Wave Rectifier. . . . . . . . . . . 50·52
Ripple Voltage, HaH Wave Rectifier. . . . . . . . . . .
, 51
,8
Scanning Systems, Television .................. 219,220
Signal Tracing, Procedure ...•.... '" ......... 337·339
Superheterodyne
Adjustment of the Oscillator Circuit ........ .
38
Autodyne First Detector Combinations.' ....•.
32
Basic Oscillator Circuits ........... '...•.....
27
Circuit Constant Considerations ............ . 39,40
Colpitts Oscillator ...•.............•.......
27
Control.Grid Types of Autodyne Detectors ... .
33
Converter Circuit, Silver·Marshall Mode~ R .. .
45
Coupling-First Detector and Oscillator ..... . 29·37
Definition ................................ .
22
Diode Converter ......................... .
46
Direct Interferenc~ at IF Frequencies ....... .
26
406
Electron Coupling with Suppressor Grid Injec.
tion ....•............................. I
30
Harmonics Beating Harmonics •.... '. . . . . . . . .
26
Hartley Oscillator . . . . . . • . . . . . . . . . . . . . . . . . .
27
First
Detector·Oscillator
Operation.
.
.
.
.
.
.
.
.
.
23
,
Grid Leak and Condenser ...•.............. , 28, 39
24
Images ...•...............•...... ',' . . . . . . .
Lecault "Ultradyne" . . . . . . . . . . . . . .. . . . . . . . .
45
45
Miscellaneous Circuits ........... " . . . . . . . . .
Oscillator Anode Resistor. . . . . . . . . . . . . . . . . . .
40
Oscillator Coil Coupling. . . . . . . . . . . • . . . . . . . .
36
Oscillator Harmonics' . . . . . . . . . . . . . . . . . . . . . .
25
Oscillator Performance ... . . . . . . . . . . . . . . . . .
,27
Pentagrid COQ,verters • .. . . . . . . . . . . . . . . . . . . .
35
Philco Converter • . . . • . . . . . . . . . . . • . . . . . . . . .
46
37
Single.Ended Converters ....•.... '... ...... .
Spurious Responses . . . . . . . . . . . . . . . . . . . . . . . .
2,4
Suppressor Grid Type -of Autodyne Detector. .
34
Typical Circuits . . . . . • . . . . . . . . . . . . . . . . . . . . .
40
Use of 6J8G Converter Tuhe. . . . . . . . . . . . . . . . .
32
Use of 6L7 Mixer Tube.....................
31
Use of 6SA7·12SA7,Converter Tuhe..........
37
T
Tahle, Field Coil Excitation Ratings. . . . . . . . . . .
9
Television
Aperture Distortion ....................... 219, 220
Cathode Ray Tube
Description of •..... .' ...•............•.. 228·234
~lectromagnetic Deflection ............... 231·234
Electron Beam Deflection Methods ........ 231·234
Electrostatic Deflection .................. 231, 233
Luminescence .......................... 229, 230
Foreign Developments ...................... 245·249
Frequency Band Width Determination. . . . . . .
221
History of Cathode.Ray Tube. . . . . . . . . . . . . . .
227
Necessity f~r Wide Frequency Bands ......... 220·222
Projection Cathode.Ray Tuhes ..,........... .
230
Promising Developments ............ " ...... 250·252
Proposed Stan:dards ....................... 222, 223
~lse Generation . . . . . . . . . . . . . . . . . . . . . . . . . .
237
Pulse Separation ...........••...........•. 236,237
INDEX
(Continued)
Pages
Receiving Antenna ... . . . . . . . . . . . . . . . . . . . . .
241
Receiving Systems .......... , ...: .......... 237·241
RMA Standard Signal ...................... 235, 236
Scanning Systems ............. ' .... , ....... 219, 220
Standards of Transmission. . . . . . . . . . . . . . . . . .
222
Synchronization .......................... 234·237
The Cathode.Ray Tube as a Television Repro.
ducer .................................. 227·234
Television Cameras, Analysis of ............... 223·226
Television System, Essential Elements .......... 217·220
Television Transmission ., .................... 241·244
Band Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
241
Distortion Requirements ......... '" ....... 242, 243
Interconnecting Links ............, ........ .
244
Modulation System ...........' ............ .
242
Television Transmitting Antenna .... '" ....... 243,244
Transmission Lines, Loudspeaker. . . . . . . . . . . . . . 15, 16
Transmitters, Frequency Modulation .......... 202·204
u
Useful Servicing Information
Application of Ohm's Law in Power Supply
Systems . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . .. 346·348
Methods for Calculating Parallel Resistor
Values ................................. 347, 348
Methods for Calculating Voltmeter Multipliers
and Milliammeter Shunts .................. 348·350
Power Transformer Designing and Rebuilding 351·353
v
VacuUln Tubes, Definition of Terms .... '........ 371, 372
Vacuum Tube Voltmeters. . . . . . . . . . . . . . . . . . .. 326·344
Amplifier Circuit ...• : . . . . . . . . . . . . . . . . . . . . .
329
Checking Distortion with ................... 339, 340
Clough Brengle 88A .r...................... 327, 328
General Radio 726·A ....................... 328·331
Hickok 110 ........•.......•.............. 331, 332
Meissner Analyst . . . • . . . . . . . . . . . . . . . . . . . . . .
333
Operation at High Frequencies. . . . . . . . . .. . . .
330
Pe~ Voltage Measurements. . . . . . . . . . . . . . . . .
328
Power Absorption .................. , •..... 329, 330
RCA·Rider Chanalyst ...................... 333, 334
RCA·Rider Volt Ohmyst. . . . . . . . . . . . . . . . . . . .
334
Pages
Rectifier Circuit ..................... ,..... 328, 329
Slide Back Type. . . . . . . . . . . . . . . . . . . . . . . . . . .'
326
Special Signal.Tracing Equipment ........... 335·337
Theory of RMS Measurements ............... 327, 328
Triplett 1252 ............................. 326, 327
Use in Special Control Circuits ......... : .... 340·344
Vibrator
Application Considerations ................ .
69
Buffer Condenser ........................ .
71
Characteristics ........................... .
70
Dual Reed Type .......................... .
66
Eight Contact Type ....................... .
67
Full Wave Interrupter Type ............... .
67
Full W a~e Synchronous or Self.Rectifying Type
66
General T;h.eory .......... '................ .
64
Half Wave Interrupter .................... .
65
Past and Present Designs .................. . 65·69
69 '
Split Reed Type .......................... .
Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tuned Reed Type. . . . . . . . . . . . . . . . . . . . . . . . .
Vibrator Powered Equipment, Service Informa·
tion ...................................
Vibrator Power Supplies
Bias Supply Systems. . . . . . . . . . . . . . . . . . . . . . .
Chassis Construction . . . .. . . . . . . . . . . . . . . . . . .
Design ........ ' ............. 1..............
Filtering of Leads. . . . . . . . . . . . . . . . . . . . . . . . .
Fusing ................... ,'...............
Operation on A.C. Lines. . . . . . . . . . . . . . . . . . • .
Paralleled Operation ................... , . .
,RF Interference Suppression .............•..
Selection of Ground Connection ....•........
70
69
74·76,
88
80
78
86
80
80
78
Shielding and Ventilating ....•..........•..
83
85
77,84
Special Applications ................•. , ..•.
81
Voltage Addition Systems ............•........
60
Voltage Dividers, Calculation of .............. .
Voltage Doubler
347
Common Line or Series Line Feed .......... .
56·58
Full Wave, Symmetrical. .................. .
53·56
Series Line Feed or Half Wave with Common
Cathode Condenser . . . . . . . . . . . . . . . . . . . . . .
' 59
Voltage Multiplier System. . . . . . . . . . . . . . . . . . . .
59, 60
Voltmeter Multipliers, Calculation of .......... 348·350
407
Source Exif Data:
File Type : PDF File Type Extension : pdf MIME Type : application/pdf PDF Version : 1.3 Linearized : No XMP Toolkit : Adobe XMP Core 4.2.1-c041 52.342996, 2008/05/07-21:37:19 Create Date : 2015:08:09 18:53:11-08:00 Modify Date : 2015:08:09 18:44:22-07:00 Metadata Date : 2015:08:09 18:44:22-07:00 Producer : Adobe Acrobat 9.0 Paper Capture Plug-in Format : application/pdf Document ID : uuid:7bc9e7e6-caa8-ab49-80bb-c6042004ce96 Instance ID : uuid:148189ba-1db1-5a4d-8671-2acc4b698050 Page Layout : SinglePage Page Mode : UseNone Page Count : 409EXIF Metadata provided by EXIF.tools