94X004_Hallicrafters_SX 28 A_Super_Skyrider_Receiver_Instruction_Book_Apr1944 94X004 Hallicrafters SX A Super Skyrider Receiver Instruction Book Apr1944
User Manual: 94X004_Hallicrafters_SX-28-A_Super_Skyrider_Receiver_Instruction_Book_Apr1944
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INSTRUCTION BOOK
for
MODEL SX-28-A
-
SUPER SKYRIDER RECEIVER
FREQUENCY RANGE-.55 to 43. MEGACYCLES
co.
CHICAGO, Ill.,
u. s. A.
April 10, 1944
INSTRUCTION BOOK
for
MODEL SX-28-A
SUPER SKYRIDER RECEIVER
FREQUENCY RANGE-.)) to 43. MEGACYCLES
co.
the
CHICAGO, ILL., U. S. A.
TABLE OF CONTENTS
Page
Subject
TITIE PAGE
1
TABLE OF CONTENTS ................................................................
2
A. Installation .. -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
l. Speaker .......................................................................
2. Antenna ................. '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
3. Phono jack ....................................................................
4. DC power socket ...... _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
5. "S" meter zero set ... " ....................................... '. . . . . . . . . . . . . . . . . . ..
4
4
4
4
4
5
B. Operation ......................... :................................................
l. Bandswitch ......................................... _ . . . . . . . . . . . . . . . . . . . . . . . . ..
2.' Bandspread .............. _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
3. Tone control ...................................................................
4. Send-Receive switch _................................. _ . . . . . . . . . . . . . . . . . . . . . . . . ..
5. R.F. Gain control ..... __ ......................... _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
6. Antenna trimmer ....... _...................................................... ,
7. A. F. gain controL ... , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
8. Selectivity control ...............................................................
9. Crystal Phasing control.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
10. Automatic noise limiter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
11. "A VC-BFO" switch .............................................................
12. Bass "IN-OUT" switch . .'. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
13. Head phone jack..... . ... .. .... ... . .. . .. . . . . .. . .. . .. .. . . .. .. . . . .. . .. . . . . .. . .. ...
5
5
5
5
5
5
5
5
6
6
6
6
7
7
C. Summary of related circuits.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
1. The 2 stage preselector. . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
2. The oscillator and converter......................................................
3. The I F amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
4. Variable selectivity ................................ '...............................
5. Crystal filter circuit ............................................................ "
5a. Single signal adjustment ..... -. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
5b.Crystal ............................. _...... _...................................
6. Noise limiter ..................................................................
7. A VC action ...................................................................
8. "s" or signal intensity meter ............................ _. . . . . . . . . . . . . . . . . . . . . . ..
9. The second detector ......................................... , . . . . . . . . . . . . . . . . . . ..
10. The beat frequency oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
11. The audio amplifier ...... , ................ , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
12. The power supply....................................... . . . . . . . . . . . . . . . . . . . . . . ..
13. Specifications ................................. _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
7
7
7
7
7
8
8
8
9
11
11
11
11
11
11
11
D. Receiver Alignment .............
l. I. F. Alignment. .......
2. BFO adjustment .......
3. Noise limiter and AVC amplifier adjustment
4. RoF. and OSC. alignment ....
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Page
Subject
E. Table of tube socket voltages
......................................... 16
F. Guarantee ........................................................................... 16
G: List of replaceable parts. . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 17
H. Index to parts manufacturers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30
I.
Drawings illustrations
Fig. I-IF. Selectivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
Fig. 2-Crystal filter schematic .... ' . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
Fig. 3-Single signal operation ............................. , . . . . . . . . . . . . . . . . . . . . . . . ..
Fig. 4-Crystal selectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
Fig. 5-Noise limiter schematic......................................................
Fig. 6-Noise limiter action .............................................. '. . . . . . . . . ..
Fig. 7-AVC curve. : ..............................................................
. Fig. 8-SX28-A Top view .........................................................
Fig. 9-SX28-A Rear view . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . ..
Fig. la-Audio fidelity curve. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . ..
Fig.ll-Audio filter curve ...........................................................
Fig. 12-RF and Oscillator adjustment location and alignment procedure .....................
Fig. 13-SX28-A Schematic .........................................................
- 3 -
6
8
8
8
9
10
10
13
13
14
14
15
31
INSTRUCTION BOOK FOR MODEL SX-28-A
SUPER SKYRIDER
INSTALLATION
A
It is recommended that, upon receipt, the carton and
then the receiver be carefully examined for any damage
which might have occurred in transit. Should any sign
of damage be apparent immediately file claim with the
carrier stating the extent of the damage.
IMPORTANT: Unless otherwise marked, the receiver is to
be operated from 110-125 volts of 50/60 cycle alternating
current. A universal 110-220 volt model is obtainable on
order. This model can be operated at either of those two
voltages with 50/60 cycle current. If· the voltages are
higher than indicated an external stepdown transformer
must be used. A switch, mounted on the top of the universal transformer case, will allow convenient 110-220
voltage change.
The standard model SX-28-A receiver comes equipped
with a cabinet for table mounting. The standard 8%" x
19" panel dimension with holes suitably spaced make it
possible for the chassis to be mounted in a standard relay
rack. Maximum overall chassis length is 17%" and depth
13¥2". When the model SX-28-A is so mounted the table
cabinet is replaced with a dust cover. The maximum
over-all length of the receiver will then allow it to be
mounted in a rack with upright channel clearance of 17%".
TERMINALS AND CONNECTIONS ON
REAR OF RECEIVER
(1) .
SPEAKER
On the rear apron of the receiver's chassis appear two
terminal strips for connecting either a 500 or 5000 ohm
speaker to the receiver. Should a matching HALL!CRAFfERSBass-Reflex speaker be used with the receiver, it should be connected to the 5000 ohm terminals.
The 500 ohm terminals can be connected to a speaker or
other load of that impedance value.
(2)
ANTENNA
To the terminals marked AI-A2 and G should be connected the antenna you have chosen to use with the model
SX-28-A receiver.
'
Very satisfactory results throughout the tuning range
of the SX-28-A will be obtained with a conventional inverted ','L" Marconi type of antenna 75 to 100 feet long
including lead-in. This antenna should be erected as high
as possible and removed from surrounding objects'. Be
sure that the antenna is insulated from the ground at all
points. When this type of antenna is used it is connected
to terminaL A-I. The Jumper between A-2 and G should
remain connected.
In the event a doublet antenna is used with the model
SX-28-A SUPER. SKYRIDER receiver, the two wires of the
doublet lead-in shoula be connected to terminals Al and
A2. The Jumper between A2 and G can remain' connected
or removed, depending upon its effect on favorable reception.
A ground can be used if desired and should be connected to the G terminal. Connecting the receiver to a
good ground (cold water pipe or 6 foot rod driven in
moist soil) might improve reception and reduce noise.
Under normal conditions no noticeable difference will
exist so a ground is suggested only if it aids reception.
Should you wish to hav~ a separate antenna for some
one short wave frequency or band, a half-wave antenna
cut to the proper length for the desired frequency will
prove very effective. The following formula will give the
length of the % wavelength antenna depending on the
desired frequency.
463
Length in feet = - - r - - - - ; - . - - - - , - - frequency 10 megacycles.
or, for example, a half wave 40 meter antenna woulcJ.
463
be- T= 66.14 feet long.
The antenn'a should preferably be of solid soft drawn'
enameled copper wire for ease in handling. The center of
the wire is cut and an insulator inserted at that point.
The twisted pair, or open wire transmission line, is then
soldered to each 33 foot length, after the enamel has
been scraped off, directly on either side of this center
insulator. The other end of the transmission line should
be connected to Al and A2 on the receiver. It should be
remembered that such an antenna has directional properties broadside to its length and should be so oriented
if maximum pickup from 'l certain direction is to be
expected.
In designing transmission line systems for a more accurate match of the line to the antenna input circuit, it
will be helpful to know that the approximate antenna
input impedance of the receiver is 400 ohms.
(3)
PHONO-)ACK
The Phono-Jack enables you to use the high fidelity·
audio amplifier of the receiver for phonograph record or
transcription play-back purposes. A high impedance crystal or magnetic pick-up arm should be used for this purpose and connected to a standard headphone plug. This'
plug is then inserted in the PHONO-JACK when record
playing is desired. The receiyer is inoperative to radio
signals, when the plug is in the phono-jack.
- The volume of the audio amplifier is varied by rotating
the AF Gain control until the proper level is obtained.
Removal of the plug from the Phono-Jack once more
places the RF and IF portions of the r~ceiver in operation.
(4)
DC POWER SOCKET
The octal socket on the rear of the chassis is used when
it is necessary to furnish power to the receiver, from a·
direct current source. For conventional AC operation, the
shorting plug must remain in the DC OPERATION
SOCKET. The shorting plug is removed for battery or
vibrapack operation. A similar plug to the shorting plug'
is then wired, as shown in Fig. 13; and inserted in the
octal socket.
A "B" supply capable of delivering 270 volts at 150
milliamperes is necessary for successful operation. Refer
to the section on receiver specifications for the total battery drain for DC operation.
In addition to its function as connector for _ a DC
supply, this socket also serves as an outlet for a remote
- 4 -
stand-by switch. If the remote stand-by switch or relay
is connected between pins # 1 and # 5 on the shorting
plug and the SEND-RECEIVE switch on the front panel
of the receiver is set at SEND, the remote switch or relay
will control the operation of the receiver in the same
manner as the SEND-RECEIVE switch.
(5)
"s"
METER ZERO SET
"S" METER CONTROL is obtained by varying the
knurled ~nob appearing on the left hand chassis apron
edge. ThIS control enables you to properly set the . 'S"
Meter to zero. In order to make the adjustment correctly,
the RF GAIN CONTROL must be advanced clockwise
as far as it will go. In addition, the switch directly below
the bandspread hand-wheel must be in the AVC-ON
P~sition. When these conditions have been complied
wIth, remove the antenna from the Receiver and then
adjust the S meter control until the S meter reads zero.
Reconnecting the antenna to the receiver will then make
the meter indicate the relative carrier strength of each
incoming signal as various signals are tuned in.
B
OPERATION
Each control of the Model SX-28-A SUPER SKYRIDER
receiver performs a definite function that contributes to
the outstanding reception capabilities of the unit. Full
appreciation of the receiver is to be expected only after
you have become familiar with each of the controls and
the effect their operation has on the receiver's performance.
The large calibrated main dial shows the frequencies
covered throughout the 6 band, 550 kc to 43 mc frequency range of the reciever. They are as follows:
Band 1-550 to 1,600 kilocycles
Band 2- 1.6 to 3.0 megacycles
Band 3- 3.0 to 5.8 megacycles
Band 4- 5.8 to 11.0 megacycles
Band 5- 11.0 to 21.0 megacycles
Band 6-- 21. to 43. megacycles
. (1 )The BAND SWITCH, directly below the main dial, will
place the proper set of coils in the circuit to cover the
desired frequency. The main dial is turned by the large
handwheel which is equipped with a micrometer scale
for maximum accuracy in resetting or logging puq_)ses.
Of particular interest is.the locking clutch which will be
found directly below the handwheel. This feature will
aHow you to lock the main dial after a desired signal
has been tuned in. Subsequent movement of the handwheel will not detune the receiver because the control is
provided with a clutch which disengages the handwheel
once the dial lock has been set.
The International Shortwave broadcast bands are indicated on. the main dial by heavier lines showing the
frequencies on which these transmissions will be heard.
The Amateur band setting positions of the main dial
are indicated by a '>mall 0 appearing over the red numbers
which identify each amateur band. The hairline on the
main dial window should be set so that it intersects this
small circle when the main dial is placed in position for
the desired amateur band.
(2)The BANDSPREAD dial is calibrated for the 10-20-40
and 80 meter amateur bands. When tuning on the 160
meter band the main dial should be used.
Note: The calibration on the main dial will be accurate
on~y
if the bandspread condenser is set at minimum capacity which is indicated by a setting of 100 on the bandspread logging scale. It should be recognized that if the
bandspread condenser is left at any other setting but 100,
that small amount of bandspread condenser capacity,
added to the main tuning condenser capacity, would
throw off the main tuning dial calibration because the
receiver is calibrated with the Bandspread condenser set
at minimum capacity. The portions of the amateur bands
on which type A3, or telephone, transmissions will be
heard are underscored with another dark line.
The numbered outer edge of the bandspread dial will
prove to be of grea(help for logging or pre-setting purposes when the bandspread tuning control is used for
easier tuning on frequencies other than those covered bv
the amateur bands.
When "bandspreading" any frequency throughout the
tuning range of the receiver remember the main dial must
then be set to a slightly higher frequency than the desired signal. The difference depends on the amount of
bandspread condenser capacity used and the frequency
of the received signal.
.
When switching from one range to another, an indicator moves vertically behind both the main and bandspread dials. Tuning fatigue is thereby greatly minimized
by focusing attention on only the frequencies covered hy
that particular setting of the bandswitch.
The translucent, indirectly lighted dials are easily read
and so arranged that parallax is reduced to an absolute
minimum.
To operate the ,receiver adjust the following controls
in the order in which they are mentioned:
(3) The TONE CONTROL turns the receiver on and off
and in addition emphasizes either the base or treble frequencies to the extent required by various receiving conditions. The effect the Tone Control has on the fidelity
of reproduction is shown in Fig. 10.
( 4) Place the SEND-RECEIVE switch in the RECEIVE
position-have the ANL control off (turned to the left
until the switch operates).
Place the bandswitch in position. 55 to 1.65 mc, which
will then enable you to tune in stations on the standard
Broadcast Band .
(5) Rotate the RF GAIN control to the right until #9 on
the skirt of the control appears under the panel marker.
(The RF Gain must be full ON as above indicated before
the S meter will indicate correctly.) So that the S meter
will be properly connected in the circuit, the AVC-BFO
switch appearing to the lower right of the bandspread
handwheel, must be in the AVC ON position.
( 6 ) Note: The A ntenna Trimmer control is operated on all
Bands. Proper adjustment of this control is indicated by
the maximum signal.
(7)Afrer complying with the above conditions, the AF
GAIN control should be advanced to the right until the
desired volume is obtained. Tuning the receiver by operating the main dial handwheel will now allow you to
pick up stations throughout the .55 to i.65 me tuning
range of the Broadcast band. Maximum deflection of the
S Meter will indicate when each station is accurately
tuned in.
When covering the short-wave or higher frequency
bands the above procedure should be foHowed-except
that greater care should be used because it is so easy to
completely pass over a station.
..
The other controls on the model SX-28-A SUPER SKYRIDER receiver will enable. you to obtain the best results
- 5 -
from the .r~ceiver once: you have become used to their
effects on the reception of various types of signals. .
(8)The SELECTIVITY control acts as a shutter or gate
and varies the width of the path on which signals reach
the second detector of the receiver. Six different selectivity steps are provided so that you can successfully cope
with different degrees of interference. Reference to Fig. 1
and Fig. 4 will show, graphically, how the control trims
the width of the signal so that what interference might
b~ present in the signal's skirts or sidebands is effectively
clIpped off. Should an interfering signal lap over into the
desired signal, adjustment of the SELECTIVITY control
will reduce that interference.
'
At this point, it is suggested that the CRYSTAL
SHARP setting be used only in cases of extreme interference-the receiver must then be tuned exactly to the
signal. Only then will ~hesignal be intelligible because
you have dipped off its sidebands in which the sibilants
and overtones are embodied.
The CRYSTAL SHARP position of the selectivity
switch is to be used principally for the reception of code,
or CW, signals. By proper associated operation of the
CRYSTAL PHASING control true single signal operation and the maximum in selectivity can be obtained
(crystal circuit discussed in detail in the summary of
related circuits). See Fig. 3.
.
(9)
FIG. 1-1. F. SELECTIVITY
10,000
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1000
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100
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ct
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10
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-20
-10
\1 J
455. +10
+20
+30
KILOCYCLES OFF RESONANCE
Once more refer to Fig. 1 and Fig. 4 and recognize the
fact that with the control set in the BROAD IF position,
the signal proper and all its parts, which are combined in
the side bands, or skirts, will be passed to the 2nd detector,
audio amplifier, and then Speaker. As the selectivity of the
receiver is increased from BROAD·IF to XTALSHARP,
the gate, or admittance path, is so narrowed that only the
main ~rtion of the signal is allowed to pass through. This
fact and its effect on the quality of reproduction is readily
appreciated 'by listening to a signal and noting the reduction
in higher frequency response in the more. selective settings
of the switch. (See Fig. 10 and Fig. 11)
CRYSTAL PHASING CONTROL
The Phasing Control is in the circuit on three positions
of the selectivity control namely-XTAL Sharp, XTAL
Medium andXTAL Broad.
The control is used to remove heterodyne interference
as well as to minimize other forms of interference having
a predominance of high frequency components-such as
static and interference from electrically operated devices.
(lO)The A.N.L., or Automatic Noise Limiter, materially conI
tributes to the satisfactory operation of the receiver by
limiting objectionable interference caused by ignition
systems or other man made causes of electrical disturbances. With the A;N.L. control retarded to the left as
far as it will go, or until the A.N.L. switch is heard to
operate-the noise limiter circuit is not functioning.
Turning the control to the right closes the switch which
is mounted on the control. The noise limiter is now operating. Progressively turning the control clockwise
varies the threshold at which the noise limiter starts to
take hold. The setting at which the control will be left
depends entirely on the type and amount of interference
present as well as the signal strength. The noise limiter
should be judiciously adjusted because through its operation 'the desired signal can even be eliminated or badly
distorted which destroys its usefulness. Only after you
have become familiar with the operation of this control
by actual practice can you determine how far it shoukl
be advanced before the best compromise between noise
and sig~ is obtained. (See Fig. 6.)
( 11) The A VC-BFO OFF-ON switch performs a dual function. The A'VC circuit should be operating for the reception of telepl.tone, or modulated, signals in order to
reduce fading toa minimum. As previously mentioned,
'the functioning of the S Meter is dependent upon AVC
action so the switch must be in the AVC ON position
when the, S meter is used to measure relative' carrier
intensity.
Inasmuch as the AVC circuit levels ail signals toa
predetermined value (See Fig. 7) no one signal can
overload the receiver and cause distortion. At times, in
searching for distant or weak signals, it might be
desirous to use the full sensitivity of the Model SX-28-A.
In that case place the AVCswitch in the AVC OFF position. Remember that with the receiver operating with
no AVC action, strong signals will overload the input
circuit with resultant distortion. Under such a condition
of operation the sensitivity of the set. must be then controlled, manually, by properly retarding the RF Gain
control until you have reached the point below which
overloading takes place.
The other function of this switch is to turn on the
Beat Frequency oscillator. When receiving code signals,
a beat 'note is absolutely essential. \\ ith the BFO switch
in the ON position, each signal tuned in will be accompanied with a' peat note or whistle. For proper adjust- 6 -
ment of the BFa control which appears directly under
the TONE CONTROL the following procedure is suggested. Set the BFa control to zero, now tune in a signal
either voice or code. If a code signal is received, only
the carrier or thump of the signal will be audible because
no beat note is present. Be sure that you have the signal
accurately resonated. Now, without retuning the receiver, rotate the BFa control until a beat note of the
desired pitch is obtained. You now have introduced a
beat note which differs from the IF frequency of the
receiver, namely 455 kc, by the frequency of the audible
signal. Variation of the BFa control will allow you to
change the pitch, or frequency, of the oscillator which
~ill prove to be of hdp under various conditions of
tnterference.
( 12) Directly under the fiFO control will be seen the BASS
IN-OUT Switch. With this switch in the BASS IN position you will have normal audio fidelity. Placing the
switch in the BASS OUT position, the audio filter C~
is inserted. The effect of this filter on the band of frequencies passed is shown Fig. 11. This filter will contribute
greatly to the intelligibility of the received signal when
the receiver is operated in the advanced positions of
selectivity.
(13 ) The Head Phone Jack is connected to a tap on the output transformer. The signal in the headphones is of the
proper volume for satisfactory communications reception. Since no direct current is present in the headphone
circuit crystal type phones can be used.
SUMMARY OF RELATED CIRCUITS
C
(1)
THE 2-STAGE PRESELECTOR
The RF AMPLIFIER, or pre-selector, of the Model
SX-28-A SUPER SKYRIDER has 1-6AB7; 1-6SK7 tubes in
cascade on Bands 3, 4, 5, and 6. On Bands 1 and 2 more
than one stage is unnecessaty to obtain the required
image ratio and reduction of spurious interference. With
two RF stages using three pre-selection circuits, the band
width would be narrowed to such an extent that even
expanding the IF Amplifier to its utmost would still not
provide high-fidelity reception. The modern communications receiver requires two stages of preselection on the
higher frequencies to accomplish only one primary object
-satisfactory image rejection.
.
.
The Model SX-28-A has an image ration of 20 to 1 at 28
mc-350 to 1 at 14 me and a proportionately increasing
ratio as the frequency is lowered. While the two RF
stages are principally needed to obtain such image ratios
they also perform two other us\!ful functions-more favorable signal to noise ratio and slightly increased selectivity.
Examining the coil assembly will immediately show
how rigidly it is constructed and what care has been
taken to completely shield each section from the other.
The manner in which the RF and antenna coils are tuned
on bands 3, 4, 5, and 6 will be interesting. Rather than
push turns to compensate for variations in inductance,
each coil is permeability tuned. This results in exact
adjustment of inductance with improved tracking and
gain as the result. On Bands 1 and 2 the inductance of
the antenna coils is sufficiently large so that lead length
differences do not cause any noticeable inductance change.
(2)
THE OSCILLATOR AND CONVERTER
'A separate 6SA7 tube is used as the High Frequency
Oscillator in the Model SX-28-A SUPER SKYRIDER.
This tube proves desirable in this function because of its
very high value of transconductance which enables the
oscillator to operate with very little coupling to the coil.
This feature reduces the unfavorable effects of tube variations and voltage fluctuations on the tuned circuit. The
HF Oscillator is coupled to the 6SA 7 converter tube at
the Cathode Tap--a point where variations of operating
parameters of the converter tube will least affect the
6SA7 Oscillator. A 6SA7 tube is used in the Mixer Circuit
because tests indicated that changes in operating voltages
caused less reflection in the injector grid loading than
would occur in Q:lost converter tubes. Another feature in
favor of the 6SA 7 tube is that a negative loading is
- 7 -
applied to the tuned circuit feeding its control grid. This
characteristic improves the. gain and selectivity of the
tuned circuit which in turn improves the image and signal to noise ratio.
(3)
THE IF AMPLIFIER
The IF Amplifier of the Model SX-28-A was designed
with a view towards permanency of adjustment under
conditions oDf extreme changes in temperature and humidity as well as unusual mechanical vibration.
The Lirst two IF Transformers arc perineability tUllcd.
In comparing this type of transformer with one having
compression mica tuning condensers, it must be remembered that it takes many more turns of the adjusting
screw to cause the equivalent change in tuning of the
permeability tuned type. Hence a slight change in the
position of the screw will have negligible effect upon the
tuning. The adjusting screw is under spring tension
thereby making it impossible to turn under vibration.
The diode transformer is air-tuned with two variable'
condensers each with a lump capacity of 50 mmf and
variable of 50 mmf. These air trimmers are also under
spring tension so that they can withstand considerable
vibration. Being of the air tuned type, their capacity
change is negligible wit~ w,ide changes in humidity.
Reference to the Schemattc wlll show that the IF transformers are expanded in two steps-thereby enabling
medium or full reproduction of tIie higher frequencies
to be obtained.
(4 )
VARIABLE SELECTIVITY
Six ranges of selectivity are provided in the model
SX-28-A receiver. They are:
I-Broad IF-Cfor high fidelity reception)
2-Medium IF-(more selectivity-less highS)
3-Sharp IF-(reduces annoying interference-far less
highs)
.
.
4-Crystal Broad-(Similar to Sharp IF but cleaner
cutting of side bands)
5-Crystal Medium-(nextse!ectivity step to #4gready increased sideband cutting-more prono.unced crystal "Slot" for interference-very
li ttle highs present)
.
6--Crystal Sharrlposition of extreme selectivitypractically no sideband content-very pronounced crystal "slot")
The graphic effects of the different steps of selectivity
on a signal are shown in Fig. 1 and Fig. 4.
FIG. 2-CRYSTAL FILTER SCHEMATIC
SELECTIVITY
CRYSTAL FILTER CIRCU~T
(5)
6SK1
In positions 1, 2, 3 the crystal is short circuited. In positioi14 the short
across the crystal is opened and the iron core in the secondary of the:
transformer is ad jus ted for Broad Crystal Action and at this point is
accurately tuned to the crystal frequency.·.Due to the. dose coupling
0'£ the secondary to the crystal, the sharply rising resonance curve of
the crystal causes, in contrast, a sharply. falling resonance curve in the
secondary. The combined action of these two characteristics results in
a relati vel y broad resonance curve for the CR YSTAL BROAD selectivity
settin~. In the MEDIUM CRYSTAL No.5 position, C•• is adjusted for
selectlvitv midwaY between the BROAD and CRYSTAL SHARP
settings. (See Fig. 2 and Fig. 4)
In poSItIOn 0, or CRYSTAL SHARP, the trimmer C30 is adjusted for
the Sharpes£, crystal action. Under this condition, the Secondaty is
slightly Cletuned from the resonant crystal frequency sufficientlr so
that its resonance curve is not greatly affected by the crystal but still
coupled tightly enough so that it can transfer energy to the cryst'al
circuit. When this point is reached it is indicated by a rise in the output.
Two such points of increased output will normally occur-one for each
adjustment of the secondary on either side of t.he resonant frequency
of the crys tal.
SWITCH' POSITIONS
FIG. 3-'-SINGLE SIGNAL OPERATION
(Sa),
SINGLE SIGNAL ADJUSTMENT
It is extremely simple to attain, single
sig!lal reception with. the SX-28-A. First,
turn on the BFO to the desired Beat Note
and turn the selectivity switch to the
XTAL SHARP position. Pick a good solid
CW signal, preferably a commercial station
because a commercial is likely to stay on
long enough for you to complete the phasing adjustment for single signal reception.
You will find on' tuning across this signal
that it has two amplitudes. Tune first to
the weaker of these two amplitQdes. Now,
turn the PHASING control until this
weaker of the two amplitudes is reduced
to a minimum. (If the weaker amplitude
ap~ears on the right the above procedure
still holds.) Then tune to stronger of the
two amplitudes and adjust the BFO cantrol to a tone most pleasing to you. This
adjustment for single signal selectivity will
hold with no further adjustment unless you
change the phasing control. (See Fig. 3.)
With Selective Switch in XTAL
Sharp position identify the
weaker amplitude-Tune Receiver to the weaker.
-..djust phasing control carefully
until tliis weaker amplitude is
reduced to a minimum.
Retune Receiver to the
stronger amplitude and then
ad just pitCI1 control until
you get note most 'pleasing
to copy.
FIG. 4-CRYST AL SELECTIVITY
..
..
..
,(5b)
CRYSTAL '
XTAL
XTAL
XTAL
r-
f-
BIIOAD
The CR YST AL FILTER and
holder are wired directly into the receiver
and do not plug in as heretofore. In this
manner exceptional crystal filter action is
obtained because of the elimination of the
capacity and losses of a sock~t. So .mounting the crystal prevents possible change in
polarity which would occur if the crystal
were improperly inserted in the circuit.
The size of the crystal has been clU"efully
determined to allow the BROAD CR YSTAL position to tune as broadly as possible. The capacity of the crystal holder
has been reduced to. a minimum through
the use of a specially,Jesigned polystyrene
hoider.
r-
MEDIUM
SHARP
.
ti.
~
!-.•
III
.
/
\
•
",
•
• - - I\.
-4
I
\ ~V
lJ
.L
1-1"+1+1+'+4+1+'
"
V
1\
/
.........
I'--'
II
t'-
r\
-a -4 -I -I -I 411'" +2 +1 +4 ... "
KILOCYCLES OFF RESONANCE
-5
8. -
-2
-I
455 +I
+1
.,
+4
(6)
NOISE LIMITER
The principle of operation of the limiter is very similar
to that of the Lamb limiter which has been described in
detail in past issue of QST. The carrier of the received
signal is first converted over to the intermediate frequency and then fed into the 6L7 amplifier and 6B8 AVC
amplifier and 6AB7 noise amplifier. A broadly tuned IF
transformer is used in the plate of the 6B8 with its
primary and secondary closely coupled. The secondary
feeds into the 6B8 diode where rectification of the carrier
furnishes AVC voltage for the RF and mixer tube as well
as for the 6AB7 noise amplifier. A broadly tuned IF
transformer is used in the plate of the 6AB7, the secondary feeding into the 6H6 noise rectifier. A 455 kc wave
trap (CH4 and CSS) is used which allows the passage
of the higher audio frequencies without attenuation. In
the form of further explanation of our apploach toward
noise elimination, it must be remembered that noise in
general is composed of a random mixture of high and
low frequencies. Of this mixture the predominating
higher frequencies are the most objectionable. It is to
our advantage to retain the high frequency compo\1ents.
Thus, these transients will be allowed to rise to a point
far above the carrier level with the result that they will
be applied to the injector grid of the 6L7 tube without
being reduced in value. Transients, such as ignition interference having a steep wave front, consist largely of high
frequency components. The voltage applied to the gri(1
of the 6L7 tube has a negative polarity because of the
6H6 noise rectifier. By varying the ANL control, we
raise or lower the negative voltage applied to the 6L7
tube until it is barely sufficient to overcome the noise
impulses applied to the grid of this tube without allowing the modulation peaks of the carrier to become badly
distorted.
FIG. 5-NOISE LIMITER SCHEMATIC
688
6L7
C.,
...
".,
..
"
••
"",
- 9 -
FIG. 6-NOISE LIMITER ACTION
COnstant tone signal no interference ANL OFF.
Same Signal ANL OFF. (Note
transient, peaks extend well be·
yond range of screen. Signal not
readahle. )
If the noise limiter adjustment permits too great a
value of transient voltage to be applied to the 6L7 injector grid, detection will take place and rectified components of this modulated carrier will appear in the 6L7 .
plate circuit. This effect will appear as distortion in the
output of the receiver. If, on the other hand, not enough
Same signal. Same noise. -ANLON adjusted for most favorable
signal to noise ratio.
noise voltage is applied, then the momentary decrease in
sensitivity will not be great enough to stop the noise
from getti.ng through and some of it will appear in the
plate circuit of the 6L7 tube and consequently in the output of the receiver. As a result the noise limiter must be
carefully adjusted to the particular carrier and noise
level being received. (See Fig. 6)
FIG. 7-A.V.C. CURVE-AT 3 MC.
+8
+4
,,---
U)
&j
0
m
0
'"0
-4
-8
/
/
/
V
/
-12
10
100
1000
10,000
MICROVOLTS INPUT
- 10 -
100,000
1,000,000
(7)
AVC ACTION
A double AVC system is used. The RF and mixer tubes
are operated by the broadly tuned carrier coming through
only three tuned IF circui:s. The final signal however
passes through six-tuned IF circuits. As a result, when
the signal is slightly detuned, the receiver output has
dropped considerably while the AVC action has dropped
but very little. This results in a reduction of betweenstation noise and a more sharply defined aural tuning
action.
(8)
"S" OR SIGNAL INTENSITY METER
The apprpximate DB per S unit equivalent is 6 DB's.
As is known, a DB, or decibel, is a unit of change in
signal level and is defined as being the least detectable
change the average ear can appreciate when listening to
a single pitched tone. 3DB is the least change the ear
detects when listening to sounds varying in both amplitude and pitch. By comparison, a variation of one S unit
on the meter will indicate a change of two detectable
steps in signal level. Quanti tati vel y, a DB gain or los~
is equal to 20 log
E~ =
(9)
,,(~:) where El
=
input voltage and
output voltage.
THE SECOND DETECTOR
As will be noted, a diode type of second detector is
used in the Model SX-28-A. Its choice was prompted by
the fact that such a detector is capable of handling large
percentages of modulation with very little distortion.
This is due to the output of the diode being easily filtered
(IF Removed). In addition, the rectified output contains
a DC component which can be used for AVC purposes.
(10) THE BEAT FREQUENCY OSCILLATOR
The BFa is turned on with the switch below the bandspread handwheel and adjusted by the skirted knob
directlv below the tone control. The BFa circuit, as will
~e .seen by referring to Fig. ·13, is the well known
Hartley oscillator. It will be noticed that a plate dropping resistor is used to compensate for plate voltage
variations. An increase in receiver voltage causes an
'increase in the plate current of the oscillator. This in- .
crease in turn causes the voltage drop across the resistor
to increase, thus maintaining a more constant voltage
at the plate of the beat oscillator tube. A favorable ratio
of capacity to inductance is used. The fixed tank capacity
has been artifically aged by alternately exposing it to
very high and then low temperatures. In this manner
any residual strains of the component parts are removed
and the capacity of the condenser remains constant.
The BFa coil is permeability tuned which further removes the possibility of drift which would occur should
a compression variable be used to resonate the circuit.
Proper location of the Beat Oscillator tube and its
associated components plus excellent shielding and mechanical rigidity do much to keep stray fields from being
established. Little BFa leakage is to be expected in the
Model SX-28-A so "tweets" or BFO harmOnICS will not
prove to be bothersome.(11)
THE AUDIO AMPLIFIER
The second or output stage of the audio amplifier in
the Model SX-28-A receiver uses two 6V6GT tubes connected in push-pull. These tubes ar~ driven by the 6SC7
double triode. One of the triode sections of the 6SC7
tube is used as the 'inverter to the 6V6GT tubes. A portion of the signal from the plate circuit of the first 6SC7
,
triode is fed to the grid of the othet· 6SC7 triode Section,
thereby giving two output voltages' in opposite phase
suitable for exciting the push-pull 6V6GT output amplifier.
(12)
THE POWER SUPPLY
The power supply in the Model SX-28-A is quite normal
except that it supplies voltage for the 6V6GT output
tubes directly from the rectifier or before the filter system.
Voltage fluctuations in the receiver are greatly reducedincreasing the audio output of the receiver and stabiliZing
the operation of all circuits.
The filter circuit consisting of a total of 60 mfds of
capacity plus an additional filter in the 6SC7 plate supply
and a 12 henry choke keep the hum level of the receiver
in excess of 60 DB below maximum output. The power
transformer is built to withstand continuous operation
at 2S0 degrees F but has been designed to run at approximatelv 160 degrees F under normal conditions.
(13 )
SPECIFICATIONS
Tubes:
1~6AB7
1st RF Amplifier
1---6SK7
2nd RF Ampl ilier
16SA7
Mixer
1 _.. 6SA 7
HF Oscillator
1 -6L7
1st IF Amplifier Noise Li mi ter
1-6SK7
2nd IF Amplifier
1-6B8
2nd Detector and S meter tll he
1--6B8
AVC Amplifier
1-6AB7 Noise Amplifier
1-,-6H6
Noise Rectifier
1-6JS
Beat Oscillator
1-6SC7
1st Audio Amplifier
2-6V6GT Push-Pull Output Amplifiers
1-SZ3
Rectifier
Power Consumption-at 117 volts-60 cycles-138 watts
Power Consumption-DC operation-18 amp. at 6 volts
or 108 watts
Power Output
-8 watts undistorted
SensitivitY-Cfor 500 milliwatts output) varies between
the limits of 6 to 20 microvolts over the entire frequency
range of the receiver.
2x
1000 xSelectivity-IF broad (high fidelity) 12 kc
36 kc
IF Sharp
4.1 kc
22 kc
Frequency Range RF-Note: These are the actual frequencies covered corresponding to nominal figures indicated on the front panel.
')')0
to 1,620 kilocycles
I.S to 3.1 megacycles
2.9 to S.9 megacycles
S.7S to 11.S megacycles
10.3 to 21.S megacycles
20.4 to 43 megacycles
Frequency response AF (audio filter out-broad IF-tone
control high)-70 to 3000 cycles ± 2~ DB
Speaker Output Impedances-SOOO and SOO ohms
Intermediate Frequency-4SS kc
Table cabinet dimensions-20Y2" long x 10" high x 143 ;"
deep
.
Relay Rack dust cover dimensions-14:l(" deep x 173 ;;"
long x 8%" high
Panel dimensions-19" x 8%"
Chassis dimen~ions-17%" x 13Y2"
Weight-(unpacked)-~7) lhs. packed 11,7 lhs.
- 11 -
D
RECEIVER ALIGNMENT
Equipment Needed for Aligning:
I-Art all wave signal generator which will provide
an accurately calibrated signal at the test frequencies
indicated.
2-output indicating meter connected to 5000 ohm
output terminals.
3-Non-metallic screw driver.
4-Dummy antenna of 200 mmf and also 400 ohm
carbon resistor.
Setting of controls p~ior to alignment-IF and RF.
Tone control at maximum high frequency position
(#9)-BFO at o-Bass switch at Bass IN-AF Gain at
#9--RF Gain at #9--Band switch-IF alignment position ,55 to 1.6 band-RF alignment depending on band
aligned.
parent when the correct adjustment has be~n reached.
Switch to "Xtal Sharp" and adjust C- 30 for maximum
output while varying signal generator frequency. Two
points of maximum output will be noted corresponding
to two adjustments 0(C- 30 . Either one of these points
may be used at which to leaveC- 3o • a sharply peaked
tone will result at the correct adjustment.
Switch to "Xtal Medium" and adjust (:-Z9 till .the
output is midway between the outputs reache4 while
aligning the "Xtal Sharp" and "Xtal Broad" positions.
The apparent sharpness of tone should be.midway between the "Sharp" and "Broad" positions.
Switch again to "Xtal Sharp" and set the signal generator to exact crystal frequency. Set BFa front panel
control to a tone. of approximately 1000 cycles. Switch
again to "Sharp IF" and carefully realign the IF transformers as earlier described in the 6rst paragraph of these
instructions.
Selectivity control at sharp IF-~nd-Receive switch
in Receive---Crystal phasing at #3 on left side-ANL-OFF at o-AVC OFF.
(2) BFa Adjustment: Set front panel control to zero-BFa
switch ON-Signal Generator tuned to crystal frequency
Important: Have bandspread control so logging scale
-selectivity switch in IF Sharp position-now, adjust
reaas 100.
screw on top of T4, after loosening lock nut, to zero best.
Antenna trimmer adjusted for Maximum gain at each.
(See Fig. 8)
RF alignment point on. all bands.
(3) Noise Limiter and A VC A~plifier Adjustment: Have
the Controls .set as before except that the AVC switch is
(1) 455 KC-IF Alignment: Tune main dial to 1400 kc on
now in the ON position. Connect a high resistance type
.55 to l.(5.mcband. Connect the hot lead from the signal
.voltmeter across R49 which is connected between termigenera tot to 6SA7 mixer terminal IS-Ground to chassis.
nal #5 of the 6L7 tube and cru;,ssis. Connect a 50,000 (P
ohm resistor across primary ofTS (Rec1and 'Blue leads). .
Roughly adjust the aligning screws of Tl, the lower
Set generator at 455 ~c as for IF alignment. Connect genscrew of which is accessible through hole in right mounterat,?r to grid of 6AB7 tube (pin #4). RotateANL control
ing bracket, for maximum gain. Now adjust lower screw
all the way to the right, or position #9. Adjust screws
on T2 (do not adjust upper screw). Also adjust C31 and
on top-of T5 for maximum indication on DC meter coqthe air trimmer condensers at the top of T3 for maximum
n~ctea across R47. Reconnect generator, as for IF aligngain. (See Fig. 8 for location of IF adjustments)
ment, to mixer grid of 6SA7· tube .. RemQve 50,000 ohm
~sistor which was inserted across primary of T5 during
Switch to Crystal Broad Position-Turn on BFO and
alignment. Remove grid clip off top of 6L7 tube. With
adjust to a tone of about 1000 cycles. Vary the frequency
generator set at 455 kc and ANL control at extreme right
of the signal generator while adjusting the top screw on
adjust wave trap trimmerC55 for mi~imum signal ~s
indicated on output meter. (See Fig. 8 and Fig. 1:4 for
1'2 until the 4)utput goes through a maximum, dips down
location of adjustments).
and starts going up again. Adjust th!! phasing control
With generator connected to 6SA7 mixer grid as above,
for maximum selectivity and then back off the top screw
replace 6L7 grid and turn ANL control to extreme left
on T2 until the output reaches a minimum value between
until switch clicks. Connect high resistance DC meter
the tWo maximum values first noted. The frequency of
across 6BS diode filter condenser C64. Adjust, screw 0.1'1
the signal generator should be varied over a small range
top of T6 for maximum indication on DC meter across
while adjusting the top screw of T2. A swishing note,
C64.
in. contrast to the usual sharp crystal tone will be ap- (4)
For RF and oscillator adjustment location and alignment procedure see Fig., 12.
- 12 -
FIG. 8-SX28-A- TOP VIEW
6AB7(tJs\)
9-SX28-A-REAR VIEW
- 13 -
FIG. 10-AUDIO FIDELITY CURVE
,," BASS IN"
+10
-r--:.
o fP-,
-
r... 1--0
'" "'" "
(/)-10
..J
'"
'"
~ -20
~"""'--~
'.
....
,~
~~'
(,)
"\
0 - 30
"
-40
"
~
'~. ,
~
i--
-50
(I) I.F. BROAD-TONE 'CONTROL ou,r
(2) I.F.SHARP-TONE CONTROL OUT
(3) I.F. SHARP-TONE CONTROL IN
r\..
.,\
1\
I\.
I\. \,
",-'
I\.
1\
10,000
1000
100
30
~.
CYCLES PER SECOND
FIG. ll-AUDIO FILTERG:URVE
I 1
I--
+15
"-
+[0
(/)
'"m6
'"o
0
""-6
, , ~.r
+5
..J
FREQUENCY RESPONSE WITH'
BASS SWITCH IN a OUT-
i""'1'-0
/ '"
.....
BASS
L,
-5
SELECTIVITy-"CRYSTAL SHARP"
14;
"
OUT
f'..
,
" ....
'\.
\
~
\
1' ....
"'\
-10
~
-15
r--- I-1\
\
-\
':'20
30
1000
100
CYCLES PER SECOND
.;. 14 -
'\
IOPOO
FIG. 12-RF AND OSC ADJUSTMENT LOCATION AND ALIGNMENT PROCEDURE
R-F AMP.
R-FAMP
C91
Caa Ca9 C 90
57 5 10 5 ,3
16
1ST oET.
'ST OET.
C91 C93 C92
C94 C 95 C9G
S6 S9 S'2
S'5 S4 S2
OSC.
05C.
CIOOC'OI CI02
C103C99C98'
S5
Sa S"
SI
FP
FP
FP
RF &
osc.
ALIGr\'MENT PROCEDURE
Connect hot lead of signal generator to AI - through dummy antenna shown ;n table, Leave jumper connected
between A2 and G , Ground of Generator to Chassis, "FP" indicates fixed pad-do not adjfJst.
Band
Rec Dial
Setting
I
I
1.'65 me
2
3.0
2
1.8
3
3
5.4
3.0
Sig , Gen,
Freq ,
,
.
I
I.
1.5 me
.6
3.0
1.8
5.4
3.0
Dummy
Antenna
HIGH FREQTJENCY E;{ J
200
200
400
400
mmf
ohms;
ohms
Adjust Osc.
With
C9H
. .. .
C99
....
400
400
400
400
ohms
ohms
ohms
ohms
.. - C I00
....
C I01
.....
mmE
Adjust Trimme-rs
for Max. Gain
•.
C 92
. . . . . .. . . .
Cn
. .. .. . . .. .
C 94
LOW FREQUENCY END
Adjust Osc
With
• •• •
Css
. r.. .......
I>
I Permeability
Tuned By _
I
SI
....
S3
I
S2
I
I
54
....
55
....
58
I ........ '..
I
S6
57
10.0
10.0
C 9:\
C 89
I
,.
7.0
7.0
.... .. ....
59
S10
====1======~=======I=~~~=II===~==~==~==~==j~====~======~
1___
5__ r-~20~'70_~_720~'70___ I _~40~O_o~h_m_s_' II ___C~I~02~-+____C~96~__C
. _9~.0__ ~1__~.~
.._._~I~
..~.~..~.~.~..~.~,
5
12.0
12.0
400 ohms
....
... .......
S11
S 12
S 13
4
4
I
I
C103
C97
C91
. . •.
I ... ...... .
~-__6=__~
1 ~_2_
4 ._0__~___24_._0____~~4~
00~o~h~m~s~~__~
..~.~.__~___
.._._. _. _,,_,_, _,__~___S~14~__~I__
S~15__~___S~16~
6
36.0
36.0
400 ohms
E
The following measurements made with a 20,000 ohms per volt meter and taken from the socket terminal indicated
to ground or r!!ceiver chassis. Antenna and ground were disconnected from the receiver when these measurements
were taken and the RF and AF gain controls set at maximum. "DL" means Dead Lug but will indicate
when used as a tie" Normal tolerance allows a variation of ± 10% from the indicated values.
TUBE
FUNCTION
SOCKET TERMINALS
1
2
3
4
5
0.1
4.15
170
0.1
4.35
105
V r 6AB7
RF Amp. (1)
., .
.. .
. ..
V2 -6SK7
RF Amp. (2)
., .
. ..
4.35
Mixer
.. .
250
V4 -6SA7
HFOsc.
.. .
.. .
116
116
------
Va-6L7
IF Amp. (1)
Noise Limi ter
.. .
..
.
245
IF Amp. 2
.. .
..
.
4
., .
2nd Det.
S Meter Tube
.. .
.. .
17.2
~.255
AVC Amp.
., .
. ..
225.5
Vg -6AB7
Noise Amp.
., .
. ..
V1o -6H6
Noise Rectifier
.. .
. ..
Vn -6J5
Beat Osc.
., .
.. .
V7 -6B8
100
0.12
---
.......
279
- - - --------_.
.. .
.......
6.3
..
6.3
116
.......
...
. ..
6.3
4
,-.075
4
107.5
6.3
235
.......
6.3
...
-.17
6.3
2
.......
0.3
102
.... .. .
4.1
_
-.255 108
--0.2
0.2
107
.07
...
150
1.1
6.3
225
------.1
17.6DL 6.3
-
1st Audio Amp.
V14 -6V6GT P.P. Audio Amp.
VIl:,-5Z3
6.3
Cap.
-
.. .
140
--. ..
.. .
V1s-6V6GT P.P. Audio Amp.
V12 -6SC7
8
7
--6.3
227
~--
V3 -6SA7
Vg -6B8
6
I
Va-6SK7
~lOltage
Rectifier
*
.. .
320
.. .
.. .
.. .
.1
.. .
140
.. .
...
.. .
.......
6.3
...
BFO ON
ONLY FOR TEST
6.3
.. .
.......
198 DL
6.3
17
.......
.
.. .
6_3
17
........
.. .
. ..
.. .
.. .
.......
-7.4
137
1.4
0
310
290
.. .
310
290
..
340 AC 340 AC 320
. ......
* 5 V. AC between Terminals 1 & 4
F
GUARANTEE
This receiver is guaranteed to be free from any defect
in workmanship and material that may develop within
a period of ninety (90) dfys from date of purchase, under
the terms of the standard guarantee, as designa.ted by the
Radio Manufacturers Association. Any part or parts that
prove d~fectivewithin this period will be replaced without charge when subjected to examination at our factory,
providing such defect, in our opinion, is due to faulty
material or workmanship, and not caused by tampering,
abuse or normal wear. All such adjustments to be made
FOB the factory.
Should this receiver reqriire any adjustments, your
dealer or distributor has complete technical service in- 16 -
formation, or the factory will be glad to assist you in
any problem direct.
Should it be necessary to return any part or parts to
the factory, a "Return Material Permit" must be obtained in advance by first wrijng the Adjustment Departmertt, who will issue due authorization under the
terms of the guarantee.
The Hallicrafters Company. reserve the right to make
changes in design or add improvements to instruments
manufactured by them, without incurring any obligation to install the same in any instrument previously
purchased.
All Hallicrafters receivers are built under patents of
Radio Corporation of America and Hazel tine Corporation
G.
REF.
SYMBOL
Rl
R2
R3
R4
R5
R6
&,
I-}-
RS
R9
RIO
Rll
R12
R13
R14
R15
R16
',~
R17
RIS
R19
R20
R21
R22
R23
R24
R25
R26
R27
H2S
R29
R30
~l}
R32
LIST OF REPLACEABLE PARTS MODEL SX-28-A
NAME OF PART AND DESCRIPTION
Resistor, 100,000 ohm :t 10'fb; i watt, carbon
Resistor, variable, 10,000 ohm:t 2o;'c; carbon, type 35
Resistor, 330 ohm ± 10%, i watt, carbon
Resistor, 27,000 ohm ± 10%, 1 watt, carbon
Resistor, 1000 ohm ± iO%, i watt, carbon
Resistor, 6,SOO ohm :t 10%, 2 watt, carbon,
Same as Rl
Same as H3
Same as %
Resistor, 2700 ohm, ± 10%, i watt, carbon
Same as RI
Resistor, 390 ohm ± 10%, i watt, carbon
Same as %
Same as RIO
Same as Rl .
Resistor, 270 ohm ± 10%, i watt, carbon
FUNCTION
A-V-C decoupling for tube VI
R. F. Gain c ont rol
Cathode bias for tube VI
Voltage drop for screen of tube VI
Plate decoupling for tube VI
Plate decoupling for tube V4
A-V-C decoupling for tube V2
Cathode bias for tube V2
Vol tage drop for screen of tube V2
Plate decoupling for tube V2
A-V-C decoupling for tube V3
Cathode bias for tube V3
Voltage drop for screen of tube V·
3
Plate decoupling for tube V3
A-V-C decoupling for tube V5
Cathode bias for tube V5 on bands
1,2 and 6
Voltage drop for screen of tube V5
Same as R5
Plate decoupling for tube V5
Same as RIO
Grid
return for tube V6
Same as Rl
rvfI
1
.
Grid return for tube V6
Resiston, 470,000 ohm .:t lv/o,
"2 watt, carbon
Resistor, 270 ohm:t 10%, i watt, carbon
Cathode bias for tube V6
Vol
tage drop for screen 0 f tube V6
Same as R5
Plate
decoupling for tube V6
Same as RIO
Diode load for tube V7
Same as Rl
Diode load for tube V7
Same as %0
Cathode bias for tube V5 for bands
Resistor, 1,SOO ohm :t 10%, i watt, carbon
3 and 5
Same as R20
A-V-C decoupling for tube V5 and grid
isolation for tube V7
Carrier level meter shunt
Resistor, 100 ohm:t 10%" i watt, carbon
Resistor, variable, 500 ohm :t 20%, carbon, type 25 Carrier level meter, zero adjustment
Voltage drop for plate of tube V7
Resistor, 27,000 ohm :t 10%, 2 watt, carbon
Resistor, two sect ions; sect ion #1 (R3 ;J.) ,
Voltage divider for screen grids of
11,000 ohm :t 10%,
watts; section,2 (R 32 )
4,000 ohm ± 10%, 7 watts; met al clad, wire
tubes V2 ' V3 ' V5 ' V6 ' V7 and Vs
wound
Ii
MFR.
CODE
CONI'R'S.
PARI' NO.
ASA
CT
ASA
ASA
ASA
ASA
RC2IAEI04K
25C066
RC2lAE33lK
RC31AE273K
RC2IAEI02K
RC41AE6S2K
ASA
RC2lAE272K
ASA
RC2IAE391K
ASA RC21.AE27lK
ASA RC21.AE474K
ASA RC21.AE271K
liSA RC2iAEI82K
liSA RC2lAEI0lK
CT
25C022
ASA RC41.AE273K
CS
24A046
G.
REF.
SYMBOL
R33
R34
R35
R36
R37
R3a
R39
R40
R41
R42
R43
R44
R45
R46
R47
R4a
R49
R50
%1
%2
R53
R54
R55
R56
R57
R5a
R59
R60
R61
R62
R63
LIST OF REPLACEABLE PARTS
NAME OF PART AND DESCRIPI'ION
Resistor, variable, 500,000 ohm ± 20%, carbon
Same as R5
Resistor, variable, 500,000 ohm ± 20%, carbon
type AE-.35-500M
Same as Rl
Same as·R l
Resistor, 47,000 ohm ± 10%, i watt, carbon
Resistor, lao,OOO ohm ± 10%, i watt, carbon
Resistor, 270,000 ohm ± 10%, i watt, carbon
Same as R40
Resi st or, 220 ohm ± 10%, 2 watt, wire wound, type
BW2
Resistor, 20,000 ohm ± 5%, 2 watt, carbon
(Cont'd.)
FUNCTION
A.F. gain control
Cathode bias for tube V12
TONE control
Plate load for tube V12
Plate load for tube V12
Plate decoupling for tube V12
Grid return for tubes V12' V13 and
V14
Grid return for tube V13
Grid return for tube V14
Cathode bias for tubes V13 and V14 .
Load for primary winding of transformer Ta
Resistor, 5,000 ohm ± 20%, 10 watt, wire wound,
. 'toad for secondary of transformer Ta
viterous enamel, type CC
during headset operation.
Plate load for tube Vn
Same as R43
Grid return for tube VII
Same as R38
Resistor, 10 ohm ± 10%, i watt, carbon
Parasitic suppressor for tube V4
Cathode bias for tube VIO
Same as Rl
Resistor, I megohm ± 10%, i watt carbon,
Diode load for A-N-L tube VIO
Resistor, 560 ohm ± 10%, ~ watt, carbon
Plate decoupling for tube Vg
Resistor, '20,000 ohm ± 5%, 1 watt, carbon
Screen decoupling for tube Vg
A-N-L bias voltage divider
Same as R38
Resistor, variable, 50,000 ohm ± 20%, carbon with
A-N-L Control
DPST switch, type WR-35
Resistor, 33 ohm ± 10%, i watt, carbon
Cathode bias for tube Vg
Same as R20
Grid return for tube Vg
Same as R5
Voltage drop for screen of tube Va
Same as Rl
A-V-C decoupling for tube Vg
Resistor, 180 ohm ± 10%, i watt, carbon
Cathode bias for tube Va
Same as Rl
Diode load for tube Va
Same as R40
Diode load for tube Va
Same as H20
A-V-C decoupling for r-f stages
Same as R20• Part of transformer TI. Shown for
Grid return for tube Va
reference only.
Plate decoupling fpr tube VA
Same as RIO
MFR.
CONTR'S.
CODE
PARI' NO.
CT
25C065
CT
25C064
ASA RC2lAE473K
ASA RC2lAE184K
ASA RC2lAEl274K
IRC
24BV221E
ASA
RC4lAE203J
U.
24BG502F
ASA R02lAEIOOK
ABA RC21AEI05K
ASA RC2lAE56lK
ASA RC3lAE203J
CT
25C067
ASA RC2lAE330K
ASA RC21AEla IK
G. LIST OF REPLACEABLE PARTS - (Cont'd.}
REF.
SYMBOL
R64
R65
R66
R67
R68
R69
R,o
~l
&'2
R73
~4
NAME OF PART AND DESCRIPTION
SaIne as R20
'Same as R38
Same as R38
Same as R50
Resistor, 1,200 ohm ± 10%, t watt, carbon
Same as Rl
Same as R49
Resistor, 4700 ohm ± 10%, 1 watt, carbon
Same as R50
Not used
Same as R47
Cl
Cl. 1
......
fD
C1. 2
Cz
C2 • 1
CZo2
Capacitor, variable, 4 unit gang f each unit consists of 2 sections, except unit 4 at rear which
contains only one section (section #2), air dielectric, special; Section #I-min. cap. 16.3
mmfd., max. cap. 187.5 mmfd. (C l , C1 l' C1 • 2 );
Section #2-min. cap. 21. 5 mmfd., max: cap. 250.0
mmfd. (C 2 , C2 • l , C2 • 2 , C2 • 3 ).
CZ• 3
~
C3 • 1
C3 • 2
C3 • 3
C4
C4 • 1
Capacitor, variable, 4 unit gang, each unit consists of 3 sections, air dielectric, special;
Section #I-min. cap. 6 mmfd., max. cap. 16 mmfd.
(C 3 , C3 • 1 , C3 • 2 , C3 • 3 ); Section #2-min. cap. 6.5
mmfd~, max. ~ap. 2.5 mmfd. (C4 , C4 • 1 , C4 • 2 , C4 ,3);
Sect lon #3-mmo cap. 6.5 mmfd., max. cap. 27
mmfd. (C5 , C5 • 1 , C5 • 2 , C5 • 3 )
FUNCTION
A-V-C decoupling for r-f stages
Injector grid return for tube V3
Grid return for tube V4
Plate load for tube VI on Band I
Cathode bias for tube V5 on Band 4
Primary load for transformer T5
A-N-L circuit balance
Plate decoupling for tube V4
Plate load for tube VI on Band 1
MFR.
CODE
CONTR'S.
PART NO.
ASA RC2lAE1'22K
ASA RC3l.AE472K
Parasitic suppressor for tube VI
Oscillator stage tuning for Band 1
only
Converter stage tuning for Band 1
only
Antenna stage tuning for Band 1 only
Oscillator stage tuning for Bands 3,
4, 5 and 6
Converter stage tuning for Bands 3,
4, 5 and 6
R-F amplifier stage tuning for Bands
3, 4, 5 and 6
Antenna stage tuning for Bands 3, 4,
5 and 6
Oscillator stage bandspread tuning
for 80 and 20 meter bands
Converter stage bandspread tuning
for 80 and '20 meter bands
R-F amplifier stage bandspread tuning
for 80 and 20 meter bands
Antenna stage bandspread tuning
for 80 and 20 meter bands
Oscillator stage bandspread tuning
for 80 and 40 meter b~ds
Converter stage bandspread tuning
for 80 and 40 meter bands
RC
48B050
RC
48B051
G.
REF.
NAME OF PART AND DESCRIPTION
SYMBOL
C4 • 2
C4 • 3
C5
C5 • 1
C6
C7
C8
N
o
C9
CIO
Cll
C12
C13
C14
C15
C16
C17
C18
Cl9
C20
C21
LIST OF REPLACEABLE PARTS - (Cont'd.)
.
Capacitor, variable, 4 unit gang, each unit consists of 3 sect ions, air dielectric, special;
Section #l-min; cap.
mrofd., max. cap. 16 mrnfd.
(C3 ' C3 .1' C3 • 2 ' C3 • 3 ); Section #2-min. cap. 6.5
mmfd., max. cap. 2.5mmfd. (C4 ' C4 • 1 , C4 • 2 , C4 • 3 )j
Section #3-min. cap. 6.5 mmfd., max. cap. 27
mmfd. (C5 ' C5 • 1 ' C5 • 2 , C5 .-3 )
Capacitor, variabie, min. cap. .5 mmfd., max.
cap. 50 mmfd., air dielectric, ceramic insulation, type 22
Capacitor, 2980 mmfd. adjustable ± 5%, mica dielectric, steel mtg. frame, special
Capacitor, 2400 mmfd. adj ustable :!: 5%, mica dielectric, steel mtg. frame, special
Capacitor, 2240 mmfd. adjustable :!: 5%, mica dielectric, steel mtg. frame, special
Capacitor, 1700 mmfd. adjustable ± 5%, mica dielectric, steel mtg. frame, special
Capaci tor, 8'22 mmfd. adjustable ± 5%, mica dielectric, steel mtg. frame, special
Capacitor, 541 mmfd. adjust able :!: 5%, mica dielectric, steel mtg. frame, special
Capacitor, adjustable, 5 mmfd. ± 0.2 mmfd. at
250 C., capacity change -0.02 mmfd. per 0 C.,
type 8-2739
Capacitor, 0.02 mfd. -10 + 40%, 400 V.D-C working, paper dielectric
Same as C14
Capacitor, fixed, 0.02 mfd. - 10 + 40%, 600
D-C working, paper dielectric
Capacitor, fixed, 0.05 mfd. - 10 + 40%, 200
V. D-C working, paper dielectric
Same as C14
Same as C14
Same as C16
Same as C17
v.
FUNCTION
MFR.
CODE
CONTR'S.
PARI' NO.
R-F amplifier stage bandspread tuning for 80 and 40 meter bands
Antenna stage bandspread tuning
for 80 and 40 meter bands
Oscillator stage bandspread tuning
for 80 and 20 meter bands
COnverter stage bandspread tuning
for 80 and 20 meter bands
ANT. TRIMMER control
RC
48B051
RC
48A053
Oscillator padding for Band 6
UE
44BIIO
Oscillator padding for Band 5
UE
44BI09
Osc illator padding for Band 4
UE
44BI08
Os~illator
UE
44BI07
padding for Band 3
Oscillator padding for Band 2
44BI06
Oscillator padding for Band 1
UE
44BI05
Temperature compensating capacity
for oscillator
UE
44A06'2
Cathode by-pass for tube VI
SP
46AW203J
Screen by-pass for tube VI
Plate return by-:-pass for tube VI
SP
46AY.203J
A-V-C by-pass for tube VI
SP
46AU503J
Cathode by-pass for tube V2
Screen by-pass for tube V2
Plate return by-pass for tube V2
A-V-C by-pass for tube V3
G.
REF.
SYMBOL
C22
C23
C24
C25
C26
C27
C28
C29
C30
N
I-'
C3l
C32
C33
C34
C35
C36
C37
C38
C39
C40
C'4l
C42
C43
C44
LIST OF REPLACEABLE PARTS -
NAME OF PART AND DESCRIPI'ION
Same as C14
Same as C14
Same as C16
Capacitor, fixed, 2200 mmfd. ± 10%, 500 v. D-C
working, mica dielectric
Same as C17
Same as Cu
Same as C16
Capacitor, variable, min. cap. 2 mmfd., max.
cap. 6 mmfd., ceramic dielectric, .special mtg.
bracket, type B-820-202
Capacitor, variable, min. cap. 4 mmfd., max.
cap. 20 mmfd., ceramic dielectric, special mtg.
bracket, type B-820-304
Same as C30
Capacitor, variable, min. cap. 3.0 mmfd., max.
cap. 25 mmfd., air dielectric, ceramic insulat ion, type 22-7
Same as C14
Same as C17
Same as C14
Same as C16
Capacitor, fixed, 47 mmfd. ± 10%, 500 v. D-C
working, mica dielectric
Not used
Same as C14
Capacitor, fixed, 470 mmfd. ± 10%, 500 V. D-C
working, mica dielectric
Capacitor, fixed, one unit of dual unit, 40 mfd.
- 10 + 40%, 25 v. D-C working, electrolytic
(See C44 )
Same as C16
Capacitor, fixed, 5100 mmfd. ± 5%, 300 v. D-C
working, mica dielectric
Capacitor, fixed, one unit of dual unit, 10 mfd.
- 10 + 40%, 300 v. D-C working, electrolytic
(See C4l )
(Cont'd~)
MFR.
CONTR' S.
CODE
PART NO.
Cathode by-pass for tube V3
Screen by-pass for tube V3
Plate return by-pass for tube V3
A-V-C by-pass for tube V5
ASA
CM30A222K
Cathode by-pass for tube V5
Screen by-pass for tu~e V5
Plate return by-pass for tube V5
MED. XTAL crystal filter adjustment
CRL
44A079
SHARP XTAL crystal filter adjustment
CRL
44A078
SHARP I.F. crystal filter adjustment
CRYSTAL PHASING control
RC
48A039
ASA
a~40A470K
ASA
CM20A471K
SP
42A032
ASA
CM35A5l2J
FUNCTION
Grid return by-pass for tube V6
Cathode by-pass for tube V6
Screen by-pass for tube V6
Plate return by-pass for tube V6
Diode load by-pass for tube V7
R-F by-pass on grid of tube V7
Parasitic suppressor in plate of tube
V12
Cathode by-pass for tube VJ:2
Tone control, high frequency audio
shunt
Resonating capacitor for bass boost
Plate decoupling for tube V12
G.
REF.
SYMBOL
C48
C49
C50
C51
C52
C53
C54
C55
C56
C57
C58
C59
C60
C61
C62
C63
C64
C65
C66
C67
G68
liST OF REPLACEABLE PARTS - (Cont'd.)
NAME OF PART AND DESCRIPTION
Capacitor, fixed, 0.05 mfd. - 10 + 40%, 400 v. D-C
working, paper dielectric
Same as C45
Capacitor, fixed, one unit of dual unit, 40 mfd.
- 10 + 40%, 5 V. D-Cworking, electrolytic
(See C4S )
Capacitor, fixed, one unit of dual unit, 30 mfd.
- 10 + 40%, 400 V. D-C working, electrolyt ic
in same container with C47
Capacitor, fixed, 30 mfd. - 10 + 40%, 450 v. D-C
working, electrolyt ic, type D8290
Same as C14
Capacitor, fixed, 0.01 mfd. - 10 + 40%, 600 V.
D-C working, paper dielectric
Same. as C51
Same as C17
Same as C45
Capacitor, variable, compression type, 50 mmfd.
(nominal), mica dielectric, type SW-1530
Same as C16
Same as C14
Same as C17
·Same as C17
Same as C37
Capacitor, fixed, 250 mmfd. ± 20%, 500 v. D-C
working, mica dielectric, type 146S. Part of
transformer Tl • Shown for reference only.
Same as C14
Same as C17
Capacitor, fixed, 100 mmfd. ± 10%, 500
D-C
working, mica dielectric
Same as C14
Same as C17
Same as C16
Same as C37
v.
FUNCTION
MFR.
CODE
CONTRt S.
PART NO.
Coupling between tubes V12 and V14
SP
46AW503J
Coupling between tubes V12 and V13
Cathode by-pass for tubes V13 and
V14
SP
42A031
Plate power supply input filter cap- . SP
acitor
Audio coupling between diode of tube
V7 and grid of tube V12
A-C line by-pass capacitor
SP
42A030
Plate power supply output filter
capacitor
A-C line by-pass capacitor
A-N-L by-pass
Cathode by-pass for tube VIO
Resonating trimmer for inductor CH3
46AYI03J
SWI
53A012
ASA
CM20AIOlK
Plate return by-pass for tube Vg
Screen by-pass for tube V9
Cathode by-pass for tube V9
A-V-C by-pass for tube V9
Coupling between tube V3 and tube Vg
Coupling between tube V.3 and tube Vs
Screen by-pass for tube Vs
Cathode by-pass for tube V8
A-V-C diode load by-pass at tube V8
A-V-C by-pass for Bands 2,3,4,5 and 6
A-V-C by-pass for Band 1
Plate return by-pass for tube V8
Coupling between oscillator tube V4
and converter tubeV3
G.
REF.
SYMBOL
C74
C~5
C76
C77
C7S
C79
CSO
CSI
CS2
CS3
CS4
CS5
CS6
CS7
CS8
LIST OF REPLACEABLE PARTS - (Cont'd.)
NAME OF PARI' AND DESCRIPTION
Same as C37
Same as C25
Same as C64
Capacitor, variable, min. cap. 5 mmfd., max. cap.
25 mmfd., air dielectric, special
Capacitor, -fixed, 500 mmfd. :!: 5%, 500 V. D-C
working, silver mica, type 1469, Part of transformer T4 • Shown for reference only.
Capacitor, fixed, 0.01 mfd. -10 :!: 40%, 600 v. D-C
working, paper dielectric, braided leads, type AB
Capacitor, 2 mmfd., twisted leads
Same as C25
Same as C17
Not used
Not used
Not used
Not used
Not used
Capacitor, fixed, 2.5 mmfd. :!: 20% 500 V. D-C
working, bakelite dielectric
Not used
Not used
Same as C40
Capacitor, fixed, 0.25 mfd. - 10 + 40%, 200 V.
D-C working, paper dielectric
Capacitor, variable, min. cap. 4 mmfd., max.
cap. 20 mmfd., ceramic insulation, temp. coeff.
- 0.005 mmfd / mmfd/ 0 C., type 82Q-B
Same as C8S
Same as CS8
Same as CS8
Same as CS8
Same as CS8
Same as CSS
Same as C88 '
Same as CS8
MFR.
CODE
FUNCTION
CONTR'S.
PART NO.
Grid coupling for tube V4
Plate return by-pass for tube V4
Grid coupling for Tube VIl
B. F. O. control
RC
4SA06'4
Shunt capacitor across C72
A
47BT50lD
Plate by-pass for tube Vl l
SP
46A021
Coupling between tubes V7 and VII
"mpedance equalizer for transformer
TS
A-V-C by-pass for tube VI
Coupling between tubes V2 and V3 on
Band 5
Plate decoupling for tube V4
Cathode return by-pass
Trimmer for transformer T15
Trimmer
Trimmer
Trimmer
Trimmer
Trimmer
Trimmer
Trimmer
Trimmer
for
for
for
for
for
for
for
for
transformer
transformer
transformer
transformer
transformer
transformer
transformer
transformer
TI6
TI7
T18
TI9
T20
T21
122
T23
-49AOOI
SP -46AT254.T
CRL 44Al02
G.•
REF.
STIffiOL
LIST OF REPLACEABLE PARTS - (Cont'd.)
NAME OF PART AND DESCRIPTION
YVNCTION
MFR.
CODE
CONTR'S.
PART NO.
Trimmer for transformer T24
Same as CSS
Trimmer for transformer T25
Same as CSS
Trimmer for transformer T26
Same as CSS
Sa:rne as CSS
Trimmer for transformer T27
Same as CSS
Trimmer for transformer T28
Trimmer for transformer T29
Sa:rne as CSS
Same as CSS
Trimmer for transformer T30
Capcitor, fixed, 275 mmfd., silver mica. Part
{ Primary capacitor of Transformer Tl
of transfOrnler Tl' Shown for reference only.
Secondary capacitor of transformer Tl
Capacitor, fixed, 125 mmfd., silver mica. ,Part
Primary capacitor of transformer T2
of transfornler T'2' Shown for reference only.
Capacitor, fixed, 85 mmfd., silver mica. Part
Secondary capacitor of transformer T2
of transformer T2 , Shown for reference only.
Capacitor assembly; fixed capacitor, 25 mmfd. ±
5%, silver mica; variable capacitor, min. cap.
70 mmfd., max. cap. 90 mmfd.,- ceramic dielec[ Primary trimmer of transformer T.3
Secondary trimmer of transformer T3
tric; both capacitors connected in parallel to
form assembly. Part of transformer T3 , Shown
for.refere~ce only.
Capacitor, variable, compression type,
trimm~r of transformer T5
(nominal), mica dielectric. Part of ~~a:~~~er ffrimary
t~econdary trimmer for transformer T5
T5 • Shown for reference only.
Capacitor, fixed, 100 mmfd. ± 10%, 500 v. D-C
Primary capacitor of transformer T6
working, mica. Part of transformer T6 , Shown
for reference only
Capacitor, fixed, 25 mmfd. ± 10%, 500 v. D-C
Secondary capacitor of transformer T6
working, mica. Part of transformer T6, Shown
for reference only
Transformer, I-F, 455KC, primary and secondary
tuned by adjustable iron core, secondary has
expander winding, special.
Transformer, I-F, 55KC; primary and secondary
tuned by adjust able iron core, secondary tapped
for crystal filter and variable band width,
primary has expander winding, special
Coupling between converter V3 and 1st
i-f amplifier V5
SI
50B082
Coupling and filter between i-f amplifier tubes Vo and V6
SI
50BOSI
G. LIST OF REPLACEABLE PARTS - (Cont'd.)
REF.
SYMBOL
TIO
Tll
T12
T13
T14
T15
T16
MFR.
CODE
N.MrE OF PART AND DESCRIPTION
FUNCTION
Transformer, I-F, 455KC, primary and secondary
tuned by variable capacitor, iron core coils,
type 3365
Transformer, 455KC, tuned by adjustable iron
core, special
Transformer, I-F, 55KC, primary and secondary
tuned by variable capacitor, iron core coils
special
Transformer, I-F, 455KC, primary tuned by adjustable iron core, secondary untuned air core,
special
Transformer, power, standard; primary, 117 V. A-C,
single phase, 50/60 cycles; secondary, 580 V.
A-C @ 185 rna., center t appedj 6.3 V. A-C @ 5.5
amperes, 5 V. A-C @ 3 amperes, type 6K53
Transformer, power, universal; primary, 117/230 V.
A-C, single phase, 50/60 cycles; secondary-same
as standard transformer, type 9G62
Transformer, A-Fj primary, 10,000 ohm winding cent er t appedj secondary, 5000 ohm winding tapped
at 500 and 100 ohms, iron core,type 3A347
Transformer, R-F, range 3.0-5.8 megacycles, air
core, special
Transformer, R-F, range 5.8-11.5 megacycles, air
core, special
Transformer, R-F, range 10.5-21 megacycles, air
core, special
Transformer, R-F, range 21-43 megacycles, air
core, special
Transformer, R-F, range. 55-1. 6 megacycles,. air
core, special
Transformer, R-F, range, 1.6-3.0 megacycles, air
core, special
Transformer, R-F, range, 3.0-5.S megacycles, adjustable iron core, special
Transformer, R-F, range 5.8-11.5 megacycles, adjustable iron core, special
Coupling between i-f amplifier tube
V6 and diode of 2nd detector tube
CONTR'S.
PART NO.
SWl
50B083
Beat frequency oscillator inductance
8WI
54B014
Coupling between
VlO
8WI
50B097
8WI
50B080
GT
52B03-3
GT
5'2B034
Couples a-f amplifier to load.
GT
55B009
Coupling between
for Band 3
Coupling between
for Band -4
Coupling between
for Band 5
Coupling between
for Band 6
Coupling between
for Band 1
Coupling between
for Band 2
Coupling between
for Band 3
Coupling between
for Band 4
antenna and tube VI
SWI
5lB568
antenna and tube Vl
8WI
5lB569
antenna and tube VI
8WI
51B570
antenna and tube VI
SWI
5lB571
,
antenna and tube Vz
8WL
5lB566
Vz
8m
5lB567
tube VI and tube V z
8WI
51B572
tube VI and tube V2
SWl
5lB573
V.,
~N-L
tubes Vg and
Coupling for A-V-C amplifier tube Vs
Filament and plate power
tra~sformer
antenna and tube
G.
REF.
SYMBOL
T17
T18
T19
T20
T2l
T22
T23
ro
m
T24
T25
T26
T27
T 28
T29
T30
LIST OF REPLACEABLE PARTS - (Cont'd.)
NAME OF PART AND DESCRIPTION
MFR.
CODE
FUNCTION
Transformer, R-F, range 10.5-21 megacycles, adjustable iron core, special
Transformer, R-F, range 21-42 megacycles, adjustable iron core, special
Transfprmer, R-F, range .55-1.6 megacycles, adjustable iron core, special
Transformer, R-F, range 1.6-3.0 megacycles, adjustable iron core, special
Transformer, R-F, range 3.0-5.8 megacYQles, adjustableiron core, special
Transformer, R-F, range 5.8-11.5 megacycles adjustable iron core, special
Transformer, R-F, range 10.5-21 megacycles, adjustable iron core, special
Transformer, R-F, range 21-4'2 megacycles, adj ustable iron core, special
Transformer, R-F, range,.55-l.6 megacycles, adjustable iron core, special
Transformer, R-F, range 1.6-3.0 megacycles, adjustable iron core, special
Transformer, R-F, range 3-5.8 megacycles, adjustable iron core, special
Transformer, R-F, range 5.8~11.5 megacycles, adjustable iron core, special
Transformer, R-F, range 10.5-21 megacycles, adjustable iron core, special
Transformer, R-F, range 21-42 megacycles, adjustable iron core, special
Coupling between tube VI
for Band 5
Coupling .between tube VI
for Band 6
Coupling between tube V2
for Band 1
Coupling between tube V2
for Band 2
Coupling between tube V2
for Band 3
Coupling between tube V2
for Band 4
ing between tube V2
for Band 5
Coupling between tube V2
for Band 6
Oscillator coil for Band
Inductor, 13 henries ± 10%, @ 100 milliamperes
D-C, d-c resistance 300 ohms ± 10%, iron core,
type lD25
Inductor, 4 henries ± 10% d-c reslstance 220 ohms
± 10%, iron core, type lOC5
.
Inductor, universal winding, iron core, designed
to resonate at 455KC with 47 rnrnfd. ± 7% across
the coil, type 774
CONI'R'S.
PART NO.
and tube V2
SWI
5lB574
and tube V2
SWI
5lB575
and tube V3
SWI
5lB576
and tube V3
SWI
5lB577
and tube V3
SWI
5lB578
and tube V3
sm
5J.B579
and tube V3
SWI
5lB580
and tube V3
SWI
5lB581
1
swr
51B582
Oscillator coil for Band 2
5lB583
Oscillator coil for Band 3
swr
swr
5lB584
Oscillator coil for Band 4
SliI
5lB585
Oscillator coil for Band 5
swr
518586
Oscillator coil for Band 6
SWI
51B587
Plate supply filter choke
GT
56B008
Bass boost choke
ST
55AOIO
A-N-L wave trap coil
swr
53B012
G.
REF.
SYMBOL
LIST OF REPLACEABLE PARTS - (Cont'd.)
FUNCTION
NAME OF PART AND DESCRIPTION
MFG.
CODE
CONTH'S.
PART NO.
Phonograph pickup connection
u
36B003
Headphone connect ion
u
36B011
A-C line overload protection
LF
39A320
Shorting plug for a-c operation
AP
35A003
Line cord
E
87A078
Socket, octal, female, low loss mica-filled bakelite insulation, type MIPST
Connection for D-C power supply
AP
6A042
Terminal strip, black bakelite, marked "A2" "AI",
special
Terminal strip, black bakelite, marked "5000",
special
Terminal strip, black bakelHe, marked "500",
special
Connection for antenna
H
SA039
Audio output connection for 5,000
ohm load
Audio output connection for 500 ohm
load
H
BA040
H
BA041
Meter 0,5 milliamperes, S.S ohms internal resistance, pointer swing 90 degrees, special mtg.
bracket, special
Carrier level indicator
BE
82A070
Crystal, frequency 455KC ± 5KC, type CF6
Cryst al filter
BL
19A1 23
OM
60B052
Jack, single circuit, switching type, single pole
double throw, 1 pair contacts normally closed,
bushing 3/8-32 x 5/16" long, type 503C
Jack, switching type, single pole double throw,
1 pair contacts normally closed, bushing 3/8-32
x 3/8" long, type ST-627A
Fuse, 1.5 amperes @ '250 V"
type 1041
4AG, glass enclosed,
Plug, octol, male, bakelite body, jumpers connect
terminals 6 and 7, and terminals 3 and 4, type
CP-8
Plug and line cord assemble, 2 conductor rubber
covered #18 copper stranded wire moulded rubber
plug at one end, length 6 feet
Switch, rotary selector, single section, 3 position, shorting type rotar contacts, bakelite
wafer, shaft 2-1/16" long x 1/4" dia. bushing
1/4" deep, type H
Carrier level meter SWitCh}
{ B-F-O switch
t
G.
REF.
SYMBOL
LIST OF REPLACEABLE PARTS - (Cont'd.)
NJlli1E OF PART AND DESCRIPTION
FUNCTION
SW~_l
Switch, SPST, toggle action t located on rear of
resistor R35
Swit ch, SPST, bat handle toggle, rated 3 amperes
@ 250 V., type 21350GA
1 Switch, DPST, toggle act ion, locat ed on the rear
of resistor R53
SW6
SW
7
} Same as SWI
SW4
SW
J
MFR.
CODE
CONTR'S.
PART NO.
Power switch
SEND-RECEIVE switch
HH
60Al03
Band switch, antenna stage
CM
62B025
Band switch, r-f amplifier stage
OM
62B013
Band switch, oscillator st age
OM.
6213015
A-V-C switch (gauged with band
switch)
OM
62B023
SELECTIVITY switch
OM·
60B048
BASS switch
HH
60.Al02
Illumination for band spread dial
GE
39A003
Illumination for main tuning dial
Illumination for meter scale
GE
39.A004
A-N-L switch
A- V~C- switch
A-V-C- switch
1
SWS-l
SW
S- 2 SWit.Ch, rot ary selector, 3 sect ion, 6 posit ion,
SWS- 3
bakelite wafers, sections are assembled to
SWS_4 J
strut s, type H
SWS- 5 1 Switch, rotary selector, 2 section; 6 position,
SWS_ 6
bakeli te .~afe~s ,~~c~ ions are assembled to
SWS_ 7
struts, vype .LSgGe HZ
'SW
1· Sa'7le as SWS- 5 ' SW8 - 6 and SWS-7
SWS- 10J
SWS - 11l Switch, rotary selector, 2 section, 6 position,
S~8-12~ ~~:~lite w~fers, sections are assembled to
SWS- 13 [ c ~ ~ ut s t yp to: H
Jo..,
.+ h
""
•
1
t .
~
.'
SW _ 1
u'I'[1 vCll, ro ~ary se.tector, slng e sec lon, 0 POSle w8- H }
tion, shorting type rotor contacts, bakelite
u
8
.
-~v
wafer, type 235S6-H
SW9_1 ISwitch, rotary selector, 3 section, 6 position,
SW 9_ 2 ~ short ing tyn.",e rotor, cont acts, bakelite wafers,
.SWg...3
shaft '2-3/8 VI long x 1/4" dia. bushing 1/4" deep,
,) type 22659-H3
Switch, SPDT, bat handle toggle, rated 1 ampere
@ 250 V. and 3 amperes @ 125V., type'20994KF
r
J
sw~=~
,~
I
Lamp 6.3 V. @ 250 milliamperes, bayonet base type
Band switch, converter stage
44
1M2
L'Vl3
S&'1le as LMI
Lamp, 6.3 V. @ 150 milliamperes,
47
bayon~t
base type
G.
REF.
SYMBOL
VI
V2
V3
V4
V5
V6
V7
Ve
Vg
VIO
VII
Vl2
V 13
V14
VIS
LIST OF REPLACEABLE PARTS - (Cont'd.)
FUNCTION
NAME OF PART AND DESCRIPTION
Tube, pentode type 6AB7
Tube, -triple-grid super-control amplifier, type
6SK7
Tube, multi-electrode pentagrid converter, type
6SM
Same as V3
Tube, multi-electrode pentagrid mixer amplifier,
type 6L7
Same as Y.2
Tube, duplex-diode pentode, type 6Be
Same as V7
Same as VI
Tube, twin diode, type 6H6
Tube, triode, type 6J5
Tube, twin triode, type 6SC7
Tube, beam power amplifier, type 6V6GT
Same as V 13
Tube, full wave high vacuum rect ifier; type !5Z3
MFR.
CODE
CONTR'S.
PART NO.
R-F amplifier
R-F amplifier
RCA
RCA
90X6AB7
90X6SK7
Converter
RCA
90X6SM
R-F oscillator
I-F amplifier
RCA
90X6L7
RCA
90X6Be
RCA
90X6H6
RCA
RCA
RCA
90X6J5
90X6SC7
90X6V6GT
RCA
90X5Z3
I-F amplifier
Detector and meter amplifier
A-V-C rectifier and amplifier
A-N-L noise amplifier
Noise rectifier and noise peak
limiter
B-F-O
Audio amplifier and phase inverter
Audio power amplifier
Audio power amplifier
Reet ifier
H.
SYMBOL
A
ASA
INDEX TO PARTS MANUFACTURERS
MANUFACTURER
SYMBOL
Aerovox Corp.
New Bedfora, Mass.
H
The Hallicrafters Co.
Chicago, Illinois
American Phenolic Corp.
Cicero. Illinois
HH
Hart & Hegeman Elec. Co.
Hartford, Conn.
Any manufacturer
IRC
the applicable
American St andard Assoc iation specification
International Resistance Co.
Philadelphia, Pa.
LF
Littlefuse Inc.
Chicago, Illinois
Beede Electrical Inst. Co.
Penacook, N. H.
OM
Oak Mfg. Co.
Chicago, Illinois
Bliley Electric Co.
Erie, Pa.
RC
Radio Condenser
Camden, N. J.
Chicago Molding Co.
Chicago, Illinois
RCA
R. C. A. Mfg. Co.
Harrison, N. J.
Centralab
Milwaukee, Wis.
SI
F.W. Sickles Co.
Springfield, Mass.
Clarostat Mfg. Co:.
Brooklyn, N. Y.
SP
Sprague Specialties Co.
North Adams, Mass.
Chicago Telephone Supply Co.
Elkhart, Ind.
ST
Standard Transformer Corp.
Chicago, Illinois
me~ting
BE
BL
CM
CRL
CS
CT.
MANUFACTURER
E
Essex Wire Co.
Chicago, Illinois
SWI
S. W. Inductor
Chicago, Illinois
GE
General Electric Co.
Schenectady, N.Y.
U
Utah Radio Products 00.
Chicago, Illinois
GT
General Transformer Corp.
Chicago, Illinois
UE
Underwood Elec. Co.
Chicago, Illinois
- 30 -
6AB7
(1853)
6SK7
G
6SA7
6SK7
6L7
SELECTIVITY
I.
2.
3.
4.
5.
6.
SWITCF
688
POSITIONS
I.F. BROAD.
I.F. MEDIUM BROAD.
I.F SHARP.
XTAL BROAD
XTAL MEDIUM.
XTAL SHARP.
METER
ZERO ADJ.
6SA7
GANGED WITH BAND SW.
SW7
~49
~59
TO HEATERS
SWIT CHES V7,
OPERATED BY BFO-AVC.
"
10
FREQUENCY
I.
2.
3.
4.
5.
6.
0.55MC.
1.6 MC.
3.0 MC.
5.B MC.
II.OMG.
21.0 MG.
sw
TONE CONTROL
BASS
PL,
RANGES.
TO
TO
TO
TO
TO
TO
1.6 MC.
3.0MG.
5.8 MG.
II.OMG
21.0MG.
43.0 MG.
AVG - BFO
SWITCH
LEFT CENTER RIGHT
SWI OPEN GLOSED GLOSED
SW6 OPEN CLOSED GLOSED
SW7 JJPEN CLOSED CLOSED
SW2 l)PEN OPEN
CLOSED
8
SHORTING
MUST BE
FOR A.C.
PLUG WHICH
IN SOCKET "p"
OPERATION.
~C51
FOR
270
6
D.C. OPERATION CONNECT
VOLTS + TO PIN 3, TO
+"
7, -
"
FIG. 13-SX28-A-,-SCHEMATIC
- 31 -
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