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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Page Count: 33

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

the co.

CHICAGO,

ILL.

, U. S. A.

Subject

TITIE

PAGE

TABLE

OF

CONTENTS

Page

1

TABLE

OF

CONTENTS

................................................................

2

A.

Installation

..

-.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

4

l.

Speaker

.......................................................................

4

2.

Antenna

.................

'.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

4

3.

Phono jack

....................................................................

4

4.

DC

power socket

......

_.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

4

5.

"S"

meter zero set

...

"

.......................................

'.

. . . . . . . . . . . . . . . . .

..

5

B.

Operation

.........................

:................................................

5

l.

Bandswitch

.........................................

_ . . . . . . . . . . . . . . . . . . . . . . . .

..

5

2.' Bandspread

..............

_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

5

3. Tone control

...................................................................

5

4. Send-Receive switch _

.................................

_ . . . . . . . . . . . . . . . . . . . . . . . .

..

5

5.

R.F. Gain control

.....

__

.........................

_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

5

6. Antenna trimmer

.......

_

......................................................

, 5

7.

A.

F.

gain controL

...

, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

5

8. Selectivity control

...............................................................

6

9.

Crystal Phasing

control....

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

6

10.

Automatic noise limiter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

6

11. "A VC-BFO" switch

.............................................................

6

12. Bass "IN-OUT" switch . .'. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

7

13. Head phone

jack.....

.

...

..

....

...

.

..

.

..

. . . .

..

.

..

.

.. ..

. .

..

..

. . .

..

.

..

. . . .

..

.

..

...

7

C.

Summary

of

related

circuits..

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

7

1.

The 2 stage preselector. . . . . .

....

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

7

2.

The oscillator and

converter......................................................

7

3.

The I F amplifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

7

4.

Variable selectivity

................................

'...............................

7

5.

Crystal filter circuit

............................................................

" 8

5a. Single signal adjustment

.....

-.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

8

5b.Crystal

.............................

_

......

_...................................

8

6.

Noise limiter

..................................................................

9

7.

A VC action

...................................................................

11

8.

"s"

or signal intensity meter

............................

_ . . . . . . . . . . . . . . . . . . . . . .

..

11

9.

The second detector

.........................................

, . . . . . . . . . . . . . . . . . .

..

11

10.

The beat frequency oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

11

11.

The audio amplifier

......

,

................

, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

11

12.

The power

supply.......................................

. . . . . . . . . . . . . . . . . . . . . .

..

11

13.

Specifications

.................................

_ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

11

D.

Receiver Alignment

.............

0

•••••••••

0

••••

0 • 0 0 0 • 0

••

0

•••••

0 0

••••

0 • 0

•••••

0 •

o.

0

••

0

12

l.

I.

F.

Alignment.

.......

0

••••

00

•••••••

0 • 0

•••

0 •

00

•••••

0

••

0 o

......

0 • 0 0 • • • • • • • • • • •

••

12

2.

BFO adjustment

.......

0

••••••

0 • 0 0 :

••••

0

••••••

0

••

0 • 0 0

.0

0 0 • 0

••••••••••••••

0

••

0 •

o.

12

3.

Noise limiter and AVC amplifier adjustment 0

•••

0

••••

0 0

•••

0 • 0

••

0

••••••

0 • 0

••••

o

....

0

••

12

4.

RoF.

and

OSC.

alignment

....

0

••••••••••••••••

0

••••

0 • 0

••••

o

.......

0

•••

0 0

•••••

0

•••

o.

Ii

:...

2 -

Subject

Page

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

6

Fig.

2-Crystal

filter schematic

....

' . . . . . . . . . .

..

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

8

Fig.

3-Single

signal operation

.............................

, . . . . . . . . . . . . . . . . . . . . . . .

..

8

Fig.

4-Crystal

selectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

8

Fig.

5-Noise

limiter

schematic......................................................

9

Fig.

6-Noise

limiter action

..............................................

'.

. . . . . . . .

..

10

Fig.

7-AVC

curve.

:

..............................................................

10

. Fig.

8-SX28-A

Top view

.........................................................

13

Fig.

9-SX28-A

Rear view . . . . . . . . . . . . . . . . . . . .

..

. . . . . . . . . .

..

. . . . . . . . . . . . . . . . . . . . .

..

13

Fig.

la-Audio

fidelity

curve.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

..

. . . . . . . . . . . . . . . . . .

..

14

Fig.ll-Audio

filter curve

...........................................................

14

Fig.

12-RF

and Oscillator adjustment location and alignment procedure

.....................

15

Fig.

13-SX28-A

Schematic

.........................................................

31

- 3 -

INSTRUCTION

BOOK

FOR

MODEL

SX-28-A

SUPER SKYRIDER

A INSTALLATION

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 uni-

versal 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%".

(1)

.

TERMINALS

AND

CONNECTIONS

ON

REAR

OF

RECEIVER

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 re-

ceiver,

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

con-

nected 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 in-

verted ','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

re-

ception.

A ground can be used

if

desired and should be con-

nected

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 prop-

erties 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 accu-

rate 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 crys-

tal

or magnetic pick-up arm should be used for

this

pur-

pose 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 bat-

tery 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 A

VC-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 perform-

ance.

The large calibrated main dial shows

the

frequencies

covered

throughout

the

6 band, 550 kc

to

43

mc fre-

quency 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

hand-

wheel

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 indi-

cated 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 capac-

ity

which

is

indicated by a setting

of

100

on

the

band-

spread 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 pur-

poses

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

de-

sired 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 indi-

cator moves vertically behind

both

the

main and band-

spread 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 fre-

quencies to the extent required by various receiving con-

ditions. 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

oper-

ating

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

SKY-

RIDER 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 selectiv-

ity

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. '

10,000

1000

o

I-

«

0::

I-

::>

a.

z

100

UJ

(!)

«

~

o

>

10

FIG.

1-1.

F.

SELECTIVITY

~

\ \ . 8'

\ \ \ I

J~

\ \ \ ,

'4..

, \ \

/...:

~\\

,/~II

-

0

\

I.LJ

I

~

\

4,.1

I

\

....;/

/

\

I'

,

~

a.

0:

ct

:r

(J)

II

La.:

-

,

1

U

I

\1

J

-30

-20

-10

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)

At

this

point,

it

is

suggested

that

the

CRYSTAL

SHARP

setting

be used

only

in

cases

of

extreme inter-

ference-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 opera-

tion

and

the

maximum

in

selectivity can be obtained

(crystal circuit discussed

in

detail in

the

summary

of

related circuits).

See

Fig.

3.

.

(9) 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 con-

I tributes

to

the

satisfactory operation

of

the

receiver by

limiting

objectionable interference caused by

ignition

systems

or

other

man made causes

of

electrical disturb-

ances.

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

op-

erating. 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

opera-

tion

'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 func-

tion.

The

A'VC

circuit should be operating for

the

recep-

tion

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 A VC

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 A

VC

OFF

posi-

tion. Remember that with the

receiver

operating with

no A

VC

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

con-

trolled, 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 accom-

panied

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 sug-

gested. 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

re-

ceiver,

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

posi-

tion 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

fre-

quencies 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

out-

put transformer.

The

signal in the headphones is

of

the

proper volume for satisfactory communications recep-

tion. Since no direct current is present

in

the

headphone

circuit crystal type phones can be used.

C

SUMMARY

OF

RELATED

CIRCUITS

(1)

THE

2-ST AGE 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 communi-

cations 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

fav-

orable signal to noise ratio and slightly increased

selec-

tivity.

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 vari-

ations 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 sig-

nal

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 humid-

ity

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

remem-

bered

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

trans-

formers 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

#4-

gready

increased sideband

cutting-more

pro-

no.unced crystal

"Slot"

for

interference-very

li

ttle

highs

present) .

6--Crystal

Sharrlposition

of

extreme

selectivity-

practically

no

sideband

content-very

pro-

nounced 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 SWITCH'

POSITIONS

(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

phas-

ing

adjustment

for

single signal

reception.

6SK1

(5)

CRYSTAL FILTER

CIRCU~T

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

YST

AL 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 C

30

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.

FIG. 3-'-SINGLE SIGNAL OPERATION

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

With Selective Switch in XTAL

two

amplitudes

and

adjust

the

BFO

can-

Sharp

position

identify

the

trol

to

a

tone

most pleasing

to

you.

This

weaker

amplitude-Tune

Re-

adjustment

for

single signal selectivity will ceiver

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.

hold

with

no

further

adjustment

unless

you

change

the

phasing

control.

(See

Fig.

3.)

FIG.

4-CRYST

AL

SELECTIVITY

..

..

XTAL XTAL

XTAL

..

r-

f-

r-

BIIOAD

MEDIUM

SHARP

ti.

~

..

III

-

..

! •

\

.L

•

..

/

/

"

I'--'

V

1\

" \

~V

• ,

lJ

• I\.

- -

-4

I

1-1"+1+1+'+4+1+'

.........

t'-

r\

-a

-4

-I -I

-I

411'"

+2

+1

+4

...

"

II

-5

-2

-I

455

+I

+1

.,

+4

KILOCYCLES OFF RESONANCE

8.

-

,(5b)

CRYSTAL '

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

.mount-

ing

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

YS-

TAL position

to

tune

as

broadly

as

pos-

sible. The capacity

of

the crystal holder

has been reduced

to.

a minimum through

the

use

of a specially,Jesigned polystyrene

hoider.

(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 fre-

quency and then fed

into

the

6L7 amplifier and 6B8 A VC

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 A

VC 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

secon-

dary 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 inter-

ference 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

allow-

ing

the

modulation peaks

of

the

carrier

to

become badly

distorted.

FIG.

5-NOISE

LIMITER

SCHEMATIC

6L7

688

C.

,

...

".,

"

..

••

"",

- 9 -

FIG.

6-NOISE

LIMITER

ACTION

COnstant tone signal no inter-

ference ANL OFF. Same Signal ANL OFF.

(Note

transient, peaks extend well be·

yond range

of

screen. Signal not

readahle. )

Same signal. Same noise.

-ANL-

ON adjusted for most favorable

signal to noise ratio.

If

the

noise

limiter

adjustment permits

too

great a

value

of

transient voltage

to

be

applied

to

the

6L7 injec-

tor

grid, detection

will

take

place and rectified compo-

nents

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

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

out-

put

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)

U)

&j

m

0

'"

0

+8

+4

0

-4

/

-8

/

-12

10

/ V

100

FIG.

7-A.V.C.

CURVE-AT

3 MC.

,,---

/

1000

10,000

100,000

1,000,000

MICROVOLTS INPUT

-

10

-

(7)

AVC

ACTION

A double A VC 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

between-

station

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

ampli-

tude 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

,,(~:)

where

El

= input voltage and

E~

=

output

voltage.

(9)

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 A

VC

purposes.

(10)

THE

BEAT FREQUENCY

OSCILLATOR

The

BFa

is turned on

with

the

switch

below

the

band-

spread 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 drop-

ping 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 re-

moves 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 me-

chanical 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 connec-

ted 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 por-

tion

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

am-

plifier.

(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

reduced-

increasing 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

approxi-

matelv

160

degrees F under normal conditions.

(13

)

Tubes:

SPECIFICATIONS

1~6AB7

1st RF Amplifier

1---6SK7 2nd RF Ampl ilier

16SA7

Mixer

1 _

..

6SA

7

HF

Oscillator

1 -6L 7 1st IF Amplifier Noise

Li

mi

ter

1-6SK7

2nd

IF

Amplifier

1-6B8

2nd Detector and S meter tll he

1--6B8 A

VC

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. 2 x 1000 x-

Selectivity-IF

broad

(high

fidelity) 12 kc

36

kc

IF

Sharp 4.1 kc

22

kc

Frequency Range

RF-Note:

These are

the

actual fre-

quencies covered corresponding to nominal figures in-

dicated 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

17

3;;"

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 posi-

tion ,55

to

1.6

band-RF

alignment depending on band

aligned.

Selectivity control

at

sharp

IF-~nd-Receive

switch

in

Receive---Crystal phasing

at

#3

on left

side-ANL--

OFF

at

o-A

VC OFF.

Important:

Have bandspread control so logging scale

reaas 100.

Antenna trimmer adjusted for Maximum gain

at

each.

RF alignment point on. all bands.

(1)

455

KC-IF

Alignment:

Tune main dial to 1400 kc on

.55

to

l.(5.mcband. Connect

the

hot

lead from

the

signal

genera

tot

to

6SA

7 mixer terminal

IS-Ground

to

chassis.

Roughly

adjust

the

aligning screws of

Tl,

the

lower

screw

of

which

is accessible

through

hole in

right

mount-

ing

bracket, for maximum gain.

Now

adjust lower screw

on T2

(do

not

adjust upper screw). Also adjust

C31

and

the air trimmer condensers at the top of

T3

for maximum

gain. (See

Fig.

8 for location of IF adjustments)

Switch

to

Crystal Broad

Position-Turn

on BFO and

adjust

to

a tone

of

about 1000 cycles. Vary

the

frequency

of

the

signal generator

while

adjusting the

top

screw on

1'2 until

the

4)utput goes

through

a maximum, dips down

and starts going

up

again. Adjust

th!!

phasing control

for maximum selectivity and then back off

the

top

screw

on

T2 until

the

output

reaches a minimum value between

the

tWo

maximum values first noted. The frequency

of

the

signal generator should be varied over a small range

while

adjusting

the

top

screw

of

T2. A swishing note,

in.

contrast

to

the usual sharp crystal tone will be ap-

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 be-

tween the

"Sharp"

and

"Broad"

positions.

Switch again

to

"Xtal

Sharp"

and set the signal gen-

erator

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

trans-

formers

as

earlier described in

the

6rst paragraph

of

these

instructions.

(2)

BFa

Adjustment: Set front panel control

to

zero-BFa

switch

ON-Signal

Generator tuned

to

crystal frequency

-selectivity

switch in

IF

Sharp

position-now,

adjust

screw on

top

of T4, after loosening lock nut,

to

zero best.

(See

Fig.

8)

(3)

Noise

Limiter

and

A VC

A~plifier

Adjustment: Have

the Controls .set

as

before except

that

the

A

VC

switch is

now

in

the

ON

position. Connect a

high

resistance type

.voltmeter across R49

which

is connected between termi-

nal

#5

of the

6L7

tube and

cru;,ssis.

Connect a 50,000

(P

ohm

resistor across primary

ofTS

(Rec1and 'Blue leads). .

Set generator

at

455

~c

as

for

IF

alignment. Connect gen-

erat,?r to grid of 6AB7 tube

(pin

#4).

RotateANL control

all

the

way

to

the

right,

or

position

#9.

Adjust screws

on top-of T5 for maximum indication on DC meter coq-

n~ctea

across R47. Reconnect generator, as for

IF

align-

ment,

to

mixer grid

of

6SA

7·

tube .. RemQve 50,000

ohm

~sistor

which

was inserted across primary

of

T5

during

alignment. Remove grid clip off

top

of

6L7 tube.

With

generator set

at

455

kc and

ANL

control

at

extreme

right

adjust wave trap

trimmerC55

for

mi~imum

signal

~s

indicated on output meter. (See Fig. 8 and

Fig.

1:4

for

location of adjustments).

With

generator connected

to

6SA7

mixer grid

as

above,

replace 6L7 grid and turn

ANL

control

to

extreme left

until switch clicks. Connect

high

resistance DC meter

across

6BS

diode filter condenser C64. Adjust, screw

0.1'1

top

of

T6 for maximum indication on

DC

meter across

C64.

(4)

For RF and oscillator adjustment location and align-

ment procedure

see

Fig.,

12.

-

12

-

FIG.

8-SX28-A-

TOP

VIEW

6AB7(tJs\

)

9-SX28-A-REAR

VIEW

-

13

-

+10

o

(/)-10

..J

'"

~

-20

(,)

'"

0-

30

-40

-50

+15

+[0

+5

(/)

..J

0

'"

m

6

-5

'"

o

-10

-15

':'20

fP--

,

'~.

,

~

i--

30

I--

/

30

FIG.

10-AUDIO

FIDELITY

CURVE

,,"

BASS

IN"

-r--:. -

r...

1--0

~"""'--~

'"

'.

~.

"'"

....

"

,~

r\..

~~'

"

1\

~

.,\

I\.

"\

" I\.

\,

I\.

(I)

I.F.

BROAD-TONE

'CONTROL

ou,r

",-'

1\

(2)

I.F.SHARP-TONE

CONTROL

OUT

(3)

I.F.

SHARP-TONE

CONTROL

IN

100

1000

10,000

CYCLES

PER

SECOND

FIG.

ll-AUDIO

FILTERG:URVE

I 1

i""'1'-0

FREQUENCY

RESPONSE

WITH'

"-

BASS

SWITCH

IN

a

OUT-

""-6

SELECTIVITy-"CRYSTAL

SHARP"

, ,

~.r

14;

"

'"

.....

BASS

OUT

f'.. "

....

'\.

L,

,

~

\

1'

....

\

"'\

~

r---

I--

1\

'\

\

-\

100

1000

IOPOO

CYCLES

PER

SECOND

.;.

14

-

FIG

.

12-RF

AND OSC ADJUSTMENT LOCATION AND ALIGNMENT

PROCEDURE

R-F

AMP.

R-FAMP

C

aa

C

a9

C

90

C

91

57

5

10

5

,3

16

1ST oET.

'ST

OET.

C

94

C

95

C

9G

C

91

C

93

C

92

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

I

I

2

2

3

3

4

4

Rec

Dial

Setting

Sig

,

Gen,

Freq

,

Dummy

Antenna

HIGH

FREQTJENCY

E

;{

J

LOW

FREQUENCY

END

Adjust

Osc.

Adjust

Trimme-rs

Adjust

Osc

I

Permeability

With

for

Max.

Gain

With

Tuned

By _

1.

'65

me , 1.5 me 200 mmE C

9H

C92 •. • • • • I

. .6 200

mm

f .

..

. . . . . .

..

. . .

SI

I

S2

I 3.0 400

ohms

; C

99

Cn . . . . I

1.8

400

ohms

. . . . .

.. ..

. .

..

. S3 I 54

3.0

1.8

I 5.4 400

ohms

..

- C

I00

C

94

C

ss

. . . . I ........ '

..

. 3.0 400

ohms

....

.

r.

.

.......

I>

5 5 I

S6

5 7

5.4

3.0

10.0

7

.0

,

.

10.0

400

ohms

C

I01

C9

:\

C

89

. . . . I

7.0

400

ohms

.....

....

..

....

5 8 I 5 9

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

I S

12

S

13

6 36.0 36.0 400

ohms

C1

03

C

97

C91 . . • . I .

..

...... .

~

-

_

-

_6=

__

~

1

~_2_

4

._0

__

~

___

24

_.

_0

____

~~4~

00

~o~h~m~

s

~~

__

~

..

~

.

~

.

__

~

___

..

_._._. _

,,

_,_,

_,

__

~

___

S~14~

__

~

I

__

S~1

5

__

~

_

__

S~16~

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

~lOltage

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 6 7 8 Cap.

---

Vr6AB7 RF Amp.

(1)

. , . .. . .

..

0.1 4.15 170 6.3

227

. . . . . . .

V2-6SK7

RF

Amp.

(2)

. , . . .. 4.35 0.1 4.35 105 6.3

279

.......

I

~--

---

--------_.

V3-6SA7 Mixer

..

.

250

100 0.12 4.1 6.3

..

.

.......

---

V4

-6SA7

HFOsc.

..

.

..

. 116 116 0.3 _

..

6.3 116

.......

---

---

Va

-6L7

IF

Amp.

(1)

,-.075

Noise Limi ter

..

.

..

.

245

102

...

.

..

6.3 4

Va-6SK7

IF

Amp. 2

..

.

..

. 4 . , . 4 107.5 6.3

235

.......

V7

-6B8

2nd Det.

S Meter Tube

..

.

..

. 17.2

~.255

-.255

108 6.3

...

-.17

---

Vg

-6B8

AVC Amp. . , . .

..

225.5 0.2 0.2 107 6.3 2

.......

-

Vg-6AB7 Noise Amp. . , . .

..

...

.07 1.1 150 6.3 225 .

......

-

---

---

V

1o

-6H6 Noise Rectifier

..

. .

..

..

.

.1

..

.

17.6DL

6.3

-.1

.......

Vn-6J5 Beat Osc. . , .

..

.

140

..

.

-7.4

..

. 6.3

...

BFO

ON

ONLY

FOR TEST

V

12

-6SC7

1st Audio Amp.

..

. 140

..

.

...

137 0 1.4 6.3

..

.

.......

---

V

1s

-6V6GT P.P. Audio Amp. .. . .

..

310 290

..

. 198

DL

6.3

17

.......

V

14

-6V6GT P.P. Audio Amp. .. .

..

.

310

290

..

.

..

.

6_3

17

........

Rectifier * 320

340

AC

340

AC

320

V

Il

:,-5Z3

..

. .

..

..

.

..

.

.......

* 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

with-

out

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-

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 ob-

tained in advance by first

wrijng

the

Adjustment De-

partmertt,

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 obliga-

tion

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

-

16

-

REF.

SYMBOL

Rl

R2

R3

R4

R5

R6

&,

RS

R9

RIO

Rll

R12

R13

R14

R

15

I-}-

R16

',~

R17

R

IS

R19

R20

R21

R22

R23

R24

R25

R26

R27

H

2S

R29

R30

~l}

R32

G.

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

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

Same

as

R5

Same

as

RIO

Same

as

Rl

rvfI 1 .

Resiston,

470,000

ohm

.:t

lv/o,

"2

watt,

carbon

Resistor,

270

ohm:t

10%,

i

watt,

carbon

Same

as

R5

Same

as

RIO

Same

as

Rl

Same

as

%0

Resistor,

1,SOO

ohm

:t

10%,

i

watt,

carbon

Same

as

R20

Resistor,

100 ohm:t

10%"

i

watt,

carbon

35

Resistor,

variable,

500

ohm

:t

20%,

carbon,

type

25

Resistor,

27,000

ohm

:t

10%,

2

watt,

carbon

Resistor,

two

sect

ions;

sect

ion

#1

(R

3

;J.)

,

11,000

ohm

:t

10%,

Ii

watts;

section,2

(R

32)

4,000

ohm

±

10%,

7

watts;

met

al

clad,

wire

wound

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

V

2

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

Plate

decoupling

for

tube

V5

Grid

return

for

tube

V 6

Grid

return

for

tube

V6

Cathode

bias

for

tube

V6

Vol

tage

drop

for

screen

0 f

tube

V6

Plate

decoupling

for

tube

V6

Diode

load

for

tube

V7

Diode

load

for

tube

V

7

Cathode

bias

for

tube

V5

for

bands

3 and 5

A-V-C

decoupling

for

tube

V5

and

grid

isolation

for

tube

V

7

Carrier

level

meter

shunt

Carrier

level

meter,

zero

adjustment

Voltage

drop

for

plate

of

tube

V

7

Voltage

divider

for

screen

grids

of

tubes

V

2' V3' V

5' V

6' V

7 and

Vs

MFR. CONI'R'S.

CODE

PARI'

NO.

ASA

RC2IAEI04K

CT

25C066

ASA

RC2lAE33lK

ASA

RC31AE273K

ASA

RC2IAEI02K

ASA

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

REF.

SYMBOL

R33

R34

R35

R36

R37

R3a

R39

R

40

R41

R42

R43

R44

R45

R46

R47

R

4a

R

49

R50

%1

%2

R53

R54

R55

R56

R57

R5a

R

59

R60

R61

R62

R63

G.

LIST

OF

REPLACEABLE

PARTS

(Cont'd.)

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

R

40

Resi

st

or,

220

ohm

±

10%,

2

watt,

wire

wound,

type

BW2

Resistor,

20,000

ohm

±

5%,

2

watt,

carbon

Resistor,

5,000

ohm

±

20%,

10

watt,

wire

wound,

viterous

enamel,

type

CC

Same

as

R43

Same

as

R38

Resistor,

10

ohm

±

10%,

i

watt,

carbon

Same

as

Rl

Resistor,

I

megohm

± 10%, i

watt

carbon,

Resistor,

560

ohm

±

10%,

~

watt,

carbon

Resistor,

'20,000

ohm

±

5%,

1

watt,

carbon

Same

as

R38

Resistor,

variable,

50,000

ohm

±

20%,

carbon

with

DPST

switch,

type

WR-35

Resistor,

33

ohm

±

10%,

i

watt,

carbon

Same

as

R20

Same

as

R5

Same

as

Rl

Resistor,

180

ohm

±

10%,

i

watt,

carbon

Same

as

Rl

Same

as

R

40

Same

as

H

20

Same

as

R

20

•

Part

of

transformer

TI.

Shown

for

reference

only.

Same

as

RIO

FUNCTION

A.F.

gain

control

Cathode

bias

for

tube

V

12

TONE

control

Plate

load

for

tube

V12

Plate

load

for

tube

V12

Plate

decoupling

for

tube

V 12

Grid

return

for

tubes

V1

2'

V1

3 and

V

14

Grid

return

for

tube

V13

Grid

return

for

tube

V

14

Cathode

bias

for

tubes

V

13 and V

14 .

Load

for

primary

winding

of

trans-

former

Ta

.

'toad

for

secondary

of

transformer

Ta

during

headset

operation.

Plate

load

for

tube

Vn

Grid

return

for

tube

VII

Parasitic

suppressor

for

tube

V

4

Cathode

bias

for

tube

V

IO

Diode

load

for

A-N-L

tube

VIO

Plate

decoupling

for

tube

Vg

Screen

decoupling

for

tube

Vg

A-N-L

bias

voltage

divider

A-N-L

Control

Cathode

bias

for

tube

Vg

Grid

return

for

tube

Vg

Voltage

drop

for

screen

of

tube

Va

A-V-C

decoupling

for

tube

Vg

Cathode

bias

for

tube

Va

Diode

load

for

tube

Va

Diode

load

for

tube

Va

A-V-C

decoupling

for

r-f

stages

Grid

return

for

tube

Va

Plate

decoupling

fpr

tube

VA

MFR.

CODE

CONTR'S.

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

REF.

SYMBOL

R64

R65

R66

R67

R68

R69

R,o

~l

&'2

R73

~4

Cl

Cl.

1

......

C1.

2

fD

C

z

C2•1

C

Zo2

C

Z•3

~

C

3•1

C

3•2

C

3•3

C

4

C

4•1

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.}

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

Capacitor,

variable,

4

unit

gang

f

each

unit

con-

sists

of

2

sections,

except

unit

4

at

rear

which

contains

only

one

section

(section

#2),

air

di-

electric,

special;

Section

#I-min.

cap.

16.3

mmfd., max.

cap.

187.5

mmfd.

(C

l, C

1

l'

C1•2

);

Section

#2-min.

cap.

21. 5 mmfd., max:

cap.

250.0

mmfd.

(C

2, C2•l, C

2•2, C

2•3

).

Capacitor,

variable,

4

unit

gang,

each

unit

con-

sists

of

3

sections,

air

dielectric,

special;

Section

#I-min.

cap.

6 mmfd., max.

cap.

16

mmfd.

(C

3, C

3•1, C

3•2, C

3•3

);

Section

#2-min.

cap.

6.5

mmfd~,

max.

~ap.

2.5

mmfd.

(C

4, C

4•1, C

4•2, C

4

,3);

Sect

lon

#3-mmo

cap.

6.5

mmfd.,

max.

cap.

27

mmfd.

(C

5, C

5•1, C

5•2, C

5•3)

FUNCTION

A-V-C

decoupling

for

r-f

stages

Injector

grid

return

for

tube

V3

Grid

return

for

tube

V

4

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

V

4

Plate

load

for

tube

VI on Band 1

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

MFR.

CODE

CONTR'S.

PART

NO.

ASA

RC2lAE1'22K

ASA

RC3l.AE472K

RC

48B050

RC

48B051

N

o

REF.

SYMBOL

C

4•2

C

4•3

C

5

C5•1

C6

C

7

C

8

C

9

C

IO

Cll

C

12

C

13

C

14

C

15

C

16

C

17

C18

C

l9

C

20

C

21

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

NAME

OF

PART

AND

DESCRIPTION

.

Capacitor,

variable,

4

unit

gang,

each

unit

con-

sists

of

3

sect

ions,

air

dielectric,

special;

Section

#l-min;

cap.

mrofd., max.

cap.

16

mrnfd.

(C

3' C

3

.1'

C3•2' C

3•3

);

Section

#2-min.

cap.

6.5

mmfd.,

max.

cap.

2.5mmfd.

(C

4' C

4•1, C4•2, C

4•3

)j

Section

#3-min.

cap.

6.5

mmfd.,

max.

cap.

27

mmfd.

(C

5' C

5•1' C

5•2, C

5

.-

3)

Capacitor,

variabie,

min.

cap.

.5

mmfd., max.

cap.

50

mmfd.,

air

dielectric,

ceramic

insula-

tion,

type

22

Capacitor,

2980

mmfd.

adjustable

±

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capacitor,

2400 mmfd.

adj

ustable

:!:

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capacitor,

2240

mmfd.

adjustable

:!:

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capacitor,

1700

mmfd.

adjustable

±

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capaci

tor,

8'22 mmfd.

adjustable

±

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capacitor,

541

mmfd.

adjust

able

:!:

5%,

mica

di-

electric,

steel

mtg.

frame,

special

Capacitor,

adjustable,

5 mmfd. ±

0.2

mmfd.

at

25

0

C.,

capacity

change

-0.02

mmfd.

per

0

C.,

type

8-2739

Capacitor,

0.02

mfd.

-10

+ 40%,

400

V.D-C

work-

ing,

paper

dielectric

Same

as

C

14

Capacitor,

fixed,

0.02

mfd.

-

10

+ 40%,

600

v.

D-C

working,

paper

dielectric

Capacitor,

fixed,

0.05

mfd.

-

10

+ 40%,

200

V.

D-C

working,

paper

dielectric

Same

as

C14

Same

as

C

14

Same

as

C

16

Same

as

C17

FUNCTION

R-F

amplifier

stage

bandspread

tun-

ing

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

Oscillator

padding

for

Band 6

Oscillator

padding

for

Band 5

Osc

illator

padding

for

Band 4

Os~illator

padding

for

Band

3

Oscillator

padding

for

Band

2

Oscillator

padding

for

Band

1

Temperature

compensating

capacity

for

oscillator

Cathode

by-pass

for

tube

VI

Screen

by-pass

for

tube

VI

Plate

return

by-:-pass

for

tube

VI

A-V-C

by-pass

for

tube

VI

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

MFR.

CODE

RC

RC

UE

UE

UE

UE

UE

UE

SP

SP

SP

CONTR'S.

PARI'

NO.

48B051

48A053

44BIIO

44BI09

44BI08

44BI07

44BI06

44BI05

44A06'2

46AW203J

46AY.203J

46AU503J

REF.

SYMBOL

C

22

C23

C

24

C25

C26

C

27

C28

C29

C

30

C

3l

N C

32

I-'

C

33

C

34

C

35

C

36

C

37

C

38

C

39

C

40

C'4l

C

42

C

43

C

44

G.

LIST

OF

REPLACEABLE

PARTS

-

(Cont'd~)

NAME

OF

PART

AND

DESCRIPI'ION

Same

as

C

14

Same

as

C

14

Same

as

C

16

Capacitor,

fixed,

2200

mmfd.

±

10%,

500

v.

D-C

working,

mica

dielectric

Same

as

C

17

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

C

30

Capacitor,

variable,

min.

cap.

3.0

mmfd., max.

cap.

25 mmfd.,

air

dielectric,

ceramic

insula-

t

ion,

type

22-7

Same

as

C

14

Same

as

C

17

Same

as

C14

Same

as

C

16

Capacitor,

fixed,

47

mmfd.

±

10%,

500

v.

D-C

working,

mica

dielectric

Not

used

Same

as

C

14

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

C

16

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 C

4l

)

FUNCTION

Cathode

by-pass

for

tube

V3

Screen

by-pass

for

tube

V3

Plate

return

by-pass

for

tube

V3

MFR.

CODE

CONTR

'

S.

PART

NO.

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

RC

48A039

CRYSTAL

PHASING

control

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

V

7

ASA

a~40A470K

R-F

by-pass

on

grid

of

tube

V

7

Parasitic

suppressor

in

plate

of

tube

ASA

CM20A471K

V

12

Cathode

by-pass

for

tube

VJ:2

SP 42A032

Tone

control,

high

frequency

audio

shunt

Resonating

capacitor

for

bass

boost

ASA

CM35A5l2J

Plate

decoupling

for

tube

V12

REF.

SYMBOL

C

48

C

49

C

50

C

51

C

52

C

53

C

54

C

55

C

56

C

57

C

58

C59

C

60

C

61

C

62

C

63

C

64

C

65

C

66

C

67

G

68

G.

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

C

45

Capacitor,

fixed,

one

unit

of

dual

unit,

40

mfd.

-

10

+

40%,

5

V.

D-Cworking,

electrolytic

(See

C

4S

)

Capacitor,

fixed,

one

unit

of

dual

unit,

30

mfd.

-

10

+

40%,

400

V.

D-C

working,

electrolyt

ic

in

same

container

with

C

47

Capacitor,

fixed,

30

mfd. -

10

+ 40%,

450

v.

D-C

working,

electrolyt

ic,

type

D8290

Same

as

C

14

Capacitor,

fixed,

0.01

mfd.

-

10

+

40%,

600

V.

D-C

working,

paper

dielectric

Same.

as

C

51

Same

as

C17

Same

as

C

45

Capacitor,

variable,

compression

type,

50

mmfd.

(nominal),

mica

dielectric,

type

SW-1530

Same

as

C16

Same

as

C

14

Same

as

C

17

·Same

as

C

17

Same

as

C

37

Capacitor,

fixed,

250

mmfd. ± 20%,

500

v.

D-C

working,

mica

dielectric,

type

146S.

Part

of

transformer

Tl• Shown

for

reference

only.

Same

as

C

14

Same

as

C

17

Capacitor,

fixed,

100

mmfd. ± 10%,

500

v.

D-C

working,

mica

dielectric

Same

as

C

14

Same

as

C17

Same

as

C16

Same

as

C

37

FUNCTION

MFR.

CODE

Coupling

between

tubes

V12

and

V

14

SP

Coupling

between

tubes

V1

2

and

V1

3

Cathode

by-pass

for

tubes

V

13

and

SP

V

14

Plate

power

supply

output

filter

capacitor

Plate

power

supply

input

filter

cap-

. SP

acitor

Audio

coupling

between

diode

of

tube

V7

and

grid

of

tube

V

12

A-C

line

by-pass

capacitor

SP

A-C

line

by-pass

capacitor

A-N-L

by-pass

Cathode

by-pass

for

tube

VIO

Resonating

trimmer

for

inductor

CH

3

SWI

Plate

return

by-pass

for

tube

Vg

Screen

by-pass

for

tube

V 9

Cathode

by-pass

for

tube

V 9

A-V-C

by-pass

for

tube

V 9

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

ASA

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

V

4

and

converter

tubeV

3

CONTRt

S.

PART

NO.

46AW503J

42A031

42A030

46AYI03J

53A012

CM20AIOlK

REF.

SYMBOL

C

74

C~5

C

76

C77

C

7S

C

79

C

SO

CSI

C

S2

C

S3

C

S4

C

S5

C

S6

C

S7

C

S8

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

NAME

OF

PARI'

AND

DESCRIPTION

Same

as

C

37

Same

as

C

25

Same

as

C

64

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

trans-

former

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

C

40

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

C

8S

Same

as

C

S8

Same

as

C

S8

Same

as

C

S8

Same

as

C

S8

Same

as

C

SS

Same

as

C

88'

Same

as

C

S8

FUNCTION

Grid

coupling

for

tube

V4

Plate

return

by-pass

for

tube

V

4

Grid

coupling

for

Tube V

Il

B.

F.

O.

control

Shunt

capacitor

across

C

72

Plate

by-pass

for

tube

V

ll

Coupling

between

tubes

V

7 and

VII

"mpedance

equalizer

for

transformer

TS

A-V-C

by-pass

for

tube

VI

Coupling

between

tubes

V

2 and

V3

on

Band 5

Plate

decoupling

for

tube

V4

Cathode

return

by-pass

Trimmer

for

transformer

T15

Trimmer

for

transformer

TI6

Trimmer

for

transformer

TI7

Trimmer

for

transformer

T18

Trimmer

for

transformer

TI9

Trimmer

for

transformer

T20

Trimmer

for

transformer

T21

Trimmer

for

transformer

122

Trimmer

for

transformer

T23

MFR.

CODE

CONTR'S.

PART

NO.

RC

4SA06'4

A 47BT50lD

SP 46A021

-49AOOI

SP

-46AT254.T

CRL

44Al02

REF.

STIffiOL

G

.•

LIST

OF

REPLACEABLE

PARTS

-

(Cont'd.)

NAME

OF

PART

AND

DESCRIPTION

Same

as

C

SS

Same

as

C

SS

Same

as

C

SS

Sa:rne

as

C

SS

Same

as

C

SS

Sa:rne

as

C

SS

Same

as

C

SS

Capcitor,

fixed,

275 mmfd.,

silver

mica.

Part

of

transfOrnler

Tl'

Shown

for

reference

only.

Capacitor,

fixed,

125 mmfd.,

silver

mica.

,Part

of

transfornler

T'2'

Shown

for

reference

only.

Capacitor,

fixed,

85

mmfd.,

silver

mica.

Part

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-

tric;

both

capacitors

connected

in

parallel

to

form

assembly.

Part

of

transformer

T3,

Shown

for.refere~ce

only.

YVNCTION

Trimmer

for

transformer

T24

Trimmer

for

transformer

T25

Trimmer

for

transformer

T

26

Trimmer

for

transformer

T27

Trimmer

for

transformer

T28

Trimmer

for

transformer

T29

Trimmer

for

transformer

T30

{

Primary

capacitor

of

Transformer

Tl

Secondary

capacitor

of

transformer

Tl

Primary

capacitor

of

transformer

T2

Secondary

capacitor

of

transformer

T2

[

Primary

trimmer

of

transformer

T.3

Secondary

trimmer

of

transformer

T3

MFR.

CODE

Capacitor,

variable,

compression

type,

(nominal),

mica

dielectric.

Part

of

T5•

Shown

for

reference

only.

~~a:~~~er

ffrimary

trimm~r

of

transformer

T5

t~econdary

trimmer

for

transformer

T5

Capacitor,

fixed,

100

mmfd.

±

10%,

500

v.

D-C

working,

mica.

Part

of

transformer

T6,

Shown

for

reference

only

Capacitor,

fixed,

25

mmfd.

±

10%,

500

v.

D-C

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

Primary

capacitor

of

transformer

T6

Secondary

capacitor

of

transformer

T6

Coupling

between

converter

V3

and

1st

SI

i-f

amplifier

V5

Coupling

and

filter

between

i-f

amp-

SI

lifier

tubes

Vo

and

V6

CONTR'S.

PART

NO.

50B082

50BOSI

REF.

SYMBOL

T

IO

Tll

T12

T

13

T14

T

15

T16

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

N.MrE

OF

PART

AND

DESCRIPTION

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

ad-

justable

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

cen-

t

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,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

5.8-11.5

megacycles,

ad-

justable

iron

core,

special

FUNCTION

Coupling

between

i-f

amplifier

tube

V6

and

diode

of

2nd

detector

tube

V.,

Beat

frequency

oscillator

inductance

Coupling

between

~N-L

tubes

Vg

and

VlO

Coupling

for

A-V-C

amplifier

tube

Vs

Filament

and

plate

power

tra~sformer

Couples

a-f

amplifier

to

load.

Coupling

between

antenna

and

tube

VI

for

Band 3

Coupling

between

antenna

and

tube

Vl

for

Band

-4

Coupling

between

antenna

and

tube

VI

for

Band 5

Coupling

between

antenna

and

tube

VI

for

Band 6

Coupling

between

antenna

and

tube

V

z

for

Band 1

Coupling

between

antenna

and

tube

Vz

for

Band 2

Coupling

between

tube

VI and

tube

Vz

for

Band 3

Coupling

between

tube

VI and

tube

V

2

for

Band 4

MFR.

CODE

CONTR'S.

PART

NO.

SWl

50B083

8WI 54B014

8WI

50B097

8WI 50B080

GT

52B03-3

GT

5'2B034

GT

55B009

SWI

5lB568

8WI

5lB569

8WI 51B570

SWI

5lB571

,

8WL 5lB566

8m

5lB567

8WI 51B572

SWl

5lB573

ro

m

REF.

SYMBOL

T17

T18

T19

T

20

T2l

T22

T23

T24

T25

T26

T27

T28

T29

T30

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

NAME

OF

PART

AND

DESCRIPTION

Transformer,

R-F,

range

10.5-21

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

21-42

megacycles,

ad-

justable

iron

core,

special

Transfprmer,

R-F,

range

.55-1.6

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

1.6-3.0

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

3.0-5.8

megacYQles,

ad-

justableiron

core,

special

Transformer,

R-F,

range

5.8-11.5

megacycles

ad-

justable

iron

core,

special

Transformer,

R-F,

range

10.5-21

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

21-4'2

megacycles,

ad-

j

ustable

iron

core,

special

Transformer,

R-F,

range,.55-l.6

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

1.6-3.0

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

3-5.8

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

5.8~11.5

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

10.5-21

megacycles,

ad-

justable

iron

core,

special

Transformer,

R-F,

range

21-42

megacycles,

ad-

justable

iron

core,

special

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

FUNCTION

MFR.

CODE

CONI'R'S.

PART

NO.

Coupling

between

tube

VI

and

tube

V2

SWI

5lB574

for

Band 5

Coupling

.between

tube

VI and

tube

V

2

SWI

5lB575

for

Band 6

Coupling

between

tube

V2

and

tube

V3

SWI

5lB576

for

Band 1

Coupling

between

tube

V2 and

tube

V3

SWI

5lB577

for

Band 2

Coupling

between

tube

V

2

and

tube

V3

SWI

5lB578

for

Band 3

Coupling

between

tube

V2 and

tube

V3

sm

5J.B579

for

Band 4

ing

between

tube

V2

and

tube

V3

SWI

5lB580

for

Band 5

Coupling

between

tube

V

2 and

tube

V3

SWI

5lB581

for

Band 6

Oscillator

coil

for

Band 1

swr

51B582

Oscillator

coil

for

Band 2

swr

5lB583

Oscillator

coil

for

Band 3

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

REF.

SYMBOL

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

NAME

OF

PART

AND

DESCRIPTION

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"

4AG,

glass

enclosed,

type

1041

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

Socket,

octal,

female,

low

loss

mica-filled

bake-

lite

insulation,

type

MIPST

Terminal

strip,

black

bakelite,

marked

"A2"

"AI",

special

Terminal

strip,

black

bakelite,

marked

"5000",

special

Terminal

strip,

black

bakelHe,

marked

"500",

special

Meter

0,5

milliamperes,

S.S

ohms

internal

re-

sistance,

pointer

swing 90

degrees,

special

mtg.

bracket,

special

Crystal,

frequency

455KC

±

5KC,

type

CF6

Switch,

rotary

selector,

single

section,

3

posi-

tion,

shorting

type

rotar

contacts,

bakelite

wafer,

shaft

2-1/16"

long

x

1/4"

dia.

bushing

1/4"

deep,

type

H

FUNCTION

Phonograph

pickup

connection

Headphone

connect

ion

A-C

line

overload

protection

Shorting

plug

for

a-c

operation

Line

cord

Connection

for

D-C

power

supply

Connection

for

antenna

Audio

output

connection

for

5,000

ohm

load

Audio

output

connection

for

500

ohm

load

Carrier

level

indicator

Cryst

al

filter

{

Carrier

level

meter

SWitCh}

B-F-O

switch

MFG.

CODE

u

u

LF

AP

E

AP

H

H

H

BE

BL

OM

CONTH'S.

PART

NO.

36B003

36B011

39A320

35A003

87A078

6A042

SA039

BA040

BA041

82A070

19A1t23

60B052

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

REF.

SYMBOL

SW

4

NJlli1E

OF

PART

AND

DESCRIPTION

Switch,

SPST,

toggle

action

t

located

on

rear

of

resistor

R35

Swit

ch,

SPST,

bat

handle

toggle,

rated

3

amperes

@

250

V.,

type

21350GA

SW

1

Switch,

DPST,

toggle

act

ion,

locat

ed

on

the

rear

SW~_l

J

of

resistor

R53

SW

6 }

SW

7 Same

as

SW

I

SWS-l 1

SW

S-2 SWit.Ch,

rot

ary

selector,

3

sect

ion,

6

posit

ion,

SWS-

3

bakelite

wafers,

sections

are

assembled

to

SW

S_4 J

strut

s,

type

H

SW

S-5 1

Switch,

rotary

selector,

2

section;

6

position,

SW

S_6 r

bakeli

te

.~afe~s

,~~c~

ions

are

assembled

to

SW

S_7 J

struts,

vype

.LSgGe HZ

'SW

sw~=~

1·

Sa'7le

as

SW

S-5'

SW

8-6

and

SWS-7

SWS-

10J

SW

S-

11

l

Switch,

rotary

selector,

2

section,

6

position,

S~8-12~

~~:~lite

w~fers,

sections

are

assembled

to

SW

S-

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

POSl-

e

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

I

shaft

'2-3/8

VI

long

x

1/4"

dia.

bushing

1/4"

deep,

,)

type

22659-H3

1M2

L'Vl3

Switch,

SPDT,

bat

handle

toggle,

rated

1

ampere

@

250

V.

and

3

amperes

@

125V.,

type'20994KF

Lamp

6.3

V. @

250

milliamperes,

bayonet

base

type

44

S&'1le

as

LMI

Lamp,

6.3

V. @

150

milliamperes,

bayon~t

base

type

47

FUNCTION

Power

switch

SEND-RECEIVE

switch

A-N-L

switch

A-

V~C-

switch

A-V-C-

switch

Band

switch,

antenna

stage

Band

switch,

r-f

amplifier

stage

Band

switch,

converter

stage

Band

switch,

oscillator

st

age

A-V-C

switch

(gauged

with

band

switch)

SELECTIVITY

switch

BASS

switch

Illumination

for

band

spread

dial

Illumination

for

main

tuning

dial

Illumination

for

meter

scale

MFR.

CODE

CONTR'S.

PART

NO.

HH

60Al03

CM

62B025

OM

62B013

OM.

6213015

OM

62B023

OM·

60B048

HH

60.Al02

GE

39A003

GE

39.A004

REF.

SYMBOL

VI

V2

V3

V4

V5

V6

V7

Ve

Vg

V

IO

VII

V

l2

V

13

V

14

VIS

G.

LIST

OF

REPLACEABLE

PARTS

-(Cont'd.)

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

V

7

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

R-F

amplifier

R-F

amplifier

Converter

R-F

oscillator

I-F

amplifier

I-F

amplifier

FUNCTION

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

MFR.

CODE

RCA

RCA

RCA

CONTR'S.

PART

NO.

90X6AB7

90X6SK7

90X6SM

RCA

90X6L7

RCA

90X6Be

RCA

90X6H6

RCA

90X6J5

RCA

90X6SC7

RCA

90X6V6GT

RCA

90X5Z3

H.

INDEX

TO

PARTS

MANUFACTURERS

SYMBOL

A

ASA

BE

BL

CM

MANUFACTURER

Aerovox Corp.

New

Bedfora,

Mass.

American

Phenolic

Corp.

Cicero.

Illinois

Any

manufacturer

me~ting

the

applicable

American

St

andard

Assoc

ia-

tion

specification

Beede

Electrical

Inst.

Co.

Penacook,

N.

H.

Bliley

Electric

Co.

Erie,

Pa.

Chicago Molding

Co.

Chicago,

Illinois

CRL

Centralab

CS

CT.

E

GE

GT

Milwaukee, Wis.

Clarostat

Mfg.

Co:.

Brooklyn,

N.

Y.

Chicago

Telephone

Supply

Co.

Elkhart,

Ind.

Essex

Wire

Co.

Chicago,

Illinois

General

Electric

Co.

Schenectady,

N.Y.

General

Transformer

Corp.

Chicago,

Illinois

-

30

-

SYMBOL

H

HH

IRC

LF

OM

RC

RCA

SI

SP

ST

SWI

U

UE

MANUFACTURER

The

Hallicrafters

Co.

Chicago,

Illinois

Hart

& Hegeman

Elec.

Co.

Hartford,

Conn.

International

Resistance

Co.

Philadelphia,

Pa.

Littlefuse

Inc.

Chicago,

Illinois

Oak

Mfg.

Co.

Chicago,

Illinois

Radio Condenser

Camden,

N.

J.

R.

C.

A.

Mfg.

Co.

Harrison,

N.

J.

F.W.

Sickles

Co.

Springfield,

Mass.

Sprague

Specialties

Co.

North

Adams,

Mass.

Standard

Transformer

Corp.

Chicago,

Illinois

S.

W.

Inductor

Chicago,

Illinois

Utah

Radio

Products

00.

Chicago,

Illinois

Underwood

Elec.

Co.

Chicago,

Illinois

G

6AB7

(1853)

6SA7

6SK7

GANGED

WITH

BAND

SW.

SW7

SWIT

V7,

CHES -

OPERATED

BY

BFO-AVC.

sw

" TONE

CONTROL

10

BASS

FREQUENCY RANGES.

I.

0.55MC.

TO

1.6

MC.

2. 1.6 MC.

TO

3.0MG.

3.

3.0

MC.

TO

5.8

MG.

SWI

4.

5.B MC.

TO

II.OMG

SW6

5.

II.OMG.

TO

21.0MG.

SW7

6.

21.0

MG.

TO

43.0

MG.

SW2

AVG

-BFO

SWITCH

LEFT CENTER

RIGHT

OPEN

GLOSED

GLOSED

OPEN

CLOSED

GLOSED

JJPEN

CLOSED CLOSED

l)PEN OPEN CLOSED

6SA7

~59

PL,

8

SHORTING PLUG

WHICH

MUST BE

IN

SOCKET

"p"

FOR

A.C. OPERATION.

6L7

~C51

SELECTIVITY

SWITCF POSITIONS

I.

I.F. BROAD.

2.

I.F.

MEDIUM

BROAD.

3.

I.F

SHARP.

4.

XTAL BROAD

5.

XTAL

MEDIUM.

6.

XTAL SHARP.

~49

FOR

D.C. OPERATION CONNECT

270

VOLTS +

TO

PIN

3,

-

TO

6

+"

7,

- "

6SK7

TO

HEATERS

688

FIG.

13-SX28-A-,-SCHEMATIC

-

31

-

METER

ZERO ADJ.