hallicrafters SX-28-A Super Skyrider Receiver

Product Information

Specifications

• Model: SX-28-A Super SkyRider Receiver
• Frequency Range: .55 to 43 Megacycles
• Manufacturer: Chicago, Illinois, U.S.A.
• Date: April 10, 1944

Product Usage Instructions

Installation
Upon receipt, carefully examine the carton and receiver for any damage. If damage is found, file a claim with the carrier.

Operating Voltage: The receiver operates on 110-125 volts of 50/60 cycle AC. A universal 110-220 volt model is available on order. Use an external stepdown transformer if operating at a voltage higher than indicated.

Mounting: The standard model comes with a cabinet for table mounting. The chassis can also be mounted in a standard relay rack.

Terminals and Connections on Rear of Receiver

1. SPEAKER: Connect a 500 or 5000 ohm speaker to the terminal strips. Use the 5000 ohm terminals for a matching HALLICRAFTERS Bass-Reflex speaker.
2. ANTENNA: Connect the antenna to terminals marked AI-A2 and G.

Frequently Asked Questions (FAQ)

Q: What should I do if I receive the product damaged?
A: If any damage is noticed upon receipt, file a claim with the carrier immediately stating the extent of the damage.

Q: Can the receiver operate at voltages other than 110-125 volts?
A: A universal 110-220 volt model is available, or an external stepdown transformer can be used for other voltages.

INSTRUCTION BOOK FOR MODEL SX-28-A SUPER SKYRIDER

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%”.

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 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 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 = -fr-erqu-e-n-cy-1;0-m.-eg-a-cy-c,le-s-. –

or, for example, a half wave 40 meter antenna woulcJ.
be-4T63= 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 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~ceiv

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~siton.

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 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 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 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 Antenna 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~ceiv

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.

‘

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.

.

10,000
1000
o I« –
0:: I-
::>
az. 100
UJ
«(!) ~o>

FIG. 1-1. F. SELECTIVITY

, \ \

~

,

~. 8’
,I ‘4J~ ..
/…:
,/~I -0
I.LJ I
~
4,.1 I
….;/ /
I~ ‘

a.
0:
:crt
(J) II
-La.:

10

,

1

U

1

I
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)

(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 AVC-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 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 posi-

tion. 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 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 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 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 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 ~il 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 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-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 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 variations and voltage fluctuations on the tuned circuit. The HF Oscillator is coupled to the 6SA7 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 6SA7 tube is that a negative loading is

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 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 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 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

little highs present)

.

6–Crystal Sharrlposition of extreme selectivity-

practically 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.

– 7-

FIG. 2-CRYSTAL FILTER SCHEMATIC
6SK1
SELECTIVITY SWITCH’ POSITIONS

(5)

CRYSTAL FILTER CIRU~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 justed 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 relatively broad resonance curve for the CRYSTAL BROAD selectivity

setin~.

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 crystal.

(Sa),

FIG. 3-‘-SINGLE SIGNAL OPERATION

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.

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~ers

on the right the above procedure

still holds.) Then tune to stronger of the

two amplitudes and adjust the BFO can-

trol 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-CRYSTAL SELECTIVITY

.. .. .. XTAL
rBIIOAD

ti.

.

-.~
III
!

. ·

·
“, ·

.L ~V

lJ · – – I. -4 I 1-1″+1+1+’+4+1+’

XTAL
f-
MEDIUM
/
/ ……… t’-
r
-a -4 -I -I -I 411′” +2 +1 +4 …” KILOCYCLES OFF RESONANCE

XTAL
rSHARP

”

V I’–‘

1

II

-5 -2 -I 455 +I +1 . , +4

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 CRYS-

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 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 compo1ents. 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

6L7

688

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. )

Same signal. Same noise. -ANLON 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 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

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 -12 10

,,—
V
/

100

1000

10,000

MICROVOLTS INPUT

/

100,000

1,000,000

– 10 –

(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 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 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 o,f 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_.. 6SA7 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.

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 173 ;;”

long x 8%” high

Panel dimensions-19″ x 8%”

Chassis dimen~os-17%”

x 13Y2″

Weight-(unpackd)~7

lhs. packed 11,7 lhs.

– 11 –

D

RECEIVER ALIGNMENT

Equipment Needed for Aligning:

parent when the correct adjustment has be~n reached.

I-Art all wave signal generator which will provide

Switch to “Xtal Sharp” and adjust C-30 for maximum

an accurately calibrated signal at the test frequencies output while varying signal generator frequency. Two

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.

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.

Setting of controls p~ior

to alignment-IF and RF.

The apparent sharpness of tone should be.midway be-

Tone control at maximum high frequency position tween the “Sharp” and “Broad” positions.

(#9)-BFO at o-Bass switch at Bass IN-AF Gain at

Switch again to “Xtal Sharp” and set the signal gen-

9–RF Gain at #9–Band switch-IF alignment posi- erator to exact crystal

frequency. Set BFa front panel

tion ,55 to 1.6 band-RF alignment depending on band control to a tone. of approximately 1000 cycles. Switch

aligned.

again to “Sharp IF” and carefully realign the IF trans-

Selectivity control at sharp IF-~ndReciv

switch

in Receive—Crystal phasing at #3 on left side-ANL–

formers as earlier described in the 6rst paragraph of these instructions.

OFF at o-AVC OFF.

(2) BFa Adjustment: Set front panel control to zero-BFa

Important: Have bandspread control so logging scale reaas 100.

switch ON-Signal Generator tuned to crystal frequency -selectivity switch in IF Sharp position-now, adjust

Antenna trimmer adjusted for Maximum gain at each. screw on top of T4, after loosening lock nut, to zero best.

RF alignment point on. all bands.

(See Fig. 8)

(3) Noise Limiter and AVC A~plifer

Adjustment: Have

(1) 455 KC-IF Alignment: Tune main dial to 1400 kc on .55 to l.(5.mcband. Connect the hot lead from the signal generatot to 6SA7 mixer terminal IS- Ground to chassis. Roughly adjust the aligning screws of Tl, the lower screw of which is accessible through hole in right mounting 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

the Controls .set as before except that the AVC 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 6SA7· tube.. RemQve 50,000 ohm

~sitor

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~u

signal ~s

1’2 until the 4)utput goes through a maximum, dips down and starts going up again. Adjust th!! phasing control

indicated on output meter. (See Fig. 8 and Fig. 1:4 for location of adjustments).

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,

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.

in. contrast to the usual sharp crystal tone will be ap- (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 –

FIG. 10-AUDIO FIDELITY CURVE

,,” BASS IN” +10

o fP–

,
(/)-10

..J

‘”~

-20

‘~. ,

(,)

-r–:.

– ‘” r… 1–0

~”‘-
“‘”
”

‘…..
~’

,~

~

~.

r..

”
.,

1

I.

‘”0 – 30

”

”

I. ,

I.

(I) I.F. BROAD-TONE ‘CONTROL ou,r

“,-‘

1

-40 ~ (2) I.F.SHARP-TONE CONTROL OUT

i– (3) I.F. SHARP-TONE CONTROL IN

-50

30

100

1000

CYCLES PER SECOND

10,000

FIG. ll-AUDIO FILTERG:URVE

I–

+15

i””‘1’-0

+[0

+5

‘”(/)
..J 0
m /

‘” …..

‘”6 -5
o

-10

-15

‘:’20

I 1

FREQUENCY RESPONSE WITH’

“”-6 “, , ~.r

BASS SWITCH IN a OUT-
SELECTIVITy-“CRYSTAL SHARP”

“14;
BASS OUT f’..

L,

” ,

…. ~

‘.

1’ ….

“‘

~ r— I–

1

‘

–

30

100

1000

IOPOO

CYCLES PER SECOND

.;. 14 –

FIG. 12-RF AND OSC ADJUSTMENT LOCATION AND ALIGNMENT PROCEDURE

R-F AMP.
Caa Ca9 C90 57 5 10 5 ,3
1ST oET. C94 C95 C9G S6 S9 S’2
OSC. CIOOC’OI CI02 S5 Sa S”
FP FP

R-FAMP C91
16 ‘ST OET. C91 C93 C92 S’5 S4 S2
05C. C103C99C98’
SI
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

Sig, Gen, Freq ,

I I

2 2

3 3

4

4

=1~I 1 5

_

r-~20’7_

5

6
~ – _ – _6= __~1 ~_2

1.’65 me , .

1.5 me .6

3.0

3.0

1.8

I 1.8

5.4 3.0

I 5.4
. 3.0

10.0

,. 10.0

7.0

7.0

__ I ~40Oohms

12.0

12.0

36.0

36.0

4 ._0 __~ _24_._0__~4

Dummy Antenna
200 mmE 200 mmf 400 ohms; 400 ohms 400 ohms 400 ohms 400 ohms 400 ohms

400 ohms

400 ohms

0 ~ohm

s~

HIGH FREQTJENCY E;{ J
Adjust Osc. Adjust Trimme-rs

I LOW FREQUENCY END
Adjust Osc Permeability

With

for Max. Gain

With

Tuned By _

C9H . .. .

C92

·.

. . . . . .. . . .

· · · ·

I

SI

I S2

C99

Cn

. . . .

I

. . . .

. .. .. . . .. .

S3

I 54

..- CI00 ….

C94

Css

. r.. …….

. . . . I> 5 5

I …….. ‘..

I S6

57

C I01 ….. ‘ I ___C~I ~02 -+ ~= ….

C9: C89

. . . .

…. .. ….

58

____C~96

__C. 9~.0 j~= ~1 ~ . ~...~I

… …….

S11

I
I 59

I

..~. ..~.
S 12

S10
.. ~.,
S 13

C103

C97

C91

. . · . I … …… .

~..~ . ~ . ~ ..... ,,,,,~ _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 ~lOtage when used as a tie” Normal tolerance allows a variation of ± 10% from the indicated values.

TUBE

FUNCTION

SOCKET TERMINALS

Vr 6AB7 V2-6SK7 V3-6SA7 V4-6SA7 Va-6L7

RF Amp. (1) RF Amp. (2) Mixer HFOsc. IF Amp. (1) Noise Limi ter

Va-6SK7 V7-6B8

IF Amp. 2
2nd Det. S Meter Tube

Vg-6B8 Vg-6AB7 V1o-6H6

AVC Amp. –
Noise Amp.
Noise Rectifier

Vn -6J5

Beat Osc.

1

2

3

4

5

6

7

8

—

., .

.. .

. ..

0.1

4.15 170 6.3 227

Cap.
…. .. .

. , . . ..

4.35 0.1

I

.. .

250 100

—

.. . .. . 116 116

——

4.35 105

6.3 279

…….

~-

———–_.

0.12 4.1 6.3 .. .

…….

0.3 _ .. 6.3 116

…….

.. . .. . 245 102

… . .. 6.3

4

,-.075

.. . .. . 4

., .

4

107.5 6.3 235

…….

.. .

.. . 17.2 ~.25

-.255 108

—

. , . . .. 225.5 0.2 0.2 107

6.3 …

6.3

2

-.17 …….

., .

. ..

…

.07 1.1 150 6.3 225

–

——

.. .

. ..

.. .

.1

.. . 17.6DL 6.3 -.1

. …… …….

., .

.. . 140

.. . -7.4 .. . 6.3 …

BFO ON

ONLY FOR TEST

V12-6SC7 1st Audio Amp.

.. . 140

.. .

… 137 0

1.4 6.3

.. .

—

V1s-6V6GT P.P. Audio Amp. .. . . .. 310 290

.. . 198 DL 6.3 17

V14-6V6GT P.P. Audio Amp. .. . .. . 310 290

.. . .. . 6_3 17

VIl:,-5Z3

Rectifier *

320 340 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~fectivwhn

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 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

– 16 –

G. LIST OF REPLACEABLE PARTS MODEL SX-28-A

REF. SYMBOL

NAME OF PART AND DESCRIPTION

FUNCTION

MFR. CONI’R’S. CODE PARI’ NO.

Rl

R2

R3

R4

R5

R6
&,

RS

R9

RIO

Rll

R12

R13

R14 R15

I-}-

R16

‘,~

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

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 Voltage 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 V3· Plate decoupling for tube V3 A-V-C decoupling for tube V5 Cathode bias for tube V5 on bands
1,2 and 6

ASA RC2IAEI04K CT 25C066 ASA RC2lAE33lK ASA RC31AE273K ASA RC2IAEI02K ASA RC41AE6S2K
ASA RC2lAE272K ASA RC2IAE391K
ASA RC21.AE27lK

R17 Same as R5

RIS Same as RIO

R19 R20 R21

Same as Rl

Resiston,

470,000 ohm .:t

rvfI
lv/o,

“12 watt,

c.arbon

Resistor, 270 ohm:t 10%, i watt, carbon

R22 Same as R5 R23 Same as RIO

R24 Same as Rl

R25 R26

Same as %0 Resistor, 1,SOO ohm :t

10%,

i

watt,

carbon

Voltage drop for screen of tube V5 Plate decoupling for tube V5 Grid return for tube V6 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 V7 Cathode bias for tube V5 for bands
3 and 5

ASA RC21.AE474K ASA RC21.AE271K
liSA RC2iAEI82K

R27 Same as R20

A-V-C decoupling for tube V5 and grid

H2S Resistor, 100 ohm:t 10%” i watt, carbon

isolation for tube V7 Carrier level meter shunt

liSA RC2lAEI0lK

R29 Resistor, variable, 500 ohm :t 20%, carbon, type 25 Carrier level meter, zero adjustment CT 25C022

R30 Resistor, 27,000 ohm :t 10%, 2 watt, carbon

Voltage drop for plate of tube V7

ASA RC41.AE273K

~l}
R32

Ii Resistor, two sect ions; sect ion #1 (R3;J.) , 11,000 ohm :t 10%, watts; section,2 (R32) 4,000 ohm ± 10%, 7 watts; met al clad, wire

Voltage divider for screen grids of tubes V2 ‘ V3 ‘ V5 ‘ V6 ‘ V7 and Vs

CS 24A046

wound

G. LIST OF REPLACEABLE PARTS (Cont’d.)

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

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·Rl
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

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 R40 Same as H20 Same as R20· Part of transformer TI.
reference only.

Shown for

Same as RIO

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
. ‘toad for secondary of transformer Ta during headset operation.
Plate load for tube Vn Grid return for tube VII Parasitic suppressor for tube V4 Cathode bias for tube VIO 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. 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

NAME OF PART AND DESCRIPTION

FUNCTION

MFR. CONTR’S. CODE PART NO.

R64 SaIne as R20

R65 ‘Same as R38

R66 Same as R38

R67 R68

Same as R50 Resistor, 1,200

ohm

± 10%,

t

watt,

carbon

R69 Same as Rl

R,o Same as R49

~l

Resistor, 4700 ohm ± 10%, 1 watt, carbon

&’2 R73

Same as R50 Not used

~4

Same as R47

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
Parasitic suppressor for tube VI

ASA RC2lAE1’22K ASA RC3l.AE472K

Cl

Oscillator stage tuning for Band 1

only

……
fD

Cl. 1 C1. 2
Cz
C2 · 1

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. (Cl , C1 l’ C1· 2 ); Section #2-min. cap. 21. 5 mmfd., max: cap. 250.0

Converter stage tuning for Band 1

only

Antenna stage tuning for Band 1 only

Oscillator stage tuning for Bands 3, 4, 5 and 6

RC

48B050

Converter stage tuning for Bands 3,

CZo2 mmfd. (C2, C2· l , C2· 2 , C2·3 ).

4, 5 and 6 R-F amplifier stage tuning for Bands

3, 4, 5 and 6

CZ· 3

Antenna stage tuning for Bands 3, 4, 5 and 6

~

Oscillator stage bandspread tuning

for 80 and 20 meter bands

C3 · 1 Capacitor, variable, 4 unit gang, each unit consists of 3 sections, air dielectric, special;

Converter stage bandspread tuning for 80 and ’20 meter bands

C3 ·2 C3 ·3

Section #I-min. cap. 6 mmfd., max. cap. 16 mmfd. R-F amplifier stage bandspread tuning

(C3 , C3· 1 , C3· 2 , C3·3 ); Section #2-min. cap. 6.5

for 80 and 20 meter bands

mfd~,

max. ~ap.

2.5 mmfd. (C4 , C4 · 1 , C4 · 2, C4,3); Antenna stage bandspread tuning

RC

Sect lon #3-mmo cap. 6.5 mmfd., max. cap. 27

for 80 and 20 meter bands

48B051

C4

mmfd. (C5 , C5· 1, C5 · 2, C5 ·3 )

Oscillator stage bandspread tuning for 80 and 40 meter b~ds

C4· 1

Converter stage bandspread tuning for 80 and 40 meter bands

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF.
SYMBOL
C4 ·2 C4 · 3 C5
C5 · 1

NAME OF PART AND DESCRIPTION
.
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 )

FUNCTION
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

MFR. CONTR’S. CODE PARI’ NO.
RC 48B051

C6

Capacitor, variabie, min. cap. .5 mmfd., max.

ANT. TRIMMER control

cap. 50 mmfd., air dielectric, ceramic insula-

RC 48A053

tion, type 22

C7

Capacitor, 2980 mmfd. adjustable ± 5%, mica di-

Oscillator padding for Band 6

electric, steel mtg. frame, special

UE 44BIIO

C8

Capacitor, 2400 mmfd. adj ustable ❗ 5%, mica di-

Oscillator padding for Band 5

electric, steel mtg. frame, special

UE 44BI09

C9

Capacitor, 2240 mmfd. adjustable ❗ 5%, mica di-

Osc illator padding for Band 4

N o

electric, steel mtg. frame, special

CIO Capacitor, 1700 mmfd. adjustable ± 5%, mica di-

Os~ilator

padding for Band 3

electric, steel mtg. frame, special

UE 44BI08 UE 44BI07

Cll Capaci tor, 8’22 mmfd. adjustable ± 5%, mica dielectric, steel mtg. frame, special

Oscillator padding for Band 2

44BI06

C12 Capacitor, 541 mmfd. adjust able ❗ 5%, mica dielectric, steel mtg. frame, special

Oscillator padding for Band 1

UE 44BI05

C13 Capacitor, adjustable, 5 mmfd. ± 0.2 mmfd. at 250 C., capacity change -0.02 mmfd. per 0 C.,

Temperature compensating capacity for oscillator

UE 44A06’2

type 8-2739

C14 Capacitor, 0.02 mfd. -10 + 40%, 400 V.D-C working, paper dielectric

Cathode by-pass for tube VI

SP 46AW203J

C15 Same as C14

C16

Capacitor, fixed, 0.02 mfd. – 10 + 40%, 600
v. D-C working, paper dielectric

Screen by-pass for tube VI Plate return by-:-pass for tube VI

SP 46AY.203J

C17 Capacitor, fixed, 0.05 mfd. – 10 + 40%, 200 V. D-C working, paper dielectric

A-V-C by-pass for tube VI

SP 46AU503J

C18 Same as C14 Cl9 Same as C14 C20 Same as C16 C21 Same as C17

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. LIST OF REPLACEABLE PARTS – (Cont’d~)

REF. SYMBOL

NAME OF PART AND DESCRIPI’ION

FUNCTION

MFR. CONTR’ S. CODE PART NO.

C22 Same as C14

C23 Same as C14

C24 C25

Same as C16 Capacitor, fixed,

2200 mmfd.

± 10%,

500 v.

D-C

working, mica dielectric

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

C26 Same as C17

Cathode by-pass for tube V5

C27 Same as Cu

Screen by-pass for tu~e

V5

C28 Same as C16

Plate return by-pass for tube V5

C29 Capacitor, variable, min. cap. 2 mmfd., max.

MED. XTAL crystal filter adjustment CRL 44A079

cap. 6 mmfd., ceramic dielectric, .special mtg.

bracket, type B-820-202

C30 Capacitor, variable, min. cap. 4 mmfd., max.

SHARP XTAL crystal filter adjustment CRL 44A078

cap. 20 mmfd., ceramic dielectric, special mtg.

bracket, type B-820-304

C3l Same as C30

SHARP I.F. crystal filter adjustment RC 48A039

N I-‘

C32 Capacitor, variable, min. cap. 3.0 mmfd., max.

CRYSTAL PHASING control

cap. 25 mmfd., air dielectric, ceramic insula-

t ion, type 22-7

C33 Same as C14 C34 Same as C17 C35 Same as C14

Grid return by-pass for tube V6
Cathode by-pass for tube V6 Screen by-pass for tube V6

C36 C37

Same as C16 Capacitor, fixed,

47 mmfd.

± 10%,

500 v.

D-C

working, mica dielectric

Plate return by-pass for tube V6 Diode load by-pass for tube V7

ASA a~40A7K

C38 Not used C39 Same as C14 C40 Capacitor, fixed, 470 mmfd. ± 10%, 500 V. D-C
working, mica dielectric

R-F by-pass on grid of tube V7 Parasitic suppressor in plate of tube ASA CM20A471K
V12

C’4l

Capacitor, fixed, one unit of dual unit, 40 mfd.
– 10 + 40%, 25 v. D-C working, electrolytic

Cathode by-pass for tube VJ:2

SP 42A032

(See C44 ) C42 Same as C16
C43 Capacitor, fixed, 5100 mmfd. ± 5%, 300 v. D-C
working, mica dielectric

Tone control, high frequency audio shunt
Resonating capacitor for bass boost

ASA CM35A5l2J

C44

Capacitor, fixed, one unit of dual unit, 10 mfd.
– 10 + 40%, 300 v. D-C working, electrolytic

Plate decoupling for tube V12

(See C4l )

G. liST OF REPLACEABLE PARTS – (Cont’d.)

REF. SYMBOL

NAME OF PART AND DESCRIPTION

FUNCTION

MFR. CONTRt S.
CODE PART NO.

Capacitor, fixed, 0.05 mfd. – 10 + 40%, 400 v. D-C Coupling between tubes V12 and V14
working, paper dielectric

SP 46AW503J

Same as C45 Capacitor, fixed, one unit of dual unit, 40 mfd.
– 10 + 40%, 5 V. D-Cworking, electrolytic

Coupling between tubes V12 and V13 Cathode by-pass for tubes V13 and
V14

SP 42A031

(See C4S )

C48

Capacitor, fixed, one unit of dual unit, 30 mfd.
– 10 + 40%, 400 V. D-C working, electrolyt ic

Plate power supply output filter capacitor

C49

v. in same container with C47
Capacitor, fixed, 30 mfd. – 10 + 40%, 450 D-C

Plate power supply input filter cap- . SP 42A030

working, electrolyt ic, type D8290

acitor

C50 Same as C14
C51 Capacitor, fixed, 0.01 mfd. – 10 + 40%, 600 V.
D-C working, paper dielectric

Audio coupling between diode of tube

V7 and grid of tube V12

A-C line by-pass capacitor

SP 46AYI03J

C52 Same. as C51
C53 Same as C17 C54 Same as C45 C55 Capacitor, variable, compression type, 50 mmfd.
(nominal), mica dielectric, type SW-1530

A-C line by-pass capacitor
A-N-L by-pass
Cathode by-pass for tube VIO Resonating trimmer for inductor CH3

SWI 53A012

C56 Same as C16

C57 Same as C14

C58 Same as C17

C59 ·Same as C17

C60
C61

v. Same as C37
Capacitor, fixed, 250 mmfd. ± 20%, 500 D-C

working, mica dielectric, type 146S. Part of

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

transformer Tl · Shown for reference only.

C62 Same as C14

C63 C64

v. Same as C17
Capacitor, fixed, 100 mmfd. ± 10%, 500 D-C

working, mica dielectric

Screen by-pass for tube Vs Cathode by-pass for tube V8 A-V-C diode load by- pass at tube V8

ASA CM20AIOlK

C65 Same as C14 C66 Same as C17 C67 Same as C16 G68 Same as C37

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. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF.
SYMBOL

NAME OF PARI’ AND DESCRIPTION

FUNCTION

MFR. CONTR’S. CODE PART NO.

Same as C37

Grid coupling for tube V4

Same as C25 Same as C64 Capacitor, variable, min. cap. 5 mmfd., max. cap.

Plate return by-pass for tube V4 Grid coupling for Tube VIl B. F. O. control

RC 4SA06’4

25 mmfd., air dielectric, special

Capacitor, -fixed, 500 mmfd. ❗ 5%, 500 V. D-C

Shunt capacitor across C72

A 47BT50lD

working, silver mica, type 1469, Part of trans-

C74

former T4· Shown for reference Capacitor, fixed, 0.01 mfd. -10 ❗

only. 40%, 600

v.

D-C

Plate by-pass for tube Vl l

working, paper dielectric, braided leads, type AB

SP 46A021

C~5

Capacitor, 2 mmfd., twisted leads

C76 Same as C25

Coupling between tubes V7 and VII “mpedance equalizer for transformer

C77 Same as C17 C7S Not used

TS A-V-C by-pass for tube VI

C79 Not used

CSO Not used

CSI Not used CS2 Not used

CS3 Capacitor, fixed, 2.5 mmfd. ❗ 20% 500 V. D-C working, bakelite dielectric

Coupling between tubes V2 and V3 on Band 5

-49AOOI

CS4 Not used CS5 Not used CS6 Same as C40 CS7 Capacitor, fixed, 0.25 mfd. – 10

• 40%, 200 V.

Plate decoupling for tube V4 Cathode return by-pass

SP -46AT254.T

D-C working, paper dielectric

CS8 Capacitor, variable, min. cap. 4 mmfd., max.

Trimmer for transformer T15

cap. 20 mmfd., ceramic insulation, temp. coeff.

CRL 44Al02

– 0.005 mmfd / mmfd/ 0 C., type 82Q-B

Same as C8S Same as CS8

Trimmer for transformer TI6 Trimmer for transformer TI7

Same as CS8

Trimmer for transformer T18

Same as CS8 Same as CS8 Same as CSS

Trimmer for transformer TI9 Trimmer for transformer T20 Trimmer for transformer T21

Same as C88′ Same as CS8

Trimmer for transformer 122 Trimmer for transformer T23

G.· LIST OF REPLACEABLE PARTS – (Cont’d.)

REF. STIffiOL

NAME OF PART AND DESCRIPTION

YVNCTION

MFR. CONTR’S. CODE PART NO.

Same as CSS Same as CSS

Same as CSS Sa:rne as CSS

Same as CSS Sa:rne as CSS Same as CSS 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.e~c

only.

Capacitor, variable, compression type, (nominal), mica dielectric. Part of

~a:er

T5 · Shown for reference only. 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

Trimmer for transformer T24

Trimmer for transformer T25

Trimmer for transformer T26

Trimmer for transformer T27

Trimmer for transformer T28

Trimmer for transformer T29

Trimmer for transformer T30

{

Primary capacitor o Secondary capacitor

f Transf of tran

ormer Tl sformer T

l

Primary capacitor of transformer T2

Secondary capacitor of transformer T2

[

Primary trimmer of transformer Secondary trimmer of transform

T.3 er T3

ffrimary trim~

of transformer T5

t~econdary

trimmer for transformer T5

Primary capacitor of transformer T6

Secondary capacitor of transformer T6

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 SI i-f amplifier V5
Coupling and filter between i-f amp- SI lifier tubes Vo and V6

50B082 50BOSI

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF.
SYMBOL

N.MrE OF PART AND DESCRIPTION

FUNCTION

MFR. CONTR’S. CODE PART NO.

Transformer, I-F, 455KC, primary and secondary

Coupling between i-f amplifier tube SWl 50B083

tuned by variable capacitor, iron core coils,

V6 and diode of 2nd detector tube

type 3365

V.,

Transformer, 455KC, tuned by adjustable iron

Beat frequency oscillator inductance 8WI 54B014

core, special

Transformer, I-F, 55KC, primary and secondary

Coupling between ~N-L

tubes Vg and 8WI 50B097

tuned by variable capacitor, iron core coils

VlO

special

Transformer, I-F, 455KC, primary tuned by ad-

Coupling for A-V-C amplifier tube Vs 8WI 50B080

justable iron core, secondary untuned air core,

special

Transformer, power, standard; primary, 117 V. A-C,

GT 52B03-3

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

Filament and plate power tra~sfome

Transformer, power, universal; primary, 117/230 V.

GT 5’2B034

A-C, single phase, 50/60 cycles; secondary-same

as standard transformer, type 9G62

Transformer, A-Fj primary, 10,000 ohm winding cen- Couples a-f amplifier to load.

GT 55B009

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

Coupling between antenna and tube VI SWI 5lB568

core, special

for Band 3

TIO Transformer, R-F, range 5.8-11.5 megacycles, air Coupling between antenna and tube Vl 8WI 5lB569

core, special

for Band -4

Tll Transformer, R-F, range 10.5-21 megacycles, air core, special

Coupling between antenna and tube VI 8WI 51B570 for Band 5

T12 Transformer, R-F, range 21-43 megacycles, air core, special

Coupling between antenna and tube VI SWI 5lB, 571 for Band 6

T13 Transformer, R-F, range. 55-1. 6 megacycles,. air core, special

z Coupling between antenna and tube V 8WL 5lB566 for Band 1

T14 Transformer, R-F, range, 1.6-3.0 megacycles, air Coupling between antenna and tube Vz 8m 5lB567

core, special

for Band 2

T15 Transformer, R-F, range, 3.0-5.S megacycles, ad- Coupling between tube VI and tube Vz 8WI 51B572

justable iron core, special

for Band 3

T16 Transformer, R-F, range 5.8-11.5 megacycles, ad- Coupling between tube VI and tube V2 SWl 5lB573

justable iron core, special

for Band 4

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF.
SYMBOL

NAME OF PART AND DESCRIPTION

FUNCTION

MFR. CONI’R’S. CODE PART NO.

T17 Transformer, R-F, range 10.5-21 megacycles, adjustable iron core, special

Coupling between tube VI and tube V2 SWI 5lB574 for Band 5

T18 Transformer, R-F, range 21-42 megacycles, adjustable iron core, special

Coupling .between tube VI and tube V2 SWI 5lB575 for Band 6

T19 Transfprmer, R-F, range .55-1.6 megacycles, adjustable iron core, special

Coupling between tube V2 and tube V3 SWI 5lB576 for Band 1

T20 Transformer, R-F, range 1.6-3.0 megacycles, adjustable iron core, special

Coupling between tube V2 and tube V3 SWI 5lB577 for Band 2

T2l Transformer, R-F, range 3.0-5.8 megacYQles, adjustableiron core, special
T22 Transformer, R-F, range 5.8-11.5 megacycles adjustable iron core, special

Coupling between tube V2 and tube V3 SWI 5lB578 for Band 3
Coupling between tube V2 and tube V3 sm 5J.B579
for Band 4

T23 Transformer, R-F, range 10.5-21 megacycles, adjustable iron core, special

ing between tube V2 and tube V3 SWI 5lB580 for Band 5

T24 Transformer, R-F, range 21-4’2 megacycles, ad-

Coupling between tube V2 and tube V3 SWI 5lB581

rmo

j ustable iron core, special T25 Transformer, R-F, range,.55-l.6 megacycles, ad-

for Band 6 Oscillator coil for Band 1

swr 51B582

justable iron core, special

T26 Transformer, R-F, range 1.6-3.0 megacycles, ad-

Oscillator coil for Band 2

swr 5lB583

justable iron core, special

T27 Transformer, R-F, range 3-5.8 megacycles, adjustable iron core, special

Oscillator coil for Band 3

swr 5lB584

T28 Transformer, R-F, range 5.8~1

megacycles, ad- Oscillator coil for Band 4

justable iron core, special

T29 Transformer, R-F, range 10.5-21 megacycles, ad-

Oscillator coil for Band 5

justable iron core, special

SliI 5lB585
swr 518586

T30 Transformer, R-F, range 21-42 megacycles, adjustable iron core, special

Oscillator coil for Band 6

SWI 51B587

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

Plate supply filter choke
Bass boost choke A-N-L wave trap coil

GT 56B008
ST 55AOIO
swr 53B012

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF. SYMBOL

NAME OF PART AND DESCRIPTION

FUNCTION

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

Phonograph pickup connection Headphone connect ion

MFG. CONTH’S. CODE PART NO.
u 36B003
u 36B011

Fuse, 1.5 amperes @ ‘250 V” 4AG, glass enclosed, type 1041

A-C line overload protection

LF 39A320

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

Shorting plug for a-c operation Line cord

AP 35A003 E 87A078

Socket, octal, female, low loss mica-filled bake- Connection for D-C power supply lite insulation, type MIPST

AP 6A042

Terminal strip, black bakelite, marked “A2” “AI”, Connection for antenna special

H SA039

Terminal strip, black bakelite, marked “5000”,

Audio output connection for 5,000

H BA040

special

ohm load

Terminal strip, black bakelHe, marked “500”, special

Audio output connection for 500 ohm H BA041 load

Meter 0,5 milliamperes, S.S ohms internal re-

Carrier level indicator

sistance, pointer swing 90 degrees, special mtg.

bracket, special

BE 82A070

Crystal, frequency 455KC ± 5KC, type CF6

Cryst al filter

BL 19A1t23

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 B-F-O switch

meter

SWitCh}

OM 60B052

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF. SYMBOL

NJlli1E OF PART AND DESCRIPTION

FUNCTION

Switch, SPST, toggle actiont located on rear of

resistor R35

SW 4

Swit ch, SPST, bat handle toggle, rated 3 amperes
@ 250 V., type 21350GA

SSW~_l W

J1 Switch, DPST, toggle act ion, locat ed on the rear of resistor R53

1 SSWW76 } Same as SWI
SSWWSS- -2l 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,

r SWS_ 6

bakeli te .~afes

,~c

ions are assembled to

J SWS_ 7

struts, vype .LSgGe HZ

‘Ssw~= W

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

SWSSW

1_31J[ou..’I,'[1c. +~v

ut
Chll,

s t ro

yp
“~ary –

to:

H se”.tector,

sl·ng1e sec t l.on,

0~ PO.S’l-

e
u

w88-

-~v

H
,~

}

tion, shorting type rotor wafer, type 235S6-H

con. tacts,

bakelite

SW9_1 ISwitch, rotary selector, 3 section, 6 position,

I SW9_ 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

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

Lamp 6.3 V. @ 250 milliamperes, bayonet base type Illumination for band spread dial

44

1M2 S&’1le as LMI

L’Vl3

Lamp, 6.3 V. @ 150 milliamperes, bayon~t

Illumination for main tuning dial base type Illumination for meter scale

47

MFR. CONTR’S. CODE PART NO.
HH 60Al03
CM 62B025
OM 62B013
OM. 6213015 OM 62B023 OM· 60B048 HH 60.Al02 GE 39A003 GE 39.A004

G. LIST OF REPLACEABLE PARTS – (Cont’d.)

REF. SYMBOL

NAME OF PART AND DESCRIPTION

FUNCTION

VI

Tube, pentode type 6AB7

V2

Tube, -triple-grid super-control amplifier, type

6SK7

V3

Tube, multi-electrode pentagrid converter, type

6SM

V4

Same as V3

V5

Tube, multi-electrode pentagrid mixer amplifier,

type 6L7

V6

Same as Y.2

V7

Tube, duplex-diode pentode, type 6Be

Ve

Same as V7

Vg

Same as VI

VIO Tube, twin diode, type 6H6

VII Tube, triode, type 6J5 Vl2 Tube, twin triode, type 6SC7 V13 Tube, beam power amplifier, type 6V6GT V14 Same as V13 VIS 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 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. CONTR’S. CODE PART NO. RCA 90X6AB7 RCA 90X6SK7 RCA 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 CRL CS CT.
E
GE GT

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

Centralab 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

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

– 30 –

6AB7 (1853) G

6SK7

6SA7

6L7

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.

6SK7

688

6SA7

GANGED WITH BAND SW.

SW7

SWITCHES –
V7,
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. 4. 5.B MC. TO II.OMG 5. II.OMG. TO 21.0MG. 6. 21.0 MG. TO 43.0 MG.

AVG – BFO SWITCH

SWI SW6
SW7 SW2

LEFT OPEN
OPEN JJPEN l)PEN

CENTER GLOSED
CLOSED CLOSED OPEN

RIGHT GLOSED GLOSED CLOSED CLOSED

~59

PL,

SHORTING MUST BE FOR A.C.

8 PLUG WHICH IN SOCKET “p” OPERATION.

METER ZERO ADJ.

~49
TO HEATERS

~C51

FOR D.C. OPERATION CONNECT

270 VOLTS + TO PIN 3, – TO

6

+”

7, – ”

FIG. 13-SX28-A-,-SCHEMATIC – 31 –

References

• The domain name getti.ng is for sale
• SWit.Ch

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