Hammarlund Sp-600-jx-17 Troubleshooting guide

INSTRUCTION

BlOD

SERVICE

WAL

THE

IUlURLm

MANUFACTURING)

CO.

INC

.

460

W.

54!i!H

St.

New

York

1,

8.

Y.

SP-600-

JXI~

COMMUNICATIONS RECEIVER

INSTRUCTION

AND

SERVICE

MANUAL

TABLE

OF

CONTENTS

SECTIONS

No,

-

I

11

I11

IV

v

VI

VII

ILLUSTRATIONS

Title

-

INTRODUCTION

CIRCUIT

DESCRIPTION

INSTALLATION

OPERATION

MAINTENANCE

ALIGIIMENT

REPLACZABLE

PARTS

LIST

Figure

Title

-

TABLES

Front Panel

Block

Diagram

Top View

of

Chassis

-

Alignment Adjustments

Audio

and

Fidelity

Curves

Selectivity Curves

Rear

View

of

Chassis

Top View of Chassis

Parts Identification

for

Locating Test Points

Schematic Diagram

Connection Diagram-Receiver Chassis

Tuning Utlit Connection Diagram

Crystal Control Unit Connection Diagram

Title

-

Tube

Socket Voltages

Tube

Socket Terminal Resistance

RF

and

HF

Oscillator Allgntnent Frequencies

and

Adjustment ~esignations

Approximate

Signal

Xnput

at

IF

&

AF

Stages

for

20

Volts

Output

Page

The

SP-6001~~17is a 20-tube superheterodyne radio communications receiver designed

specifically for diversity reception, The receiver

le

intended for use

a8

either

the "master" or "slave" wit for the reception of

MCW,

CW,

suppressed carrier, or

frequency-shift

signals,

"Master-slave" relationship

is

established by interconnecting two or

=re

receivers. These connections

snay

be

made

between

the

beat-frequency and/or the

heterodyne oscillatora of

eacb

receiver,

or

between

the

receivers

and

sn

externally

co~ectedmsster oscillator

common

to

each.

Frequency drift, after a

15

miqute warm-up,

ranges

between

,001

percent and

,01 percent of frequency, depending on

the

frequency used,

This

is

an

unusual

degree

of

frequency stabilitiy

for

variable tuned

HF

oscillators and closely approaches

crystal stability,

The frequency control unit provides

for

fixed

channel

crystal-controlled opera-

tion on

any

six frequencies

within

the range

from

.75

to

54

megacycles. Front panel

controls permit the selection

of

either

the

normal

high

stability, continuously

variable tuning or fixed frequency operation, For crystal-controlled fixed-channel

operation, it is only necessary

to

set

the

dial to the signal frequency, switch

to

the crystal frequency desired,

and

tune with

the

delta frequency control, Desired

crystals may be purchased on special

order

from

the

Harmnarlund

Manufacturing Colgpany,

The selectivity control provides

3

degrees of crystal and

3

degrees

of non-

crystal selectivity ranging from

sharp

(,2

KC)

to broad (13,O

KC),

The crystal

filter in the

SP-600-~~17

embodies the

same

circuit features

that

have proved so

effective and desirable in Hammwlund

Super-pro

receivers,

Two

stages of radio frequency amplification

are

provided on

all

bands: single!

conversion is used for signal frequencies up to

7,k

megkxcycles,

and

double coaversioq

employing a crystal-controlled oscillator, for signal

frequencies

above

7,4

mega-

cycles.

Four stages of

IF

amplification, detector

and

AVC

rectifier, noise limiter and

meter rectifier, beat frequency oscillator

aud

buffer amplifier,

IF

output,

AF

amplifier

and

output power stage,

are

among the features of the sP-600-~~17,wbich

are discussed fully under separate headings in this manual.

The Audio output circuit is designed for

a

600-ohm

load

or line and is provided

with

a

four-terminal split winding for balanced load operation,

Maximum

power out-

put is approximately

2.0

watts,

The

headphone circuit

when

referred to

aa

8,000-ohm

resistive load provitles signals attenuated approxinately 15

db

below the 600-ohm

power output, Either headphones, loud

speaker

or both may

be

used for reception of

signals,

mereceiver i,f. output or audio-output, connected to

a

suitable frequency-shift

receiver converter

and

associated

teletypewriter, provides for recorded copy

of

a

teletype signal,

A

C1d

signal may be amplitude-modulated

by

aa

external tone

generator connected to

the

receiver, so that

a

steady,

audible (monitoring) tone is

always heard when the transmitter carrier

is

on

the

air, whether

signal

intelligence

is

present, or not,

A

single tuning control of special design permits maximum traveree speed as well

as exceptional operating

ease,

It controls both the

main

and

vernier dials,

The

main dial, in addition to

being

frequency-calibrated, includes

an

arbitrary scale in

hundredths,

while

the

vernier

scale

contains

an

arbitrary

scale

b

units,

Them

8rbltPary scales,

coqlemented

by

the

anti-baclclaeh

gear

train

which

eovemo

dial

movement,

pkovlde

extremely

accurate

logging

and

resetabillty,

A

tuning

lock

assures

positive

locking

ac

tlon

without

af

fec

tang

the

43equency

getting,

Radiation is

negligible

and

complies

with.requhements

for

ship-board

operation

and

for multi-receiver installatZons.

Althow

the

antenna

input

circuit

18

designed

for

the

coaxial

cable

connectian

of

a

wave

antenna

eystem,

a

conventioml

single

wire

antenna

may

be

ueed.

me

self-contalnea

power

swply

of

the

SP-~OO-JXZ~

$8

designed

ioz

operation

on

a

sinele

phase

50

to

60

cycle

alternating

current

power

source,

The

power

trans-

former

primary

Is

provided

w$th

terminale

offerl~g

a

rkge

of

line

voltage

from

90

to

270

volts.

The

sendcreeeive

switch

deaensitlzes

the

receiver but

leaves

the

power

04

to

provide for

instant

recegtlon

between

traizsmissions,

The

SP-~OO-JX~~

is

available

as

either

a

rack

model,

suitable

for

a

mountlag

in

a

standard

19"

relay

rack,

or

as

a

cabinet

model

for

table

use,

CIRCUIT

DESCRIPTION

General

The

electrical circuitry of the

SP-600-J~-17

is

shown

schematically

in

Figure

9.

A

block diagram, Figure

2,

is

provided

to

illustrate the arrangement

and

functions

of the various circuit sections. The location of

the

various

tubes

is

shown in

Figure

3,

The circuit

for

single conversim, used

for

signal frequencies

up

to

7.4

megacycles, consists of

two

stages of

RF

amplification

V1

and V2; First Mixer

V5j

First Heterodyne Oscillstor V4; fow?' stages

of

IF

amplification,

V7,

V9,

V10 and

Vll;

Detector,

AVC

Rectifier Vb4;

Noise

Limiter Vl5;

Beat

Frequency

Oscillator

V13;

XF

output

and

AF

amplifier,

v16i

and

~16~;

Output Power

Stage

V17,

and

the

Pow-

Supply

System which includes

B

Power Rectifier V19,

C

Bias

Rectifier

C20

and

Voltage

Regulator

~18,

In

the

circuit8 for double conversion,

used

for

signal

frequencies

above

7.4

megacycles the Second

Mixer

~6

and

Second

Heterodyne Qscillator

~8

are

substituted

for the gate

tube

V7,

A

precise

rotary

turret

is used

to

change

bands,

It

associates

the

RF

tuner,

sub-assemblies of

the

antenna coupling,

the

two-stage

RF

amplifier,

and

the

first

heterodyne oscillator-of the band

selected

with

the circuitry in the

RF

strip common

to

each

band,

In

this

way,

each

RF

tuner

sub-assembly

is

positioned dPrectly

addacent

to

its

respective

tube

and

gang

section

of

main

tuning capacitor

CLA-Cm.

In ut Couplin~

-

The

antenna

input

coupling provides an optimum match

for

a

95-

ohm

-%-

coax

a

cable line connected

to

antenna input connector

V1.

On

bands,

1,

2,

3,

and

4,

the

antenna

RF

transformer

is

secondary-tuned

by

dual

section

CU-ClB

of

the

main

tuning capacitor; on

bands

5

end

6,

by

section

C1A

only.

A

capacitor, such

a8

C3

for band

I,

is

used

so

tbat

the

antenna circuit tracking matches that

of

the

RF

aarplif

ier

.

RF

Amplifier

-

The

V1

and V2

stages

of'

the

RF

amplifer

are

identical,

V1

is

secondary-the&

by

dual section

C1C-0

while

V2

is

secondary-tuned

by

dual section

CU-C1F

of

the

main tuning capacitor,

Camplexed

coupling

is

used

in

RF

stages

to

maintain

a

more

constant level of

signal

gain over

the

frequency levels of

each

band.

High

image

rejection ratios

are

achieved through the

use

of

three

High

Q

tuned

RF

circuits

and

by

double conversion on

the

three

higher freguency

bands,

The

high

gain

developed

by

two

RF

stages

assures

maximum

sensitivity athigh signal-to-noise

ratios.

First

HAgodyne

Oscillator (variable

~4)

-

First

Heterodyne OsciLlator ~4

functions

as

a

ColpXtts

o~cil~atorfor

the

three

higher

frequency

bands and

as

a

tuned-grid

oscillator for

the

three

lower

frequency

baads.

Dual

section

ClG-CI.3

of

the main tuning capacitor provides

for

the

variable

turiing

of

the oscillator, For

single conversion, the oscillator frequency

is

455

Kc

higher than the signal fre-

quency,

while

for double conversion

the

oscillator

frequency

is

3.955

mc higher

than the tuned-in signal.

First Heterodyne Oscillator

-

(crystal

Controlled

~3)

-

For services

requiring

elitrenely

stable,

fixed-frkruency operation,

a

crystal controlled high

frequency

oscillator ia provided.

Instant

change-over from varfable to crystal controlled

oscillator with

a

choice

of

six

crystal positions

is

effected by

a

front panel

XTALS

control,

A

second front

panel

control

marked

Delta

Frequency

permits

a

tolerance

adjustment

of

the

crystal ~scillatorfrequency

over

the

t

.005$

(purchased

crystal

tolerance) range,

For double conversion, the conversion oscillator output from V3

is

augmented

b

v4.

Conversion oscillator output from V3

is

availablt at HFO output connector socke

~8

at the rear of the frequency control unit &en the front panel control

is

in

a

crystal position; but when the front panel control

is

set to

its

EXT

position,

the

conversion oscillator voltage

for

the receiver

is

that which

is

externally connecte

to

58.

Intermediate Frequency Amplifier

-

Single conversion to

455~~

is

employed for

signal frequencies lielow

7.4

hc,

There are fowstages of

ICF

amplification in-

corporating the Hammarlund

-

patented filter circuit, Six positions 00 selectivity

provide

6

db bandwidths of

.2,

.5,

1.3,

3,

8,

and

13

kc.

On the three narrower

bandwidth positions the crystal filter

is

in operation.

The

crystal phasing control

provides extreme selectivity for the

high

attenuation

of

cl-osely adJacent inter-

fering signals. Double conversion

is

employed for

signal

frequencies above 7,4 mcs.

The signal

is

heterodyned

to

3,955 mc by the Fir~t

Mixer

V5

and

Heterodyne Oscilla-

tor

~4,

or V3 for high image rejection.

Tile

3,955

mcs

signal

is

then heterodyned

to 455

KC

by

the Second Mixer

~6

and the

3.5

mc Fixed Crystal-Controlled Oscilla-

tor

V%

for selectivity. For double conversion,

the

tuned

circuits

and

the 3.955 mc

IF transformer

T2

assure appropriate input to the

Second

Mixer

~6.

IF

transformer

T1

in the plate circuit of

V5

is

resonant to

both

455

kc

and to

3.955

mes.

For

single conversion, the

455

kc

signal

path

is

to

455

kc

I??

gate V7; for double

conversion,

the

3,955 mc signal

path

is

to Second Mixer

~6.

The

prime function of

V7

is

to render the

signal

path

through

it

an

open

circuit for double conversion

and available to the signal for single conversion.

The

3.5

mc crystal-controlled heterodyne output from

~8

is

available at

IFO

connector socket

56

at the

rear

skirt

of the receiver, when the front panel

IF0

switch

is

set to

its

INT

position; but when the

IF0

switch

is

set to

its

EXT

posi-

tion, the

3.5

mc conversion oscillator for the receiver

is

that externally

connected to

58,

since

~8

is

now inoperative.

Detector and

AVC

-

The

~14tube

is

used

as

a

high

level Detector and

AVC

rectTfier. ~he~~~~circuit

is

provided

with

separate

time ccnsta~tsfor

CW

and

MCW

operation.

AVC

and Diode output terminals provide for connections

in

diversity

applications.

The

AVC

bias developed

is

applied to

V1,

V2,

~6,

V7, and

Vy,

but the

bias to

V1

and

V2

is

reduced through use of

a

voltage divider network (resistors

R48

and

R53).

The

BFO-AVC

witch provides choice

as

to

a

FAST

or

SLOW

time constant. Since

the switch functions also

as

a

BFO

switch,

two

positions, BFO

FAST

and

BFO

SLOW,

are

provided.

Beat Frequency Oscillator

-

The

beat fre~uencyoscillator employs

a

high

capekity Colpitts circuit irfii'ch provide

a

high

order of frequency stability

and

minimizes oscillator harmonics. The

Beat

~re~uenc~Oscillator

V13,

is

coupled into

the detector circuit through

Buffer

Amplifier V1.2, which eliminates oscillator lock-

in.

A

f'ront panel control varies the audio-beat frequency from zero beat to

?

3

kc.

The

beat frequency oscillator output from

V13

is

available also at

BFO

connector

socket

K7

at

the

rear

apron of the receiver when

the

front panel

BFO

switch

is

set

to

either

its

FAST

or

SLOW

INT

BFO

positions;

but

when

set to either of

it8

FAST

or

SLOW

EXT

BFO

positions, the functioning beat frequency oscillator

for

the

receiver

is

that

which

Is

externally connected to 57, since the output from

V13

is

suppressed.

Front

panel

switch control

MOD-CW

renders

V13

operative

for

CW

operation.

An

external switch control

connected

to

terminals

BF

of

remote connector socket

~~3102A-14$-2~

(54)

on the rear skirt

may

also be used to peyform this hmction,

since.these terminals are

in

parallel with the contacts of the cantrol switch.

Alternate to the use of the beat frequency oscillator to render

a

keyed-carrier

CW

signal intelligible,

a

local tone generator may be externally connected to

terminals

A

and

B

of

~4

to

amplitude modulate the

CW

signal. The use of a local

tone generator produce6

a

steady tone even

%?hen

the received carrler f'requency

drifts.

Jk

is

furnished with connect~rplug

A

and 3108~44~-2~and cable clap

~~3057-6.

Noise Limiter

9

The

noise

limiter circuit Vl5 limite tho noise interference

from igriPti~nsystems

or

other

sources

of

pulse-type noise,

A

separate limiter

control switch permits optional use of the limiter

on

any

mode

of

operation

when

pulse type interference

is

present,

Audio Frequency

Anplifiw

-

A

resistance-coupled amplifier triode

~16~

amplifies

the audio-frequency

signa~Tkrn

the detector,

Audio Output

-

The

audio

output

to

V17

is transformer-coupled through

a

split

balanced' winding

t~

deliver

2.0

watts undistorted

output

to

n

600-ohm load. The

split balanced winding

permits

balsncing

of

the

direct kind in the output circuit,

as used for teletype

or

similar

~ervice,

A

separate secondary winding provides

attenuated audio signal output

for

headphone

operation.

This

winding

will

deliver

an

output

of

15

milLiwatts

into an 6~00-ohmresistive

load

when the 600-ohm power

secondary

is

delivering

500

milliwatts to

a

600-ohm

resistive load.

IF Output

I.

A

cathode follower, the

~16~

provides

a

'(&ohm impedance source of

intermediate f'requency (455kc) to socket

SO-239

on

the

rear

skirt of

the

chassis.

Plug

PL-259,

and angle plug adapter

M-359

used with coaxial cable

RG-~L/U

are

not supplied.

Power

Su ply

-

The

power supply is

an

integral part of the receiver,

It

in-

cludes

t

e rectifier

Vl9

and

C

rectifier V20, together with their respective low-

pass filters and Voltage Regulator

~16.

The

power transformer

is

provided with

screw terminal primary

taps,

covering

a

power line

source

range

of

90

to

270

volts,

50 to

60

cycles. The power transformer

and

filter components

are

protected by fuses

in

the

primasy

and

plate dupply circuit.

Tuning

Meter

-

The

tuning meter

is

used on

AVC

operation

to

indicate

the

accurac

of tuning and

Ee

relative strength

of

received signals. Depression of the Meter

Switch canverts the metes circuit

for.

indication

of

output level in

db

from

6

milli-

watts,

RF

Gain Control and

Power

Switch

-

me

RF

gain control

is

provided for

manual

..-.3.IcII

cantrol of sensiti9Fy'toprsent overloading

on

strong sigpals

when

operating with

the

AVC-WAL

switch in the

"Mlh,WU1'

position. This control also operates when the

switch

is

an the

"AVC"

position. The Power

"OM-OFF"

switch

is

operated at the

counter-olockwise extremity

of

the

RF

gain control.

Send-Receive Sw$tch

-

The send-receive switch desensitizes the receiver but

leaves

the

power "on"

60

provide

for

instant reception between transmission periods.

Radiation

-

Advanced design and shielding

of

the

high frequency, second conversior

crystal 'mieatf'reguency oscillators

has

reduced

radiation to

a

negligible point

so that interference

of

this

nature, coma in multi-oeceiver installations,

is

reduced

to

a

minimum.

SECTION

If1

INSTALLATION

Tubes and packing

-

.

After un~ackinetthe receiver see that

all

t

ubes are firmly

in

their sockets and-that' all packing material

is

removed from the receiver.

Power Su ly

-

Make

sure

that the primary tap

lead

at the bottom of the power

trandonnectedto

the

tap which

most

nearly agrees

with

the

50

to

60

cycle

power source voltage. Power connector

plug

~3108~-18-3s

with cable claw

AN3057-1C

with power cord and plug

are

furnished

w$th

the

receiver.

Antenna

-

The input impedance at the antenna socket,

$50-239,

is

designed to

match a 95-ohm coaxial

cable

line, The

plug

aoanector

PL-259,

and

angle

plug

adapter

M-359, supplied with the receiver, are for use

vith

RG-11/~

coaxial cable

(not supplied).

Speaker

-

The

speaker should be

of

the

permanent-magnet dynamic type and should

include

a

speaker voice coil to 600-ohm line-matching tran~formerfor connection to

the

600-ohm audio output tera'linals

of

the receiver, Caution: When the 600-ohm out-

put

is

not used connect a 600-ohm, 2-watt resistor to these terminals to avoid

component damage from high transient

peak

voltages,

For

applications requiring the

insertion

of

direct

current

control

or

Indiesting

voltages,

the jumper connecting

the two balanced sections of the

600

ohm-output

may

be

removed

and the insertion

circuit,

such

as

a low resistance balancing potentiometer, connected in

its

place.

Headphones

-

Either high

or

low impedance headphones may be used by plug

connection

to

the phone

jack

located

at

the lower left

side

of

the

front panel.

The

high impedance type

is

recommended.

Mounting

-

The

receiver

is

designed

for

rack mounting, Top and bottom cover

plates aresupplied for mounting in

a

standard 19-inch rack.

The

panel

is

10*

inches high,

See

Section

VII,

The

receiver sh0uJ.d-be placed

in

a

position wlkh

permits the free access of air.

Crystals for Frequency Control

-

Crystals

Y1

to

~6

are not supplied with the

rece'iver, but

will

be

supplied on-special order for

any

signal frequency within the

range of from

2

to

30

megacycles.

In

order

to insure correct crystal-controlled

frequency operation, crystal units

may

be

ordered from

THJ3

HAMMARLUIQa

MFG.

CO.

INC.

The

order

should

specify

the

si~al

f~ecpency

for

which

each unit

is

to be used.

See note at end of Table

5.

To

iztx1

crystals loosen the

knurled

thumb screw on

top of the Crystal Control Unit

~34

and

push to the rear, Insert the crystals in

the sockets. Bring the retainer spring

assembly

forward so that the springs press

on top of the crystal holders, and tighten the thumb screw.

Mark

the

signal fre-

quency

for

which each crystal

was

selected in megacycles

ou

the plastic chart

provided for this purpose alongside the crystal svitch

S2,

Pencil or ink may be

used and can be erased

if

it

is

desired to

change

these

figures

at

any

time.

The

numerals on the chart should

be

used so that they agree with the numerals on the

crystal socket positions, which are also indicated

by

the crystal selector switch.

Relay Connections

-

If

external relay operation

for

the send-receive function

is

desired, connection

may

be

made

by

soldering

a

twin conductor cable to the

terminals of the Send-Receive svitch

S9.

In this case

Sg

is

left in

the

Send

or

Open

position,

AVC

and Diode Output

-

In

diversity applications, the diversity feature

is

iccentuated bmlitercoidecting

the

AVC

(-1

bus between receivers,, and utilizing

a

common

ground

(G)

connection.

This

AVC

connection

is

made

when

the

IF

or

AF

outpllJ

of

the

system

is

used

to

provide

for

the

intelligence

due

to

a

CW,

MCW,

or

fre-

quency-shift

signal;

but

for

voice

6igne~l8

wnly

the audio

output

from one

receiver

is

used.

This

is

done

by

removing

the

DIODE

OUTPUT

jumper

on

each

receiver

apart

from

one;

and

connecting

the

negative

(0)

terminal

of

each

to

that

of

the

one

whosc.

terminals remain

jumpered,

IF

Output

-

The

IF

output

s~cket

50-239

at the

rear

skirt

provides

the

signal

at

44mo"i:

diversity receiving

system

use.

Connector

plug

PL-259

end

angle

plug

adapter

M-359

(supplied)

should

be

used

with

RG-11/~

coaxial

cable

(not

supplied).

The

output provided

to

a

70-ohm

resistive load

is

approximately

200

millivolts for

normal

sensitivity

(2

microvolts

input signal).

Master Slave

Connections

-

In

diversity applications the monitoring requirements

imposed'

on

the

opera'toraaevere, but

may

be

kept

st

a

alnirnun

by

use

of

common

conversion

and

beat-frequency oscillators.

Then

$he

operator need concern

himself

mostly

with

the

signal

level

in

each

channel

and

the

signal tuning

of

the

receivers.

To

provide for

V-3

crystal-controlled

first

heterodyne,

and/or

V-8

3.5

mc.

crystal-controlled

heterodyne,

and/or

V-13

beat-frequency

oscillator

output,

respectively, from

the

master

to

the

slave

receiver,

the

HFO,

IFU,

arid

BFO

sockets

50-239,

at

the

rear

skirt

of

each,

furnished

with

plug

PL-259,

and

angle

plug

adapter

M-359

for

IFO

and

BFO

only,

are

interconnected.

The

coaxial

cable

RG-~~/u

suited

for

use

is

not

supplied.

With

the

red

Ront

panel

controls

in

each

instance

on

one

receiver

set

to

a

red

panel

marking,

that receiver

becomes

the

slave

receiver,

wherein

its

V-3

(wo),

V-13

(BFO)

and

its

V-8

(IFO)

are

rendered

inoperative.

Remote

Connector

-

The

RWOTE

connector

Jb

is

furnished

with connector

plug

AIP

3-43

'and

cable clamp

AM

3057-6.

Use

terminals

k

and

B

of

J4

for

connecting

a

local

external

tone

so&&

to

amdulate

a

Cb?

signal

and

use

terminals

C

and

D

of

34

to

perform

the

function

of

the

CW-MOD

switch

by

another

system

panel

-

swltcb,

if

desired.

SECTION

IV

OPERATIOW

General

-

Before attempting operation of the SP-600-~~17receiver, the operator

s

shou~~roughlyfamiliarize himself with the f'unctions

and

useo of

the

ve;rlOus

controls. When referring to the controls in this description, the words in capital

letters represent the part of the name adjacent to the control on the front panel

Qr

on the rear skirt of the chassia,

For

example,

when referring to the SELECTIVITY

C

control,

the

word,

SEU3CTIVXTY

in.

cspitals

iqdicates

the

legend

sppearing adjacent

to the control. Reference to photographs,

Fige.

1

and

6,

is

suggested while

reading

this

description. Front panel controls

aad

d$als

are

shown

in

Fig,

1

and

rear controls

and

terminals

are

shown in Fig.

6.

Selectivity'~ontro1

-

The

SELECTIVITY

control

is

a 6-position switch which

selects'three crybt=nd three eon-crystal

degrees

of

selectivity, ranging from

extremely sharp

for

Cbl reception to broad for good fidelity

MCW

pera at ion.

The

SELECTIVITY

control dial indicates the

6

db bandwidth

at

each setting.

Phasin Control

-

The

CRYSTAL 3PHASING control

is

a

differential

type,

variable

air

_?aO_r_;_f_

capac

t

permits adjustment

of

the

crystal seZectivity characteristic for

high attenuation of closely adjaceat channel. interference on either side

of

the

signal frequency.

RF

Gain Control

-

The

RF

GAIIB

control

wries

the overall gain of the receiver,

This control

is

operative

in

either position of

the

AVC-MAN

switch.

.

Power Switch

-

The

power,

~r

"on-offt' switch

is

combined with the

RF

GAIN

con*

trol, Complete counter-clockwise rotation

of

the

RF

GAIN

control throws.

the

power

switch to the "off" position,

as

indicated on

the

RF

GAIN

control dial,

Audio Gain Control

-

The Audio Gain control varies

the

input voltage to the

audio amplifier.

This

control

is

also operative in either position of the

AVC-MAN

switch.

Phone

Jack

-

The

PEONES

Jack

is

a

single circuit Jack operating

with

tho sleeve

groundeil

aiis

suitable

to

receive

any

standard single circuit phone plug.

It

is

in the circuit at all times and

is

connected

to

a

separate secondary winding of the

audio output transformer, which provides

an

attenuated signal for headphones,

See

Section

111,

Installation,

Audio Output

-

The

AUDIO

OUTPUT

is

available. at the four-screw terminal board

at the

re&

onhe chassis for connection

to

a

600-ohm load. See Section

111,

Installation.

Noise Limiter

-

The LIMITER control switches

the

noise

peak

limiter in or out

of

the

circuit, This control

is

operative independently of

any

position of any

w

other control.

See

Section

TI,

CircuSt Description.

AVC-Manual Switch

-

In the

AVC

positiop the

AVC-MAtT

switch applies automatic

bias potentials to

t6e

controlled

RF

and

IF

amplifier tubes, thereby holding

the

I

audio output relatively

constant

over

a

wide

variation

ia

the streneth of received

signals, This min$mizes

the

variation

of

output

due

to

fading

09

the received

signal and prevents blasting

and

overloading when

tuning

through signals of greatly

different strength

while

traversing

a,

frequency band,

In

the

AVC

position

the

RF

Meter circuit

Is

operative for indication

of

tuning resonance

atla

relatlye strength

of received signals.

The

RF

GAIN

control

is

operative

on

AVC

operation when

necessary

to control exceptionally strong signals or to reduce noise, but

the

RF

meter is

less effective when the

RF

GAIN

control

is

belowmaximurn setting. In the

MAN

posi-

tion the

AKC

potential

is

removed from the controlled tubes

and

the gain of the

receiver

is

manually controlled

by

the

RF

GAIN

control,

CW-Modulation Switch

-

The

CW-MOD

c~ntrol

is

the

CW

positlosl

energizes

the

beat

frequency oscilEt6r.

3h

MOD

position

the

beat

Preguency

oscillator

ts

inoperative

and

the conditions

are

e$tabl&shedfor

either

wice

modulated

or tone

modulated

signal reception,

Beat

Fre

uency Oscillator

-

The

BEAT

QSC

control

varies

the

tuning

of

the

455

kc

Beat Freq&sciilatok~]:

rr

range

from

zero

bcat

to

plus or

minus

3

kilocycles,

.

BFO-AVC

Switch

-

!The

BFO-AVC

control in either the

EXT

BFQ

SLOW

or

INT

BFO

SLOW-

positions' connect's

an

additional timing capacitor to the

AVC

circuit to accommodate

the

AVC

circuit to wtomatic

CW

keying,

as

compared

to

either

the

EXT

BFO

FAST

or

INT

BFO

FAST

positions, effective

for

MCW

and

freavency~shiftreception.

In

either

FAST

or

SLOV

-

INT

BFO

positiona,

the

internal

BFO

of"

the

receiver

is

operative

when

the

CCl-MOD

switch

is

at

C%

In

either

FAST

or

SLOW

!3XJ

BFO

positions, the

BFO

source

connected to the

BFO

connector at the

rear

skirt

is

ueed

by

the

receiver,

IF0 Switch

-

The

IF0

s~fitch

in

the

INT

position

rendere

the

internal

3*5

mc

crystal-i%qtrolled aonversion oscillator

operative.

In

the

EXT

position

We

oscillator

is

inoperative, since the

EO

of

the

master receiver (externally connect-

ed to the

IF0

connector at the

rear

skirt)

is

used,

Send-Receive

-

The

SEND-REC

control

is

a

single-pale

single-throw toggle switch,

In the

SEND

position

it

desensitizes the

RF

amplifier,

gate,

second mixer and

3,5

mc

oscillator tubes during transmission periods,

Tuning Control and Dials

-

The

TUNING

control rotates the main tuning

capacitor

as

v'l

as

the miin andvernier tuning dials.

The

main

dial

has six frequency band

scales, calibrated in megacycles, and an arbitrary outer

scale.

The

vernier dial

has

an

arbitrary

0

to

100

scale,

The

nurqeral under

the

upper or fixed pointer of

the main dial indicates

the

nwnber of complete revolutions that have been made

by

the vernier dial

at

any setting, Thus,

if

the

pointer for the

outer

scale

of

the

main dial. indicates over the figwe

"4"

and

the vernier dial indlcates

87,6,

the

reading to log for this setting

is

"487.6".

This

precise mechanical vernler

system

divides the rotation

of

the main dial over

each

frequency band into approxi~ately

600

vernier divisions, with one-half division calibration points,

Since

it

i6

essy

to

estimte

one-tenth

divisions on the vernier scale, this divides

each

frequency

band into approximately

6000

readable settings, providing

extreme

accuracy in the

logging

and

resettiw

00

etations,

Tunin Lock

-

The

!WNING

LOCK,

located to the right

of

the

TUNING

control, pro-

vides

+

a

pos

ve lock for the tuning mechanism without affecting the

frequency

setting when

it

is

desired to prevent accidental shifting

of

the

tuning,

Band

Chan

e

-

Each revolution

of

the

BANI)

CHANGE

control turns the turret,

con-

+

tain ng

he

R

and

HF

Oscillator coil,

trimmer

and switch contact assemblies,

from

one frequency

band

to

the

next,

The

turet has

no

stops and

may

be

turned in either

Mrection,

A

positive detent mecbwism assures correct location of the

various

bands,

The

BAND

CHANGE

control

simultaneously

operates

the

small

MEGACYCLES

band

indicating

v

dial, located

at

the

center

of

the

panel

and

aligns

the

dial

frequency indicator

with the proper scale

of

the main

dial,

Crystal

Controlled

HP

Oscillator

-

me

lfTAL$

control

selects

one variable

high

frequenc~oscimr'~peratiiih,w~nt?

of'

the

sir

crystal positloas. Correspondingly

numbered crystal sockets

are

provided in the Crystal Control Unit, In

its

EXT

position, the crystal-controlled

first

conversion oscillator source

is

connected

to

the

HFO

connector

at

'the

rear

skirt, See Section

I11

Installation, Tbe

DELTA

FREQ

control compensates for the

small

crystal frequency. tolerance,

Meter Switch

-

The

METER

switch

is

a

double-pole,

double-%brow

toggle

swiCch

s

with spring return to the

RF

position.

Eee

Section

11,

Circuit

Deswiption,

Tuning

Meter,

Tuning Meter

Controls

TkaeMWER

AIIJ

RF

control

is

wed,

to

&Just

the

resistatlce

t

shunting

the

meter

when

<he

METER

switch

is

in Che normi, or

RF

posttlon.

It

is

adjusted to

produce

a

reading

of

plus

20

db

OQ

the

RF

scale

of

the

wter, with a

10

microvolt

RF

input

signal

and with

the

AVC-MAN

switch in the

AVC

position.

Depressiop

of

the

MEm

switch to the

AF

position

converts

the

meter circuit

for

indication

of

the

AF

pgwer

output

level

in db from

6

milliwatts,

mis

switch

is

spring-returned

$0

the

RF

position

when

released

and

should not be

depressed

for

the

AF

scale

unles~

the

audio

output has been adjusted for low power output

by

means

of

headphones or speaker.

failure

to observe tbls precaution

may

result in

damsge

to

the

meter, The-meter

ADJ

AF

control

is

used

to replate the meter current when

operating

on

the

AF

scale,

This contr~l

lis

adjusted

to

obtain

aOdb

reading

Qn

the

AF

scale of

the

meter

and

is

wde:

wiCb

the

audio power output from the

600-ohm

AUDIO

OUTPUT

ternlinals adjusted to

6

millfvatts,

or

leg

vo3.t~across

a

600-ohm resistive

load,

PrelSminary to Operation

-

Turn

the

power

switch

"on"

by

turning the

RF

GAIN

control ~o~-ij;Xse*aiz!L! adv"?iiiEe this control to

"10".

Note that the

dial

lamps

light.

Place the

SEND-REC

switch on

REC

and

turn

the

BAND

CIIAPJGE

controk to the frequency

band

in

which

it

is

desired to

operate,

mis

should be done at least

15

minutes

before

using the receiver

in

order to

permtt

the tubes to warm

up,

Insert the

head-

phones

plug

$#

the

PHONES

jack

or

use

speaker

as

desired.

See

fnstallation, Section

111.

MCW

Reception

-

Turn

the

TUNING

LOCK

to

its

extreme counter~clockwiseposition

and

~CTIVITY

switch to

3

kc.

Put

the

CW-MOD

switch on

MOD,

the

LMITER

switch to

OW,

the

AVC-MAN

switch on

AVC,

the

XTAL

PHASING

control

at

its

center

position

and

turn the

XTALS

switch to

VFO,

With the

BAND

WE

control

in

the

proper position for the 'frequency

band

desired,

as

indicated

by

the MEGACYCLES dial,

advance the

AUDTO

GAIN

control until some noise

is

heard.

Turn

the

TUNING

control

to indicate the

deslred

frequency on

the

main

dial

and

tune the signal for

maximum

response

or

Indication

on

the

RF

Meter.

At

resonance

the

main

dial reading should

be within onequarter of one Bercent of the signal frequency, Re-adjust

the

AUDIO

GAIN

control for

the

desired output level

and

as

required to prevent overloading,

Carefully tighten

the

!WNIIOG

LOCK by

turning

clockwise,

if

desired,

The

SELECTIVITY

switch

may

be

turned

to the

8

kc

or

13

kc

poeition for improved high frequency

response

if

the sigrral-to-noise ratio

is

sflficiently

high,

If

the

noise

level

I8

high, the

SELECTMTY

switch should

be

turned to the bandvidth which provides the

most

inteJligible reception and the

LBIITER

switch

should

be thrown "on".

If

the

SELECTqITY

switch

is

used

on one

of

the

X!tAL

positions, the

XTAL

PBASIlVG

control

may

be

adjusted

to either side of

its

center position to attenuate

an

adjacent

interfering signal.

The

RF

GAIN

control

may.

be

turned

down somewhat to

reduce

noise

during

stand-by

periods

in

the

transmission

when

traversing the tuning rarrge,

or

during

deep fades of

the

signal,

RF

Meter scale calibrati~n

is

?or

maximum

RIP

GAIN

control operation and indicates only

when

the

AVC-MAN

switch

is

on

AVC,

When

searching for very

weak

signals the

CW-MOD

switch

may

be thrown

to

CW

and

the

BEAT

OSC control

set

at

"0".

Locate and tune the signal to obtain zero

beat

and

then

throw

the

CW+OD

switch

back

to

MOD,

The

Crystal

Requency

Contr~l

my

be

used

for

fixed-frequency operation

at

any

slgnal

f'requency

for

which crystals have been provided*

See

Section

1x1,

Installa-

tion, Turn

the

XTALS

switch

to

the

numeral corresponding to

that

on

the

panel

chart

for

the'

desired

signal

frequency.

Set

the main

tuning

dial

to

the

signal

frequency

and

adjust

the

4

FREQ

control

to

obtain

zero

beat

with

the

CW-MOD

switch

on

md

the

BEAT

OSC

control

at

"0".

Throw the

CW-MOD

satch

to

MOD

and

adjust

the

TUNING

control

for

maximum

RF

Meter

indication or

for

maximum

response,

CW

Reception

-

The

preliminary

procedure

for

CW

reception

is

the

same

as

for

MCW

Sceptiori

above,

Place

the

C!q-MOU

switch

on

CW

and

with

the

BEAT

OSC

control

at

"Ow,

tune

the

desired

eignal

for

zero

beat,

Adjust

the

BEAT

OSC

control,

in

either

direction,

to

obtain

the

audio

pitch

desired,

The

AVC4IAN

switch

may

be

used

in

the

position which gives

the

best

reception, Adjust

the

desired

output

level

by

the

AUDIO

GAIN

control

when

on

AVC

and

by

the

RF

GAIN

control

when

on

EUIIIN,

The

RF

Meter

does

not

operate

on

the

MAN

position,

The

SEUCTIVITY

switch

may

be

used

in

-

the

XTAL

positions,

as

found

desirable,

to

reduce

noise

or

to

provide

rejection of

an interfering signal,

The

XTAL

PHASING

c~ntrol

is

adjusted

for

minimum

interference

-om

an adjacent, interfering ~ignal,

If

interference of this

kind

persists,

fur..

ther discrimlnatioa

between

the

desired

and

the

undesired

signals

may

be

realized

by

slightly

detuning

the

desired

signal

.to

the

opposite

side

of

resonance

from

that on

which

the

undesired

signal

is

located

and

readjusting

the

XTAL

PHA$ING

control

and

the

BEAT

OSC

control

for

%he

desired

.signal.

The

Crystal

Frequency Control

may

be

used

as

described

under

MCW

Reception

above,

If

reception

is

to

be

suspended

an4

resumed

at

short

time

intervals,

the

power

should

be

left

"on"

and

for

such

operaWm

tihe

SEND-REC

switch

should

be

thrown

to

SEND

between

reception periods.

!Ibis

keeps

the

receiver

warm

and

ready

for

Instant

use,

When

operation

of

the

receiver

is

completed,

twn

the

power

"off"

by

extreme

counter-clockwise rotation

of

the

RF

GUN

control,

SECTION

V

General

-

Thi.s receiver

is

designed for continuous duty and should normally

requmtleattention beyond the replacement of tubes.

An

occasional cleaning

of the gem teeth in the

geful

train

is

recommended to prevent a heavy accumulation

of dust

which

may

cause calibration error

and

improper operation of the

gears,

This

may be done with

a

small

stiff

bristle

brush, turning the controls to obtain access

to the different portions

00

the

gears.

No grease or oil should be used on the

gears. Operation and mainteaance

of

the

receiver

will

be greatly facilitated

if

the contents

of

this instruction book

are

thoroughly digested.

Some

sectio~alizingof faults

is

possible,

if

the fault

is

not existent on all

of the frequency bands. Non operation

of

only the three lower frequency bands,

indicates that tbe fault

is

associated with the circuits of tube

V7.

If

only the

three higher frequency bands are

affected,

the

fault

is

associated with the circuits

of

V6

or

~8.

If

only

one

single band

is

affected, refer to

BF

Oscillator and

RF

Coil Assemblies in

this

section,

Visual evidence of trouble

is

usually a burned or darkened resistor, which

is

usually the result of excessive current due to a short circuited capacitor or tube

element on the load side of the resistor.

In

such a case, the short circuited

capacitor or tube and the resistor should

be

replaced as indicated, Refer to

Figures to

12

and Table

5

for location and values of components, If the checks

on

tubes, fuses and visual iuspection fail to disclose the fault, the tube socket

voltages and resistances should

be

measured

and

checked against the value given in

Tables

1

and 2,

Any

agpreciable departure beyond a normal variation of approximately

15 percent

from

the values in thege tables

will.

generally indicate the component or

circuit at fault.

If

the foregoing does

not

reveal the fault, then a stage by stage

check of amplification should

be

made

as

shown in table

4,

Any

great difference

from

the

values of input shown in the table

will

indicate the stage at fault. If a

tuned circuit component, such as an

IF

transformer, RF

or

IF

oscillator coil assembly

is

found defective, only the replaced unit need be realigned. Follow the alignment

procedure in Section

VI,

for the unit involved,

The

IF

Transformers, Crystal Filter,

Beat

Frequency Oscillator

and

the

3.5

mc

Crystal Cotltrolled Oscillator assemblies are mounted on the chassis, independently

of their respective shields. me shield can assemblies are easily removed for

inspection of these units, without disturbing the soldered connections, When re-

placing these shields, make sure that the grounding springs are in place on the

inductance adjuster screws before the shield

is

installed.

Vacuum Tubes

-

Weak or defective vacuum tubes are the

most

common cause of

decrease in sensitivity, faulty performance or failure of operation in a receiver.

In case of such faults, first remove the tubes and check them in

a

tube tester of

reliable design.

If

a

tube tester

is

not

available, substitution of a new tube for

each tube type and position should

be

tried. See Figures

2

and

3,

Such substitution

is

best made, one tube

at.

a time

in

order that

the

faulty tube may be detected

by

the improvement or restoration of performance by the new tube.

L

Locating Faults

-

If

the dial lamps do not light

when

the power switch

is

turned

on, check

for

a

blbwn line fuse,

F1

and replace

it

at the rear

of

the receiver from

the spare fuses.

If

the dial

lamps

light but there

is

no sound at all in

the

head-

phones

or

speaker, check for

a

blown, minus

B

fuse,

F2,

If

blown, replace. In

replacing fuses, make

sure

that only

a

1,6~

Fusetron

is

inserted in the line fuse

holder and that only

a

3/8

ampere

fuse

is

inserted

in

the minus

B

fuse holder.

Should neither fuse

be

blown, or

if

replacement of

the

fuses does

not

restore

operation, the receiver should

be

removed

from

its

rack

and

inspected for visual

signs of trouble.

The

rack,mdel receiver

is

provided with bottom

and

top cover

plates which should be removed for purposes of inepeetion and repair.

IF

Transformers

-

If

a

fault

is

traced to one of the variable coupled

IF

trane-

formers,

T4

or

T5,

check

whether the fault exists on all positions of the selectivity

switch

S5,

or

only

on one position of

this

switch.

If

the -faultyoperation

occurs

on only one switch position,

check

for

continuity

of

the

coupling coil associated

with that position, check

f~r

imperfect soldered connections at the coil and switch

terminals

and

check the switch contact involved, If faulty operation localized at

one transf~rmerexists on

all

positions

of

the selectivity switch, make the con-

tinuity check on the

plate

coils,

on

the

main grid coil

and

on the wiring associated

with these coils, Transformers

~4

and

T5

and Cry~tal

Filter

T3

have additional

inner shield assembZies that

are

held

in

place

by

the

tension nuts on

the

adjusting

screws. To remove

these

shields, hold the a.dJufiting screw with a screw Briver to

prevent turning the screws and losing

the

alignment adjustment and loosen the

tension nuts, using anotber

small

screw

driver

engaging

one

of

the

slots,

When

replacing these shields

and

tension nuts, employ the

same

method

and

tighten the

tension nuts just enough to prevent

the

adjusting screws

from

working loose,

Beat Frequency Oscillator

-

To

remove

the

beat frequency oscillator

T6,

it

will

be

n'ec&saary to

~iw~r~stal

selector

switch

52,

on

its

number

3

position

and

loosen

the

four

set

screws in the

rigid

shalt

coupling and

the

twoset screws in

the disc on the selector switch shaft. Slide

the

switch

shaft

forward through the

coupliug and disc.

It

may be necessary

to

remove burrs, caused by the set screws,

from the switch shaft

ia

order

to

slide

the

shaft through

the

disc, Now loosen the

four set screws

of

the

flexible

coupli~g

on

the

BE'O

shafts

and

slide

the coupling

forward on the

BFO

drive shaft in the front

panel,

Remove

the

BFO

shaft bearing

bracket

by

taking

out

the

ttm screws holding

it

to the

chassis,

Unsolder the leads

from

the six terminals of

the

BFO

unit

at

the

underside

of

the

chassis,

Be

careful

to avoid overheating

the

wire of

the

shielded cable since this wire is.in>ulated

with polystyrene ind

is

.@EiTy

'danxiged

by

heatA,-

Note

that

if

this

cable

'

w-

grounded

to

its'

shield,'

there

wnl

be no 'berfrequcncy voltage input to the buffer

tube V12

even

though

the

beat

oscillator

is

functioning properly. Therefore, with

the shielded lead disconnected from the

lug

of

the

BFO

unit,

check

with

a

continuity

or ohmeter the connection

of

this wire to

the

buffer tube V12 and its freedom from

the chassis. Carefully observe

the

wiring

of

the

BFO

unit

for

correct replacement.

See

~6

on

Figure

12.

Now remove

the

two

screws holding the

BFO

shield can

to

the

chassis

and

the two screws

at

the underside of the

chassis

and

remove the

BFO

unit,

When replacing the unit, follow

the

reverse procedure. Before tightening the two

screws holding

the

unit to the chassis and

the

two screws holding

the

shaft bearing

brackets,

ad

just

the

unit

and

shaft brackets

to

obtain alignment

of

the

two shaft6

at the coupling.

Make

sure

that

the

shield grounding

spring

is

in place, with the

bow of the spring downward against the tension

nut,,

before replacing

the

shield can

assembly.

Adjustment

of

BFO

-

With

the

AVCcMAN

switch

on

AVC,

and

the

SELECTIVITY

control

on

the

.2

kcposit=,

tune in

an

unmodulated signal for

maxirrm

tuning meter reading.

Set the

CW-MOD

switch

to

CF!

and with

the

BEAT

OSC

dial

at

0,

adjust the top screw of

the BFO

unit

for

zero beat,

Turn

the

BEAT

OSC

dial to each-

3

kE

position and check

the output beat frequency against

a

known audio frequency source such as

a

good audio

oscillator.

If

the beat frequencies obtained

at

each

3

kc

position

is

not within

the

*

range between

3

and

3.5

kc, loosen

the

set screws of the

BFO

shaft

coupling and turn

the shaft

of

the

BFO

with respect to the

drive

shaft

and

repeat the

above,

resetting

the

0

adjustment

by

the top screw of the

BFO

unit

each

time

until the above

range

is

realized. One set

screw

should

be

used

just ti$ht

enough

to

allow the drive shaft

to

operate

the

BFO

shaft until

the

range

is

correct

and

then tighten both screws.

Crystal Switch Adjustment

-

If,

the mechanical drive of the crystal control

switch Bas been dist*bed,

it

should be adjusted as follows: Carefully slide the

switch shaft-through the disc and into the rigid coupling and, being careful not to

turn the switch, tighten the four set screws in the rigid coupling, with the knob

indicator on the number

3

position as originally set under Beat Frequency Oscillator.

Now set the crystal switch on the number

1

position and, holding the disc

in

a

counter-clockwise direction so that the end of the slot in the disc

is

against the

drive pin, lightly fasten the set screws of the disc, When this disc

is

properly

adjusted on the shaf't, with the switch in the

number

1

position, the connecting bar

between the two discs should not be

under

tension and should exhibit

a

slight amount

of play when tried with the

thumb

and forefinger, When

80

adjusted, tighten the set

screws.

Crystal Cont.rol Unit

-

If

it

has been determined that the Crystal Control Unit

is

def'ectSve,it

wilm

necessary to remove the unit for repair or replacement.

Refer to Figure

11

and

12

and unsolder the lead of resistor

R71

from switch

S3

on

the gear plate. Unsolder the black, black-white, blue-red and retbwhite leads of

the crystal control unit from terminal strip

El3

wderneath the chassis and unsolder

the red lead of the unit from

filter

capacitor

~1.61,

Remove the

X!CALS

switch shaft,

as described under

Beat

Frequency

Oscillator,

Loosen set screws and remove the

delta

C

control knob, Remove the

nut

anrl lookwasher at the top of the bracket post

adjacent to the power transformer and renovc

the

bracket over the filter chokes,

The front end of this bracket

is

slottecj, and

engages

a

groove in a mounting post of

the crystal lcontrol unit.

Remove

the

four

screws that secure the filter assembly

panel to the mounting posts

at

each corner of this panel

and

move the filter assembly

sufficiently to permit removal of

the

four

scrqws holding the crystal control unit

to the chassis. When these screws

are

removed, the unit

may

be

taken from the

receiver,

In

removing the unit

an8

in subsequently handling

it,

be careful to avoid

.

strain on the delta

C

shaft,

or

the

delta

C

capacitor

may

be damaged, Remove the

four screws holding each

of

three sides of the cOver and spring the two top ends of

the cover enough to make the

flanges

clear the top of the box. Hold these flanges

apart to prevent their edges from damaging the

RF

chokes in the unit while sliding

the cover off the crystal unit box,

When

the unit

is

to be replaced, follow the

reverse of

the

above procedure. Follow the procedure under Crystal Switch

Adjust-

ment to properly reinstall the switch mechanism.

HF

Oscillator and RF Coil Asse~blies

-

If

faulty operation occurs in only one

frsquericy

'b&d7of

the receiverne

'trouble

should be

found

in one of the four coil

assemblies for that band in

the

twing unit turret, For example: Coil assemblies

T13,

19,

25

and 31 should be

examines

if

band

7.4

to

14.8

mc only, does not perform

normally.. To remove these

coil

assemblies stand the receiver

on

its

ri@t or left

side

and remve the bottom cover p1at.e from the tuning unit. Turn the band change

control to place

the

band

in

question

in

its

normal operating position and then turn

the band change control two and one-half

revolutions

counter-clockwise, This

will

place the band coil assemblies parallel and at the bottom

of

the tuning unit. Now

remove the two springs holding

one

coil assembly

in

the

turret and carefully remove

it

by

eliding

it

toward8 you and off the tongues of the shields,

It

is

best to

remove only one coil assembly at a time and inspect

it

far

defects or substitute a

replacement assembly

if

available. Caution:

Make

sure that the coil base

is

firmly

seated adsecured

by

its

retaining &ore' going

'

tb the' next assembly

i>r

turning' the

-band:

'

change contror

,'

-

F

do

'

this' may d@a&e

the

swi'tch spring

repair: Repeat thisprocedure

until.

the faulty7-amy

is

found.

L

e assFmblies,

first

check for co,&inuity

of

the

coils, particularly

the

small

primary coils

as

in the

RF

Input

assemblies, which

are

liable to dsmage

if

the receiver

is

operated in the presencq

of

very

strong transmitter signale,

In

replacing these coil

assemblies

be

csrefW

that

the

end

a$

the

assembly

nearest the

coil

is

toward

tba

ir~at

of

the

recetver,

Mixer

Plate Coil Assembly

-

Wouble in the

Mixer

Plate Coil Assembly Tl,

is

indicat-ed if the input 'required

at

7

of

V5

is

found to be greatly different than

the values shown in Table

4,.

and the gain from pin

7

of

~6

is

normal. To obtain

access to the components of the mixer plate coil assemblies

it

is

necessary to remove

the

crystal control unit and

the

filter assembly

as

described under Crystal Control

Unit.

The

cover plate

and

shield of T1 may then be removed for replacement of

a

defective component..

If

the entire assembly

is

to

be

replaced,

it

will

be necessary

to wsolder all

of

the leads at both the-bottom

and

top terminal boards

of

the unit.

Refer

to

Figure

11

for components and wiring of TI,

RF

Tube Platform

-

If the receiver fails to perform normally on any of the six

frequency bands and the previous tests indicate

that

performance

of

the

IF

and audio

frequency amplifier8

is

normal, (including the gain check in accordance with Table

4

for

the

input to

7

of

~5)

the fault

is

indicated

to

be

in

the

RF

Tube

Platform

or in the main tuning capucitor, Before removing the

RF

Tube Platform,

it

is

advisable to remove the top shield cover and inspect the main tuning capacitor

connections. Refer to Figures

8

and

11,

Observe that the tuning capacitor

is

operating properly when

the

tuning coatrol

is

rotated, Using a miniature tube

adapter, Gee Section

VI

aligrunent,

apply

a

modulated

rf

test

signal successively

to

pin'

1

of

V1

and

V2

and to pin

'7

of

Vg,

For each of these positions of the adapter

and

signal, tune through

the

proper

dial

setting for the signal frequency used,

Gain of the order of

5

or

6

should

be

indicated for

each

stage

and

loss of signal

will

indicate the section to

be

investigated

for

the fault. No signal output,

when

the input signal

is

applied to pin

7

of

V5,

will

indicate trouble

in

the

HF

oscilla-

tor section of the unit, With the covers removed from the tuning capacitor and T1,

refer to Figure

11

and unsolder

the

blue, white-black, red-white, red-green, yellow-

black and blue-red leads that come from the tube platform at

the

top of T1, Un-

solder

the

leads from the tuning capacitor rotors, stators and

ground

straps at each

section, Unaoldes the

lead

from

the tube platform

at

S3,

Turn

the

Band

Change con-

trol one-half turn from any band position in order

to

have

the band switch contacts

disengaged aqd leave the band switch

in

this position until the

RF

tube platform

is

replaced, otherwise irreparable damage to

the

switch contacts

will

occur, Remove

the four screws at the corners of

the

top

of

the platform and the four screws at

*he side flange

and

carefully remove the platform. In handling be careful

to

pre-

xent

damage

to the switch contacts

of

this assembly,

When

the unit

is

ready to

be

~eplaced,follow the reverse of the above procedure.

Main Tuning Capacitor

-

If

it

is

necessary to replace the main tuning capacitor,

the Focedure

is

'as

followc:

Remove the top cover and unsolder the leads

of

the

capacitor as described under

RF

tube Platform. Bring

the

capacitor to full mesh by

means of the tuning control, Carefully remove the spring and drive link at the

front

of

the

capacitor, Remove

the

single screw

that

secures

the

capacitor

frame

front plate to the gear plate, looping

a

piece

of

small

wire

around the spacing

washer between the capacitor and gear plate.

The

qront capacitor plate

is

located

and held in position by two dowel pins

and

will

not

move

when the

front screw

is

taken out, Now hold

the

capacitor

by

its

frame

with

one hand and remove the rear

supporting screw

and

spacer.

The

capacitor

may

now

be

rnoved to

the

rear, to dis-

engage the dowel

pins,

and

lifted

from

the

receiver. Follow the above procedure in

reverse when replacing the capacitor,

SECTION

VI

The al.ignment of

a

leodern comtnunications receiver requires precision instruments

and

a

thorough

knowledge

of

the circuits involved. Since this receiver

is

a

double

super-heterodyne type, the alignment

proceDure

is

even more involved than usual.

Under normal service the receiver

will

stay

in alignment for extremely long

periods of time, consequently realignment should not be dttempted

unless

all

other

possible

causes of

a

particular trouble have been eliminated. !#hen

it

has

been

determined that

any

realignment should

be

made,

a

great

deal

of

caution should be

exercised in makilig the adjustments, since

any

required readjustment should not

entail more

than

a

slight

angular

motion of the adjusting screw,

ALXGNMEm

OF

THX

IF

STAGES

The low frequency

IF

should be

aligned

first.

recommended method

for

aligning

the

low

frequency

IF

involves

the

use

of

a

sweep

frequency

~ignal

generator

and

an

oscilloscope. Since

these

instruments are

not

available

at

the average

ser-

vice station the alternate method

using

sn

amplitude mdulated signal generator

and

an

output

meter

will

be

aescribed

first,

The

additional informtion required

for

the visual alignment method

will.

be

covered

in

a

later

paragraph,

*

The

signal

generator should

be

coupled

*to

th.e

grid

of

the

mixer

tube

V5

through

a

capacitance

of

approximately

.01

mfd,

A

miniature

tube

adapter

will

be

required

to

make

the

mixer

grid

connection available.

A

suitable

adapter,

A/N

No.

cV-49519,

is

available

as

Part

No. 977

from

Alden

Manufacturing

Co.,

117

I?.

Main Street,

Brockton,

Mass,

An

output meter

should

be

connected across the output

of

the

receiver

or

the

speaker

voice coil.

The

receiver controls should now be

set

as

follows:

Control

--

Selectivity

Send--Receive

CW--Mod

Phasing

AVC--MAN

Audio

Gain

RF

Gain

Band Switch

Dial

BFO-AVC

IF0

Position

See

text

Receive

Mod.

Arrow

Man

Set for approx,

20

VOW

output

See

text

1.35--3-45

mc

2.5

mc

Int,

Bfo

Past

Inti.

e

The

signal generator should

be

modulated

30

percent at

400

cycles,

Turn

the

selectivity switch to the

3

kc

position

and

advance

the

RF

Gain

control to maximum.

Set

the

signal

generator frequency to

455

kc

and adjust

its

output until

some

deflection

Is

noted

on

the

output meter,

Refer

to

figure

3

for

the location

of

the

.

various alignment adjustments, Addust

L42;

Lkl,

L39,

~38,

~36,

and

L32

for

meximum

output,

reducing

the

signal

generator output

atid

the

RF

Gain

control

as

required

to

prevent

overloed

or

excessive output. Now turn the selectivity switch

to

the

narrowest

position?

,2

kc,

an4

addust

the

signal

generator

frequency

for

the

maximum

output.

This

establishes

the

correct

signal

frequency

by

the

455

kc

crystal'for the

IF

qlifier

and

the

frequency

of

the signal generator should not

be

disturbed

for

*

the

remainder

of

the

low

frequency

i.f.

alignment,

unless

it

should

be

to

re-check

this establishment

of

crystal frequency to

make

sure

that the signal generator

frequency

has

not

drilted

during

the

alignment.

me

selectivity switch

is

now

turned to the

3

kc

position and

L42,

L41,

L39,

~38,

~36

and

L32

are

again

adjusted

for

maximum

output, Before

changing

this

set-up

the

BFO

should

be

turned

on

by

throwing

the

CTJ-Mod

stritch

to

CW

and

checked

for

zero beat

with

the

BFO

knob

dial

at

its

zero reading.

If

necessary

L44

should

be

adjusted

for

zero

output. This

check

and

adjustment

of

the

BFO

should

be

done

with

$he

signal

generator

carrier

unrnodulated.

The

Procedure

for

the

visual

method

of

aligning the

low

frequency

IF,

using

the

doubl:

image

system,

shouid

be

the

same

as

the

above

except that the adJustments

are

made

for

both

maximum

amplitude

and

coincidence

of

the oscill~scopeimages.

The

oscilloscope vertical

input

should

be

connected

across

the

diode

d.etector

load

resistance,

f'rom

the junction

of

~64

and

R65

to

chassis.

The

high

frequency

IF

should

be

aligned

next.

Set

the

band

switch to

the

7.4-14,8

mc

band.

The

selectivity

switch

should

be

in

the

3

kc

position,

Adjust

the

signal

generator

frequency

to

3.955

mc

and

adjust

231,

L33,

and

L34

for

maximum

output.

The

3.5

mc

crystal

used

in

tihe

second

conversion oscilla.tor circuit

is

held

to

a

very

close frequency tolerance

and

may

be

used

as

a

frequency standard at multiples

of

3.5

mc

fram

10.5

mc

upwarda,

In

order

to

do

this,

in

view

of

the

complete

shielding against radiation

from

this oscillator,

it

will

be necessary

to

temporar-

ily

connect

a

two

foot

lengkh

of

insulated

wire

to

the

antenna

terminal

and

dress

the

free

end

of this lead

around

the

tube

shield

on

the

3.5

mc

oscillator

tube

~8,

This

test

should,

of

course,

be

removed

except

whirs

in

we

as

a

frequency

standard,

To

adequately

align

the

RF

Amplifier

apd

HF

0scil.lator

an

accurately calibrated

signal generator

and

an

output

meter

are

required.

The

frequencies

required

are

shown

in

table

3.

The

location of

the

adjustments

is

shown

in

Figure

3.

The

use

of

Table

3

and

Figure

3

should

be

made

in

following

this

part

of

the

alignment

which

will

now

be

described

for

one

f'tequency

bend.

%'he

same

procedure

should

then be

followed

for

the

other frequency bands.

To

align

the

,54&35

mc

band

the

signal

generator

is

coupled

to

the antenna

input terminal through

a

100-ohm

carbon

resistor.

The

generator

should

be

modulated

30

percent

at

400

cycles end the output

meter

connected across

the

receiver

output

terminals.

The

receiver

controls

should

be

set

as

follows:

Control

-

Position

-

Selectivity

3

kc

Send-Recei

ve

Receive

CW-Mod

Mod

AVC-Man

See

Text

Audio

Gain

Set

for

approx.

20

volts

output

RF

Gain

See

.text

Band

Switch

Sat

for

band

to be aligned

Limiter

Off

HFO

Var

Hammarlund SP-600-JX-17 Troubleshooting guide

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