Hallicrafters S-76 Operation manual

Fig.

J.

Communications

Receiver

Model

5-76 92X

17

78

DESCRI

P

TIO

N

The

Model

S-76

is

a

precision

built,

highly

sensitive,

double

conversion

superheterodyne

communica-

tions

receiver

employing

9

tubes

plus

voltage

regulator

and

rectifier

and

covering

the

frequency

range

of

538

KC

to

1580

KC

and

1720

KC

to

34 MC.

It

is

the

only

communications

receiver

,

at

present,

to

employ

a 50

KC

second

I.F.

(intermediate

frequency)

and

to

provide

the

advantages

of

double

conversion

through-

out

its

entire

frequency

range.

The

use

of

double

conversion

makes

possible

greater

image

rejection

than

is

practical

in

a

single

conversion

superheterodyne

receiver.

The

use

of a

50

KC

second

I.F.

provides

a

greater

selectivity

than

most

crystal

circuits

due

to

the

extreme

steepness

of

the

selectivity

curve.

The

five

position

SELECTIVITY

control

provides

variable

selectivity

from

5

KC

to

500

cycles

at

the

nose

of

the

curve

and

from

15

KC

to

4

KC

at

the

skirt.

This

high

degree

of.

selectivity

makes

possible

a

form

of

single

side

band

reception

of AM (phone)

signals

which

is

advantageous

under

crowded

band

conditions.

The

four

frequency

ranges

are

clearly

indicated

on the

large

main

tuning

dial

and

provide

complete

coverage

of

the

frequency

spectrum

between

538

KC

and

34

MC

with

the

exception

of a

small

gap

between

bands

1

and

2

in

the

vicinity

of 1650 KC,

which

is

the

first

intermediate

frequency

of

the

receiver.

In

ad-

dition

to

the

four

frequency

ranges,

a

special

logging

scale

has

been

provided

on

the

main

tuning

dial

for

logging

shortwave

stations

of

special

interest.

The

electrical

BANDSPREAD

control,

calibrated

specifically

for

the

80, 40, 20, 15,

11

and

10

meter

amateur

bands,

provides

a

vernier

or

fine

tuning

adjustment

throughout

the

entire

tuning

range

of

the

receiver

.

A

4-inch

rectangular

"S"

meter,

the

largest

presently

being

used

on

any

receiver

and

calibrated

in

both "s"

units

and

mi.crovolts

,

has

been

provided

to

aid in

tuning

the

receiver

and

to

give

a

relative

indi-

cation

of

received

signal

strength.

Other

special

features

included

in

the

S-76

are

automatic

volume

control

(A

VC),

automatic

series

noise

limi.ter

(ANL)

and

provision

for

headphone

operation

,

standby

operation

and

record

player

attach-

ment.

For

speaker

operation

, a

separate

external

loud

speaker

of

either

3.2

or

500

ohms

i

mpedance

is

required.

The

receiver

is

housed

in

an

attra

c

ti

ve,

well

ventila

t

ed

metal

cabinet

which

has

a

length

of

18-1/2

inches

, a

height

of

8-7/ 8

inches

and

a

depth

of

9-1/2

inches.

Page

2

The 8-76

normally

operates

from

a 105-125 volt 50-60

cycle

alternating

current

(AC)

power

source.

The 8-76U, a

universal

model of the 8-76,

permits

operation

from

25-60

cycle

AC

sources

at

voltages

ranging

from

115 to 250

volts.

Both models have

provision

for

operation

from

an

external

DC

power

source.

The

power

consumption of

each

model

is

77

watts.

IMPORTANT

Your

careful

attention

is

especially

invited

to

the

installation

and

operating

instructions.

They have

been

provided

to

insure

the

satisfaction

you have a

right

to

expect

from

a

Hallicrafters

"Precision

Built"

product.

Your

receiver

has

an

unusually high

degree

of

sensitivity

necessary

to

receive

weak

and

distant

stations.

Careless

operation

of a high

sensitivity

receiver

may

result

in

excess

noise

or

background

hiss.

These

undesirable

effects

can

be held

to

a

minimum

by

careful

adjustment

of

the

sensitivity,

tuning and

tone

controls

as

well

as

the

proper

selection

and

arrangement

of the antenna.

INSTALLATION

INSTRUCTIONS

UNPACKING -Check

all

shipping

tags

and

labels

for

instructions

before

removing

or

destroying

them.

LOCATION -The

receiver

is

equipped with

rubber

mounting

feet

for

table

top

or

shelf

mounting. When

locating

the

receiver,

avoid

excessively

warm

locations

and

recessed

installations

which

prevent

proper

air

circulation.

The

separate

loud

speaker

should not

be

placed

on the top of the

cabinet

but should be

located

as

far

from

the

receiver

as

is

practical.

A.C.

POWER

CORO

Fig. 2. Rear

View

of

Cabinet

MOUNTING

FOR

CO-AXIAL

CABLE

CONNECTOR

nC1376

POy,tER

SOURCE

-

This

receiver

may

be

operated

directly

from

an

AC

source

or

indirectly

from

a

DC

or

battery

source.

AC

OPERATION -The 8-76

can

be

operated

directly

from

a 105-125 volt, 50-60

cycle

AC

power !>utlet.

The

universal

model, the 8-76U,

is

designed for

operation

from

115, 130, 150, 220 and 250 volt, 25-60

cycle

AC

sources.

A

selector

switch,

located

on the

power

transformer,

permits

operation

of the S-76U on

any

of

the line

voltages

shown. The

normal

power consumption

of

each

model

is

77

watts.

If

in doubt

as

to

the

frequency

and voltage

rating

of

your

power

source,

contact

the

local

power

company

representative.

Attempting

to

operate

the

receiver

from

sources

of

power

not

specified

may

result

in

damage

to the

receiver.

CAUTION -When

operating

the

universal

model,

it

is

essential

that

the

selector

switch

setting

correspond

to

the

operating

line voltage

before

connecting the

receiver

to

the

AC

power

source.

NOTE: The

receiver

will

not

operate

from

an

AC

source

unless

the

JUMPER

PLUG

is

inserted

in

the

DC

POWER SOCKET. 8ee Fig. 2.

P'd.ge

3

DC

OPERATION -

The

receiver

maybe

operated

from

a 6

volt

DC

source

(storage

battery

or

equivalent)

and a 280 volt

DC

supply

in

the

form

of

"B"

batteries,

vibrator

power supply

or

motor

generator

set.

The

voltage and

current

requirements

for

DC

operation

are

listed

below.

DC

power

is

connected to the

receiver

through

the

DC

POWER SOCKET

located

on the

rear

apron

of

the

chassis.

The

JUMPER PLUG,

normally

located

in

this

socket

for

AC

operation,

is

replaced

with a

standard

octal

plug

for

DC

operation.

Wire

the

octal

plug

for

DC

operation

as

shown

in

Fig.

3.

VOLTAGE AND CURRENT REQUffiEMENTS

FOR

DC

OPERATION

"B"

Voltage

"B"

Current

Heater

Voltage

Heater

Current

280

volts

115

ma

6.3

volts

3.3

amps

BATTERIES

VIBRAPACK

"8'

280

VOLTS

+

BOTTOM

VIEW

OF

PLUG

+

"Aft

-=-

6.3

YOLTS

Fig.

3. Wiring Diagram for

DC

Operation

PILOT

LAMP

+II~

6.3YOLTS

A+

A-

B-

B+

9281388

SPEAKER

CONNECTION -

Three

screw

type

terminals,

marked

3.2,

500 and G,

are

provided

on

the

rear

apron

of the chaSSiS

for

connection

to

an

external

3.2

or

500 ohm

speaker.

It

is

recommended

that

Hallicrafters

speaker

R-46

be employed.

RECORD

PLAYER

CONNECTION -A

shielded

type phono

jack

is

provided

on

the

rear

of the

chassis

to

ac-

commodate

any

record

player

employing a

crystal

.pickup.

Refer

to

Fig.

6

for

wiring

details.

ANTENNA -The

terminals

marked

A1,

A2

and G on

the

back

of

the

receiver

are

for

antenna and ground

connection.

Satisfactory

results

can

be

obtained

in

most

localities

with

the

15

foot antenna

wire

included

with

your

receiver.

Simply uncoil the

wire,

connect one end of

it

to

terminal

A1

and then connect

the

jumper

between

terminals

A2

and

G.

An

outside

antenna

50

to

100

feet

long may

be

necessary

if

the

receiver

is

operated

in

a difficult

reception

area

or

steel

constructed

building. Reception

may

be

improved

in

some

locations

by connecting a

lead

from

terminal

G

to

a cold

water

pipe

or

outside ground

rod.

Page

4

ANTENNA

WIRE

Fig.

4. Single Wire

Antenna

Installation

92813

9

1-8

For

really

top

performance

on

the

shortwave

bands,

there

is

no

substitute

for

an

outside

antenna

such

as

used

by

the

com

mer

cia

I

radio

stations.

Provision

has

been

made

on

your

receiver

for

the connection

of

this

type

of antenna, commonly

called

a doublet. When

proper

ly

con

s t r u c

ted

and

installed,

the

doublet

antenna

will

provide

not only optimum

shortwave

reception

but

excellent

standard

broadcast

reception

as

well.

Refer

to

page

5

for

installation

details

for

the doublet

antenna.

DOUBLET

ANTENNA -

The

overall

length

(in

feet)

of

the

doublet

antenna

is

determined

by

dividing

468 by

the

frequency

(in

megacycles)

at

the

high

end

of

the

range

to

which

you

wish

to

listen.

Construct

the

an-

tenna

as

shown

in

Fig.

5. A

doublet

antenna

is

di-

rectional

broadside

to

its

length

and

should

be

so

oriented

with

respect

to

a

desired

station

for

maxi-

mum

signal

pickup.

By

feeding

the

doublet

antenna

with

a

transmis-

sion

line

of 300

ohms

surge

impedance,

a

broader

frequency

response

is

obtained

than

that

possible

with

a

50-75

ohm

line.

When

feeding·

the

antenna

with

a

ribbon

type

transmission

line,

connect

the

line

to

terminals

Al

and

A2.

Disconnect

the

jumper

between

A2

and

G.

When

using

a

coaxial

transmission

line,

connect

the

inner

conductor

to

Al

and

the

outer

conductor

to

A2.

Connect

the

jumper

between

A2

.and G.

/4-r---

LlFEETI'

FREQ~~:CY

(MCI

NO.

12

OR

NO.

14

WIRE

JUMPER

300

OHM

TWIN-LEAD

Fig.

5. Doublet

Antenna

Installation

INSULAlOR

REMOTE

STANDBY/RECEIVE SWITCH CONNECTION -

The

receiver

may

be

disabled

remotely

by

connect-

ing a

remote

spst

switch

between

pins

1

and

4 of

the

JUMPER

PLUG

(see

Fig.

2).

To

operate

the

receiver

remotely,

set

the

STANDBY/RECEIVE

switch,

located

on the

front

panel

of the

receiver,

to

the STANDBY

position.

The

receiver

can

then

be

placed

in

RECEIVE

or

STANDBY

operation

with

the

remote

switch.

CRYSTAL

PICK-UP

n

,....------++----+1-

---

-----

TO

PHONO

r-------~""-,--

~~~~~~RN

I SHIELD

I

I 1

I-

____

...l

PLUG,CINCH

TYPE

N-93

Fig.

6. Wiring Diagram for Record Player Connection

9261395-6

TRANSMITTER CONTROL SWITCH -One

section

of

the

dpst

STANDBY/RECEIVE

switch

is

available

for

transmitter

relay

control.

Thls

section

of

the

switch

connects

to

pins

2

and

5 of the

DC

POWER SOCKET

(see

Fig.

2)

and

is

in

the

open

position

with

the

STANDBY/RECEIVE

switch

at

STANDBY.

OPERA

liNG

INSTRUCTIONS

Each

control

of

the

receiver

performs

a

definite

function

which

contributes

to

the

oustanding

recep-

tion

capabilities

of

the

receiver.

Full

appreciation

of

the

receiver

is

to

be

expected

only

after

you have

become

familiar

with

the

controls

and

the

effect

their

operation

has

on

the

performance

of the

receiver.

The

control

positions

for

standard

broadcast

reception

are

marked

in

RED

for

convenience

to

the

listener.

RADIO

TELEPHONE

RECEPTION

-

To

receive

amplitude

modulated

(AM)

radio

telephone

signals,

the

follow-

ing

use

of

the

controls

is

recommended

to

obtain

optimum

performance

from

the

receiver.

SENSITIVITY

control

BAND

SELECTOR

switch

VOLUME

control

This

control

is

normally

set

fully

clockwise

for

maximum

sensitivity.

In

some

rare

'instances,

strong

local

signals

may

overload

the

receiver

input.

Distortion,

caused

by

this

condition,

can

be

eliminated

by

reducing

the

receiver

sensitivity

slightly.

For

a

correct

liS

II

meter

indication,

the

SENSITIVITY

control

must

be

set

fully

clockwise.

This

switch

is

used

to

select

the

desired

band

or

frequency

range.

The

frequen-

cies

covered

by

each

position

of the BAND

SELECTOR

are

read

directly

from

the

main

tuning

dial.

This

control

is

used

to

regulate

audio

volume.

Turning

the

control

clockwise

increases

volume.

Page

5

RADIO

TELEPHONE

RECEPTION

(Cont.)

AVC

switch

This

switch

should be

set

to the

ON

position

to

place

the

automatic

volume

control

(AVC)

circuit

in

operation

•.

The

AVC

circuit

provides

a

constant

audio output

level

over

large

variations

in Signal

strength

at

the antenna.

TUNING

control

This

control

should be

set

for

the

desired

station

frequency

after

setting

the

BAND

SELECTOR

for

the

desired

band.

Frequencies

on

all

bands

are

shown

in

megacycles.

IMPORTANT -The

main

tuning

dial

calibration

is

correct

only when the BAND-

SPREAD

control

is

fully

clockwise.

CW

/

AM

switch

This

switch

should be

set

at

AM.

BANDS

PRE

AD

control

This

control,

calibrate<;t

specifically

for

the

80,40,20,15,

11

and

10

meter

amateur

bands,

is

a fine tuning

adjustment

provided

for

electrically

spreading

out

the

con-

gested

amateur

and

shortwave

bands.

AMATEUR

BAND

RECEPTION -

To

use the BANDSPREAD

control

on the

amateur

bands,

set

the BANDSPREAD

control

fully clockwise, index the TUNING

control

for

the high end of any of the

amateur

bands

as

indicated by the white dots on the

main

tuning

dial

and then tune

through

the band using the BANDSPREAD

control.

The

station

frequency

is

read

directly

from

the bands

pre

ad

dial.

SHORTWAVE RECEPTION -

To

tune in shortwave

stations

with the BANDSPREAP

,

control,

set

the BANDSPREAD

control

fully

clockwise,

position

the TUNING

control

for

the high

frequency

end

of the

range

of

frequencies

to

be

covered

and

then

tune

through the

frequency

range

with

the BANDSPREAD

control.

Note

that

the

station

frequency

CANNOT be·

read

directly

from

either

the

main

tuning

or

bandspread

dials.

However,

it

is

possible

to

log shortwave

stations

by

recording

the

settings

of both the

bandspread

dial

and the

main

tuning logging

scale.

See

inside

of back

cover

for the sh.ortwave

station

log.

NOISE

LIMITER

This

switch

is

normally

set

at

OFF.

Set

the

switch

at

ON

when

severe

electrical

switch

disturbances

interfere

with

reception.

SELECTIVITY

This

switch

is

normally

set

at

BROAD

for

maximum

fidelity.

Positions

2, 3, 4 and

switch

5 provide

increasing

steps

of

selectivity.

Note

that

as

the

receiver

is

made

more

selective

(clockwise

rotation

of the

SE

LECTIVITY

control),

the background noise

and

interference

from

nearby

stations

is

reduced.

The

setting

of the SELECTIVITY

control

is

generally

best

determined

by

receiving

conditions, the SHARP position

providing

maximum

selectivity.

A

slight

readjustment

of the BANDSPREAD

con-

trol

may

be

necessary

when changing the position of the SELECTIVITY

control.

SINGLE SIDE

BAND

RECEPTION -

The

method of bandwidth expansion

used

in

this

receiver

makes

possible

a

form

of

single

side

band

reception.

As the

sel-

ectivity

is

changed

from

the SHARP to the

BROAD

position

the bandwidth of the

receiver

not only

increases

but

also

shifts

in

reference

to

the 50

KC

intermediate

frequency,

permitting

only one

side

band to be

accepted.

For

single

side

band

reception,

set

the

SELECTMTY

control

to SHARP, tune

in

the

AM

Signal and then

set

the SELECTIVITY

control

to

BROAD. The

"S"

meter

level

will

decrease

with

an

increase

in bandwidth and if the

receiver

is

not

retuned,

only one

side

band

will

be

accepted.

PITCH CONTROL

This

control

is

not

used

for

RADIO TELEPHONE RECEPTION.

TONE

control

Page

6

This

control

turns

the

receiver

on and off and

also

attenuates

the high audio

fre-

quencies

to.

the

extent

required

by the

various

receiving

conditions.

To

turn

the

receiver

on,

turn

the TONE

control

clockwise

beyond

the

point

of

switch

action.

For

maximum

high

frequency

audio

response,

turn

the TONE

control

fully

clockwise.

ST

ANDBY

/RECEIVE

switch

This

switch,

normally

set

at

RECEIVE,

is

particularly

useful

to

the

"ham"

as

it

permits

disabling

of the

receiver

for

standby

periods,

at

the

same

time

maintainins

the

tube

heaters

at

operating

temperature

for

instant

use.

The

receiver

is

disabled

by

setting

this

switch

to the STANDBY

position.

CW

RECEPTION -The following use of the

controls

is

recommended

for

CW

(code)

reception.

SENSITIVITY

control

BAND

SELECTOR

VOLUME

control

AVC

switch

TUNING

control

CW

/

AM

switch

BANDS

PRE

AD

control

NOISE

LIMITER

switch

SE LECTIVITY

switch

PITCH CONTROL

TONE

control

Increase

receiver

sensitivity

by

turning

the SENSITIVITY

control

clockwise.

If

strong

code

signals

block

the

receiver,

reduce

the

sensitivity

slightly.

Same

as

for

RADIO TELEPHONE RECEPTION.

Set

the VOLUME

control

clockwise

near

the

maximum

volume

position

and

use

the

SENSITIVITY

control

to

regulate

the audio output.

This

switch

should

be

set

at

OFF.

Same

as

for

RADIO TELEPHONE RECEPTION.

This

switch

should

be

set

at

CW

to

place the 50

KC

beat

frequency

oscillator

cir-

cuit

in

operation.

Same

as

for

RADIO TELEPHONE RECE PTION.

This

switch

should

be

set

at

OFF.

The

setting

of the SELECTIVITY

control

for

CW

reception

is

generally

best

deter-

mined

by

receiving

conditions. Note

that

as

the SELECTIVITY

is

increased

from

the BROAD

to

the SHARP position,

the

background noise and

interference

is

con-

siderably

reduced.

CW

reception

under

extremely

congested

conditions

is

possible

with

the SELECTIVITY

control

set

at

SHARP. A

slight

readjustment

of the BAND-

SPREAD

control

may

be

necessary

when

changingthe

position of

the

SELECTIVITY

control.

.

This

control

varies

the

frequency

of the

beat

frequency

oscillator

thus

varying

the

pitch

of the CW code

signal.

It

may

be

necessary,

after

setting

the

PITCH

CONTROL,

to

readjust

the

tuning of the

receiver

slightly

with the BANDSPREAD

control.

Alternately

adjust

the PITCH CONTROL and

BANDS

PRE

AD

control

for

a

maximum

audible

signal.

This

control

should

be

turned

counterclockwise.

STANDBY!RECEIVE

Same

as

for

RADIO TELEPHONE RECEPTION.

switch

USE

OF

THE

"5"

METER

-

The

"Sit

meter

has

been

provided

to

aid

in

tuning

the

receiver

for

RADIO

TELE-

PHONE RECE PTION and

to

give

an

indication

of the

relative

carrier

strength

of

each

incoming

AM

signal.

For

a

correct

"8"

meter

indication;

the

SENSITIVITY

control

must

be

fully

clockwise,

the

AVC

switch

must

be in the

ON

position

andthe

receiver

must

be tuned

for

a

maximum

reading

on

the

"S"

meter.

To

afford

greater

utility

of-the ''s''

meter,

it

has

been

calibrated

in both "s"

units

and

microvolts.

It

is

suggested

that

the

limitations

of

these

microvolt

indications

be fully

appreciated

before

any

assumption

as

to

the

indicated

signal

voltages

be

accepted.

The

meter

indicates

approximate

microvolts

of

signal

strength

as

developed

at

the 300

ohm

antenna

input

terminals

of the

receiver

at

14 MC.

This

approximation

Page

7

will

have a

variation

of ± 5 db on a new

receiver

and, obviously,

as

the

receiver

tubes

age the

variations

may

be

greater.

Variations

in

the

microvolt

indication

between

receivers

is

not

indicative

of the

overall

sensitivity

variation

but

is

caused

by

normal

tolerances

in

vacuum

tube

conductances

which

are

reflected

in

varia-

tions

in the

AVC/

S

METER

curve.

Thus,

two

similar

receivers

with

identical

overall

sensitivities

could,

under

the

same

signal

conditions,

indicate

signal

levels

of 5

microvolts

and

25

microvolts

and

yet

each

be

a

perfect

receiver.

All

readings

60

microvolts

or

less

will

be

more

accurate

and

correlate

more

closely

than

those

higher.

The

indicated

microvolt

reading

at

30, 7 and

3.5

MC

will

vary

± 3 db

from

that

at

14

MC. While

these

variations

may

seem

large,

the

microvolt

calibration

is

advantageous

as

it

provides

a

useful

tool

for

antenna

work

and

harmonic

measurements

with

a

suitable

converter.

RECORD

PLAYER

OPERATION

-

Set

the SELECTIVITY

control

to PHONO.

Turn

the

receiver

ON

by

rotating

the TONE

control

clockwise. beyond the point of

switch

action.

Operate

the VOLUME

and

TONE

controls

as

explained

under

RADIO TELEPHONE RECEPTION.

The

settings

of the

remaining

controls

is

immaterial

as

they

are

not

in

use

for

record

player

operation

•

.

HEADPHONE

OPERATION

-

The

PHONES

jack,

located

on the

front

panel,

permits

the

use

of headphones with

this

receiver.

Insertion

of the headphones

disables

the

speaker.

Use

any

standard

headset

with

an

im-

pedance of 500

to

12,000

ohms.

S8ES

2ND

CONVERTER

50Ke

B+

r------I

~

l

I I

:

lLJ:

L

___

J T

L-

TC

R

I

:::'

=

S8AS

50KC IFAMP

B+

Fig. 7.

50

KC

I.F. System

I I

:y:

I I

_.I

'-_

TC

I

= =

I

--!

R

AUDIO

a

A.V.C.

SAL5

=

92Cll108

50

KC

I.

F.

SYSTEM

-

Figure

7

is

a

simplified

schematic

diagram

of the 50

KC

I.F.

system.

It

is

unique

in

that

the coupling

between

primary

and

secondary

coils

is

through

a

resistive-capacitive

network

instead

of

the

more

common

mutual

inductive

arrangement.

All coupling

occurs

through

C

and

R

since

each

50KC

coil

is

completely

shielded

to

prevent

inductive coupling. By

increasing

the value of C and R

the

selec-

tivity

can

be

made

broad

or

conversely,

by

decreasing

C

and

R,

made

sharp.

This

coupling

arrangement

affords

a

more

accurate

means

of

selectivity

control

than

that

readily

obtainable

by

any

other

method.

Page

8

SERVICE

INSTRUCTIONS

GENERAL

SPECIFICATIONS

Tubes

••

. • • • • . • • • • .

••

9

plus

voltage

reg-

ulator

and

rectifier

Power

Supply -Model

S-76

••

105-125

volts,

50-60

cycles

AC

-Model S-76U . 105-250

volts,

25-60

cycles

AC

Power

Consumption

•••••..

77

watts

Speaker

Output

Impedances

•••

3.2 and 500

ohms

Headset

Output Impedance

.••

500

ohms

Antenna Input

Impedance

.•.•

300

ohms

Phono Input Impedance • •

•.

High impedance

1st

Intermediate

Frequency

..

1650

KC

2nd

Intermediate

Frequency

••

50

KC

"5"

METER

ADJUSTMENTS

MECHANICAL ADJUSTMENT -

Turn

the

re-

ceiver

OFF.

The

II

SIi

meter

mechanical

ad-

justment

screw

is

located

on the

II

S"

meter

escutcheon.

Carefully

rotate

this

screw

until

the

pointer

is

in

line with the

right

hand index

mark

on the "s"

meter.

ELECTRICAL

ADJUSTMENT

1.

Short

the

antenna

terminals

to the

chassis.

2.

Set

the STANDBY/RECEIVE

switch

at

RE-

CEIVE, AMjCW

switch

at

AM,

AVC

switch

at

ON,

NOISE

LIMITER

switch

at

OFF

and

the

SE

NSITIVITY

control

fully

clockwise.

3.

Turn

the

receiver

ON.

4.

The

electrical

adjustment

control

for

the

"s"

meter

is

located

on the

rear

apron

of the

chassis.

Turn

this

control

slowly

until

the

"s"

meter

pointer

indicates

0 on the

micro-

volt

scale.

DIAL

LAMP

REPLACEMENT

-

Refer

to

Fig.

9

for

the

location

of the

dial

lamps

used

in

the

receiver.

To

gain

access

to defective

lamps,

open the hinged

top

cover

of the

cabinet.

CAUTION -

To

avoid

electrical

shock,

discotlnect the

receiver

from

the power

source

before

making any

dial

lamp

replacement.

To

replace

the

bandspread

and

main

tuning

dial

lamps,

unclip

the

dial

lamp

assembly

from

the

mounting

bracket.

This

enables

the

defective

lamp

to

be

brought

out

into

the

open

where

it

may

be

re-

placed.

Make

replacements

with

a

6-8

volt

250

ma

(blue bead)

Mazda

#44

pilot

lamp

or

equivalent.

To

replace

the

pilot

lamps

which

illuminate

the liS"

meter,

remove

eithe.l-

:SOCKet

assembly

from

the

meter

by

pulling

it

slightly

sideways.

The

socket

assembly

and defective

lamp

may

then

be

brought

out

into the open

for

service.

Make

replacements

with a

6-8

volt,

1

c.p.

(pink bead)

Mazda

#51

pilot

lamp

or

equivalent.

TUBE

REPLACEMENT

-

The

tube

types

and

their

relative

location

in

the

receiver

are

shown

in

Fig.

9.

Access

to

all

tubes

is

possible

by opening the hinged

top

cover

of the

cabinet.

When

installing

a

replace-

ment

octal

tube,

insert

the

center

guide pin into the

center

hole of the tube socket,_

rotate

the tube

until

the

key

on the guide pin

drops

into the notch

in

the

socket

hole and

push

down

until

the

base

of the tube

rests

firmly

on the

socket.

A

slightly

different

technique

must

be

used

on the

miniature

tubes.

They

have

seven

small

pins

which

must

be

lined

up with the

socket

holes

before

pushing the tube into

place.

Handle

all

tubes

with

care

as

they

are

fragile

and

will

not

withstand

mechanical

abuse.

BANDSPREAD

GANG

DRIVE

PULLEY

10

f

MAIN

TUNING

GANG

DRIVE

PULLEY

E

LARGE

BANDSPREAD

~--'::'~I

RATIO

PULLEY

---1

I

.

. .

LENGTH-36" LENGTH-25"

.-

- - -

---

- - - -

--

- -

--

----

-

---'

.!!QlA:

MAIN

TUNING

a

BANDSPREAD

GANGS

FULLY

MESHED

Fig. 8.

Dial

Cord Stringing Diagram 92C1396-A

Page

9

EQUIPMENT

REQUIRED

I-F ALIGNMENT PROCEDURE

1.

Vacuum tube

voltmeter

(VTVM)

2.

Signal

generator

(unmodulated)

covering

50

KC

and

IS

50

KC.

If

a

50

KC

signal

generator

is

not available,

use

two

separate

generators

to

provide

a

50

KC

beat

frequency. Set the frequency

of

one

generator

to

700

I«:

and the

other

to

750

1«:.

3. 3.2

or

500 ohm

speaker

It

is

necessary

to

remove

the

receiver

chassis

from

the

cabinet

to

make the

1-1"

alignment. The

chassis

is

held in the

cabinet

by

three

screws

along

both

the

bottom edge of the

front

panel and

the

rear

of

the

cabinet

and by two

screws

on

each

side

of

t;he

front

panel.

The

I-F

alignment

should

be

made with the mail!

tuning

and

bandspread

tuning

capacitors

meshed

half

way, VOLUME, TONE and SENSITWITY

controls

fully clockwise,

NOISE

LIMITER and

AVC

switches

at

OFF,

RECEWE/STANDBY

switch

at

RECEIVE, CW/AM switch

at

AM

and

the

BAND

SELECTOR

switch

at

2.

Refer

to

Figs.

9and 10

for

the

location

of

all

adjustments.

Connect

the

high Side

of

the

VTVM

to

the junction

of

/C-75!,

IR~381,1

R-43!,!R-44!

and

IR-591. See

Fig.

13. Connect the common

side

of the

VTVM

to

the

chassis.

Use

just

enough

s1gDlll

generator

output to give a 1 volt

DC

indication on the VTVM.

SIGNAL GENERATOR SIGNAL GEN. SELECTWITY .

STEP

COUPLING FREQUENCY CON'l'ROL SETTING

AD3"UST

REMARKS

1 Connect

the

high

side

of the

gen-

50KC

5 1 Maximum output

erator

to

terminal

1

of

trans-

(No

Mod.) 5 2 Maximum output

former

~

(see

Fig. 13) and the 5 3 Maximum output

ground SIde to the

chassis.

5 4 Maximum output

5 1 Maximum output

5 2 Maximum output

5 3 Maximum output

5 4 Maximum output

2 Connect

the

high

side

of the

gen-

1650

KC

5 5 Maximum output.

After

making

adjustment

5

retune

the

erator

to

stator

plates

of

center

(No

Mod.)

generator

for

a maximum indication on

the

VTVM.

section

of

main

tuning

capacitor.

5 S Maximum output

Connect the ground

side

of the 5 7 Maximum output

generator

to

frame

of

main

tuning 5 8 Maximum output

capacitor.

5 9 Maximum output

Rotate the SELECTWITY

control

from

pOSition 5 to 1.

The VTVM

reading

should

decrease

progressively

with

each

position of

the

SELECTWITY

control.

If

this

does

not

occur,

it

is

an

indication that the 50

KC

I-F

system

is

not

properly

aligned.

This

indicates

that

steps

1 and 2

must

be

repeated.

3 Connect the high

side

of the

gen-

50

KC

4 10 Disconnect the VTVM. Set the

CW

/

AM

.switch

at

CW.

erator

t~erminal

1 of

trans-

(No

Mod.) Remove

the

PITCH CON'l'ROL knob. Using a

speaker

as

former

(see

Fig.

13)

and the

an

indicating device, adjust 10

for

a

zero

beat.

After

com-

ground SIde

to

the

chassis.

pleting

this

adjustment,

replace

the knob with

the

indell

mark

in

the

top

center

position.

R-F

ALIGNMENT

PROCEDURE

EQUIPMENT

REQUIRED

1. Output

meter.

The

AC

scale

of

a vacuum tube

voltmeter

(VTVM)

or

other

suitable

meter

may

be

used.

2. Signal

generator

covering

SOO

KC

to 30 MC.

Generator

must

have amplitude modulated output.

3.

Alignment tool

made

of polystyrene

or

other

similar

material.

It

is

not

necessary

to

remove

the

chassis

from

the

cabinet

for

the

R-F

alignment. All

R-F

alignment

adjustments

can

be

made

through

the holes

in

the bottom of the cabinet.

The

R-F

alignment should

be

made with the BANDSPREAD, VOLUME, TONE and SENSITWITY

controls

fully clockwise,

NOISE

LIMITER and

AVC

switches

at

OFF,

RECEIVE/STANDBY switch

at

RECEIVE, CW/AM

switch

at

AM

and

the SELECTWlTY

control

at

3.

Refer

to

Figs.

9 and 10

for

the

location of

all

adjustments.

CONNECTING

THE

TEST

EQUIPMENT

1.

Connect the output

meter

between the 500 ohm

speaker

terminal

and the

chassis.

2. Connect the high

side

of

the

signal

generator

to

antenna

terminal

Al

through a 330 ohm

carbon

reSistor.

Place

the

jumper

between antenna

terminals

A2

and G. Connect the ground

side

of

the

generator

to

the

chassis.

Keep

the

output of the

signal

generator

as

low

as

possible

at

all

times

to

prevent

overloading

of

the

receiver.

SIGNAL GENERATOR

BAND

SELECTOR MAIN

TUNING

STEP

FREQUENCY (MOD.) SETTING DIAL SETTING

AD3"UST

REMARKs

1

30MC

4

30MC

A AdjustA

thru

F for

maximum

output.

30MC

4

30MC

B

Oscillator

trimmer

A· should be

set

30MC

4

30MC

C

so

that the

oscillator·

operates

on

the

14MC

4

14MC

D

highside

as

indicated by

an

image

at

14

MC

4

14

MC

E 2S.7 MC.

If

the

oscillator

is

oper-

14MC

4

14MC

F

atl~on

the low

side,

an

image will

be

0

ained

at

33.3 MC.

2 11.5

MC

3 11.5

MC

G Maxililum output

11.5

MC

3

11.5MC

H Maximum output

11.5

MC

3

1l.5MC

3"

Maximum output

5.1

MC

3 5.1

MC

K Maximum output

5.1

MC

3

5.1MC

L Maximum output

5.1MC

3

5.1MC

M Maximum output

3

4.SMC

2

4.SMC

N Maximum output

4.SMC

2

4.SMC

P Maximum output

4.6

MC

2

4.SMC

Q Maximum output

1925

MC

2 1.925

MC

R Maximum output

4 1400

KC

1 1.4

Me

S Maximum output

1400

KC

1

1.4MC

T Maximum output

1400

KC

1

1.4MC

U Maximum output

SOO

KC

1

.SMC

V Maximum output

Page

10

Hallicrafters S-76 Operation manual

Popular Receiver manuals by other brands