Hallicrafters S-76 Operation And Service Instructions Manual

Fig.

J.

Communications

Receiver

Model

5-76

92X1778

DESCRIPTIO

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 impedance

is

required.

The

receiver

is

housed

in

an

attracti

ve,

well

ventilated

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

9281391-8

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

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.

IMPORT ANT - 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.