Murphy radio V310 User manual

V310,V310C

~

V310D

MURPHY

SERVICE

MANUAL

V310,

V310C

&

Y310D

Issued

by

MURPHY

RADIO

LTD

WELWYN

GARDEN

CITY

HERTS

Telephone:

WELWYN

GARDEN

3434

THE

V3

10,

V3

I

OC

&

V3

I

OD

TELEVISION

RECEIVERS

V310C

MAINS

SUPPLY:

CONSUMPTION;

AERIAL

INPUT

IMPEDANCE:

FREQUENCY

RANGE:

V310

V310D

SPECIFICATION

200-250

volts,

50

c/s

a.

c.,

or

200-250

volts

d.

c.

160

watts,

average

75

ohms,

unbalanced

Band

I

and

Band

III

INTERMEDIATE

FREQUENCY:

V1SlOn;

34.65

MC/S

Sound:

38.15

Mc/s

VALVES:

One

30L1,

one

30C1,

four

30F5,

two

6D2,

two

30FL1,

one

6/30L2,

one

30P16

(PL82)

or

30P12,

one

30P4,

one

U191,

one

U26

CATHODE

RAY

TUBE:

CRM172

Fuses:

F1:

2A

plain

cartridge

F2:

500mA,

Mag-Nickel

cartridge

LOUDSPEAKER:

V310,

V310C:

Elliptical,

6

in,

by

4

in.

permanent

magnet;

3

ohms

im-

pedance

V310D:

8

in.

diameter;

permanent

magnet;

3

ohms

impedance

OVERALL

DIMENSIONS:

V310:

17

in.

high,

19

in.

wide,

21

in,

deep

V310C:

31

in.

high,

21

in,

wide,

23

in,

deep

V310D:

33

in.

high,

22yz

in.

wide,

21

in.

deep

WEIGHT:

V310:

50

lb.

V310C:

60

lb.

V310D:

93

lb.

R

ELEnsED:

V310:

February,

1957

V310C:

April,

1957

V310D:

July,

1957

PRICE:

V310:

Standard

-

£51

15s.

6d.

plus

P.T.

V310:

Light

Wood

-

£52

2s.

lld.

plus

P.T.

V310C:

£60

6s,

lOd.

plus

P.T.

V310D:

£74

9s.

lld.

plus

P.T.

125711

2

V310,

V31OC,

&

V310D

TELEVISION

RECEIVERS

INSTALLATION

the

aerial

syste~.

Connect

the

aerial

to

the

receiver

with

7511

coaxial

cable.

Use

a

cross-

over

unit

if

two

separate

aerials

are

re-

quired.

Earth

the

receiver

by

means

of

the

upper

socket

on

the

aerial

escutcheon

if

time

-

base

radiation

is

suspected

or

if

local

inter-

fering

signals

are

being

received.

RECEIVER

ADJUSTMENTS

The

following

checks

and

adjustments

must

be

made

in

the

Customer's

house,

without

regard

to

any

made

elsewhere.

Ysins

voltage

adjustaent

A.C.

MAINS

200

TO

250V,

AND

D.C.

MAINS

220V

TO

250V

ONLY.

i.

Loosen

the

small

locking

knob

in

the

centre

of

the

mains

adjustment

dial

at

the

rear

of

the

receiver.

2.

Rotate

the

dial

so

that

the

desired

volt-

age

is

against

the

arrow

engraved

on

the

panel.

3.

Gently

press

the

dial

against

the

panel,

ensuring

that

the

two

pips

on

its

under-

side

locate

in

the

holes

in

the

panel.

4.

Whilst

still

maintaining

the

pressure,

tighten

up

the

locking

knob.

NOTE:

Wherever

possible,

arrange

the

mains

plug

connections

so

that

the

chassis

is

at

the

mains

neutral

potential.

D.C.

MAINS

200V

AND

210V

ONLY.

1.

Use

the

procedure

described

above,

but

first

set

the

dial

to

the

220V

d.

c.

posi-

tion,

and

correct

the

polarity

of

the

mains

connections

if

necessary.

Then

ro-

tate

the

dial

to

the

200V

or

210V

d.

c.

position

as

required.

The

above

procedure

is

necessary

because

the

rectifier

(MR

1)

is

out

of

circuit

on

these

taps,

and

the

fuse

(F1)

could

easily

'blow".

V810

and

V310C

On

-Off

Switch.

The

on

-off

switch

is

operated

automatically

by

a

spring

loaded

mechanism

when

the

release

button

at

the

top

of

the

cabinet

is

pressed.

Initial

test.

Check

that

the

receiver

is

operating,

but

do

not

leave

the

BRIGHTNESS

control

turned

up

if

it

is

suspected

that

the

ion

trap

magnet

is

not

in

its

correct

position.

Sensitivity

adjnstaent.

Connect

the

aerial

and,

for

optimum

signal

to

noise

ratio,

pro-

ceed

as

follows;

(a)

Set

the

STATION

SELECTOR

to

the

appro-

priate

position,

i.e.

B.B.C.

or

I.T.A.,

and

turn

the

volume

control

to

maximum

(fully

clockwise).

(b)

Adjust

the

local

oscillator

core

through

the

hole

the

STATION

SELECTOR

knob

using

(early

sets)

a

small

screw-

driver,

or

(later

sets)

the

plastic

trim-

ming

tool

supplied.

Exert

sufficient

pressure

on

the

tool

for

it

to

engage

with

the

oscillator

core

and

then

rotate

the

core

for

maximum

sound

output.

(c)

With

the

CONTRAST

control

at

minimum

(anti

-clockwise)

adjust

the

appropriate

SENSITIVITY

control

so

that

the

picture

is

only

just

synchronising.

It

will

be

necessary

to

increase

the

brightness

so

that

this

can

be

readily

ascertained.

(d)

Set

the

black

level

of

the

picture

by

means

of

the

BRIGHTNESS

control

and

ad-

just

the

CONTRAST

control

to

give

a

cor-

rectly

contrasted

picture.

In

areas

of

high

signal

strength,

if

cross

modulation

(picture

on

sound,

sound

on

pic-

ture,

or

heterodyne

patterns)

occurs,

repeat

this

procedure

with

the

CONTRAST

control

at

approximately

half

travel

instead

of

fully

anti

-clockwise,

check

afterwards

that

ade-

quate

picture

brilliance

is

obtained

with

the

CONTRAST

control

turned

fully

clockwise.

NOTE:

If

the

signal

is

so

strong

on

one

channel

that

it

is

impossible

to

adjust

the

SENSITIVITY

control

so

that

the

picture

is

just

synchronizing,

or

if

cross

modulation

is

still

present,

a

turret

attenuator

should.

be

fitted;

see

page

26.

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

3

MAINTENANCE

ADJUSTMENTS

To

enable

the

performance

to

be

kept

at

its

best

the

adjustments

described

in

the

following

three

sections

must

be

checked

and

cor-

rected

where

necessary

whenever

the

receiver

is

overhauled

or

re-

paired.

These

adjustments

should

not

be

necessary

on

installation.

I.

PICTURE

ADJUSTMENTS

The

procedure

is

normal

but

the

following

points

should

be

noted:

Tilted

Dicture.

The

cabinet

must

be

removed

from

the

chassis

for

this

adjustment.

The

scan

assembly

is

locked

in

position

and

ad-

justed

by

the

hexagonal

headed

brass

screw

at

the

top

of

the

housing.

Picture

position.

This

is

adjusted

by

the

black

insulated

lever

projecting

from

the

rear

of

the

focus

assembly,

and

through

the

back

of

the

cabinet.

Unscrew

the

lever

by

about

one

turn

and

then

move

it

as

required

to

centre

the

picture.

Tighten

after

use.

Line

linearity.

With

the

slider

at

the

top

of

its

travel,

i.e.

nearest

the

coil,

move

the

slider

down

slowly

until

the

equidistant

vertical

divisions

of

the

picture

or

test

pattern

are

as

near

to

equal

as

possible.

It

should

be

noted

that

the

correct

position

for

the

slider

should

be

near

the

top;

any

other

position

will

give

reduced

line

ampli-

tude.

2.

MECHANICAL

ADJUSTMENTS

Read

the

preliminary

note

above

Pocus

snit

position.

Whe❑

a

new

c.

r.

t.

is

fitted,

it

may

be

necessary

to

reposition

the

focus

unit.

To

do

this,

slacken

the

four

screws

visible

through

the

slots

in

the

side

of

the

large

supporting

cylinder,

and

slide

the

assembly

backwards

or

forwards

until

the

distance

between

the

c.

r.

t.

grid

plane

and

the

plate

at

the

rear

of

the

focus

unit

is

approximately

3/4

in.

(see

Fig.

1

)

with

the

focus

adjustment

fully

clockwise.

If

the

distance

is

much

less,

the

scanning

spot

wild

be

large;

if

it

is

appreciably

greater,

un-

even

focus

over

the

picture

area

will

result.

Before

retightening

the

screws,

make

sure

that

the

back

plate

is

at

right

angles

to

the

c.r.t.

neck.

Finally,

check

the

adjust-

ment

of

the

ion

trap

magnet,

as

described

in

"Electrical

Adjustments~~

below.

With

the

focus

knob

in

the

position

of

optimum

focus,

the

fixing

lugs

for

the

knob

should

be

more

than

3/4

in.

from

either

end

of

their

maximum

travel,

as

measured

around

the

outside

of

the

cylindrical

housing.

If

the

lug

is

closer

to

the

end

of

its

travel,

when

the

h.

t.

and

e.h.t.

voltages

are

normal,

and

the

unit

is

correctly

positioned,

the

focus

unit

may

be

suspected

of

having

an

incorrect

flux

density.

3.

ELECTRICAL

ADJUSTMENTS

Read

the

preliminary

note

above

Ion

trap.

To

assist

in

adjusting

the

ion

trap

magnet

it

should

be

roughly

positioned

on

the

neck

of

the

c.

r.

t.

so

that

the

paint

spot

is

towards

the

rear

of

the

receiver

and

the

two

grooves

in

the

rim

are

approximately

90

degrees

anti-clockwisefrom

the

c.r.t.

e.

h.

t.

connector,

looking

from

the

rear

of

the

re-

ceiver.

To

prevent

damage

to

the

c.

r.

t.

when

aa-

justing

the

position

of

the

magnet,

the

cathode

current

must

not

be

allowed

to

exceed

about

lOpA,

and

the

following

procedure

should

be

used.

1•

Remove

the

focus

adjusting

knob.

2.

Connect

a

meter

having

a

full

scale

de-

flection

of

1mA

or

less,

across

R153

(220

4

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

CENTRING

,

'

TILT

—

In

_

GRID

ION

TRAP

MAGNET

V

310

FOCUS

UNIT

FIXING

SCREWS

C.R.T.

FRONT

ADJUSTER

~

_

h

~•

C.R.T.

CLAM

PING

SCREW

1

C.R.T

FRONT

ADJUSTER

7

IN.

FRONT

MOULD

MARK

ON

C.R.T.

Fig.

1.

Side

view

RA)

oa

the

c.r.t.

base

connector

(+ve.

lead

to

Din

11).

3•

Turn

the

BRIGHTNESS

control

to

minimum

(fully

anti

-clockwise).

4.

Switch

the

receiver

"On"

and

allow

a

few

minutes

for

it

to

warm

up.

5•

Rotate

the

BRIGHTNESS

control

until

the

meter

reading

is

about

10µA.

g.

Position

the

ion

trap

magnet

so

that

its

forward

edge

is

just

behind

the

c.r.t.

grid

Dlane.

Slowly

rotate

the

magnet

for

maaimum

screen

brightness.

7.

Keep

the

magnet

at

right

angles

to

the

neck

of

the

c.

r.

t.

and

move

it

slightly

backwards

and

forwards

to

find

the

posi-

tion

at

which

maximum

screen

brightness

is

produced.

8.

Make

a

final

check

of

the

magnet

position

with

the

CONTRAST

and

BRIGHTNESS

controls

adjustedto

give

a

normal

viewing

picture.

B,eceiwer

oscillator.

There

is

no

Fine

Tuner

on

this

receiver

and

the

appropriate

oscil-

lator

core

must

be

adjusted

on

each

channel.

If

sore

than

one

peak

is

obtained,

select

of

the

receiver.

the

one

which

occurs

when

the

core

is

first

entering

the

coil

former.

To

make

this

ad-

justment

proceed

as

follows:

1•

Set

the

VOLUME

control

to

maximum

(clock-

wise).

2.

EARLY

SETS.

Insert

a

small

screwdriver

in

the

hole

to

the

right

of

the

STATION

SE-

LECTOR

knob

and

adjust

for

maaimum

sound.

To

do

this,

it

will

be

necessary

to

exert

a

slight

Dressure

on

the

screwdriver

and

press

the

oscillator

core

driver

down

for

a

distance

of

about

g/4

in.

Gentle

rota-

tion

will

cause

the

driver

to

engage

with

the

slot

in

the

coil

core,

which

can

now

be

tuned

for

maximum

sound

output.

LATER

SETS.

Insert

the

long

plastic

trim-

ming

tool

(Driver,

Part

No.

77219

supplied

to

all

dealers)

into

the

hole

to

the

right

of

the

Station

Selector

knob,

press

it

gently

downwards

and

rotate

it

a

little

until

it

engages

with

the

oscillator

coil

core,

and

then

adjust

the

core

for

maximum

sound

output.

Remember

to

partially

with-

draw

the

tool

before

turning

the

Station

Selector

to

another

position.

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

M

ECHAN

ICAL

NOTES

Reeoving

the

c.

r.

t.

Lay

the

receiver

on

its

face

and

remove

the

cabinet

from

the

chassis.

Remove

the

focus

knob,

the

c.r.t.

base

con-

nector,

the

ion

trap

magnet

and

the

c.r.t.

anode

connector.

Detach

the

moulded

frame

with

the

mask

and

safety

glass,

and

then

re-

turn

the

chassis

to

its

normal

upright

posi-

tion.

Slacken

the

two

c.r.t.

clamping

screws

and

ease

the

c.r.t.

out

of

the

chassis:

in

some

cases

it

may

be

necessary

to

slacken

the

four

screws

which

secure

the

c.r.t.

clamping

ring

to

th@

chassis

stays.

Refitting

the

c.r.t.

Fit

the

c.

r.

t.

into

the

chassis,

ensuring

that

the

anode

connector

is

on

the

same side

as

the

line

output

trans-

former,

then

proceed

as

follows.

NEW

C.R.TS.

Slacken

the

four

screws

which

securethe

c.r.t.

clamping

ring

to

the

chassis

stays,

and

tighten

the

c.r.t.

clamping

ring,

checking

that

the

distance

between

the

front

edge

of

the

c.r.t.

clamping

ring

cushion

and

the

front

"mould"

mark

on

the.c.r.t.

is

3/16

in.

Lay

the

moulded

frame,

with

the

mask

and

safety

glass,

on

a

flat

surface,

and

place

the

receiver

over

it,

so

that

the

c.r.t.

.fits

into

the

mask;

replacethe

four

fixing

screws

which

secure

the

frame•

to

the

chassis

stays.

Then

move

the

c.r.t.

as

required

to

position

it

squarely

in

the

mask,

so

that

it

makes

a

dust

tight

seal

and

tighten

the

four

screws

securing

the

clamping

ring

to

the

chassis

stays.

Refit

the

e.

h.

t.

connector,

the

ion

trap

magnet,

and

the

c.r.t.

base

connector.

ORIGINAL

C.R.T.

Tighten

the

c.

r.

t.

clamping

ring

checking

that

the

distance

between

the

front

edge

of

the

c.r.t.

clamping

ring

cus-

hion

and

the

front

mould"

mark

on

the

c.r.t.

is

3/16

in.

Lay

the

frame,

with

its

mask

and

safety

glass

on

a

flat

surface,

and

place

the

receiver

over

it,

so

that

the

c.r.t.

and

rubber

mask

form

a

dust

tight

seal.

Replace

the

four

frame

fixing

screws.

Refit

the

e.

h.

t.

connector,

the

ion

trap

magnet,

and

the

c.r.t.

base

connector.

Removing

the

line

output

transformer.

Take

off

V15

Polythene

anode

connector

and

the

top

connectors

of

V13

and

V14.

Remove

V15

and

detach

its

holder

complete

with

mounting

panel

by

removing

the

single

4BA

screw

and

nut.

Unsolder

the

YELLOW

lead

from

thetrans-

former,

and

then

the~8

remaining

leads

from

the

transformer,

noting

their

points

of

con-

nection.

Remove

the

line

output

transformer

c

lamp.

The

control

escutcheon.

If

the

control

escut-

cheon•

is

to

be

replaced,

care

must

be

taken

when

fitting

it,

to

make

sure

that

the

centre

line

which

is

visible

at

the

rear

of

the

moulding

coincides

with

the

centre

line

at

the

top

of

the

fibre

back

of

the

cabinet.

The

c.

r.

t.

frame.

In

the

event

of

the

thread

in

a

brass

insert

at

a

corner

of

the

moulded

frame

becoming

damaged,

use

a

self

tapping

screw,

type

PK6Y

by

3/8

in.

P.R.H.

Part

No.

103903,

in

the

alternative

hole

provided.

The

top

controls.

The

following

information

is

given

to

assist

in

the

choice,

from

exis-

ting

stocks,

of

suitable

replacements

for

the

variable

controls

at

the

top

of

the

re-

ceiver.

In

Fig.

2,

the

dimension

"A"

refers

to

the

overall

spindle

length

and

is

measured

from

the

end

of

the

spindle

to

the

mounting

face,

i.e.

the

face

of

the

control

which

makes

contact

with

the

receiver

control

panel.

CONTROL

DIM.

"A"

LAW

RESISTANCE

Brightness

1

in.

Lin.

100K11

1

(R64)

Contrast

1

13/16

in.

Lin.

100KS1

(R28)

V310,

V310C

Contrast

1

in.

Lin.

100Kf1

(R28)

V310D

only

Volume

(R96)

Y310,

V310C

1

in.

Rev.

log.

250Kf1

Volume,

On-

Off

(R96)

V310D

only

1

13/16

in.

Log.

250K(1

with

d.p.

switch

Removing

the

voltage

selector

tnob.

Unscrew

the

small

locking

knob

and

remove

the

circlip

Fig.

2.

6

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

which

is

now

visible.

Unsolder

the

ORANGE

lead

from

the

contact

nearest

the

centre

on

the

underside

of

the

voltage

selector

panel.

Withdraw

the

dial

(knob,

printed),

complete

with

its

contacts,

away

from

the

spindle.

To

refit,

reverse

the

above

procedure.

Removing

the

focus

unit.

Withdraw

the

chassis

from

the

cabinet.

Then

remove

the

focus

knob,

the

c.r.t.

base

connector

and

the

ion

trap

magnet.

Slacken

the

four

focus

unit

fix-

ing

screws

(two

pairs)

which

are

accessible

through

the

two

slots

i.n

the

upper

half

of

the

scan

coils

housing

and

withdraw

the

focus

unit

complete

with

the

Centring

control

mec-

hanism.

Removing

the

scan

coils

assembly.

Withdraw

the

c.r.t.

from

the

chassis.

Then

remove

the

scan

coils

assembly

locking

screw

at

the

top

of

the

cylindrical

housing,

slacken

the

three

brass

screws

and

disengage

the

mounting

ring

from

the

slots

in

the

housing.

The

scan

coils

assembly

can

now

be

withdrawn

and

the

leads

disconnected.

THE

TUNER

UNIT

The

"stray"

capacitance

of

the

components

and

wiring

forms

a

large

part

of

the

tuning

capacitance

acr.ass

the

aerial,

r.

f.

t.

and

oscillator

coils.

Every

effort

must

therefore

be

made,

when

replacing

components

or

wiring,

to

ensure

that

the

lengths

of

the

leads

and

the

positions

of

the

components

follow

the

original

as

closely

as

possible.

Take

care

also

with

the

"dressing"

of

leads

and

fit

sleeving

wherever

necessary

to

avoid

short

circuits

across

tags,

particularly

on

the

.valve

holders.

IMPORTANT.

It

must

be

clearly

understood

that

any

repair,

or

the

replacement

of

any

component,

makes

the

realignment

of

any

unit

essential.

Any

attempt

to

carry

out

work

on

the

unit,

without

subsequent

realignment,

can

only

lead

to

a

deterioration

of

the

per-

formance,

particularly

on

Band

III.

To

remove

the

osc.

core

driver

(early

sets

only,

see

Modifications).

Turn

the

Station

Selector

to

a

position

in

which

there

are

no

coils,

remove

V6.

.and

then

remove

the

top

end

of

the

driver

from

the

plastic

guide

by

pres-

sing

it

downwards

through

the

wide

end

of

the

slot

in

the

slotted

arm

(stop

for

driver,

74'786).

Withdraw

the

lower

end

of

the

driver

from

the

guide

on

the

tuner

unit,

taking

care

not

to

lose

the

brass

sleeve

(eyelet,

split

4774)•

Do

not

attempt

to

move

the

guide

on

the

tuner

unit;

this

has

been

carefully

assembled

in

the

factory

so

that

the

driver

will

always

engage

with

the

coil

cores.

To

remove

the

tuner

unit.

Record

the

lead

positions

and

then

proceed

in

the

following

manner:

1.

Disconnect

the

six

leads

and

the

resistor

from

the

tags

on

the

outer

side

of

the

receiver

chassis

and

the

tuner

unit.

2.

Disconnect

the

wire

from

the

lead

—through

capacitor

at

the

end

of

the

unit,

and

the

coaxial

lead

from

the

aerial

escutcheon.

Do

not

disconnect

any

of

these

leads

from

within

the

tuner

unit.

3.

Unscrew

the

switch

wafer

and

withdraw

it

from

the

end

of

the

unit;

on

early

sets,

remove

the

osc.

core

driver

as

described

above.

4.

Remove

the

three

fixing

screws

on

the

outer

side

of

the

receiver

chassis

and

withdraw

the

unit.

Take

care

not

to

mislay

the

link

from

the

Station

Selector

shaft

which

becomes

disengaged

when

the

tuner

unit

is

removed.

NOTE.

When

refitting

the

tuner

unit,

ensure

that

the

switch

wafer

and

rotor

are

cor-

rectly

positioned

at

the

end

of

the

unit.

This

can

be

checked

by

observing

that

the

appropriate

Sensitivity

control,

i.e.

B.B.C.

or

I.T.A.

,

is

switched

into

circuit

at

the

corresponding

settings

of

the

Station

Selector

knob.

Identifying

the

coil

strips.

The

aerial

coil

strips

have

four

contacts

and

are

shorter

than

the

oscillator

coil

strips

which

have

six

contacts.

According

to

the

frequency

channels

for

which

they

are

intended,

the

coil

strips

are

marked

with

spots

of

coloured

paint

using

the

resistor

colour

code,

i.e.

BROWN

for

Channel

1,

RED

for

Channel

2

etc.

Channel

10

coils

however,

will

have

CH10

printed

on

the

coil

strip.

An

additional

GREEN

code

spot

is

added,

so

that

the

coils

for

the

V310

series

can

be

identified

from

those

of

earlier

receivers.

Removing

s

coil

strip.

Press

back

the

holding

spring

and

carefully

lift

out

the

coil

strip

by

gripping

between

the

thumb

and

fore-

finger,

the

end

remote

from

the

spring.

Fitting

a

coil

strip.

Press

back

the

holding

spring

and

fit

the

coil

strip

by

pressing

its

slotted

end

against

the

holding

spring

and

then

guiding

its

other

end

into

the

slot

at

the

middle

of

the

turret.

Turret

locating

mechanism.

To

adjust

the

mechanism

while

the

tuner

unit

is

still

in

position

on

the

receiver

chassis,

proceed

as

follows:

1.

Remove

the

c.

r.

t.

from

the

chassis

as

described

on

page

5

.

2.

Remove

the

side

screens

from

the

tuner

unit,

and

loosen

the

screw

holding

the

locating

spring

(it

will

be

necessary

to

remove

certain

valves

to

gain

access

to

these

screws).

3.

With

the

locating

roller

correctly

located

in

a

groove

on

the

turret,

slowly

turn

the

turret

until

the

coil

contacts

are

in

the

middle

of

the

fixed

contacts,

and

then

re

-tighten

the

locating

spring

fixing

screw.

4.

Turn

the

turret

to

all

its

other

positions

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

to

confirm

that

the.

location

is

satisfac-

tory,

and

then

replace

the

side

screens,

valves,

and

c.

r.

t.

Lead

-through

capacitors.

If

a

lead

-through

capacitor

has

to

be

replaced,

the

faulty

one

can

be

removed

by

applying

heat

to

the

metal

screen

immediately

around

the

capacitor

body.

When

the

solder

is

sufficiently

soft,

with-

draw

the

capacitor

from

the

metal

screen,

from

the

same

side

as

the

soldered

connection

to

the

metal

screen.

Trimming

capacitors.

If

a

trimmer

screw

has

been

accidentally

unscrewed

fully,

or

if

a

trimmer

body

has

to

be

replaced,

the

refit-

ting

should

be

carried

out

as

follows:

Thread

the

trimmer

nut

on

to

the

trimmer

screw,

with

the

convex

side

of

the

nut

to-

wards

the

head

of

the

trimmer

screw,

and

en-

gage

the

screw

in

the

threaded

trimmer

body.

Press

the

trimmer

body

against

the

chassis,

making

sure

that

the

square

end

of

the

trim-

mer

locates

with

the

square

hole

in

the

chassis,

and

turn

the

trimmer

screw

until

about

half

of

its

length

is

engaged

in

the

trimmer

body.

while

still

holding

the

trim-

mer

body

against

the

chassis,

prevent

the

screw

from

turning

and

rotate

the

nut

until

it

presses

tightly

against

the

chassis.

While

still

preventing

the

screw

from

turning,

in-

crease

the

pressure

of

the

nut

on

the

screw

by

rotating

the

nut

one

half

-turn

more

in

a

clockwise

direction..

The

correct

degree

of

pressure

is

now

applied

to

prevent

the

trim-

mer

screw

from

turning

when

subjected

to

vibration.

Labrication.

During

the

course

of

assembly,

the

contacts

and

Station

Selector

(turret)

mechanism

on

the

tuner

unit

are

lubricated.

The

contacts

on

the

coil

strips

are

smeared

with

petroleum

jelly

(Vaseline)

and

the

locator

roller

and

the

spindle

assembly

are

treated with

a

medium

-bodied

grease.

When

servicing

the

tuner

unit,

it

may

be

necessary

to

replenish

this

lubrication,

particularly

on

the

coil

-strip

contacts

which

will,

no

doubt,

have

been

handled

and

the

petroleum

jelly

thereby

removed.

Cleaning

the

contacts.

The

indiscriminate

application

of

any

of

the

proprietary

brands

of

switch

-cleaning

fluid

is

strongly

depre-

cated.

If

the

cleaning

of

any

of

the

contacts

is

necessary,

a

local

application

of

the

cleaner

-

with

a

small

brush

-

should

be

all

th

at

is

required.

Afterwards,

a

smear

of

petroleum

jelly

must

be

applied

to

those

contacts

which

have

been

cleaned.

V310D

RECEIVERS

Idains

On/Off

Switch.

This

switch

is

ganged

with

the

volume

control

in

the

conventional

manner,

the

top

flap

on

the

cabinet

serving

only

as

a

protective

cover

for

the

controls.

C.r.t.

position.

With

the

chassis

correctly

located.in

the

cabinet

the

corners

of

the

c.r.t.

should

be

just

flush

with

the

wooden

frame

in

the

cabinet.

Ensure

that

the

dust

tight

seal

is

in

its

correct

position.

Re®oving

tLe

safety

glass.

First

remove

the

chassis

from

the

cabinet.

Remove

the

rubber

"stops"`at

the

rear

of

each

lower

channel

and

slide

back

each

door

to

the

maximum.

Take

out

the

three

screws

holding

the

wooden

retaining

strip

at

the

upper

edge

of

the

front

of

the

safety

glass

and

remove

the

strip.

Remove

the

glass,

by

lifting

its

lower

edge

clear

from

the

retaining

groove.

Removing

a

door

(Tambour)

or

handle.

Remove

the

safety

glass,

and

the

c.r.t.

surround

complete.

The

handles

can

then

be

removed

by

unscrewing

the

four

fixing

screws.

Slide

out

the

doors

towards

the

rear,

coiling

the®

in

the

space

available.

The

doors

may

be

re-

placed

in

a

similar

manner.

If

the

receiver

is

to

remain

in

use

tem-

porarily

without

the

doors,

these

can

be

re-

moved

without

disturbing

the

safety

glass

or

c.r.t.

surround

simply

by

taking

out

the

two

rear

"stops"

and

easing

the

handles

through

the

gap

at

each

side

of

the

front

of

the

cabinet.

This

process

cannot

easily

be

re-

versed,

however.

CIRCUIT

DESCRIPTION

This

is

a

superheterodyne

type

of

receiver

designed

for

the

reception

of

any

two

channels

in

Band

I

and

any

two

channels

in

Band

III.

It

has

r.f.

,

frequency

changer

and

1st

i.f.

circuits

that

are

common

to

both

the

sound

and

vision

signals;

channel

selection

is

by

means

of

a

four

position

rotary

coil

turret

The

r.f.

stages.

A

double

triode

cascode

amplifier

is

employed,

followed

by

a

triode

pentode

frequency

changer

stage.

Since

the

r.f.

coils

are

adjusted

to

within

very

close

limits

during

manufacture,

the

circuits

are

aligned

by

adjusting

the

residual

capaci-

tances

at

a

single

Band

III

frequency;

the

alignment

then

holds

for

all

channels

in

both

bands.

A

Fine

Tuner

is

not

fitted

to

this

receiver,

and

therefore,

the

oscillator

coils

must

be

carefully

tuned

on

installation.

A

sound

i.f.

rejector

(Li0/C10),

which

is

in

circuit

on

all

channels,

is

included

in

the

tuner

unit.

The

vision

i.f,

stages.

The

first

i.f.

amp-

g

V310,

V310C,

&

V310D

TELEVISION

RECEIVERS

lifier

after

the

frequency

changer,

is

common

to

both

sound

and

vision

signals..

The

Con-

trast

controlis

in

the

grid

-cathode

circuit

of

this

valve,

and

the

sound

i.f. signalis

taken

from

the

anode.

Another

stage

of

vision

i.f. amplification

follows,

and

feeds

the

vision

detector.

There

are

threerejectors

in

the

vision

i.f. amplifier;

L13/C41,

L14/

C46

(own

sound

i.f. rejectors),

and

L15/C50

(adjacent

sound

i.f. rejector).

The

vision

detector

and

video

stages.

One

half

of

a

double

diode

valve

(V5)

is

used

for

detection,

and

the

rectified

signalis

fed

via

the

i.f, stopping

choke

(L18)

and

the

grid

compensating

choke

(L19)

to

the

grid

of

the

video

amplifier

valve

(V6).

The

cathode

circuit

of

this

valve

includes

a

3.5

Mc/s

rejectorcircuit

(L20,

C53)

to

remove

the

beatpattern

caused

by

any

sound

carrier

which

might

pass

the

i.f, rejectors;fixed

video

response

correctionisalso

provided

by

C54.

The

output

from

the

anode

of

V6

is

fed

to

the

vision

interferencelimiter,

the

cathode

of

the

c.r.t.

via

a

series

compensa-

ting

choke

(L21),

and

the

synchronizing

sig-

nal

separator

circuit.

The

synchronizing

signal

circuits.

The

video

signal

from

V6

anode

is

applied

to

the

con-

trol

grid

of

a

conventional

sync.

separator

(V7

a)

which

suppresses

the

picture

modulation,

so

that

a

"negative

going"

sync.

pulse

wave-

form

appears

across

the

anode

resistor

(R71).

The

pulse

voltage

is

taken

to

V13

in

the

line

time

-base

and,

afterdifferentiation

by

C63

and

R79,

to

the

grid

of

the

frame

"sync".

separator

(V7b).

A

further

output

is

taken

to

the

cathode

of

V7b

via

R77,

to

keep

the

valve

biased

back

during

the

picture

period.

The

initial

frame

pulse

charges

C66

in

V7b

anode

circuit,

so

that

subsequent

pulses

are

reduced

in

amplitude.

The

resultis

an

initial

frame

synchronizing

pulse

of

high

amplitude

and

having

a

steepleading

edge,

with

the

remaining

pulses

markedly

reduced.

These

pulses

are

fed

to

the

main

charging

capacitor

(C93).

D.C.

for

V7b

is obtained

from

V12

cathode

circuit.

The

line

output

stage.

A

single

valve

wave-

form

generator

and

amplifieris

,used.

Its

mode

of

operation

is

conventional

except

for

the

method

of

increasing

the

output

effici-

ency.

This

is

achieved

in

the

following

man-

ner.

During

the

"flyback"

period

a

large

nega-

tive

potentialis

developed

in

the

screen

grid

winding

of

T3.

This

voltage

pulseis

integrated

and

fed

to

the

controlgrid

of

the

line

output

valve

(V13)and.hoidsthe

valve

inoperative

for

approximately

the

firstthird

of

each

line

scanning

period.

Scanning

is

obtained

during

this

period

by

arrangingthat

the

efficiency

diode

(V14)

conducts

and

allows

the

energy

contained

in

the

scan

coilstodrive

a

currentvia

V14

into

C109.

The

direction

of

thiscurrent

is

such

as

to

supply

the

initialpart

of

the

total

scan.

Frame.

time

-base.

This

consists

of

a

multivi-

brator

followed

by

a

pentode

output

valve.

A

secondary

circuit

on

the

output

transformer

supplies

a

suitable

wave

-form

for

frame

fly-

back

suppression,

which

is applied

to

ttie

first

anode

of

the

c.r.t.

Power

supply.

A

conventional

a.

c./d.c.

power

supply

circuitis

used,

and

the

valve

heaters

are

arranged

in

a

single

0.3

Amp.

series

chain.

On

the

lower

d.

c.

steps

of

the

mains

adjustment

switch,

the

rectifier

is

removed

from

the

circuit

to

avoid

an

unnecessary

loss

oP

h.

t.

voltage.

At

the

same

time,

thereser-

voir

capacitoris

disconnected

from

the

cir-

cuit

so

thatthere

isless

surge

current

to

'°blow"

the

mains

fuse;

see

"Installation"

on

page

2

.

VOLTAGE

READINGS

General.

The

voltage

readings

given

in

the

circuit

diagrams

and

chassis

layout

diagrams

arerepresentative

only,

and

willdiffer

slightly

from

one

setto

another.

Procedure

for

measuring

the

voltages.

To

ob-

tain

voltage

readings

corresponding

to

those

quoted

in

thecircuit

and

chassislayout

diagrams,

proceed

as

follows:

1.

Adjust

the

mains

adjustment

switch,

if

necessary,

to

suit

the

mains

input

at

the

time

of

measurement.

See

"Installation"

on

page

2

.

2.

Adjust

the

receiver

to

give

a

normal

pic-

ture

on

a

B.B.C.

channel.

3.

Measure

the

voltages,

using

a

20,OOOi1/V

meter.

If

a

20,00011/V

meter

is

not

avail-

able,

a

50011/V

meter

can

be

used;

those

readings

which

were

found

to

differ

appre-

ciably

from

the

figures

on

the

diagrams,

when

using

such

a

meter,

are

given

in

Table

1.

4.

Ascertain

whether

the

variablecontrols

are

having

the

correct

effect

on

the

volt-

ages

which

they

influence.;

follow

the

pro-

cedure

outlined

in

Table

2.

8.

h.

t. voltage.

This

was

taken

with

an

elec-

trostatic

voltmeter.

A

l0V

d.c.

meter

having

a

sensitivity

of

20,OOOII/V,

with

a

suitable

multiplier

such

as

the

AVO

25,OOOV

Multiplier

TYPe

8,

can

be.

used.

NOTE:

The

BRIGHTNESS

control

must

be

turned

to

zero

brightness

when

taking

this

reading.

Vision

and

sound

i.f. circuits.

If instabi-

lityis

experienced

when

measuring

the

anode

voltages,

connect

the

meter

instead

to

the

Murphy Radio V310 User manual

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