Philips N4307 User manual

PHILIPS

Model

N4307

General

Description:

This

model

is

basically

similar

to

the

Stella

Model

ST'9123A

which

is

described

later

in

this

volume.

It

has

a

simplified

input

stage

with

a

single

input/output

socket

and

Tr

is

omitted,

the

signal

being

applied

direct

to

the

base

of

T'2

through

the

blocking

capacitor.

PHILIPS

Model

N4308

General

Description:

This

model

is

electrically

similar

to

the

Stella

Model

ST'9123A

which

is

described

later

in

this

volume.

PHILIPS

Model

LFH0085

General

Description:

The

LFHoo85

“Pocket

Memo”

is

a

miniaturised,

battery

operated,

cassette

loaded,

dictation

machine.

It

is

completely

self

contained;

the

battery,

micro-cassette

and

combined

microphone/loudspeaker

all

being

housed

within

the

pocket

sized

casing.

A

socket

is

provided

for

the

use

of

stethoscope

headphones,

if

desired

in

lieu

of

the

internal

loudspeaker.

Provision

is

also

made

for

the

re-recording

of

recorded

matter

on

to

a

Philips

EL3581,

EL3582

or

LFHoo84

dictation

machine

by

means

of

an

inter-con-

necting

dubbing

(copying)

lead.

Battery:

gvolt

(PP3

or

equivalent),

at

35mA

approx.

Battery

Check:

The

battery

should

be

checked

periodically

to

see

if

it

still

provides

sufficient

voltage.

To

do

this,

depress

the

top

of

the

side

rocker

switch

and

press

the

battery

check

control

(above

volume

control).

If

an

audible

tone

is

heard

from

the

loudspeaker

the

battery

is

still

good.

Dismantling

Case

Removal:

Remove

battery

and

tape

cassette.

Withdraw

plastic

cap

from

headphone

socket.

Remove

screws

from

back

and

top.

Lay

machine

face

down,

depress

record

button

then

lift

off

the

rear

casing.

Ease

internal

assembly

upwards,

free

from

front

casing.

Remove

safety

button

and

foam

rubber

damping

pad

for

safe

keeping.

Reassemble

in

the

reverse

order.

Ensure

that

battery

leads

are

positioned

to

lie

in

the

slots

provided.

Removal

of

Printed

Panel:

Set

record

button

and

rocker

switch

to

the

rest

position

or

to

the

position

required

for

test.

Note

(or

mark)

position

of

motor

switch

(Sr)

slider

for

future

reference,

then

slacken

off

screw

securing

actuator

bracket

and

disengage

bracket

from

slider.

Free

lead

to

headphone

General

Description:

These

models,

utilising

an

electrically

similar

chassis,

are

four-track,

two-speed,

mains-operated,

tropicalised

tape

recorders,

employing

ten

transistors

and

three

diodes.

Recording

facilities

include

signal

input

mixing,

loudspeaker

or

headphone

monitoring

and

a

meter-type

recording

level

indicator.

Provision

is

made

for

using

the

recorder

as

a

microphone,

radio,

or

pick-up

amplifier

and,

when

used

in

conjunction

with

the

“Stereo”’

pre-amplifier

EL3787A/ooA

etc.,

Stereo

playback/Multiplay/

Duoplay

1s

also

possible.

Mains

Supply:

110,

127,

200-25o0volts

A.C.;

Frequency.

Response:

60-14,000

Hz

at

3

1.p.s.,

80-8000

Hz

at

1$

i.p.s.

Inputs:

Sktr—Radio

(diode).

Pins

1/4

and

2.—2mV

into

20K.—Pick-up.

Pins

3

or

5

and

2.—100omV

into

1M.

Skt.

2—Microphone.

Pins

1/4

and

2.—

o-2mV

into

2K.

Outputs:

Sktr—Line

(diode)

Pins

3,

5

and

2—750mV

across

20kQ;

Skt3—-Stereo;

Sktq—Ext.

L.S.

Impedance

4

or

8Q,

4

watts;

Skts—Head-

phones

Pins

4

and

1/2.

Case

Removal:

Remove

lid,

pull

off

the

four

control

knobs,

speed

change

knob

and

undo

the

four

(some

models

have

five)

ornamental

screws.

Take

off

cover

plate,

disconnect

the

speaker

leads

and

case

screening

lead

(these

are

usually

slide-on

connectors

but

in

some

cases

may

be

soldered)

and

lift

out

chassis.

‘The

chassis

can

be

operated

out

of

the

cabinet,

providing

normal

care

A

4

|

PEAS

eee

a

1

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TAPE

RECORDER

SERVICING

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FUNCTION

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Playback

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Parallel

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(R.P.)

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Recording

Playback

‘

580

Level

220

ak

110

{BCIOBA)

W256a

STELLA

is

taken

to

keep

the

chassis

level

and

a

speaker

of

correct

impedance

is

con

nected.

Reassemble

in

the

reverse

order.

On

some

models

R550

may

be

39K

R564

»

4

82

R560

#@

#8

47K

7

ts

da

ts

ib

u

Switch

coding

R

—_

Record

P

Playback

PA

Public

Address

STOP

Play

key

up

Switches

close

only

for

functions

indicated

Total

H.T.

current

GimA

X}

LozmA

(8Y126)

R

565

LP}

330

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Volume

150

2suF

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545

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22K

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495

120K

1°57

R-PA

P

2

iSKp

R

pot

Mod.

Level

indicator

Ne

+}

W256b

TAPE

RECORDER

SERVICING

Printed

Panel

Removal:

Access

to

the

printed

panel

may

be

obtained,

after

setting

the

track

switch

to

the

‘“‘PAR”

position

and

the

tape

speed

to

1%

i.p.s.,

by

undoing

the

four

screws

securing

the

printed

panel

frame

to

the

chassis.

The

frame

and

printed

panel

can

be

removed

to

the

extent

of

the

Sockets

viewed

on

solder

tags,

25:0

24:5

T&

(AD161)

8200

gia

13-25

ine

(ADI62)

W256c

All

voltages

taken,

unless

otherwise

stated,

with

respect

to

chassis

using

a

100KN/V

meter.

Mains

input

240Va.c,

to

240V

tap.

Playback

voltages

[|

Record

yoitages

240V

“oO

if)

220¥

°

o

Qs

Ns

.

On

Own

o*s

Ou

&

2

8

i

L3

vf

é

H0V

c

767

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it

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Va

Pe

m&~

>

connecting

leads,

taking

care

not

to

bend

or

deform

the

switch

blades

of

54(b).

When

refitting

the

printed

panel

frame,

ensure

that

the

switch

operating

levers

are

correctly

engaged

with

the

switch

sliders

and

that

S4(a)

and

S4(b)

operate

properly.

Recording

Bias

Current:

The

recording

bias

current

should

be

18mV,

measured

as

a

voltage,

but

may

be

set

within

the

limits

10-25mV.

Switch

to

“Record”,

set

the

track

selector

switch

to

“1-4”

and

adjust

R441

so

that

a

voltage

of

18mV,

measured

with

an

A.C,

millivoltmeter,

is

obtained

at

MPr.

Similarly,

in

track

position

“2-3”,

the

same

reading

should

be

obtained

at

MP2

by

adjusting

R442.

Check

the

overall

frequency

response

and

if

neces-

sary

make

further

adjustments

to

the

bias

current

to

obtain

the

response

required.

Reducing

the

bias

current

will

increase

the

treble

response;

conversely,

increasing

the

bias

current

will

reduce

the

treble

response.

Should

the

value

of

bias

current

be

below

the

lower

limit

specified,

it

will

cause

dis-

tortion

at

high

modulation

levels;

if

above

the

upper

limit,

it

will

result

in

poor

treble

response.

If

after

adjustment,

the

level

of

bias

current

is

outside

the

range

specified

above,

a

defect

in

the

record/playback

head

or

in

the

ampli-

fier

circuitry

should

be

suspected.

Mod.

fevel

Indicator

NOTES:

All

sockels

viewed

on

solder

tags.

Add

200

to

all

contact

numbers

on

SZ

Add

300

to

all

contact

numbers

on

S3.

WIRING

CODING

——e

On

unit

A,

lead

marked

@

ts

connected

to

unit

E

and

there

marked

(4).

Simltarly,

on

unit

D,

tead

marked

is

connected

to

unit

A

and

there

marked

(W257)

CoMPONENT

LayvouT

AND

INTERCONNECTION

DIAGRAM

—

W257d

Modulation

Level

Indicator

Calibration:

Set the

track

selector

switch

S2

to

track

“1-4”

(or

“‘2-3”’),

turn

Radio/Phono

record

level

control

R444

to

maximum

and

depress

the

“Record”

key

only.

Apply

a

1

kHz

signal

to

3,

Sktr,

adjusting

the

level

so

that

a

voltage

of

3mV,

measured

with

an

A.C.

millivoltmeter,

is

present

at

MP1

(or

MP2).

The

pointer

of

the

modulation

TAPE

RECORDER

SERVICING

JUWN}OA

OT fb

te

cc

tatage

PAAR

MATS

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(E9SY

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ee

ERLE

fe

eMIMIPsI%1

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021

/\

SSH

Pe

yD

oe)

(4)

et

:

a

dig

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0M)

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i

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08

0%

oF

af

AS

aa

eae

AOS

:

eth

ea

ac

7

nw

ere

RSTO

|

OOOO

O-ODDLDODD--

meee

eRe

ee

eet

level

indicator

may

be

adjusted

with

R446

so

that

it

registers

on

the

division

between

the

red

and

black

sectors

of

the

scale.

Remove

the

input

signal

and

switch

to

“‘Record”’;

the

meter

pointer

should

be

deflected

up

to

a

maximum

of

1mm.,

due

to

bias

current.

Correction

Coil

L2

(adjusted

only

on

replacement):

Depress

the

‘‘Record”’

key

only

and

apply

a

1

kHz

signal

to

3,

Sktz,

so

that

a

voltage

of

0-775

mV,

measured

with

an

A.C.

millivoltmeter,

is

present

at

MPx,

with

the

track

selector

switch

S2

set

to

position

“1-4”.

Change

the

input

signal

frequency

to

14kHz.

The

voltage

at

MP1

should

now

read

3-5mV;

adjust

correction

coil

L2

for

this

reading,

then

seal

it

with

locking

paint.

Cleaning:

The

magnetic

heads,

tape

guides

and

capstan

should

be

cleaned

at

regular

intervals

if

optimum

performance

is

to

be

maintained.

Remove

cover

for

access

to

these

parts,

which

can

be

cleaned

with

a

soft

cloth

wrapped

around

a

wooden

stick

and

moistened

with

methylated

spirits

or

industrial

alcohol.

Metal

objects

should

not

be

allowed

to

come

into

contact

with

the

magnetic

head

faces.

After

approximately

500

hours

of

service,

it

is

advisable

to

clean

the

follow-

ing

parts

with

methylated

spirits

or

industrial

alcohol:

Magnetic

head

faces;

Tape

guides;

Capstan

and

pressure

roller;

Drive

belts;

Grooves

in

flywheel

and

pulleys;

All

friction

driven

surfaces;

Brake

shoes

and

braking

surfaces

of

turntables.

Clean

the

inside

of

both

turntables

with

a

soft

dry

brush

and

if

necessary

clean

or

replace

pressure

felt.

D.C.

Voltages—Switch

to

“

Record”.

Stage

|

Collector

|

Base

|

Emitter

Tr

1°35

0°62

—

T2

1°38

0-6

——

13

1°82

0°62

0°16

T4

5°3

1°18

0°65

Ts

7-6

0:8

0°65

T6

13'0

1°S7

I*44

T7

—

130

13'I

TS

24'S

13°3

13'2

Tro

10°8

orl

0°78

Switch

to

“

Playback”’.

Stage

|

Collector

|

Base

|

Emitter

Tr

1°36

0°62

—

T2

1°33

0°59

—

T3

I'9

0°68

018

T'4

5°6

1°22

O'7

Ts

8-6

1'99

P37

T6

13°25

1'6

I°47

a7

—

13°25]

13°4

T8

2.5

13°6

13°5

Ti10

—

—_

=

Philips N4307 User manual

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