Sony Ps-2250 User manual

General

Speeds:

Turntable

drive:

Wow

and

flutter:

(weighted)

Signal-to-noise

ratio:

(weighted)

Motor:

Turntable

platter:

Start-up-time:

rower

consumption:

Power

requirements:

Dimensions:

PS-2250

TTS-2250

SPECIFICATIONS

33-/3,

45

rpm

+4

%,

adjustable

Direct

drive

system

Less

than

0.07

%

(DIN

45507)

Less

than

0.04

%

(WRMS)

Greater

than

58

dB

(JIS)

Greater

than

67

dB

(DIN

45544)

AC

servo-controfied

motor

310

mm

(12-/16")

dia,

1.5

kg

(3

Ib

5

oz)

diecasted

aluminium

Less

than

2.5

seconds

15

watts

110,

127,

220

and

240

V

ac,

50/60

Hz

490

mm

(width)

x

185

mm

“(height)

x

395

mm

(depth)

19-7/39""

(width)

x

77/32"

(height)

x

15-1

4/32"

(depth)

328

mm

(width)

x

146

mm

(height)

x

357

mm

(depth)

12-2°/39""

(width)

x

5-3/4”

(height)

x

14-1/;

6”

(depth)

Net

weight:

Shipping

weight:

Tonearm

(PUA-114)

Type:

Arm

length:

(Pivot-To-Stylus)

Over

hang:

Stylus

force

adjustment

range:

Anti-skating

force

compensation

range:

Tonearm

height

precise

adjustment

range:

Cartridge

weight

range:

Shelf-head

weight:

11.3

kg

(24

Ib

15

oz),

PS-2250

7.5

kg

(16

ib

9

oz),

TTS-2250

14

kg

(30

Ib

14

02),

PS-2250

10

kg

(22

Ib),

TTS-2250

Static

balanced

245

mm

(9-7"/32"")

9,

14mm

(/16

)

0

to

3g.

0.1

g

increments

0

to

3g.

0.5

g

increments

4.65

cm

~

5.15

cm

(1-°

7/32")

~(2-Y/32")

4gtoilg

CW-50

(optional

counterweight)

10g~17g

10.59

~

SERVICE

MANUAL

TABLE

OF

CONTENTS

Section

Title

Page

1.

TECHNICAL

DESCRIPTION

“4-1.

Technical

Specifications

2...

ee

1

1-2.

Principle

of

ac

Servo

System...

2...

ee

eee

1

1-3.

Block

Diagram

«ww

ee

4

2.

DISASSEMBLY

AND

REPLACEMENT

2-1.

Top

Cover

Removal

...........6.

rid

aia

Hee

TOA:

ee

a)

Ae

CO

a

5

2-2.

Bottom

Plate

Removal

..

2.

1.

et

5

2-3.

Turntable

Base

Removal

...

2...

1.

ee

ts

5

2-4.

Servo

Amplifier

Chassis

Removal...

2...

1

eee

ee ee

eee

6

2-5.

Servo

Amplifier

Cover

Removal

.

2...

eee

ee

es

6

2-6.

Power

Supply

Chassis

Removal

....

2.2...

ee

eee

6

2-7.

Motor

Replacement

..

1...

6.

ee

6

2-8.

Microswitch

Replacement

......

2.2...

ee

erase

eatin

ven

a

7

2-9.

Strobe

Lamp

Replacement...

1...

ee

8

2-10.

Power

Transistor

Replacement...

1...

ee

et ee

eee

ee

8

2-11.

Tonearm

Assembly

Removal...

0...

eee

ee

8

2-12.

Tonearm

Base

Removal

..

1...

1.

1

eee

ee

et

ee ee

eee

8

2-13.

Tonearm

Lifter

Replacement...

2...

ee

eee

ee

ee ee

ee

9

2-14,

Bias

Cord

Stringing...

2.0.

2

ee

eee

iesleet

Stet

9

3.

ADJUSTMENT

PROCEDURES

3-1.

Speed

Adjustment

2.2...

1

es

10

3-2.

Tonearm

Height

Adjustment...

2...

ee

eee

ee

es

10

3-3.

Stylus-Force

and

Anti-Skating

Force

Adjustment

..........-.

10

3-4.

Lateral

Balance

Adjustment

..

2... 2...

ee

11

3-5.

Lubrication

2...

0.

1

ee

ee ee

ee

es

11

4.

DIAGRAMS

4-1.

Wiring/Mounting

Diagram

-

AEP

Model—

.........--.-.4--.

13

4-2.

Wiring/Mounting

Diagram

—

EP

Model—

......

2.2.22

ee

eee

15

4-3.

Schematic

Diagram

..

2...

1.

ee

17

4-4.

Mounting

Diagram

..

1

2.

1

ee

19

5,

-

EXPLODED

VIEWS

203s.

5.4.

.fe

a

he

o

da

ew Be

Oe

ak

a

es

ges

28)

6.

REPAGKING:

©

cos

o.

5

6

2S

EA

ee

BG

24

7.

ELECTRICAL

PARTS

LIST

......-...

2.02252

ee

eee

26

SECTION

1

TECHNICAL

DESCRIPTION

1-1.

TECHNICAL

SPECIFICATIONS

Technical

specifications

for

PS-2250/TTS-2250

are

listed

in

TABLE

1.

Note:

TTS-2250

is

a

turntable

unit

only.

TABLE

1.

TECHNICAL

SPECIFICATIONS

Speeds:

Turntable

drive:

Wow

and

flutter:

(weighted)

Signal-to-noise

ratio:

(weighted)

Motor:

Turntable

platter:

Start-up-time:

Power

consumption:

Power

requirements:

Dimensions:

PS-2250

TTS-2250

Net

weight:

Shipping

weight:

.

General

33-1/3,

45

rpm

+4

%,

adjustable

Direct

drive

system

Less

than

0.07

%

(DIN

45507)

Less

than

0.04

%

(WRMS)

Greater

than

58

dB

(JIS)

Greater

than

67

dB

(DIN

45544)

AC

servo-controlled

motor

310

mm

(12-3/16')

dia,

1.5

kg

(3

lb

5

oz)

diecasted

aluminium

Less

than

2.5

seconds

15

watts

110,

127,

220

and

240

V

ac,

(GEP

Model)

50/60

Hz

100,

120,

220

and

240

V

ac,

(General

Export

Model)

50/60

Hz

490

mm

(width)

x

185

mm

(height)

x

395

mm

(depth)

19-9/32"

(width)

x

7-9/32”

(height)

x

15-11/32”

(depth)

328

mm

(width)

x

146

mm

(height)

x

357

mm

(depth)

12-29/32"

(width)

x

5-3/4"

(height)

x

14-1/16

(depth)

11.3

kg

(24

lb

15

oz),

PS-2250

7.5

kg

(16

lb

9

oz),

TTS-2250

14

kg

(30

lb

14

02),

PS-2250

10

kg

(22

Ib),

TTS-2250

Tonearm

(PUA-114)

Type:

Arm

length:

(Pivot-To-Stylus)

Over

hang:

Static

balanced

245

mm

(9-21/32")

14

mm

(9/16')

Stylus

force

adjustment

range:

Oto

3g.

0.1

g

increments

Anti-skating

force

compensation

range:

Oto3g.

0.5

g

increments

Tonearm

height

precise

adjustment

range:

4.65cm

~

5.15

cm

(1-27/32")

~

(2-1/32")

Cartridge

weight

range:

4gtollg

CW-50

(optional

counterweight)

10g

~17¢g

Shell-head

weight:

10.5

g

1-2.

PRINCIPLE

OF

AC

SERVO

SYSTEM

Fig.

1-1

shows

a

simplified

diagram

of

the

ac

servo

system

employed

in

this

set.

Since

the

ac

motor

speed

is

proportional

to

the

applied

ac

voltage,

it

is

controlled

by

varying

the

applied

voltage

(Em)

to

the

motor.

This

is

effectively

performed

by

means

of

series

resistor

Rv.

In

practice,

series

resistor

Rv

is

replaced

by

the

diode-bridge

circuit

and

collector-emitter

impedance

of

a

power

transistor

as

illustrated

in

Fig.

1-2.

Note

that

the

diode-bridge

determines

only

the

direction

of

the

ac

current

which

flows

in

the

power

transistor.

Motor

speed

is

converted

into

ac

signal

by

means

of

a

direct-coupled

frequency

generator.

The

servo

amplifier

compares

this

signal

against

a

very

stable

dc

reference

voltage,

and

then

controls

the

collector-emitter

impedance

of

power

transistor.

Any

error.in

motor

speed

results

in

a

correction.

voltage

supplied

to

the

motor.

SERVO

AMP

Fig.

1-1.

Principle

of

ac

servo

system

SERVO

AMP

Fig.

1-2.

Practical

ac

servo

system

Stage/Control

Function

Start

Operation

When

the

power

switch

is

turned

on,

Q06

in

the

base

circuit

of

QO7

is

cutoff.

As

a

result,

C8

in.

the

collector

circuit

is

charged

through

R27,R8,

VR2,

R10,

VRI

and

R9

when

the

33

rpm

button

is

depressed.

Note

that

VR2

and

R10

is

shorted

during

45

rpm

operation.

Q07

is

forced

into

conduction

when

C8

is

charged

up

to

some

specified

voltage.

As

a

result

the

following

conditions

exist:

:

Q09

QO10

QOlI

Q3

Q4

Q5

Q6

OFF

ON

and

a

large

enough

ac

voltage

is

applied

to

the

motor

so

the

motor

starts

to

revolve

rapidly.

Correct

Speed

Condition

Frequency

generator

When

the

motor

starts

to

revolve,

the

frequency

generator

(F.G.)

generates

ac

voltage

whose

frequency

is

pro-

portional

to

the

motor

speed.

As

the

frequency

generator

is

directly

coupled

to

the

shaft

of

the

drive

motor,

it

converts

motor

speed

into

frequency.

Differential

Q1

and

Q2

forma

differential

amplifier

which

amplifies

the

input

FG

signal

to

the

level

required

for

the

following

Ql,

Q2

limiter

circuit.

Note

that

the

output

is

extracted

from

collector

circuit

of

Ql]

and

Q2,

and

then

fed

to

the

flip-flop

stage

through

diode

limiter

D1

and

D2.

Stage/Control

Function

Diode

limiter

Removes

all

amplitude

variations

from

D1,

D2

the

signal.

Each

diode

conducts

when

the

signal

across

it

exceeds

the

barrier

potential

(0.6

V)

in

a

forward

biased

condition.

Thus,

the

output

signal

is

limited

to

about

1.2

V

peak-to-peak.

Flip-flop

Q01

and

QO02

form

a

flip-flop

circuit

which

generates

square

output

in

ac-

Q01,

Q02

cordance

with

the

input

trigger

signal

(limiter’s

output).

The

flip-flop

output

is

extracted

at

collector

circuit

of

QO2

and

then

fed

to

the

buffer

amplifier

stages.

Buffer/phase

Q0O3,

Q04

and

QOS

form

a

buffer

inverter

amplifier

stage.

Note

that

Q03

and

Q03, Q04,

Q05

are

emitter

followers

but,

Q04

Q05

acts

as

a

phase

inverter.

Differentiation

Square

wave

output

at

the

emitter

circuit

of

QO5

is

converted

into

spike

C7,

RO12

pulses

through

the

differentiator

circuit

(formed

by

C7

and

RO12)

to

trigger

the

following

saw-tooth

wave

generator

(Q06).

Saw-tooth

Q06

and

RC

components

(C8,

R9,

wave

VR1,

R10,

VR2)

in

the

collector

circuit

generator

form

a

saw-tooth

wave

generator.

Q06,

C8,

R9,

Note

that

the

frequency

of

the

saw-

VRI,

R10

tooth

wave

is

determined

by

the

RC

VR2

time

constants

in

the

collector

circuit.

Voltage

The

saw-tooth

is

fed

to

the

voltage

comparator

formed

by

QO7

and

QO8.

Q07,

Q08

is

forward

biased

through

the

FINE

control

(VR3

paralleled

by

R12)

R11

and

R28.

The

current

flow

in

Q08

is

controlled

by

the

FINE

control

(VR3),

which.

varies

its

base-emitter

voltage.

Q07

conducts

only

when

the

base

voltage

becomes

higher

than

the

emitter

voltage

which

is

determined

by

the

current

flow

in

QO8.

Note

that

the

emitter

voltage

of

QO8

serves

as

a

reference

voltage.

Referring

to

Fig.

1-3,

the

comparator

operates

as

follows:

At

time

T1

a

saw-

tooth

signal

is

applied

to

the

base

of

Q07.

At

time

T2

the

voltage

at

the

base

of

Q07

is

sufficient

to

turn

on

QO7

generating

a

negative

pulse.

Note

that

the

pulse

width

is

determined

by

saw-tooth

signal

waveform:

Stage/Control

Buffer/phase

inverter

Q09,

Q010,

Q011

Low

pass

filter

/buffer

amplifier

De

amplifiers

Q4,

QS,

Q6

Function

Q09

and

QO11

is

an

emitter

follower

but

Q010

acts

as

a

phase

inverter

providing

a

positive

pulsating

signal

to

the

following

stages.

Buffer

amplifier

Q3

and

an

RC

network

consisting

of

R15,

C11,

R16,

C12,

C13

R17

and

C14

comprise

a

low-pass

filter

having

a

sharp

rolloff

charac-

teristic.

.

Notice

that

this

stage

acts

as

an

integrator,

converting

the

input

positive

pulses

into

a

dc

voltage

proportional

to

the

input

pulse

width.

De

output

from

the

low-pass

filter

is

applied

to

the

base

of

Q4.

As

Q4,

Q5

and

Q6

are

directly

coupled,

‘a

change

in

input

dc

voltage

alters

the

con-

duction

of

Q6,

controlling

the

voltage

applied

to

the

motor.

_

Servo

Operation

When,

by

any

cause,

the

motor

speed

becomes

slightly

faster

or

slower

than

the

specified

value,

the

servo

system

works

as

follows:

Referring

to

Fig.

1-3,

assume

that

the

motor

speed

becomes

faster.

The

FG

output

signal

frequency

becomes

higher,

resulting

in

a

shorter

interval

between

pulses

for

triggering

the

saw-

tooth

wave

generator.

The

shorter

—_

1

-

;

|

oem

|

ee

When

motor

speed

becomes

faster.

Stage/Control

Power

supply

D8,

D9

C17,C19

D7

Speed

selector

switch

S1

normal

——

|

i

—

When

motor

speed

becomes

slower.

Function

interval

between

trigger

pulses

causes

lower

saw-tooth

wave

height,

which

in

turn

yeilds

a

shorter

“ON”?

period

for

comparator

QO7.

Therefore,

the

output

pulse

width

at

the

emitter

circuit

of

QO11

becomes

shorter,

reducing

the

positive

bias

upon

.Q4.

As

a

result,

the

collector-emitter

impedance

of

Q6

increases,

reducing

the

motor

speed.

Conversely,

if

the

motor

speed

becomes

slower,

the

collector-emitter

impedance

of

Q6

decreases,

increasing

the

motor

speed.

A

positive

12

volts

for

the

system

is

provided

by

the

full-wave

rectifier

consisting

of

D8

and

D9,

filter

ca-

pacitors

C19,

C17

and

zener

diode

D7.

Speed

changeover

operation

is

per-

formed

by

changing

the

saw-tooth

wave

frequency

as

previously

described.

Since

the

saw-tooth

wave

frequency

is

determined

by

the

RC

time

constant

in

the

collector

circuit

of

Q06,

a

speed

selector

switch

is

connected

in

parallel

with

VR2

and

R10.

A

smaller

time

constant

results

in

faster

motor

speed

and

vice

versa.

So

S1

is

open

when

the

speed

selector

switch

is.

set

to

33-1/3

rpm.

slower

FG

output

signal

collector

of

QO2

pase

of

Q06

collector

of

Q06

collector

of

Q07

base

of

Q3

base

of

Q6

Fig.

1-3.

Waveforms

on

servo

control

circuit

8a

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FAMOd

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YILVA

SSVd

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YOLVINIIY

Y4AMOd

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dav

MS

YOLIITIS

\

G33dS

"ts

\

O

Oo

FOVLTIOA

=

ft

cc

rc)

j0.uU02

paads

=

a

¥

800

‘Z00

oO

1100

‘0100

‘600

HOP

oy

eo

acon

900

‘p00

‘c€00

ZOD‘

:

VYINID

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VUVdWOD

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1-3.

SECTION

2

DISASSEMBLY

AND

REPLACEMENT

WARNING

Unplug

the

ac

power

cord

before

start-

ing

any

disassembly

or

replacement

procedures.

CAUTION

To

avoid

damage

to

the

stylus

while

performing

the

following

procedures,

make

sure

that

the

stylus

protecting

cover

is

in

place.

2-1.

TOP

COVER

REMOVAL

1.

Open

the

top

cover,

and

then

push

the

upper

hinge

toward

the

left

to

release

the

lock

as

shown

in

Fig.

2-1.

2.

Carefully

lift

the

top

cover

straight

up.

This

frees

the

top

cover.

Fig.

2-1:

Top

cover

removal

2-2,

BOTTOM

PLATE

REMOVAL

1,

Flip

the

wooden

case

upside

down.

Place

it

on

a

soft

protective

pad,

and

then

remove

the

six

screws

(@

PS

3

x

16)

securing

the

bottom

plate

|

to

the

wooden

case

as

shown

in

Fig.

2-2.

This

frees

the

bottom

plate.

2-3.

TURNTABLE

BASE

REMOVAL

—

Preparation

1.

Remove

the

bottom

plate

as

described

in

Pro-

cedure

2-2.

2.

~—

Up

to

serial

No.

50,550

—

(AEP

Model

Only)

Disconnect

4-p

AMPLOK

connector

from

bot-

tom

of

the

turntable

and

then

remove

the

top

cover

as

described

in

Procedure

2-1.

—

Serial

No.

50,551

and

later

—

(AEP

Model

Only)

Disconnect

4-p

connector

from

bottom

of

the

turntable

and

then

remove

the

top

cover

as

described

in

Procedure

2-1.

Procedure

1.

_

Remove

the

rubber

mat

from

the

turntable,

and

-

then

insert

your

fingers

into

the

two

holes

of

the

turntable.

with

both

thumbs

placed

on

the

center

spindle

as

shown

in

Fig.

2-3.

Carefully

lift

the

turntable

straight

up:

;

a

Remove

the

three

screws

(

@©P

5

x

16)

and

two

screws

(

@®

PS

4x

20)

securing

the

turntable

base

to

the

wooden.case.

This

frees

the

turn-

table

base.

See

Fig.

2-4.

Note:

The

turntable

base

may

not

be

easily

"ss

Temovable

due

to

the

rubber

washer.

inserted

between

the

turntable

base

and

the

wooden

case.

In:

this

case,

gently

push

the

motor

end

from

the

bottom.

Flip.

the

turntable

base

upside

down.

Place

a

support

between

the

turntable

base

and

the

service

bench

to

keep

pressure

off

the

motor

spindle.

Fig.

2-3.

Turntable

removal

Fig.

2-4.

Turntable

base

removal

2-4.

SERVO

AMPLIFIER

CHASSIS

REMOVAL

1.

Remove

the

turntable

base

as

described

in

Procedure

2-3.

2.

Remove

the

four

screws

(@

PS

4

x

6)

securing

the

chassis

to.

the

turntable

base

as

shown

in

Fig.

2-5.

Thisfrees

the

chassis.

i

@.

P

3.x

6,

self-tapping

servo

amp

cover

remova

ii

Fig.

2-5.

Bottom

view

2-5.

SERVO

AMPLIFIER

COVER

REMOVAL

1,

Remove

the

servo

amplifier

chassis

as

described

in

Procedure

2-4.

2;

Remove

the

two

self-tapping

screws(@

P

3

x

6)

securing

the

servo

amplifier

cover

as

shown

in

Fig.

2-5,

and

then

slide

it

in

the

direction

shown

by

the

arrow

as

illustrated.

This

frees

the

cover.

chassis

removal

POWER

SUPPLY

CHASSIS

REMOVAL

Note:

The

power

supply

chassis

is

an

angled

member

on

which

the

power

trans-

former,

power

transistor

and

fuse

holder

are

attached.

Remove

the

turntable

base

as

described

in

Procedure

2-3.

Remove

the

two

screws

(

@

PS

4

x

8)

and

securing

the

power

transformer

cover

to

the

heat

sink

as

shown

in

Fig.

2-6,

if

necessary.

Remove

the

three

screws

(@

PS

4

x

25)

securing

the

chassis

to

the

turntable

base

or

the

bracket,

as

shown

in

Fig.

2-5.

This

frees

the

power

supply

chassis.

Fig.

2-6.

Power

transformer

cover

removal

MOTOR

REPLACEMENT

Remove

the

turntable

base

as

described

in

Procedure

2-3.

Remove

the

two

seilf-tapping

screws

(@

P

4x

6)

securing

the

metal

cover

over

the

terminal

strip

as

shown

in

Fig.

2-5.

Unsolder

the

motor

lead

wires

at

the

terminal

strip,

and

then

remove

the

four

screws

(@

PS

4

x

12)

securing

the

motor

to

the

turn-

table

base

from

the

top

as

shown

in

Fig.

2-7.

Install

the

replacement

motor.

Fig.

2-7.

Motor

removal

CAUTION

Electromagnetic

brake

adjustment

(clearance

between

turntable

and

magnet

turntable

To

FG

coil

To

Motor

co

LK

“"

~

}

test

point

ac21+2V

3

Fig.

2-9.

Test

point

for

electromagnetic

brake

adjustment

2-8.

MICROSWITCH

REPLACEMENT

mounted

on

turntable

base)

should

be

Performed,

ab

Zollows

after

replacing:

the

1.

Remove

the

turntable

base

as

described

in

PIOPOES

Procedure

2-3.

1.

First

of

all,

confirm

that

the

turntable

2.

Unhook

the

spring

pressing

the

microswitch

does

not

touch

with

the

magnet

on

the

holding

shaft

against

its

bracket.

Carefully

turntable

base

(See

Fig.

2-8).

If

it

does,

draw

out

the

microswitches

along

with

their

adjust

the

magnet

height

by

replacing

holding

shaft

as

shown

in

Fig.

2-10.

i

ACR

OUS

Diaks.

3.

Remove

the

retaining

rings

at

one

side

of

the

Three

kind

of

mounting

plate

are

available

as

specified

in

table

below.

To

remove

the

magnet

and

mounting

plate,

apply

a

few

drops

of

cement

solvent

to

them.

shaft,

and

then

replace

the

defective

micro-

switch

as

shown

in

Fig.

2-10.

To.

reassemble,

reverse

the

aforementioned

procedure.

[EP

Model]

1

[AEP

Model]

Description

Thickness

of

plate

(mm)

|

Part

Number

Mounting

plate,

;

1.6

4-8

08-445-02

5

magnet

1.0

4-8

08-445-11

0.5

4-8

08-445-21

2.

Set

the

turntable

for

33-1/3

rpm

operation,

and

then

measure

the

voltage

applied

to

the

motor

at

the

5-p

termi-

nal

strip

as

shown

in

Fig.

2-9.

It

should

be

within

the

limits

of

21

+2

volts

ac.

If

not,

readjust

the

clearance

between

the

turntable

and

the

magnet

by

replacing

the

mounting

plate

as

previously

described.

SS

Qe

SH

Fig.

2-10.

Microswitch

replacement

2-9.

STROBE

LAMP

REPLACEMENT

1.

2.

3.

4.

Remove

the

turntable

base

as

described

in

Procedure

2-3.

Remove

the

four

screws

(@

PS

4

x

8)

securing

the

strobe

unit

to

the

turntable

base.

Pull

out

the

unit.

Unhook

the

retaining

spring

from

the

lamp

cover

and

then

apply

a

drop

of

cement

solvent

to

the

lamp.

Wait

a

few

seconds,

and

then

push

out

the

defective

lamp

as

shown

in

Fig.

2-11.

CAUTION

Too

much

cement

solvent

may

cause

damage

to

the

unit.

Only

a

few

drops

are

required

to

dissolve

the

rubber-base

ad-

hesive.

Install

a

new

strobe

lamp.

Take

care

that

the

glowing

side

(front)

of

the

lamp

is

positioned

as

shown

in

Fig.

2-11

Note:

Apply

a

drop

of

rubber-base

adhesive

to

the

rear

side

of

the

lamp

when

installing

the

lamp.

glowing

side

Fig.

2-11.

Strobe

lamp

removal

and

installation

2-10.

POWER

TRANSISTOR

REPLACEMENT

1.

2;

3.

Remove

the

power

supply

chassis

as

described

in

Procedure

2-6.

Remove

the

screw

(@

P

3

x

10)

securing

the

power

transistor

to

the

heat

sink.

Cut

the

emitter

and

base

leads

of

the

defective

power

transistor

with

a

diagonal

cutter.

This

prevents

mica-washer

damage

when

remov-

ing

the

defective

power

transistor.

When

replacing

the

power

transistor,

apply

a

coating

of

heat-transferring

grease

to

both

sides

of

the

insulation

mica

washer.

Any

excess

grease

squeezed

out

when

the

‘mounting.

screw

is

tightened

should

be

wiped

off.

with

a

clean

cloth.

This

prevents

it

from

2-11,

2-12.

accumulating

conductive

dust

particles

that

might

eventually

cause

a

short:

TONEARM

ASSEMBLY

REMOVAL

Remove

the

shell

head.

:

Remove

the

bottom

plate

as

described

in

Pro-

cedure

2-2.

Unsolder

the

leads

from.

the

terminal

beneath

the

turntable

base

(See

Fig.

2-12).

The

lead

wires

are

coded

as

follows:

White

...........0000.

L-CH

BUG

ic670

3

enon

ans

L-CH

(ground)

Reds

conn

eines

t

edie

R-CH

Green

...........00005

R-CH

(ground)

Remove

the

hexagon

nut

securing

the

tonearm

base

to

the

wooden

case.

This

frees

the

tonearm

assembly.

Fig.

2-12.

Lead

wire

connection

TONEARM

BASE

REMOVAL

Remove

the

tonearm

assembly

as

described

in

Procedure

2-11.

_

Remove

the

lock

lever

by

turning

it

counter-

clockwise.

Sony PS-2250 User manual

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