Sherwood S-9500B User manual

MODEL

S.95OOb

ALL-SILICON

SOLID.STATE

STEREO

AMPLIFIER

SERVICE

MANUAL

Tone

controls

for

both

channels.

Adjustment

of the Bass

or

Treble

control

knob

will vary the

tone

of

both channels

simultaneouslY.

Serial

No's. T704104

TO T704604

Main

control for Power

on-off

and

Loudness

of both channel

s. Auto-

matically

boosts

bass

at low

levels

(if

switch below

at

"Loudness

In").

Controls

left-to-right

stereo balance.

Stereo

head-

phone

jack.

Pilot Light

Remote

Speaker

Set On-off

Switch.

Will

disconnect

this

speaker

set

when

depressed right.

Main

Speaker Set On-off

Switch'

Will

disconnect this

speaker

set

when

depressed right.

Selector

Switch.

Chooses

phono,

tuner,

or auxrliary

i

nput

s.

Preamp

Level. Controls

preamp

level

only.

Tape

Monitor

Switch'

Normally

set to left.

will

connect

in tape

monitor

jacks

on rear

if depressed right,

Hi

Filter. Depress

right for

l2dbloctave

attenuat

ion of un-

desired

tones such

as

tecond

"scratch',,

Loudness

Compensetion Switch.

Normally

set to

left,

will remove

circuit

which boosts

bass

at low

settings of

Loudness

control if

depressed right.

MODEL

S.95OOb STEREO

AMPLIFIER SPECIFICATIONS

{<

rq

o

Io

$'

t

V)

INPUTS:6

high level

(2

tape monitor),

2

(RIAA)

Phono-

preamp.

POWER

OUTPUT:

music

power: (4O)

80 watts,

(8O)

50

watts;

continuous

power

each channel:

(4O)

30

watts,

(8Ct)

20

watts

at

l.D%o distortion.

OUTPUTS:

4 to 16-ohm

left

and right

spkr.

main

and

remote;

mono speaker, stereo headphone

and

record

output.

INVERSE

FEEDBACK: 35db.

DAMPING

FACTOR: 30:1

at

8

ohrrs"

FREQUENCYRESPONSE:

(20w)

20Hz

to

20KHz

+1

db.

TONE

CONTROL RESPONSE:

Flat

setting,

20Hz

to

z0K.llz

11

db.

TONE

CONTROL RANGE: 15KHz,

15db.

boost

or

cut

40Hz

20db.

boost

or

cut.

PREAMP.

EQUALIZER CURVES: AES/RIAA

phono.

SENSITIVITY:

Radio

-

0.20v

Phono

-

1.6mv.

(PH

Input

is

adjustable

with

Preamp

Level

control).

MAX" INPUT

CAPABILITY:

Phono:

160mv.

for

less

than 170

dist.

Radio:

2.8v.

for less

than LVo

dist"

MAX. HUM

and

NOISE:

Vol.

control

min.

,

90db

(weighted)

betow

rated output.

Tuner

input

(controls

max"),

80db.

(weighted)

below

rated

output.

Phono

input

(controls

flat),

60db.

below

rated

output.

INTERCHANNEL

CROSSTALK:

Less

than

-45db"

at

1KHz"

POWER

CONSUMPTION:

115-125v,

6QHz;10

to L20

watts

fused.

TRANSISTOR

COMPLEMENT:

22 silicon

transistors,

2 silicon

rectifiers.

SIZE:

14

x

L0-l/2

x

4

in"

high.

SHIPPING

WEIGHT:

22 lbs"

*All

specifications

taken with

120V line.

SWITCHED

AC

RECEPTACLE

LEFT

CH.

BIAS

ADJ.

I

xl

tr

x2

QIOS

L

40E6rF

o|osI

s437F

LEFT CH.

rrc-rEHIiHE

I

arzoert-t

I

Cl-

G

6

ao

202

2tr3900N

G

=

I

lrJ

G,

o.

ryll€"3i"'*

F

E

r'

o

4

Qtol

2N3900

POWER

TRANSFORMER

TI

8922T2-5C

i

-

s22oo4

{31o.1"r.

o,fi

-----'l

r------'t

lll

mll.!

11

r

r ! !i[--l---.j

QilO

s353

LEFT

FI.|SE

F2

-2AnP

F3.zAMP

FUSE

STEREO.MONO

swrTcH

tHl

FILTER

cAUTTON

!

USE

STANDARo

lll2

AMP FUSE.

DO

NOT USE

StO-BLq(2AMP

FOR

SPKR.

FUSES)

Ft

-

| l/zalP

SELECTOR

swtTcH

PHONO

TUNER

AUX.

APE MONITOR

PWR OFF

SPEAI(ERS

ttnlloJti

All

power

fuses

on

export

models

using

230V

for

power,

will

requite

50Vo

less current

rating than the comparable

domestic

unit. Voltage

rating

will

remain

the

same.

COIITIIECT TURNTABLE

OR

CHANGER

GROUNO

LEAD

HERE.

ONNECT

OI{LY

TO

-dbru.

oR,crr

uErr

Rtc"r uErro

{o

o

to

Qo

o

or

Ho

o

oE

OO

RIGHT SPKR.

+@@

MAIN

REK)TE

+

LEFT

SPKR

@-^,P

REI'OTE

@@

ll5-125V

6OHr

SPKR

FUSES

Page 3

STRYICING

YOTTAGT

CHECKS

Preliminary checks of

the

D.

C. voltages

present

at

various

points

in

the

S-9500b

can

prove

useful

in 1o-

cating defective

components.

They

are

inconclusive,

however, in

determining

if transistors

are operating

properly

in

all aspects.

They

can

only indicate

wheth

-er

the transistor is open,

shorted

or functioning,

4!

how well

the transistor

is

functioning.

IN GENERAL:

Correct

voltages

indicate a functioning transistor.

The

same voltage

at

the collector

and

emitter

indicates a shorted

transistor.

Full supply

voltageon

the

collector

and

novoltage

on

the

emitter

indieates

an open transistor.

OUTPUT

TRANSISIOR

BIAS

Of alt

the

specifications

which

require

checking to

as-

certain correet

performance

of the

S-9500b,

proper

output

transistor

operation is the

most

important

and

critical.

Adjustment

of

the

output

transistor

bias

is

necessary

if

output

transistors

are

replaced*,

or

the

amplifier exhibits

one or

more

of

the

following symp-

toms:

1. Overheating

of the output transistors

under

nor-

mal

operating conditions.

2.

Excessive

low level Intermodulation

Distortion-

more

than 0,5Vo

at

2.0

volts

across 8

ohms

(0.8

watts, IM

power).

Adjustment

of output

transistor

bias

should then

pro-

ceed as follows:

Connect

D. C.

voltmeter of at

least 370

known

ac-

curacy

to transistor

side of appropriatechannel's

output terminals.

Turn arnp. on

and

adjust

output

balance

pot

for

that channel

so

that

approx.

L/28+ voltage is

on

the

output capacitor"

Connect

an

Intermodulation

Distortion

analyzer

to

to the

amplifier TP.

MON.

(aux.

)

input

,

turn

volumn

control

to

ma:<imum

and adjust

the

ana-

lyzer

output

for

an amplifier output

of.

2.0V

across

I

ohms.

(Because

the

output

stages have been

set into

heavy

class

"8"

operation

by

the

"pre-

setting"

in Step 2,

a elass

"8"

notch in the

dis-

tortion

waveform

will be obvious.

)

NOTE:

When

adjusting

bias

for class

"A8",

adjust

until class

"8"

notch

is

almost eliminated.

Class

"A"

begins

beyond

this

point,

and

notch

shifts

to right.

Inerease

analyzer

output

until

clipping

can be

observed.

Fine adjust

output

balance

pot

so

that

clipping is

symmetrical"

3.

a.

6.

IMPORTANT: Misadjustment

of

the

bias

pot

car.

cause heavyclass

"A"

operationof

the output

transis-

tors,

causing

them

to overheat.

The

followingperformance

indicates

a

properly

oper-

ating

output

stage

with

8

ohm

load.

-Less

than

0.57oIM

distortion at

2.0V"

-Typically

0.

goIM

distortion at

t0

Volts.

-18

watts

of

power

per

channel

at clipping"

1"

Turn amplifier

off.

2. Set

output

balance

pots

(left

and right channels)

to mechanical

center

and bias

pots

fully counter-

clockwise.

{<

ft is extremely

important

that the

miea

insulating wishers

used to separate

the

output transistors fro

be

unbroken

and instilled

properly

with silicon

grease

liberally

applied

to

all surfaces

in contar

Make certain

the

emitter

and

base

pins

of

the

output

transistors do

not

contact

any

part

of

the he

NOTE:

Refer

to

speaker load

connections

on schematic,

being

careful to

observe

ground-connections.

Page

4

cL-Ass

"B'

CLASS H

SE RVICIN G

1.

AMPLIFIER/PREAMP

STAGE ISOLATION:

Eval-

uat

thus,

B+

supply

should be suspected for

malfunction.

If one

channel

only, evaluate with

test

signal

whether signal

feeds

properly

through

phono preamp,

auxiliary

high-

level

input, or into volume control

at high side

(this

isolates

power

amplifier section from tone

amplifier

section).

2.

FAULT

ISOLATED

TO POWER AMPLIFIER:

With

DC

upply

voltages,

colleetor,

emitter, ild base

voltages

of

transistors

on the

driver-circuit boards and

of

output

transistors

in the faulty

power

amplifier

channel.

The

voltages

should be verified

against

those

shown

on

the

schematic

for

120V

power

line and also

against

those

in

the

2nd

channel

(assumed

to

be operating

comectly).

Note

that

output electrolytic

coupling capacitor

DC

voltage

(on

transistor feed side) should

read

approx.

L/2

of.

g+

supply

voltage.

Note in

most cases

of a

defective

driver or output

transistor,

the fuse

will

open

and

prevent

the taking of a usable

center-point

voltage

reading. Therefore, it is valuable

to

operate

the

amplifier

with

a

variable

voltage

power

line

(Variac)

equipped

with

a

line

wattmeter

(or

ammeter)

to

identify abnormal

power

consumption.

With

the

Variac,

reduce thepower

linevoltage

to

zero,

replace fuse,

and

slowly increase

power

line

voltage

upward

while

observing

wattmeter.

(The power

con-

sumption

should

not

exceed 10-15 watts as

the

voltage

is increased

up to rated

120 volts. If

power

consump-

tion

reading

begins to

exceed

15 watts, starting

from

zero

voltage,

do

not

increase

power

line voltage

fur-

ther.

)

Now verify center-point voltage for

half-voltage

reading.

If center-point

voltage

reads extremely

low,

suspect

defective

output

or driver transistors

on

low side

(schematic

shows

these

as

bottom

devices

in each

channel). lf center-point

voltage

reads extremely

hrgh, suspect

defective

high-side

output

or

driver

transistors.

Remove

both

driver

transistors

from their

sockets.

If

power

consumption

drops

considerabll',

then faulty

driver

transistors

should

be suspected. If

power

con-

sumption

remains

unusually high, then

faulty

output

transistors

should

be suspected.

If

not,

suspect

pre-

driver or bias-regulator

transistor

or assoeiated

components.

H afl above

seems

not to

be at fault,

then verify

that

output coupling

electrolytic

capacitor

is not shorted,

other

capacitors

are not

shorted,

circuit

board

contains

no solder

or etching shorts, open

resistors,

or

poor

solder

connections.

(Note:

a

small

error

voltage

at

pre-driver

bas e and/or emitter

will disruptgrossly

the operation

of

the

driver and

output

transistors.

)

If

center

-point

voltage

reads

approximately

l/2

voltage

in

accordance

with above

check,

apply

audio

signal

to

channel

being

investigated

and

measure distortion

as

per

service

instruction

manual.

Distortion

which

exceeds

amplifier

ratings might

be due

to one

of

the

following:

1.

Output

transistors

do

not

have

matched beta"

2.

Output bias

requires readjustment.

3. Driver

transistor

has

low

beta.

3.

FAULT

ISOLATED

TO TONE

CONTROL

A

collec-

6r,

ernlii6,

ild base

on

tone

circuit

board

and

compare

with

schematic

and with

good

channel.

Feed

1KC

audio signal

to

input

connection

to

tone

circuit

board.

Compare outpuf voltage

to

input

voltage

which

should

have

a

gain

ratio

of about

6db

(2X).

Isolate

inoperate

stage

by checking signal

at input of

treble control.

Compare this

voltage

to

input voltage

which should rezult in

lst

stage

gain

-

approximately

6db

(2x)"

Evaluate

distortion

in conjunction

with

power

amplifier.

Verify

bass

and

treble

frequency

response

with bass

and

treble

boost

and

cut characteristic

curves

shown

in

service

manual.on

Page

8.

4.

FAULT

ISOLATED

TO

PREAMP: Check

DC

voltages

at

t

d

base

on

preamp.

circuit board

and compaJ'e

with

schematic

and with

good

channel.

Feed

1KC

audib

signal

to

phono

input

jack.

Compare

output voltage

at

input

of

tone circuit

board

to

input voltage.

The resulting

calculated

gain

ratio

should

be

approximately

40db

(100X)

with

preamp.

gain

(phono

level)

control

at

maximum

gain.

Isolate

the

inoperative stage

by checking

signal

voltage at

collectorof

1st stage.

Verify

frequency

responsewith

phono

and

tape

equalization

curves

shown

in service

manual

on

Page

B.

5.

FAULT ISOLATED

TOPOWER SUPPLY:

CheckDC

vol

er

capaci-

tor

sections

and compare

with

those shown

oh schema-

tic. If

a

voltage measures

low,

remove

leads

to

amplifier

or receiver

loads

to isolate

possibility

of

Ieaky or shorted electrolytic

capacitor

section.

Page

5

PARTS

LIST

TRANSISTORS

(All

are

silicon)

PART

NO"

PRICE

Audio,

Low

signal-no

dot

(Hi

beta),

(Q101,

105,

20L,

205)

Audio,

Low

signal-Green

dot

(Low

Noise),

(Q102,

202)

Audio, Low signal

-no

dot

(Hi

beta),

(Q103,

104,

107,2A3,204,207)

Pre-Driver,

NPN

(Q106,

206)

Driver,

NPN,

(Q108,

208)

Driver,

PNP,

(Q109,

209)

Output,

NPN,

(Q110,

111,

210,

211)

2N3900

s22004

sPs41

2N3900N

s22004N

SPS41N

s22004

SPS41

16E1330

40361F

S43?F

s353

$1.04

0.63

0.81

L"t4

0.73

0.91

0.63

0.81

L.26

2.92

3.36

2.84

you

will

note

that all

transistors used in

the

S-?800

are

color-coded

with a

dot or

mark of some

co

located

on

the

top of

their case.

(Some

transistors

have

no

mark, but

this also is

identification"

)

replacement

transistors,

it

is imperative

that

you

indicate

not only

its

part

no"

,

but

the color

dot

o

noOy:

red,

yellow, none,

(1,

-2-, -

or

-3).

This

is

particularly

important when

replacing

out;

DESCRIPTION

PART

NO.

PRICE

1500pf,

45V

(C190,

290)

2500pf.,

80V

(342)

0.5pf, 50V

(C170,

L12,

210,

272')

Sttf

,

5V

(C136,

236)

5pf,

20V,

(C143,

2431

Ittf,

25V,

(C111

,

L32,

ztL,

232)

201tf, 5V

(C160,

260)

100pf,

3V

(C100,

t02,

200, 203)

Ittf, 15V

(C150,

250)

201tf., 50V

(C171,

271')

500pf,

50V

(C343,

344)

500prf,

25V

(C345)

Insulator,

Thermo-Film,

(T03)

tr\rse,

2

AMP,

3AG

(F2,

3)

Fr\rse, t-t/z

AMP,

3AG

(F1)

Knobs,

Medium

(Vindicator)

Knob, Small

Plastic,

Unmar'lsed,

Phono

Level

Light Bulb,

Pilot

#53

Control, 50K

ohm hd,

w/AC Sw.

(R150A,

B,

s4)

Control,

Bass, lM

ohm D'ual

(R134A,

B)

Control,

Treble,

250K

ohm Duat

(R140A,

B)

Control,

Balance,

100K

ohm

(R153)

Control,

Phono Level,

1.5K ohm

(R120A,

B)

Pot.

,

P. C.

,

500 ohm Bias

(R184,

284)

Pot.

,

P.

C.

,

250K ohm

Output Bal"

(R1?0,

270)

Rectifier,

Silicon

(X1,

2)

Socket,

Driver

Transistor

Socket,

Output

Transistor

Stereo Headphone

Jack

Fuse Post

Switch,

Selector,

3

Pos.

(S1A,

B)

Switch, Function, 5

Pos.

(S2)

Switch,

Rocker,

(Non-shorting),

DPDT

(S3AB)

Switch,

Rocker,

(Shctrting)

DPDT,

(SrtA;

5A,

B;

6^A,

B;7A, B;8A,

B)

Transformer,

Power, 60

Hz Domestic

(T1)

Transformer, Power,

50-60

Hz

Export

(T1)

At20T7

-2

A.120T11

8120X3

8120X4

8120X6

8120X7

8120X12

B120x24

8120X?5

8120814

8120830

8120831

A021Rl-0

312002.

31201.5

B,467X4

4604B5

630853

A6?1T1-6

A670T5

-3

A6?0T6-3

A6?0T7-3

4670T11-1

^A675T1-0A

A675T9-0A

A692T3

-0

A?90T4M-1

A790T7-0

A795L1-0

A?96X2

-1.A

A860T6-0

A8 60K5

-3

A8 64T22

-5

A864T23-5

8922T2-5C

28922T2-5CX

$2.70

3.80

0.59

0.63

0.59

0.63

0.53

0.59

0.36

1.48

0.99

0.05

0.15

2.43

0.15

4.28

2.84

1.04

1.89

0.90

0.45

L.26

0.23

0.18

1.08

0.95

3.47

2.25

0.86

1?.10

32.85

Page 6

FREQUENCY

lN

Hz

20 50

tOO 2OO

5OO

lx

2x 5x

lox

2Ox 5Ox

l00x

0

v,

J

ul

-5

g

.:

-r0

E

o

_t5

POWER

AIiPLIFIER

RESPONSE

tl

AUDIO

RANGE

rl

fow

at

-N

\

,llF

rorc

50u^aa

w^va

\

20w

frlcucfacY

lx HEtlz

tO

lO0 2OO 5OO

rr

tor{c coNrrot

araD

FrtTCr

cH^tactEitsrtcs

OUTPUT

I'T

WAVTS

(?EAT}

lll1610a0

z

o

Ft

c

o

c

o

ul

2

o

a

3

II

E

laa

OUT'UT

IN

trolo

watTt

(ir.rs

I

Cont

inuous

Power Output

vs.

Distortion

4&8

Ohms

(recr cxrxx:r)

8

)xt{

\

4l

txr{

-t

I

CLEANING

ESCUTCHEON

FACE

PLATE:

The

beige

es-

cutcheon

on

your

Sherwood

equipment

has

been

finished

with

a durable

baked

enalnel. To clean, wipe

with

a

chamois

or

cloth

dampened

with a water

solution

of

liquid

detergent.

Do

not use

an

abrasive

scouring

powder.

EXPORT

MODELS

ARE

AVAII"ABLE

WITH

SPECIAL

TRANSFORMERS

FOR 50-60

CYCLE

POWEI

24OV

AND

ARE

I\IIARKED THUS ON THE

REAR

OF

THE

CHASSIS.

THESE SPECIAL

MODELS

HAV

TREATED

WITH

FUNGICIDE

AND ANTI-CORONA

IVIATERIALS

FOR

ADDED PROTECTION

IN

HU

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Sherwood S-9500B User manual

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