Sherwood S-9500c Service Manual

SI{ER\

TOOD

Function

Switch.

Controls

stereo or

mono operation.

Selector Switch.
Chooses

phono,
tuner, or auxiliarr
inputs.

Preamp

Level. Controls

preamp

level

only.

Tape Monitor

Switch.

Normally

set

to left.

If

depressed

right

will

connect

in

tape

monitor

jacks

on

rear.

Hi Filter. Depress
right

for l2db,/octave

attenuation

of un-

desired

tones such.

as

record

"scratcht'.

INPUTS:8high

level

(2

tape

monitor),2

(RIAA)

Phono-

preamp.
TOTAL

POWER

OUTPUT: 4

ohms:

140

watts

i ldb;

115

watts IHF;90

watts

RMS.8

ohms:

100

watts t ldb;

80

watts

IHF;

70

watts RMS.

OUTPUTSz 4

to

lGohm

left and right

spkr.

main and

remote;

mono speaker,

stereo

headphone

and record

output.
INVERSE

FEEDBACK:

35

db.

DAMPING

FACTOR: 30:l

at 8

ohms.

FREQUENCY

RESPONSE:

2O Hz

to 20

KlIz r 1

db.

TONE

CONTROL

RESPONSE:

FIat setting,

20

Hz

to

20

KHz

tl db.

TONE

CONTROL RANGE: 15

KHz,

15

db,

boost or

cut

4O

Hz 20

db,

boost

or cut.

PREAMP.

EQUALIZER

CURVES:

AES,zRIAA phono.

SENSITIVITY:

Radio - 0.25v Phono

-

1.6

mv.

Tape

head

1.2mv.

(PH

and TP

inputs

are

adjustable

with

Preamp

I-evel

control).

Tone controls

for both

channels.

Adjustment

of the

Bass

or

Treble

control knob will

varl'

the tone of

both

channel s simultaneouslv.

5

1s&c

MODEI

S-95OOc

STEREO AMPLIFIER

SERVICE

MANUAL

Main control for Power on-off and
Loudness of

both channels.

Auto-

matieally

boosts bass

at low

levels

(if

switch

below

is

at

t'Loudness

Int').

.S-.Control

s left-to- ri

ght

stereo

balance.

Pilot

Light

Remote

Speaker Set On-off Switch.

ll'ill

disconnect

this

speaker set when

depressed right.

Main Speaker Set

On-off Switch.

lf ill

disconnect

this

speaker set urhen

depressed

right.

Loudne

ss Compensation

Switch.

Normally set

to left"

If

depressed

right, it removes

circuit

whlch

boosts bass

at

low

listening levels.

SPECTFICATIONS

*

MAX. INPUT

CAPABILITY: Phono:

160

mv.

for

less

than

1%

dist.

Radio:

2.8v.

for less

than

1%

dist.

MAX.

HUM

and NOISE:

Vol. control

min.,

90

db.

(weighted)

below rated

output. Tuner

input

(controls

max.), 80

db,

(weighted)

below

rated

output. Phono

input

(controls

flat),

60

db, below

rated

output.

INTERCHANNEL

CROSSTALK: Less

than

-45

db, at

1

KHz.

POWER

CONSUMPTION:

115-125 v, 60

Hz; 10

to l2O

watts fused.

TRANSISTOR

COMPLEMENT:

22

silicon

transistors,

2 silicon

rectifiers.

SIZE:

14 xl0-L/2

x 4

in.

high.

SHIPPING WEIGHT:

22 lbs.

*All

specifications

taken

with l20V

line.

5-9

500c

AMPLIFIER

SERVICING AND

ADJUSTMENT

NOTE:

To

simplify the following

descriptions only

the left channel

and

its related circuitries are

deseribed. The

right chan-

nel is identical except

for reference

symbol numbers.

(

see

schQmatic

diagrams

)

Preliminary

checks

of the

dc

voltages

present

at various

points

in

the

5-9500c

can indicate

whether a transistor

is

open, shorted, or

functioning.

FauLt

isolation

in

the

pre-

amplifier, tone

amplifier, and driver stages can

g

enerally

be

isolated

by

checking

the dc

voltages or by comparing

gain

measurements

of

1

KHz

as

indicated

on the

schematic

or

by

comparing

the operating channeL

with

the defective channel.

FUSE AND

SPEAKER

5Y5TEM

CHECKS:

Your amplifier

incorporates

two

speaker

fuses, one

for each

channel.

If

the fuse opens,

check

the

speaker

connections

for shorted

wires ox

a shorted

speaker.

(The

speaker

resist-

ance should

not

be less

than

4

ohms.)

If

the

speaker

and

connections

are

not

shorted

replace

the fuse

with

the

Proper

val-ue as marked

on

the rear

panel.

If

the

speaker

fuse

still

opens

your

amplifier needs

servicing.

lrr/hi1e

servicing

the

ampli.fier

it

will-

be valuabl-e

to

opergte

the

amplifier using

a variable

voltage

power line

(VnnIAC)

equipped

with a line

wattmeter

to identify

abnormal

power

consumption.

Increase

the

power line

voltage upward

while

observing

the wattmeter.

Power

consumption

shoul-d

not ex-

ceed t

O-20

watts ( loudness

control

at

volume

minimum

)

.=

the

voltage

is increased

to

the

rated 1ZBVAC.

If the

power

con-

sumption

begins

to

exceed

2A watts,

do

NOT

increase

the

Power

line

voltage

any

further

and

determine

whether

the

malfunc-

tion

is in

the

power

supply,

oI

amPlifier

section.

If the

power amplifier

is

suspected,

verify

center-point

voltage

on the

dc side

of

the

output

el-ectrolyticr_C29O

for

app=o*imately

one-hal-f

of

the

B+

supply

voltage.

If the

cen-

ter-point

voltage

reads

extremely

]ot

r

susPect

a defective

output

transistor

on

the l-ow

side

(schematic

shows

transis-

tor

as

bottom

device

in

each channel

)

.

If

center-point

volt-

age

reads

extremely

high

r

suspect

a

defective

high

side

out-

put

transistor.

If the

output

transistors

are

not

at

fau1t,

then

verify

that

the

output

coupling

electrolytic

capacitor

is

not

shortedt

other

capacitors

are not

shorted,

circuit

board

contains

no

sol-der

or

etching

shorts,

open

resistors

r

poor

solder

con-

nections

or

broken

pads.

The following

perfoxmance

indicates

a

properly

operating

am-

plif

ier

with

an

I ohm

.resistive load.

v

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