Sherwood AM 8500 Service Manual

Page 1

SERVICE MAN UAL '

AM-8500G/B

STEREO POWER AMPLIFIER

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I CONTENSTS
Safety Precations--~
Specifications ----------
Electrical Parts List .......................
Top & Bottom View of P.C Boards"-

-2 Point to Point Wiring Diagram (I - ll - III) ---------- 13
-3 Mechanical Parts List» .

>4 Exploded View of Cabinet & Chassis-
Schemafic Diagram ................................................... 19

NOTICE

- This manual is for authorized and qualified service personnel, so the basic service procedure and

commonsense of safety are not described in this manual.
- Sherwood always every endeavor to improve the products, therefore the specifications and data

provied are subject to change without notice.

S Sherwood

Page 2

SAFETY PRECAUTIONS

WARNING

Before. servicing this unit, familiarize yourself with the following precautions:

1. Many electrical and mechanical parts in this
player have special safety characteristics that
often pass unnoticed and the protection
afforded by them cannot necessarily be
obtained by using replacement components
rated for higher voltage, wattage, etc.
Replacement parts that have these special
safety characteristics are identified in this
manual and its supplements; electrical
components having such features are identified
by A in the schematic diagram and the parts
list.

Before replacing any of these components,
read the parts list in this manual carefully.
The use of substitute replacement parts that
do not have the same safety characteristics as
specified in the parts list may create shock,
fire, or other hazards.

2. Before returning the set to the customer,
always do an AC leakage current check on
the exposed metal parts of the cabinet, such

as terminals, screw heads, and metal overlays,
to be sure the set is safe to operate without
danger of electrical shock.

Plug the AC line cord directly into a 120V AC
outlet (120 V AC version only). (Do not use a
line isolation transformer during this check.)

Be sure your AC voltmeter has a sensitivity

of 5000 9 per volt or greater. Then connect a
1500 Q 10 watt resistor, paralleled by a 0.15 pF
150 V AC capacitor, between a known good

,earth ground (water pipe, .or conduit)

and the exposed metallic parts, one at a time.
Measure the AC voltage across the combination
of a 1500 Q resistor and a 0.15 pF capacitor.
Reverse the AC plug at the AC outlet and

repeat AC voltage measurements for each
exposed metallic part. Voltage measured must
not exceed 0.75V HMS. This corresponds to 0.2
mA AC. Any value exceeding this limit constitutes
a potential shock hazard and must be corrected
immediately.

At 5000 £2 per volt or greater sensitivity,
the reading should not exceed 0.75 V.

Set

Q 0 AC Voltmeter

AC Outlet

Place the probe on each exposed metallic part.

0.15 #F 150V AC

Good earth ground, such as
a water pipe or conduit.