Sherwood R 925R R 925RDS Service Manual

Page 1

SERVICE MANUAL

R-925R / R-925RDS

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I CONTENTS I
SAFETY PRECAUTIONS ---------------- 2 MECHANICAL PARTS LIST ------------- 30
SPECIFICATIONS ...................... 3 EXPLODED VIEW ................... . 31
BLOCK DIAGRAM -------------------- 1o PRINTED CIRCUIT BOARDS ............ .33
WIRING DIAGRAM ------------------- 12 ELECTRICAL PARTS LIST -------------- -43
CIRCUIT DESCRIPTION - --------------- 14 Ic FUNCTIONAL BLOCK DIAGRAM ------ -55
ALIGNMENT PROCEDURES ------------- 25 SCHEMATIC DIAGRAMS (I), (I). (II), (N), M . .59
TROUBLESHOOTING ------------------ 23 SCHEMATIC DIAGRAMS M). M). (VI), (1X) - -69

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Page 2

SAFETY PRECAUTIONS

WARNING

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

1. Many electrical and mechanical parts in this
chassis 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 voltge, 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 danger of
electrical shock. Plug the AC line cord directly
into a 120 V 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 S2 10 watt resistor,
paralleled by a 0.15 uF 150 V AC capacitor,
between a known good earth ground (such as
a water pipe, or conduit) and the exposed
metalic is parts, one at a time. Measure the
AC voltage across the combination of a 1500
S2 resistor and a 0.15 uF capacitor. Reverse the
AC plug at the AC outlet and repeat AC
voltage measurements for each exposed
metalic part. Voltage measured must not
exceed 0.75V RMS. This corresponds to 0.2
mA AC. Any value exceeding this limit
constitutes a potential shock hazard and must
be corrected immediately.

Set

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

0 OJ AC Voltmeter

AC Outlet

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

15000.
10Walt v

l3; -.-

0.15 FF 150V AC

Place the probe on each exposed metalic part.