Sherwood TD 2220 C Service Manual

Page 1

TD 2220C

AM/F M
STEREO DIGITAL TUNER

To~azaoc $55!.

I CONTENTS

Safety Precaution ........................... 3
Specifications ............................... 4
Circuit Description ........................... 6
Block Diagram ............................... 7
Alignment Procedures ........................ 9
RC. Boards (Top & Bottom Views) .............. 13

A.

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Wiring Diagram ........................ . V .21
Exploded View .............................. 23
Electrical Parts List .......................... 25
Mechanical Parts List ......................... 28
Schematic Diagram ........... Separate Sheet (ll

Separate Sheet (Ill

/32

/32

Page 2

Safety Precaution

WARNING,

Service should not be attempted by anyone unfamiliar with the necessary precautions on this player. The following

precautions are necessary during servicing.

1. Many electrical and mechanical parts in this player
have special characteristics often pass unnoticed
and the protection afforded by them cannot neces-
sarily be obtained by using replacement compo-
nents rated for higher voltage, wattage, etc.
Replacement parts that have these special safety
characteristic are identified in this manual and its
supplements: electrical components having such
features are identified by a 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
perform an AC leakage current check on the
exposed metallic parts of the cabinet, such as

terminals, screwheads, metal overlays, etc. 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 (120V Version only). (Do not use
a line isolation transformer during this check.) Use
an AC voltmeter having 5000 9 per volt or more sen-
sitivity in the following manner: g

Connect a 1500 TI 10 watt resistor paralleled by a
0.15;).F, 150V AC capacitor, between a known good
earth ground (water pipe, conduct, etc) and the
exposed metallic parts, one at a time. Measure the
AC voltage across the combination of 1500 (2 resis-
tor and 0.15pF capacitor. Reverse the AC plug at
the AC outlet and repeat AC voltage measure-
ments for each exposed metallic part. Voltage
measured must not exceed 0.3volts RMS. This
corresponds to 0.2mA AC. Any value exceeding
this limit constitutes a potential shock hazard and
must be corrected immediately.

Stereo
Tuner

AC VOLT METER

(5000 (I per volt or more sensitivity)
Reading should not exceed 0.8V

AC Outlet

Place this probe on each exposed metallic pans.

0 0
150°" S::.i.ii§£§2°:."§.i¥°2.§s
10 Watt ' '
J.
H *-J '_"
0.15,.F 150v Ac