Sharp LC-20A2U Service Manual Download Page 2

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LC-20A2U

C A U T I O N : F O R C O N T I N U E D
PROTECTION AGAINST A RISK OF
FIRE REPLACE ONLY WITH SAME
TYPE FUSE. F3701 (2.5A, 125V),
F3702 (3.15A, 125V), F7751 (6.0A,
125V) FUSE.

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SAFETY NOTICE

Many electrical and mechanical parts in LCD television
have special safety-related characteristics.
These characteristics are often not evident from visual
inspection, nor can protection afforded by them be
necessarily increased by using replacement components
rated for higher voltage, wattage and etc.
Replacement parts which have these special safety
characteristics are identified in this manual; electrical
components having such features are identified by “

”

IMPORTANT SERVICE SAFETY PRECAUTION

Service work should be perfomed only by qualified service technicians who are thoroughly
familiar with all safety checks and the servicing guidelines which follow:

and shaded areas in the

Replacement Parts Lists and

Schematic Diagrams.
For continued protection, replacement parts must be
identical to those used in the original circuit.
The use of a substitute replacement parts which do not
have the same safety characteristics as the factory
recommended replacement parts shown in this service
manual, may create shock, fire or other hazards.

WARNING

1. For continued safety, no modification of any circuit

should be attempted.

2. Disconnect AC power before servicing.

BEFORE RETURNING THE RECEIVER
(Fire & Shock Hazard)

Before returning the receiver to the user, perform
the following safety checks:

1. Inspect all lead dress to make certain that leads are

not pinched, and check that hardware is not lodged
between the chassis and other metal parts in the
receiver.

2. Inspect all protective devices such as non-metallic

control knobs, insulation materials, cabinet backs,
adjustment and compartment covers or shields,
isolation resistor-capacitor networks, mechanical
insulators and etc.

3. To be sure that no shock hazard exists, check for

leakage current in the following manner.

•

Plug the AC cord directly into a 110~240 volt AC outlet,
and connect the DC power cable into the receiver's
DC jack. (Do not use an isolation transformer for this
test).

•

Using two clip leads, connect a 1.5k ohm, 10 watt
resistor paralleled by a 0.15µF capacitor in series with
all exposed metal cabinet parts and a known earth
ground, such as electrical conduit or electrical ground
connected to an earth ground.

•

Use an AC voltmeter having with 5000 ohm per volt, or
higher, sensitivity or measure the AC voltage drop
across the resisor.

•

Connect the resistor connection to all exposed metal
parts having a return to the chassis (antenna, metal
cabinet, screw heads, knobs and control shafts,
escutcheon and etc.) and measure the AC voltage drop
across the resistor.
All checks must be repeated with the AC cord plug
connection reversed. (If necessary, a nonpolarized
adaptor plug must be used only for the purpose of
completing these checks.)
Any reading of 35V peak (this corresponds to 0.7
milliamp. peak AC.) or more is excessive and indicates
a potential shock hazard which must be corrected
before returning the monitor to the owner.

TO EXPOSED
METAL PARTS

CONNECT TO
KNOWN EARTH
GROUND

DVM

AC SCALE

50k ohm

10W

0.15

TEST PROBE

A V