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1 Precautions


1 Precautions
Follow these safety, servicing and ESD precautions to prevent damage and to protect against potential hazards such as electrical shock.

1-1 Safety Precautions


1-1-1 Warnings
1. For continued safety, do not attempt to modify the circuit
(READING SHOULD
board. NOT BE ABOVE 0.5mA)


2. Disconnect the AC power and DC Power Jack before
servicing. DEVICE
LEAKAGE
CURRENT

1-1-2 Servicing the LCD TV
UNDER TESTER
TEST
TEST ALL
EXPOSED METAL
1. When servicing the LCD_TV Disconnect the AC line SURFACES

cord from the AC outlet.
2-WIRE CORD
2. It is essential that service technicians have an accurate
voltage meter available at all times. Check the
calibration of this meter periodically. ALSO TEST WITH
PLUG REVERSED
(USING AC ADAPTER


1-1-3 Fire and Shock Hazard
PLUG AS REQUIRED) EARTH
GROUND



Before returning the LCD_TV to the user, perform the Figure 1-1. Leakage Current Test Circuit
following safety checks:
1. Inspect each lead dress to make certain that the leads are 4. With the unit completely reassembled, plug the AC line
not pinched or that hardware is not lodged between the cord directly into a 120V AC outlet. With the unit's AC
chassis and other metal parts in the LCD_TV. switch first in the ON position and then OFF, measure
2. Inspect all protective devices such as nonmetallic control the current between a known earth ground (metal water
knobs, insulating materials, cabinet backs, adjustment pipe, conduit, etc.) and all exposed metal parts,
and compartment covers or shields, isolation resistor- including: metal cabinets, screwheads and control shafts.
capacitor networks, mechanical insulators, etc. The current measured should not exceed 0.5 milliamp.
3. Leakage Current Hot Check (Figure 1-1): Reverse the power-plug prongs in the AC outlet and
WARNING: Do not use an isolation repeat the test.
transformer during
this test. 1-1-4 Product Safety Notices
Use a leakage current tester or a metering system that
Some electrical and mechanical parts have special safety-
complies with American National Standards Institute related characteristics which are often not evident from visual
(ANSI C101.1, Leakage Current for Appliances), and inspection. The protection they give may not be obtained by
Underwriters Laboratories (UL Publication UL1410, replacing them with components rated for higher voltage,
59.7). wattage, etc. Parts that have special safety characteristics are
identified by ! on schematics and parts lists. A substitute
replacement that does not have the same safety characteristics
as the recommended replacement part might create shock, fire
and / or other hazards. Product safety is under review
continuously and new instructions are issued whenever
appropriate.




LT15M23C 1-1
1 Precautions

1-2 Servicing Precautions
WARNING: An electrolytic capacitor installed with the wrong polarity might explode.
Caution: Before servicing units covered by this service manual, read and follow the Safety Precautions
section of this manual.
Note: If unforeseen circumstances create conflict between the following servicing precautions and any of the safety
precautions, always follow the safety precautions.


1-2-1 General Servicing
Precautions
1. Always unplug the unit's AC power cord from the AC 4. Check the insulation between the blades of the AC plug
power source and disconnect the DC Power Jack before and accessible conductive parts (examples: metal panels,
attempting to: input terminals and earphone jacks).
(a) remove or reinstall any component or assembly, (b) 5. Insulation Checking Procedure: Disconnect the power
disconnect PCB plugs or connectors, (c) connect a test cord from the AC source and turn the power switch ON.
component in parallel with an electrolytic capacitor. Connect an insulation resistance meter (500 V) to the
2. Some components are raised above the printed circuit blades of the AC plug.
board for safety. An insulation tube or tape is sometimes The insulation resistance between each blade of the AC
used. The internal wiring is sometimes clamped to plug and accessible conductive parts (see above) should
prevent contact with thermally hot components. Reinstall be greater than 1 megohm.
all such elements to their original position.
6. Always connect a test instrument's ground lead to the
3. After servicing, always check that the screws, instrument chassis ground before connecting the positive
components and wiring have been correctly reinstalled. lead; always remove the instrument's ground lead last.
Make sure that the area around the serviced part has not
been damaged.


1-3 Electrostatically Sensitive Devices (ESD) Precautions
Some semiconductor (solid state) devices can be easily damaged by static electricity. Such components are commonly called
Electrostatically Sensitive Devices (ESD). Examples of typical ESD are integrated circuits and some field-effect transistors. The
following techniques will reduce the incidence of component damage caused by static electricity.


1. Immediately before handling any semiconductor 6. Do not remove a replacement ESD from its protective
components or assemblies, drain the electrostatic charge package until you are ready to install it. Most
from your body by touching a known earth ground. replacement ESDs are packaged with leads that are
Alternatively, wear a discharging wrist-strap device. To electrically shorted together by conductive foam,
avoid a shock hazard, be sure to remove the wrist strap aluminum foil or other conductive materials.
before applying power to the monitor. 7. Immediately before removing the protective material
2. After removing an ESD-equipped assembly, place it on a from the leads of a replacement ESD, touch the
conductive surface such as aluminum foil to prevent protective material to the chassis or circuit assembly into
accumulation of an electrostatic charge. which the device will be installed.
3. Do not use freon-propelled chemicals. These can Caution: Be sure no power is applied to
generate electrical charges sufficient to damage ESDs. the chassis or circuit and
4. Use only a grounded-tip soldering iron to solder or observe all other safety
desolder ESDs. precautions.
5. Use only an anti-static solder removal device. Some
8. Minimize body motions when handling unpackaged
solder removal devices not classified as "anti-static" can
replacement ESDs. Motions such as brushing clothes
generate electrical charges sufficient to damage ESDs.
together, or lifting your foot from a carpeted floor can
generate enough static electricity to damage an ESD.




1-2 LT15M23C