ViewSonic VPW425 - 42" Plasma TV, Service Manual

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IMPORTANT SAFETY PRECAUTIONS VER1.0
1-02
4. Hot Chassis Warning
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a. Some Monitor chassis are electrically connected directly to one conductor of the AC
power cord and may be safely serviced without an isolation transformer only if the AC power plug is inserted so
that the chassis is connected to the ground side of the AC power source. To confirm that the AC power plug is
inserted correctly, with an AC voltmeter measure between the chassis and a known earth ground. If a voltage
reading in excess of 1.0V is obtained, remove and reinsert the AC power plug in opposite polarity and again
measure the voltage potential between the chassis and a known earth ground.
b. Some Monitor chassis normally
have 85V AC (RMS.), between chassis and earth ground regardless of the AC plug polarity. These chassis can
be safely serviced only with an isolation transformer inserted in the power line between the receiver and the AC
power source, for both personnel and test equipment protection.
c. Some Projection Monitor chassis have a
secondary ground systems in addition to the main chassis ground. This secondary ground system is not isolated
from the AC power line. The two ground system are electrically separated by insulating material that must not be
defeated or altered.
5. Observe original lead dress. Take extra care to assure correct lead dress in the following areas: a. near sharp
edges, b. near thermally hot parts
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be sure that leads and components do not touch thermally hot parts, c. the
AC supply, d. high voltage, e. antenna wiring. Always inspect in all areas for pinched, out-of-place, or frayed
wiring. Do not change spacing between components, and between components and the printed-circuit board.
Check AC power cord for damage.
6. Components, parts, and/or wiring that appear to have overheated or are otherwise damaged should be replaced
with components, parts, or wireing that meet original specifications. Additionally, determine the cause of
overheating and/or damage and, if necessary, take corrective action to remove any potential safety hazard.
7. PRODUCT SAFETY NOTICE
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Many Monitor electrical and mechanical parts have special safety-related
characteristics some of which are often not evident from visual inspection, nor can the protection they give
necessarily be obtained by replacing them with components rated for higher voltage, wattage, etc. Parts that have
special safety characteristics are identified in this service data by shading with a mark on schematics and by
shading or a
＊
mark in the parts list. Use of a substitute replacement part that does not have the same safety
characteristics as the recommended replacement part in this service data parts list might create shock, fire,
and/or other hazards.