Panasonic TH-50PF30U, Service Manual

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TH-50PF30U
1 Safety Precautions
1.1. General Guidelines
1. W hen conducting repairs and servicing, do not attem pt to modify the equipment, its parts or its materials.
2. W hen wiring units (with cables, flexible cables or lead w ires) are supplied as repair parts and only one wire or som e of the
w ires have been broken or disconnected, do not attem pt to repair or re-wire the units. Replace the entire wiring unit instead.
3. W hen conducting repairs and servicing, do not tw ist the Fasten connectors but plug them straight in or unplug them straight
out.
4. W hen servicing, observe the original lead dress. If a short circuit is found, replace all parts which have been overheated or
dam aged by the short circuit.
5. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly
installed.
6. After servicing, make the following leakage current checks to prevent the custom er from being exposed to shock hazards.
1.1.1. Leakage Current Cold Check 1.1.2. Leakage Current Hot Check (See
Figure 1 .)
1. Plug the AC cord directly into the A C outlet. D o not use
an isolation transform er for this check.
2. Connect a 1.5kohm, 10 watts resistor, in parallel with a
0.15|iF capacitors, between each exposed metallic part
on the set and a good earth ground such as a w ater pipe,
as shown in Figure 1 .
3. Use an AC voltmeter, with 1000 ohm s/volt or more sensi­
tivity, to m easure the potential across the resistor.
4. C heck each exposed m etallic part, and m easure the volt­
age at each point.
5. Reverse the AC plug in the AC outlet and repeat each of
the above m easurements.
6. The potential at any point should not exceed 0.75 volts
RMS. A leakage current tester (Simpson Model 229 or
equivalent) may be used to make the hot checks, leakage
current must not exceed 1/2 milliamp. In case a mea­
surem ent is outside of the limits specified, there is a pos­
sibility of a shock hazard, and the equipm ent should be
repaired and rechecked before it is returned to the cus­
tomer.
1. Unplug the AC cord and connect a ju m pe r between the
two prongs on the plug.
2. Measure the resistance value, with an ohmmeter,
between the jum pered AC plug and each exposed m etal­
lic cabinet part on the equipm ent such as screwheads,
connectors, control shafts, etc. W hen the exposed m etal­
lic part has a return path to the chassis, the reading
should be between 1Mohm and 5.2Mohm.
W hen the exposed metal does not have a return path to
the chassis, the reading must beO O .
Figure 1
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