Panasonic PV-D4742 Service Manual page 3

servicing of DVD VCR whose chassis is not isolated from the AC
power line. Use a transformer of adequate power rating as this
protects the technician from accidents resulting in personal injury
from electrical shocks. It will also protect DVD VCR from being
damaged by accidental shorting that may occur during servicing.
3. When servicing, observe the original lead dress. If a short circuit
is found, replace all parts which have been overheated or
damaged by the short circuit.
4. After servicing, see to it that all the protective devices such as
insulation barriers, insulation papers shields are properly
installed.
5. After servicing, make the following leakage current checks to
prevent the customer from being exposed to shock hazards.
LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs on the plug.
2. Measure the resistance value, with an ohmmeter, between the
jumpered AC plug and each exposed metallic cabinet part on the
equipment such as screwheads, connectors, control shafts, etc.
When the exposed metallic part has a return path to the chassis,
the reading should be between 1 M and 5.2 M . When the
exposed metal does not have a return path to the chassis, the
reading must be infinity.
LEAKAGE CURRENT HOT CHECK
(See figure 1.)
1. Plug the AC cord directly into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a 1.5 k , 10 W resistor, in parallel with a 0.15
capacitor, between each exposed metallic part on the set and a
good earth ground, as shown in figure 1.
3. Use an AC voltmeter, with 1 k /V or more sensitivity, to measure
the potential across the resistor.
4. Check each exposed metallic part, and measure the voltage at
each point.
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