Safety Precautions; General Guidelines - Panasonic TC-32LX700 Service Manual

2 Safety Precautions

2.1.

General Guidelines

1. 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.
2. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly
installed.
3. After servicing, make the following leakage current checks to prevent the customer from being exposed to shock hazards.
2.1.1. 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
1Mohm and 5.2Mohm.
When the exposed metal does not have a return path to
the chassis, the reading must be
Figure 1
2.1.2.
1. Plug the AC cord directly into the AC outlet. Do not use an
2. Connect a 1.5kohm, 10 watts resistor, in parallel with a
3. Use an AC voltmeter, with 1000 ohms/volt or more
.
4. Check each exposed metallic part, and measure the
5. Reverse the AC plug in the AC outlet and repeat each of the
6. The potential at any point should not exceed 0.75 volts
5
Leakage Current Hot Check (See
Figure 1.)
isolation transformer for this check.
0.15µF capacitors, between each exposed metallic part on
the set and a good earth ground such as a water pipe, as
shown in Figure 1.
sensitivity, to measure the potential across the resistor.
voltage at each point.
above measurements.
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
measurement is outside of the limits specified, there is a
possibility of a shock hazard, and the equipment should be
repaired and rechecked before it is returned to the
customer.
TC-32LX700