Panasonic TH-42PWD8WK, Service Manual, Page: 10 / 398

2.1.2. 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 1.5k , 10 watts resistor, in parallel with a 0.15 F capacitors,
between each exposed metallic part on the set and a good earth ground such as
a water pipe, as shown in
Figure 1 .
3. Use an AC voltmeter, with 1000 ohms/volt or more sensitivity, to measure the
potential across the resistor.
4. Check each exposed metallic part, and measure the voltage at each point.
5. Reverse the AC plug in the AC outlet and repeat each of the above measurements.
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 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.
3. Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by static
electricity. Such components commonly are called Electrostatically Sensitive (ES)
Devices. Examples of typical ES devices are integrated circuits and some field-
effect transistors and semiconductor "chip" components. The following techniques
should be used to help reduce the incidence of component damage caused by
electro static discharge (ESD).
1. Immediately before handling any semiconductor component or semiconductor-
equipped assembly, drain off any ESD on your body by touching a known earth
ground. Alternatively, obtain and wear a commercially available discharging ESD
wrist strap, which should be removed for potential shock reasons prior to
applying power to the unit under test.
2. After removing an electrical assembly equipped with ES devices, place the
assembly on a conductive surface such as alminum foil, to prevent electrostatic
charge buildup or exposure of the assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.
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