Panasonic TH-42PA25U-P Service Manual page 23

exposed metal does not have a return path to the chassis, the
reading must be
2.1.2. Leakage Current Hot Check (See
1. Plug the AC cord directly into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a 1.5k
capacitors, between each exposed metallic part on the set and a
good earth ground such as a water pipe, as shown in
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 outsideof 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 transistorsand 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
.
Figure 1
Figure 1
, 10 watts resistor, in parallel with a 0.15
4
.)
F
Figure 1 .