Safety Precautions; General Guidelines - Panasonic TX-22LT2 Service Manual

1. Safety Precautions

1.1. 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.
1.2. Touch-Current Check
1. Plug the AC cord directly into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a measuring network for touch currents 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 Leakage Current Tester (Simpson 228 or equivalent) to
measure the potential across the measuring network.
4. Check each exposed metallic part, and measure the voltage at
each point.
5. Reserve the AC plug in the AC outlet and repeat each of the above
measure.
6. The potential at any point (TOUGH CURRENT) expressed as
voltage U and U
1
For a. c.: U
1
For d. c.: U
1
Note:
The limit value of U
2
mA (peak) a. c. and 2.0 mA d. c.
The limit value U = 35 V (peak) for a. c. correspond to the value 70 mA (peak) a. c. for
1
frequencies greater than 100 kHz.
7. In case a measurement is out of the limits specified, there is a
possibility of a shock hazard, and the equipment should be
, does not exceed the following values:
2
= 35 V (peak) and U
= 1.0 V,
= 0.35 V (peak) for a. c. and U
= 0.35 V (peak);
2
= 1.0 V for d. c. correspond to the values 0.7
1
3