Safety Precautions; General Guidelines; Touch-Current Check - Panasonic TH-103PF12E Service Manual

1 Safety Precautions

1.1.

General Guidelines

1. W hen conducting repairs and servicing, do not attem pt to modify the equipment, its parts or its materials.
2. W hen wiring units (with cables, flexible cables or lead w ires) are supplied as repair parts and only one wire or some of the
wires have been broken or disconnected, do not attem pt to repair or re-wire the units. Replace the entire wiring unit instead.
3. W hen conducting repairs and servicing, do not tw ist the Faston connectors but plug them straight in or unplug them straight
out.
4. W hen servicing, observe the original lead dress.If a short circuit is found, replace all parts which have been overheated or
dam aged by the short circuit.
5. After servicing, see to it that all the protective devices such as insulation barriers, insulation papers shields are properly
installed.
6. After servicing, make the following leakage current checks to prevent the custom er 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 transform er 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 m easure the potential across the m easuring network.
4. C heck 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
For a. c.: U = 35 V (peak) and U
1
For d. c.: U 1 = 1.0 V,
Note:
The limit value of U
mA d. c.
The limit value U
1
7. In case a m easurem ent is out of the limits specified, there is a possibility of a shock hazard,
repaired and rechecked before it is returned to the customer.
COLD
WATER PIPE
(EARTH GROUND)
JQ
APPLIANCES
EXPOSED
METAL PARTS
Resistance values in ohms (Q)
V: Voltmeter or oscilloscope
(r.m.s. or peak reading)
Input resistance:
Input capacitance: < 200 pF
Frequency range: 15 Hz to 1 MHz and d.c. respectively
NOTE - Appropriate measures should be taken to obtain the correct value in case of non-sinusoidal waveforms.
= 0.35 V (peak);
2
= 0.35 V (peak) for a. c. and U
2
= 35 V (peak) for a. c. correspond to the value 70 mA (peak) a.
Measuring network for TOUCH CURRENTS
Rs= _ L Cs=
1500Q
-I
Ro=
J
500Q
LjJ JUUii
---------------
> 1 MQ
and U
1
= 1.0 V for d. c. correspond to the values 0.7 mA (peak) a. c. and 2.0
1
0.22| F
j
10kQ
1
k 1 - ------
U1 — |— и.игігфГ = 0.022|
Ui =
r
'
Figure 1
3
, does not exceed the following values:
2
c. for frequencies greater than 100 kHz.
and the equipm ent should
^ V F J ( V ) | U
j
TH-103PF12E
be
(V)
2