Panasonic TX-29FX20R, Service Manual, Page: 3 / 48

1. It is advisable to insert an isolation transformer in the AC supply before
servicing this hot chassis.
2. When servicing, observe the original lead dress, especially the lead
dress in the high voltage circuits. If a short circuit is found, replace all
parts which have been overheated or damaged by the short circuit.
3. After servicing, see to it that all the protective devices such as
insulation barriers, insulation papers, shields and isolation R-C
combinations, are properly installed.
4. When the receiver is not to be used for a long period of time, unplug
the power cord from the AC cord outlet.
5. Potential, as high as 32.0kV is present when this receiver is in
operation. Operation of the receiver without the rear cover involves the
danger of a shock hazard from the receiver power supply. Servicing
should not be attempted by anyone who is not thoroughly familiar with
the precautions necessary when working on high voltage equipment.
Always discharge the anode of the picture tube to the receiver chassis
before handling the tube. After servicing make the following leakage
current checks to prevent the customer from being exposed to shock
hazards.
1.2. Leakage Current Cold Check
1. Unplug the AC cord and connect a jumper between the two prongs on
the plug.
2. Turn on the receiver’s power switch. / Measure the resistance value,
with an ohmmeter, between the jumper AC plug and each exposed
metallic cabinet part on the receiver, such as screw heads, aerials,
connectors, control shafts, etc. When the exposed metallic part has a
return path to the chassis, the reading should be between 4 M and 20
M . When the exposed metal does not have a return path to the
chassis, the reading must be infinite.
1.3. Leakage Current Hot Check (Fig. 1)
1. Plug the AC cord directly into the AC outlet. Do not use an isolation
transformer for this check.
2. Check a 2 k non-inductive resistor and an AC/DC current meter, in
series with each exposed metallic part on the receiver in turn and an
earth such as a water pipe.
3