Panasonic TC-42PD1F, Service Manual

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Safety Precautions
General Guide Lines
1. It is advisable to insert an isolation transformer in
the AC supply before servicing a hot chassis.
2. When servicing, observe the original lead dress,
especially the lead dress in the high voltage cir-
cuits.
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 be used for a long period
of time, unplug the power cord from the AC outlet.
5. Operation of the Wide Plasma Display without the
rear cover involves the danger of a shock hazard
from the 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 projection tube to the Projection Mon-
itor chassis before handling the tube.
6. After servicing make the following leakage current
checks to prevent the customer from being
exposed to shock hazards.
Leakage Current Cold Check
1. Unplug the AC cord and connect a jumper
between the two prongs on the plug.
2. Turn on the Projection Monitor’s power switch.
3. Measure the resistance value, with an ohmmeter,
between the jumpered AC plug and each exposed
metallic cabinet part on the projection monitor,
such as screw heads, connectors, control shafts,
etc. When the exposed metallic part has a return
path to the chassis, the reading should be between
4 M
Ω
and 20 M
Ω
.
When the exposed metal does not have a return
path to the chassis, the reading must be
∞
.
Leakage Current Hot Check (See Fig.1)
1. Plug the AC cord directly into the AC outlet. Do not
use an isolation transformer for this check.
2. Connect a 2k
Ω
, 10W resistor, in series with an
exposed metallic part on the projection monitor
and an earth such as a water pipe.
3. Use an AC voltmeter, with high impedance type, 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 1.0V
rms. In case a measurement is outside of the limits
specified, there is a possibility of a shock hazard,
and the projection monitor should be repaired and
rechecked before it is returned to the customer.
Hot-Check Circuit
Fig. 1
AC Voltmeter
To
Instrument's
Exposed
Metallic Parts
2k , 10W
Water Pipe
( Earth )
# !"