Safety Precautions - Panasonic TX-51P100X Service Manual

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 to be used for a long
period of time, unplug the power cord from the AC
outlet.
5. Potential, as high as 34.5kV, is present when this
monitor is in operation. Operation of the Projection
Monitor 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 Monitor 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 MΩ and 20 MΩ.
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 2kΩ, 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
To
Instrument's
Exposed
Metallic Parts
X-Radiation
Warning :
1. The potential sources of X-Radiation in projection
monitor are the High Voltage section and the pro-
jection tube.
2. When using a projection tube test jig for service,
ensure that jig is capable of handling 32.5kV with-
out causing X-Radiation.
Note: It is important use an accurate periodically cali-
brated high voltage meter.
1. Set the brightness to minimum.
2. Set the service switch to the service position.
3. Measure the High Voltage. The meter reading
should indicate 34.5 ( ± 0.5 ) kV. If the meter indi-
cation is out of tolerance, immediate service and
correction is required to prevent the possibility of
premature component failure.
4. To prevent an X-Radiation possibility, it is essential
to use the specified projection tube.
- 3 -
AC Voltmeter
Water Pipe
( Earth )
2k , 10W
Fig. 1