Panasonic TX-W28D2F/P, Service Manual

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2
CONTENTS
SAFETY PRECAUTIONS 2
LOCATION OF CONTROLS 3
SERVICE HINTS 3
ADJUSTMENTS 4
SELF CHECK 6
WAVEFORM PATTERN TABLE 7
CONDUCTOR VIEWS 8
BLOCK DIAGRAM 15
SCHEMATIC DIAGRAMS 17
PARTS LOCATION 26
REPLACEMENT PARTS LIST 27
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 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 that all the protective devices such as
insulation barriers, insulation papers, shields and isolation R-
C combinations are correctly installed.
4. When the receiver is not being used for a long period of time,
unplug the power cord from the AC outlet.
5. Potentials as high as
32kV
are 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 familiar with the precautions necessary when
working on high voltage equipment. Always discharge the
anode of the picture to the 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 of the plug.
2. Turn on the receiver's power switch.
3. Measure the resistance value with an ohmmeter, between
the jumpered 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 4M ohm and 20M ohm. When the exposed metal
does not have a return path to the chassis the reading must
be infinite.
LEAKAGE CURRENT HOT CHECK
1. Plug the AC cord directly into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a 2kW 10W resistor in series with an exposed
metallic part on the receiver and an earth such as a water
pipe.
3. Use an AC voltmeter with high impedance to measure the
potential across the resistor.
4. Check each exposed Metallic part and check the voltage at
each point.
5. Reverse the AC plug at the outlet and repeat each of the
above measurements.
6. The potential at any point should not exceed 1.4 Vrms. In
case a measurement is outside the limits specified, there is a
possibility of a shock hazard, and the receiver should be
repaired and rechecked before it is returned to the customer.
X-RADIATION WARNING
1. The potential sources of X-Radiation in TV sets are the high
voltage section and the picture tube.
2. When using a picture tube test jig for service ensure that the
jig is capable of handling
32kV
without causing X-Radiation.
NOTE : It is important to use an accurate periodically calibrated high
voltage meter
1. Set the brightness to minimum.
2. Measure the high voltage. The meter should indicate
30.5kV "1kV if the meter indication is out of tolerance,
immediate service and correction is required to prevent the
possibility of premature component failure.
3. To prevent any X-Radiation possibility, it is essential to use
the specified tube.
HOT CHECK CIRCUIT
2K ohm 10W
A.C. VOLTMETER
WATER PIPE
(EARTH)
TO INSTRUMENT'S
EXPOSED
METALLIC PARTS
Fig.1
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