SAFETY PRECAUTIONS
1 CAUTION:Note: High voltage is present when this CRT display is
No modification of any circuit should be attempted.operating. Always discharge the anode of the
Service work should only be performed after you arepicture tube to the display chassis to prevent
thoroughly familiar with all of the following safety checksshock hazard.
and servicing guide lines.
2 SAFETY CHECKAC VOLTMETER
Care should be taken while servicing this CRT display
because of the high voltage used in the deflection
(EARTH
circuits. These voltages are exposed in such areas as
GROUND)
the associated flyback and yoke circuits.To
INSTRUMENTOS0.15?F
EXPOSED
3 FIRE & SHOCK HAZARDMETAL PARTS1500 ?, 10W
3-1 Insert an isolation transformer between the CRT
display and AC power line before servicing the
Fig.1
chassis.
3-2 In servicing pay attention to original lead dress
6 IMPLOSION PROTECTION
especially in the high voltage circuit. If a short circuit
Picture tubes are equipped with an integral implosion
is found, replace all parts which have been
protection system, but care should be taken to avoid
overheated as a result of the short circuit.
damage and scratching during installation. Use only
3-3 All the protective devices must be reinstalled per
Panasonic replacement picture tubes.
original design.
3-4 Soldering must be inspected for possible cold solder7X-RADIATION
joints, frayed leads, damaged insulation, solderWARNING : The only potential source of X-Radiation is
splashes or sharp solder points. Be certain tothe picture tube. However when the high voltage circuitry
remove all foreign material.is operating properly there is no possibility of X-
Radiation problem. The basic precaution which must be
4 LEAKAGE CURRENT COLD CHECK
exercised is to keep the high voltage at the following
4-1 Unplug the AC cord and connect a jumper between
factory-recommended level.
the two prongs on the plug.
4-2 Turn the CRT display power switch Oon� .Note: It is important to use an accurate periodically
4-3 Measure the resistance value with an ohmmetercalibrated high voltage meter.
between the jumpered AC plug and each exposed7-1 The procedure for adjustment high voltage is as
metallic part on the CRT display such as the metalshown on page 22.
frame, screwheads, control shafts, etc. When the7-2 If can not be adjust 25.0 kV at immediate service is
exposed metallic part has a return path to therequired to prevent the possibility of premature
chassis, the reading should be 1.8 megohm component failure.
minimum.7-3 To prevent X-Radiation possibility it is essential to
5 LEAKAGE CURRENT HOT CHECKuse the specified picture tube.
5-1 Plug the AC cord directly into the AC outlet. Do not
use an isolation transformer during this check.
5-2 Connect a 1500 ohm, 10 watt resistor, paralleled by
a 0.15?F capacitor between each exposed metallicIMPORTANT SAFETY NOTICE
part and a good earth ground (as shown in Fig.1).There are special components used in this CRT
5-3 Use an AC voltmeter with 1000 ohm/volt or moredisplays which are important for safety. These
sensitivity and measure the AC voltage across theparts are identified by the international symbol l
combination 1500 ohm resistor and 0.15?F on the schematic diagram and on the
capacitor.replacement parts list. It is essential that these
5-4 Move the resistor connection to each exposedcritical parts should be replaced with
metallic part and measure the voltage.manufactureOs specified parts to prevent X-
5-5 Reverse the polarity of the AC plug in the AC outletRADIATION, shock, fire or other hazards. Do not
and repeat the above measurement.modify the original design or this will void the
5-6 Voltage measured must not exceed 7.5 volt RMS,original parts and labor guarantee.
from any exposed metallic part to ground A leakage
current tester may be used in the above hot check,
in which case any current measured must not
exceed 5.0 milliamp. In the case of a measurement
exceeding the 5.0 milliamp value, a rework is
required to eliminate the chance of a shock hazard.
� 2 � |
ACEC
PANASONIC
