ViewSonic E95 - Safety Precautions

1 CAUTION
No modification of any circuit should be attempted.
Service work should only be performed after you are
thoroughly familiar with all of the following safety checks
and servicing guide lines.
2 SAFETY CHECK
Care should be taken while servicing this CRT display
because of the high voltage used in the deflection circuits.
These voltages are exposed in such areas as the
associated flyback and yoke circuits.
3 FIRE & SHOCK HAZARD
3-1 Insert an isolation transformer between the CRT
display and AC power line before servicing the
chassis.
3-2 In servicing pay attention to original lead dress
especially in the high voltage circuit. If a short circuit is
found, replace all parts which have been overheated
as a result of the short circuit.
3-3 All the protective devices munt be reinstalled per
original design.
3-4 Soldering must be inspected for possible cold solder
joints, frayed leads, damaged insulation, solder
splashes or sharp solder points. Be certain to remove
‘all foreign material.
4 LEAKAGE CURRENT COLD CHECK
4-1 Unplug the AC cord and connect a jumper between
the two prongs on the plug.
4-2 Tum the CRT display power switch “on”.
4-3 Measure the resistance value with an ohmmeter
between the jumpered AC plug and each exposed
metallic part on the CRT display such as the metal
frame, screwheads, control shafts, etc. When the
exposed metallic part has a return path to the chassis,
the reading should be 1.8 megohm minimum.
5 LEAKAGE CURRENT HOT CHECK
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
0.15uF capacitor between each exposed metallic part
and a good earth ground(as shown in Fig.1).
5-3 Use an AC voltmeter with 1000 ohm/volt or more
sensitivity and measure the AC voltage across the
combination 1500 ohm resistor and 0.15uF capacitor.
5-4 Move the resistor connection to each exposed metallic
part and measure the voltage.
5-5 Reverse the polarity of the AC plug in the AC outlet
and repeat the above measurement.
5-6 Voltage measured must not exceed 7.5 volt RMS,
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 shock hazard.
ViewSonic Corporation
SAFETY PRECAUTIONS
Note: High voitage is present when this CRT display
is operating. Always discharge the anode of
the picture tube to the display chassis to
prevent shock hazard.
AC VOLTMETER
{EARTH
GROUND)
INSTRUMENT'S.
EXPOSED
METAL PARTS 15000, 10W
Fig. 1
6 IMPLOSION PROTECTION
Picture tubes are equipped with an integral implosion
protection system, but care should be taken to avoid
damage and scratching during installation.
7 X-RADIATION
WARNING : The only potential source of X-Radiation is
the picture tube. However when the high voltage circuit
is operating properly there is no possibility of X-
Radiation problem. The basic precaution which must
be exercised is to keep the high voltage at the
following factory- recommended level.
Note: It is important to use an accurate periodically
calibrated high voltage meter.
7-2 If high voltage cannot be set to 24kV, immediate
service is required to prevent the possibility of
premature component failure.
7-3 To prevent X-Radiation possibility it is essential to use
the specified picture tube.
IMPORTANT SAFETY NOTICE
There are special components used in this CRT
displays which are important for safety. These
parts are identified by the international symbol
A\ on the schematic diagram and on the
replacement parts list. It is essential that these
critical parts should be replaced with
manufacture’s specified parts to prevent X-
RADIATION, shock, fire, or other hazards. Do
not modify the original design or this will void
the original parts and labor guarantee.
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