Precautions And Safety Notices - ViewSonic VX912-4 Service Manual

1. Precautions and Safety Notices

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 line
2. Safety Check :
Care should be taken while servicing this LCD display. Because of the high voltage used in the inverter circuit. These voltage
are exposed in such areas as the associated transformer circuits .
3. POWER SUPPLY REQUIREMENTS
The external power converter for this display utilizes AC and DC cords , AC cord is detachable , but DC cord is
permanently attached . Any attempt to replace another adapter could result in serious problem on the display .
4. LEAKAGE CURRENT HOT CHECK
4-1 Plug the AC cord directly into the AC outlet. Do not use an isolation transformer during this check.
4-2 Connect a 1500 ohm , 10 watt resistor , paralleled by a 0.15uF capacitor between each metallic part and a good earth
ground
4-3 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.
4-4 Move the resistor connection to each exposed metallic part and measure the voltage.
4-5 Reverse the polarity of the AC plug in the AC outlet and repeat the above measurement.
4-6 Voltage measured must not exceed 1.5 volt RMS, from any exposed metallic part to the ground. A leakage current
tester may be used in the above hot check, in which case any circuit measured must not exceed 1.0 milliamp. In the case of a
measurement exceeding the 1.0 milliamp value, a rework is required to eliminate the chance of a shock hazard .
ViewSonic Corporation
AC VOLTMETER
V
0.15u
.
1500 10W
To Metal Parts
1
Earth Ground
Confidential - Do Not Copy
VX912-4