KEYSMART TFT30WL31
Service Manual

SAFETY PRECAUTIONS
GENERAL GUIDELINES 1. It is advised to insert an isolation transformer in the
AC supply before servicing a hot chassis. 2. Always use the manufacturer�s replacement safety components. The critical safety components marked with on the schematics diagrams should not be by other substitutes. Other substitute may create the electrical shock , fire or other hazards. Take attention to replace the spacers with the originals. Furthermore where a short circuit has occurred , replace those components that indicate evidence of overheating. 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 time of period of time , unplug the power cord of the Adaptor from the AC outlet.

There are electro-static sensitive components such as CMOS in LCD Module. Please earth human body when handle the LCD.In addition, please do not touch the interface connector pin with bare. 8 - Do not operate for a long time under the same pattern Operating LCD for a long time under the same pattern can cause image persistence and can damage it. Please follow following guidance. 1. Turn the power off when do not use. 2. Change the pattern periodically. LEAKAGE CURRENT COLD CHECK 1. Unplug the AC cord and connect a jumper
between the two prongs of the plug. 2. Turn 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. When the exposed metallic part a return path to the chassis the reading should be between 4Mohm and the 20Mohm. When the exposed metal does not have a return path to the chassis, the reading must be infinite.

Color TFT LCD Module is very sensitive both electrically and physically.Users, therefore, are requested to follow the �Guidance of handling color TFT LCD Module�on the followings.
polarizer. Surface of polarizer is soft and can be physically damaged easily.Please do not touch, push or rub polarizer surface with materials over HB hardness. 2 - Keep clean the surface. Please wear rubber glove when touch the surface of LCD screen. Please use soft and anti-static material as cleaner. 3 -Keep out of water.Water on/in the LCD may cause electrical short or corrosion. Please wipe out dry or water carefully. 4 -Prevent swift Temperature & Humidity change.Instantaneous temperature and/or humidity change can make dew or ice which cause nonconformance such as malfunction. 5 - High temperature & high humidity reduce the life-time. LCD is not proper to be used at high temperature and high humidity. Please keep specified temperature and humidity condition. 6 - Keep out of Corrosive Gas.Corrosive gas effect the polarizer and the circuit chemically and cause defects accordingly. 7 - Electrostatic discharge can make Damage
1 -Be careful not to make scratch on the

LEAKAGE CURRENT HOT CHECK 1. Plug the AC cord directly in to the AC outlet. Do

not use an isolation transformer for this check. 2. Connect a 2Kohm 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 the each point.

5. Reverse the AC plug at the outlet and repeat each of
the above measurements.

6. The potential at the any point should not exceed 1.4
Vrms. In case a measurement is outside the limits specified , there is the possibility of a shock hazard , and the receiver should be repaired and rechecked before it is returned to the customer.

HOT CHECK CIRCUIT AC-Voltmeter
TO INSTRUMENTS EXPOSED METALLIC PARTS

Water pipe (earth)

2 K Ohm