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Common fault judgment of LCD TV backlight

  1. The LCD screen lights up and goes off when the AC is switched on. At this point, the sound, remote control and panel button control functions are all normal. This phenomenon is caused by the circuit protection of backlight lamp, which is mostly caused by abnormal power supply of backlight lift plate. For CCFL backlight circuits, this fault can be caused by an open backlight (usually circuit protection caused by an unplugged or unplugged socket on the backlight riser) or by a broken LED bar.

  2. No change in backlight switch, sound, remote control, panel button control are normal. This failure to check the following conditions: 1), back light lifting clamp circuit power supply, common big screen is 24 v, very few use 120 v, a small screen normally for 12 v, 2), CPU control circuit output backlight work clamp oscillator rise of the switch control signal, common for high level start, mostly 3 v to 5 v lamp light control signals. If the above working conditions are met, then the backlight lamp lift plate can be replaced. If the backlight lift plate is replaced, the fault remains unchanged, most of the backlight lamp tubes in the LCD panel components are damaged.

  3. The backlight is on and off. Common for backlight lamp pressure plate lamp socket and lamp tube contact is bad, backlight lamp power supply is high or low. In actual maintenance, there should be no 1V error measured by 24V power supply with digital meter (the 24V voltage output on the power board should be stable no matter no load or with load).


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