1. When the backlight is turned on, the LCD screen will be turned off. At this time, the sound, remote control, and panel button control functions are normal. This phenomenon is caused by the backlight circuit protection. The reason is mostly that the backlight booster board is abnormally powered. CCFL backlight circuit, if one of the backlight tubes is open (commonly the circuit protection caused by the lamp socket on the backlight booster board is open or the socket is not inserted) or a certain lamp is broken, the above fault can be caused.

2. There is no change in the backlight switch, sound, remote control, panel button control are normal. This fault needs to detect the following working conditions: 1), the power supply of the backlight booster circuit, the common large screen is 24 volts, very few 120 volts, the small screen is generally 12 volts, 2), the CPU control circuit output backlight backlight booster oscillator working switch control signal, usually high level start, mostly 3V-5V lamp lighting control signal if If the above working conditions are met, the backlight booster board can be replaced. If the backlight booster board is replaced, the backlight is damaged. The backlight tube in the LCD panel is damaged.

3. When the backlight is on, it is not bright. It is common for the backlight of the backlight booster board to have poor contact with the lamp. The backlight supply is high or low. In actual maintenance, the 24V power supply digital meter should not have 1V error. The 24V output on the board should be stable whether it is empty or loaded.)