How to repair LCD TV backlight?

LCD TVs have been used for a long time, and there will always be big and small problems. The problem we often encounter is LCD TV backlight failure. I believe this term sounds very rusty, but it doesn’t matter. Next, let's listen to the editor to analyze it in detail. Analysis, you know how to repair the LCD TV backlight failure.

1. The phenomenon of LCD TV backlight failure

A. Fuzzy screen at boot

During maintenance, I have also seen that the lamp in the screen is damaged; when the screen is turned on, the sound is normal. This phenomenon is the bad digital board, and the second is the bad internal connection.

B. There is no sound when starting up

There is no sound when booting up, the power light flashes once and turns into a constant light, and the screen flashes white light at the moment of booting. This fault is mostly caused by damage to the backlight driver board.

C. Three nos at boot

There are three failures when booting, and the power light does not light up. One is that the power board is broken, and the second is that the CPU part is not working properly; the light flashes and it can not be turned on: the CPU bus is not working properly or the boot program IC is bad, and the contact between the BIOSIC and the CPU is poor.

2. Causes of LCD TV backlight failure

The backlight is turned off when the LCD screen is on when the AC is turned on. At this time, the sound, remote control, and panel button control functions are all normal. This phenomenon is caused by the backlight circuit protection, and the reason is mostly the abnormal power supply of the backlight booster board. For the CCFL backlight circuit, if a certain backlight tube is open (usually the circuit protection caused by the opening of the tube socket on the backlight booster board or the socket is not plugged tightly) or a certain tube break can cause the above failures .

3. LCD TV backlight repair

The LCD TV's backlight switch has no change, and the sound, remote control, and panel button control are all normal. Then this fault needs to detect the following working conditions: the power supply of the backlight booster board circuit, the common large screen is 24 volts, a few use 120 volts, and the small screen is generally 12 volts; the backlight booster board output by the CPU control circuit The switching control signal of the oscillator is usually a high-level start, and most of it is a three to five volt lamp lighting control signal. If all the above working conditions are met, the backlight booster board can be replaced. If the backlight booster board is replaced, the failure remains the same, mostly because the backlight tube in the LCD screen assembly is damaged.