Common Faults and Solutions of Liquid Crystal Displays

1. The power indicator is on when the power is on but the screen does not display or it goes out after one display:

The capacitor on the power supply board or the capacitor on the high voltage board is faulty: bulging, false welding...

2. The power indicator does not light up, no display:

There are three situations:

A short circuit on the power board itself, the mainboard will lower the voltage from the power supply by 0V, push the button out of control. Our company provides digital displays.

3. White screen after power-on, and white screen after power-off:

The MOS tube on the power supply line on the high-voltage board is broken down, or the PWM chip and the surrounding electronic components are faulty.

4. Intermittent black screen:

The fault is the breakdown of the MOS tube or triode controlled by the PWM chip on the high-voltage board.

5. After being dropped, the monitor turns on and then goes out:

The lamp is broken.

6. No display, indicator light is on, the screen is off:

Failure of high voltage board, test chip or capacitance, insurance, etc.

7. Nothing happens:

Check the circuit from the power supply.

8. No power on, the indicator light is yellow:

Check up routinely.

9. White screen after half an hour after booting:

After testing the screen with the universal board, determine where the fault is: whether it is the screen or the drive board.

10. Three failures:

Check the voltage first: whether 3.3V, 5V, 12V are normal, whether the voltage on the driver board is normal, and whether the keys on the keypad are normal.

11. Huaping:

The IC on the driver board or the screen is broken.

12. No boot after the lightning strike:

The power board is faulty.

13. The image has a red tail and the image is blurred:

Use a universal driver board to rule out whether the bottom is the driver board or the LCD screen itself. (If the phenomenon is still on the LCD screen, if the appearance is normal, you can consider replacing its main control IC.)

14. The indicator light flashes without display after booting:

Light flashing means that the circuit has a short circuit or the voltage is too low to drive the load. You can disconnect the screen cable to see if it is normal and see that part of the fault is at the bottom. (Generally, the related capacitor or diode is broken down.)

15. Black screen after connecting the VGA data cable:

Because the MCU is damaged, you can flash the program to see if it is normal, if not, you can replace the MCU.

16. After turning on, the indicator light is green:

High voltage protection. High-voltage bar failure: replace the PWM control IC of the high-voltage bar, and check the related circuit electronic components.

17. The high voltage is not controlled, and the control interface on the high voltage is broken:

You can find a flying lead from the drive board to the high-voltage control terminal with a voltage of 3V for startup and 0V for the shutdown.

18. Boot white screen:

The fault is on the screen or the driver board: Use a general driver board to eliminate it, whether it is the screen or the driver board. (Generally the problem of screen power supply: check whether the screen power supply components on the driver board are normal and whether the insurance of the screen itself is normal.)

19. Automatic shutdown:

MCU or other ICs have poor thermal stability, so you can feel which chip is hot.

20. The voltage is abnormally low:

Because the capacitor at the output terminal is faulty, the capacitor can be replaced.

21. The menu will be automatically displayed after a period of time after booting:

The MCU is faulty.

22. The color is abnormal, the image lacks color, is blue, red, etc.:

The VGA interface or data line is open.

23. The screen will be black from time to time, sometimes a menu will pop up:

The MCU is faulty.

24. The image and the indicator light flash together:

If the power supply is insufficient, measure the relevant voltage, and replace the capacitor.

25. White screen after connecting the data cable:

Generally, the power supply is insufficient or the VGA control IC is broken.

The above information is provided by LCD manufacturers.