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        CN
        4News

        Maintenance of several common faults of the LCD driver board


        1. Visually check the board for component abnormalities. Power on the board to touch the board to see if there is any abnormal temperature. Sometimes the chip is broken and the temperature is very high.

        2, then I am used to checking the power supply on the driver board first.

        Since the power board output is typically only 12v and 5v, there are several DC/DC regulators on the driver board to convert the voltage required by the driver board.

        (A small number of models of the power board will also output 3.3v, 2.5v and other voltages to the driver board)

        Generally, there are 5v, 3.3v, 2.5v, 1.8v, etc. Measure the input and output voltages of several voltage regulator chips. If the machine is fault caused by the power supply problem, the fault point will be found soon.

        3. If the voltages of the regulators are normal, then continue to check, or simply come,

        The power supply is normal, then each button on the keypad should have voltage, and then measured with a multimeter. When the switch is pressed, the voltage on the button is pulled down by 0v. If not, the key is broken, and the button is changed. Can fix the fault.

        4. If there is a switching voltage jump, then the switch button is also excluded, continue to check, the power supply is available, then check the clock required for the chip work. (The crystal frequency required for different processing chips is different)



        Use a multimeter to measure the voltage across the crystal with or without the voltage difference. Of course, this can only be judged. It is of course best to have an oscilloscope to see the waveform.

        5, the clock required for the operation of the mcu chip is also available, and then check the conditions required for the chip to be reset, because the chip pdf is not easy to find, and even if found, the pins defined by different manufacturers may be different, which takes time.

        The general reset is generated by a capacitor, a resistor and two diodes. This board is easy to find. Two red glass diodes are obvious next to the mcu.

        Mcu microprocessor working conditions are available (some boards processing chips and mcu are integrated in one chip, some are separate, the reason is the same), but mcu to start work must be in conjunction with software control to complete the corresponding operation, Therefore, causing the key to be pressed but not booting is also related to the muc program (there are a lot of problems caused by the program not being turned on during the maintenance), which requires a brush program.

        There is also the failure of the non-drive board itself, such as the resistance deterioration on the button board, open circuit, poor capacitance, short circuit, will also cause the boot, I prefer to be violent, directly pick all the capacitors with a soldering iron

        The reason of the screen will also cause the power to be turned off. For example, the screen power supply is short-circuited. This is a good judgment. The screen cable is disconnected and the driver board is normal.

        (If the mcu of the driver board is the card holder, pay attention to whether the mcu contact is bad)
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