analyze:
A white screen is displayed, and the backlight board is working normally. First of all, we can judge whether the motherboard can work normally. We can check the response of the indicator light according to the power switch.
A. If the indicator light can change color, it means that the motherboard is working normally.
1. Check whether the connection line of the main board signal output to the screen is bad (the connection line or the screen can be replaced).
2. Check whether the voltage of each operating point of the motherboard is normal, especially whether the screen power supply voltage is normal.
3. Use an oscilloscope to check the signals of the traveling wave field and clock (from input to output)
B. If the indicator light does not respond or does not light up, it means that the motherboard is not working properly.
1. Check the voltage of each operating point of the motherboard, pay attention to the voltage of the EEPROM (about 4.8V), the reset voltage (high level or low level, according to different models), and the voltage of the microcontroller.
2. Find out if the MCU pin is in good contact with the motherboard.
3. Check whether the motherboard chip and single-chip microcomputer are working. The oscilloscope can be used to measure whether the crystal oscillator is started.
4. Replace or rewrite the microcontroller if necessary;
