First of all, the value of the clock is normal, that is, the internal work of the power supply is abnormal, which leads to the lack of power supply, and the CPU cannot work normally, which leads to the failure of starting the machine. After replacing the PM7325 power supply chip in the figure, the starting current is normal, but the screen does not display.
Focus on the inspection of the periphery of the 4G power amplifier chip. After careful observation, it is found that there are corrosion marks around a chip on the right side of the 4G chip, and there is a small amount of electrolyte. Redo this chip.