1, check whether the power socket has electricity, whether it is normally connected to the computer.
2, check whether the computer power supply can work normally (whether the power supply fan rotates after the power is turned on), and whether the monitor is connected to the host normally.
3, open the chassis cover to check whether the power supply and the computer backplane or motherboard connection is normal, whether the socket between the backplane and the motherboard is loose, whether the backplane or the motherboard is energized after booting up, whether the ATX power supply is incorrectly wired.
4, unplug the memory boot whether the alarm.
5, replace the CPU or motherboard.