Question Old computer in boot loop - can somebody check my debugging work?

Sep 19, 2022
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Yesterday my PC, which had been gaming strong for several years, shut down on its own during a game. After a moment it attempted to boot back up and the CPU/case fans went on, but it immediately turned off again. The power button didn't work, but switching the PSU off and then on caused the same behavior: LEDs on, fans spin up, shutdown seconds later. Now, leaving the computer plugged in with the PSU on causes this process to repeat on its own at irregular time intervals between 5 and 45 seconds, with the boot-up lasting a different amount of time each time. I've never been able to get as far as BIOS setup.

Here's what I've done to debug so far:
  • Removed the whole assembly from the case. No change.
  • Unplugged both disk drives, all RAM sticks, and the GPU. No change.
  • Hard reset mobo CMOS by removing the battery and holding the power button. No change.
  • Observed mobo debug LEDs, where I've seen the shutdown happen during all of them (CPU, DRAM, and VGA) seemingly randomly.
This leads me to believe that the PSU is the problem and needs to be replaced. Does this sound reasonable? I've never had to deal with an issue like this before so I'm not sure if I'm going in the right direction.
 
Yesterday my PC, which had been gaming strong for several years, shut down on its own during a game. After a moment it attempted to boot back up and the CPU/case fans went on, but it immediately turned off again. The power button didn't work, but switching the PSU off and then on caused the same behavior: LEDs on, fans spin up, shutdown seconds later. Now, leaving the computer plugged in with the PSU on causes this process to repeat on its own at irregular time intervals between 5 and 45 seconds, with the boot-up lasting a different amount of time each time. I've never been able to get as far as BIOS setup.

Here's what I've done to debug so far:
  • Removed the whole assembly from the case. No change.
  • Unplugged both disk drives, all RAM sticks, and the GPU. No change.
  • Hard reset mobo CMOS by removing the battery and holding the power button. No change.
  • Observed mobo debug LEDs, where I've seen the shutdown happen during all of them (CPU, DRAM, and VGA) seemingly randomly.
This leads me to believe that the PSU is the problem and needs to be replaced. Does this sound reasonable? I've never had to deal with an issue like this before so I'm not sure if I'm going in the right direction.
this might be a motherboard issue... sign of corrupted bios. you could try to order a CH341A programmer and reprogram the bios chip or bring it to local authorized/authentic pc repair shop and let them diagnose this.