PC bootsfor <5 seconds and then reboots continuously. Dead power supply or mobo?

nickt031292

Reputable
Jan 25, 2016
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4,510
Hi all.

I came home from work today and turned my monitor on. I found that my PC was completely frozen so I gave it a hard restart.

After that, it would boot for about 3 to 5 seconds. All fans would turn on (all case fans, CPU fan, GPU fan) and then it would shut off. It would then continue this loop.

I know how to build PCs but I'm not sure how to troubleshoot them. I suspect it's the motherboard but how can I be sure that it's not the power supply?

Here is a video of the boot shutdown loop.
https://www.youtube.com/watch?v=jj_78Dk86gY