PC switching itself off, no explanation!

[Ultimoz]

I had an issue about a month back where my PC wouldn't immediately turn on when I pressed the power button, but eventually the issue went a way so I just ignored it ever happened. But suddenly on saturday it got really bad and started switching itself off a few seconds after switching on. It started happening every 5 minutes or so, but is now taking up to a couple hours

I tried switching the PSU to an older one, the same issue happened
I tried laying out the pieces on cardboard and, using only a single stick of old ram + removing the GPU, the same issue happened. In this scenario though, it first lasted 2 hours, and then lasted about 20 hours before finally switching off, maybe this is notable

By this point, it has to either be the motherboard, cpu, or ssd that is causing the issue. I don't think it's likely to be the ssd, so does anybody have ANY idea?

Specs when it last shut off:
-ASRock Z77 Extreme 4
-i7-3770k
-CX600M
-250GB samsung SSD

I know my PSU is trash, but I'm not convinced the issue is PSU related since I tried an older one and it still happened.

 

[Ultimoz]

I tried the brand new PSU that arrived today and nothing happened.

Don't know which one,but it shouldn't be the problem. So motherboard seems likely to be the next to look at.

One other thing comes to mind and that is a heat issue. Is the cpu cooler still well attached to the motherboard? What cooler are you using? mIght be a stupid thought,but is easily checked.

Would that stop a motherboard from switching on at all?

 

[InvalidError]

An outright lack of HSF shouldn't prevent the CPU from booting long enough from a cold-start to at least see the POST screen.