Help me troubleshoot my PC's sudden refusal to turn on please

Yesterday I was browsing and my PC shut down as if it had lost power, when I tried to turn it back on nothing happened. The motherboard has power the green led is on. When I switch the PSU off wait for the led to go off then turn it back on and press the power button the fans move to start then stop and nothing happens, if I press the power button again nothing happens I have to turn the PSU on and off and on to get the same result again. I have re-plugged all the wiring re-seated the GPU. Not sure what else to do, I was considering a complete tear down but I have to wonder if its worth the time. Any ideas?


Motherboard: asus sabertooth 990fx r2.0
CPU: AMD 8350
CPU cooler: Corsair H100i
GPU: 7950

My first thought was CPU overheat, or maybe issues with your RAM. The last time I had an issue like this though, something had fallen behind the motherboard and was shorting out the system.

It's possible you blew a cap in the PSU.

These are always super tricky to debug. Is there no beeping at all? does anything change on the monitor at all? I think you are probably going to need to take it apart and try put pieces back one at a time to see whats causing it. It's an absolute pain but its the only thing I can think of at the moment.

I would look at the psu first. Have it tested or try a different one. Even a smaller psu would work as long as you dont plug everything up. Like the gpu.

I think I'll probably go ahead and start taking things apart, if I open the PSU would I be able to see if there was a problem or would I require some piece of equipment to test the PSU? Unfortunately I don't have access to another PSU so I can't try swapping it out.

I had exactly the same issues and it was because my PSU had died but unfortunately I couldn't see any visible damage on the unit its self even after opening it up.

Did your PSU still seem to be working normally, in that it still provided power to the board?

Yes, i have seen that before. Once you go to boot, nothing?

Yes, it would spin the fans and flash the LED on the power button before turning off again almost instantly.

So I took it apart, connected the PSU to the motherboard outside of the case with nothing else connected and shorted the power on pins on the board. The fan on the PSU spins up then turns off. Does this say anything about the PSU or is it normal for it to just shut off because it's only connected to the motherboard which has nothing connected to it?

Providing you have the ATX and CPU power connectors on the board it isn't normal for this to happen. Even if you short the power pins it should still boot the motherboard with only ATX/CPU power.