System won't turn on. Is it the Mobo? PSU?

[estevancarlos]

That sounds more like a bad motherboard or a grounding issue.

Lets do a bare bone test.

Take out all but one stick or RAM, disconnect everything except cpu heatsink fan, video card power connectors and power connections to motherboard, take motherboard out of case and place on a non-conductive surface.

Attempt to turn it on.

If it still only stays on for a split second its probably a bad motherboard or a bad power supply.

Might have to try another power supply just to be sure.

If I have a power supply that is potentially not great and provides less voltage would be a bad idea to test it out with that? Or perhaps that would be pointless?

 

[Ste]

Depends on how much lower end it is, If its under 350 watts, don't bother.

 

[Runfox]

Just a thought, I have had simialr problem with accumilated dust in comuter case. I took my power supply out of the case and thoroughly cleaned it, blew out dust and dirt, blew out computer case, no more problems. A good cleanout could help.