PC wont turn on Power supply and CPU turn on for 2 seconds and then stop Replaced power supply but does the same thing?

Answer 1

If you've replaced the power supply with a known good power supply (I've seen more than one case where the 'new' power supply was defective) there are 2 other things I can think of that may be causing this. First of all, it could be that there's a cooling problem with your CPU. More than likely, if this is the case, the heat sensor on the motherboard that lets the computer know the CPU temperature is faulty. This is fairly rare. My second idea, unfortunately, is the motherboard. There just aren't too many things that cause a computer to turn off that quickly. One good way to make narrow it down to the motherboard is to strip it down to just the CPU and motherboard and power supply. Disconnect all drives and remove all add-on cards (video, sound, NIC, etc.) The goal isn't to get it to boot per se, but to see if it stays on. You should have ONLY the motherboard with the CPU and power supply plugged in. If it DOES stay on, start putting things in one at a time to figure out what's causing the problem. If this doesn't help or you need additional info, let me know and I'll get back to you ASAP! :)