PC won't boot for no known reason.

[Lethbridge]

OK, here is my sad story.
Last week my old PC died, time to build a new machine.
Bought all of the components (had to buy the motherboard twice as the first one had a faulty PCIE slot).
Put everything together, works great. Running Vista Ultimate 32bit.
I use this machine as a Media Center machine primarily.
I have 2 xbox 360's hooked up as Media Center Extenders.
This morning I was watching tv on one of the extenders when it froze. I went downstairs to check the pc and it was off. I tried turning it back on and nothing. Turned the PSU off and on, then hit the power switch on the PC, for a split second all of the fans spun up and then died. Pressing the power switch again does nothing. If I power cycle the PSU it does the same thing (fans spin up briefly then nothing).
I've read several forums, but can't seem to find the right answer. I tried resetting the CMOS with the jumper, that didn't work.
I should mention that there are 2 lights on the motherboard that are on (which indicates to me that it is not my PSU or my motherboard), and that the power LED always stays on.
My other concern is that my CPU was running at around 47-51 Celsius. I had originally thought that my system had overheated, but I have had the case open for a couple of hours with a fan blowing on it, it has cooled down but it still won't boot back up. I am planning on picking up a new CPU cooler, but right now I need to get my system going first.

Any thoughts?

 

[Daveskater]

Hello, Lethbridge, and welcome to Techspot :wave:

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With regards to your problem, it sounds like your psu has gone. Take a look at this thread to check: Suspect a Dead PSU? How to be sure

Also, 51C would be ok for a cpu. It's a bit on the warm side but it won't cause the pc to shut down. Just don't stray too close to 60

 

[Lethbridge]

Thanks for the input.

I tried the PSU troubleshooting. When I jumpered the case power switch pins, and then hit the switch on the back of the PSU, same thing, the fans spun up briefly and then died. I then tried the "paperclip" trick, once I hit the PSU switch, fans spun up and then died again. When I plugged the PSU back into the motherboard, the 2 LED lights on the motherboard light up and stay lit up, as well as the power LED light on the case.

This makes me think that the PSU is fine. But it might be something with the motherboard (although this is already my second motherboard.

Any other options?

 

[Daveskater]

if the fans stop before you remove whatever it is that you're using to short the pins then you will need a new power supply, if they only go off after you take the short out or switch it off then it should be ok and you should replace the mobo

 

[aspirulito]

I have a PSU tester that I use to make sure the PSU is not the problem.. and according to what u describe I would almost swear you have a bad PSU, it is easy to see if it is the PSU, get a hold of another one, may be the one form your old computer and plug it into your new computer to see if that fixes the problem....

 

[Lethbridge]

OK, this time I tried the paperclip trick again, but unplugged everything else from the power supply, and plugged in one spare case fan. When I turned the PSU on, the case fan spun up without a problem, is it possible that my PSU is only partly fried? I ask because it won't work with everything plugged in, but is giving off enough power to light up the 2 LED's on the motherboard.

 

[aspirulito]

That is why I suggested to try a different power supply. Many times the PSU will work apparently without a flaw, but if you use a tester you will see that one of the different voltages (in my experience the -5 V most often) is failing so it causes the computer to have random shutdowns or even not to boot at all, the problem is that if you keep trying to get it to run with the same PSu you are taking the risk to fry the motherboard.

 

[Lethbridge]

I have had a new development.
I hooked up 3 case fans to see if it would start them (my PSU was not hooked up to the motherboard at this point). Started up the PSU and all fans started up. I then hooked up the power to the motherboard and the 3 case fans. When I powered it up, my spare video card (XFX Geforce 6600)actually caught on fire. (Never seen that before). I took that out, plugged in everything else and it now boots up without a problem, (my cpu is even running 10 degrees cooler), is it possible that my other video card was the problem? I was using it before without a problem.

 

[nickc]

if everything is working now, I would say the video card was definately the problem. The fact that the cpu is running 10 degrees cooler is even better.

 

[Lethbridge]

I am not sure how the video card was causing this. I had used it for 2 years prior without a problem. My new concern is that it might have caused damage to the pcie slot it was plugged into (my first motherboard had to be returned as one of the pcie slots did not work at all).
Also, my cpu is back in the 47-49 range at idle. I am buying a PSU tester and a new cpu fan today.

 

[Cinders]

Save your money on the PSU tester unless you build a bunch of computers. I'm pretty sure the video card was the problem, and yes it could have damaged your motherboard. Only time will tell. Your PC wouldn't boot because your video card told it not to. It said, Hey there is a problem here and I need to power down now. Many video cards will do the same thing if their quick checks tell them to do so. By way of example. I had an Radeon X1900XTX I converted to water cooling. Because the heat sink fan was no longer installed, my computer would not boot because the video card could not detect the fan spinning. Until I reinstalled the fan and disabled the card's fan monitoring in its BIOS my computer would not boot. Your card tried to do the same thing untill it broke and then caught on fire.