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Won't power on - is it CPU or mobo?

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November 24, 2011 4:42:52 PM

I built a home desktop six years ago using an Intel D915GAV motherboard and a Pentium i4 processor. Recently, it started getting flaky (when I logged in, it would functionally go the desktop, but the display wouldn't refresh). Then, it wouldn't turn on at all. I've swapped the power supply, and tested that the power on switch is working, but it still won't power on. I swapped the hard drive into another desktop, and it's working fine as a secondary drive (thanks to advice from geofelt on the Storage/Hard drive forum).

Therefore, there are only so many things left: motherboard, processor, or RAM. All my RAM failing seems fairly unlikely. One possible scenario is that the fan to cool the CPU failed, I didn't notice it, and I fried my CPU. This might be consistent with the flaky behavior before failure.

So the question: Is there any way to debug whether it's the motherboard or CPU? I plan on doing a new build soon anyway, but I'd be willing to buy a $40 CPU (I think I could get a Celeron 775 socket for about that much) just for the convenience of easily offloading all my stuff. But I don't think I could even get a D915GAV mobo any more, and I'd just as soon not buy an old CPU just to find out it's the mobo.

Any ideas as to what might be wrong, or how else to determine what's wrong?

More about : power cpu mobo

a b B Homebuilt system
November 25, 2011 12:33:19 AM

Did the CPU fan fail? Even if it did, that usually doesn't cause a CPU to fry. I'd suspect the motherboard more than the CPU.
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a b B Homebuilt system
November 25, 2011 1:07:18 AM

The easiest way to determine if the CPU or the motherboard failed is to put your CPU into another computer with a compatible motherboard.

RAM can be checked by plugging in only one DIMM at a time and trying to boot. It only takes one bad DIMM to cause the whole computer to fail to boot up.

The last option would be to get an exact replacement motherboard. I just checked and you can get that model on EBAY for around $35 to $50. However, since you said that you plan to upgrade soon anyway, that might be a waste of money and you can't ignore the fact that most of those are used.

You could also try following this troubleshooting guide: http://www.tomshardware.com/forum/261145-31-perform-ste....

Even though it is intended for new builds it is also useful for trouble shooting "won't boot" and "no video" problems of any type.
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December 2, 2011 10:57:31 AM

GhislainG said:
Did the CPU fan fail? Even if it did, that usually doesn't cause a CPU to fry. I'd suspect the motherboard more than the CPU.


I don't know that the CPU fan failed; that was speculation, because I'm not really sure how/why other components would fail, since the machine was on a surge suppressor. I really don't have any feel for how often a motherboard fails, or what possible causes are.
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a b B Homebuilt system
December 2, 2011 11:10:29 AM

Since you already swapped the PSU, the next component to try should be the motherboard. Motherboards can fail for several reasons (cold solder joint, busted caps, failed component, etc.) The system won't boot without RAM, but it should still power up. If it doesn't with only the CPU, then follow JKatwyopc's advice and buy a used Intel D915GAV motherboard on eBay.
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December 10, 2011 6:20:35 PM

JKatwyopc said:
The easiest way to determine if the CPU or the motherboard failed is to put your CPU into another computer with a compatible motherboard.

RAM can be checked by plugging in only one DIMM at a time and trying to boot. It only takes one bad DIMM to cause the whole computer to fail to boot up.

The last option would be to get an exact replacement motherboard. I just checked and you can get that model on EBAY for around $35 to $50. However, since you said that you plan to upgrade soon anyway, that might be a waste of money and you can't ignore the fact that most of those are used.

You could also try following this troubleshooting guide: http://www.tomshardware.com/forum/261145-31-perform-ste....

Even though it is intended for new builds it is also useful for trouble shooting "won't boot" and "no video" problems of any type.


Thanks for the detailed post. This morning, I had the time to try the system with no RAM, based on GhialainG's advice, and it still won't power on. Therefore, I'm assuming it's the motherboard, and at this point I think I'll focus on my new build, and be thankful that the hard drive is accessible.
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December 10, 2011 6:21:11 PM

Best answer selected by saundja3.
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