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Motherboard or CPU Failure (or something else?)

Last response: in CPUs
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May 7, 2012 9:44:22 PM

I woke up today to a computer that will turn on for a few seconds, but then shut down. No beeps. I can tell from sound and sight that both the power supply is working and the motherboard receives power both when turned off (passive yellow light) and when on (additional lights turn on).

So I started pulling components to see if I could identity the root cause.
- USB connections
- Drives
- Video card
- Memory

Identical behavior.

I pulled the CPU and the behavior is similar, but it tries to turn itself back on every few seconds after failing the last attempt.

Suggestions? I think it has to be one of the CPU or motherboard, but I'm at a loss as to how to identify which one. Unfortunately I don't have any parts laying around of the same CPU design to swap things around and test.

Thanks in advance
May 7, 2012 10:01:00 PM

I've never dealt with a bad power supply, but i imagine that a bad power supply could still power on the LED and still be compromised. The power supply could break completely and supply no power, or it could be "half-broken" where it still supplies power but at the wrong voltage or something. You may want to get a voltmeter and test the voltages to see if your power supply is compromised.

This symptom sounds like a failed overclock, although I assume you haven't been overclocking otherwise you would have said so. Maybe BIOS is messed up for some reason. You can try to hard reset the BIOS.
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a b V Motherboard
May 7, 2012 10:02:29 PM

If you pull the CPU it shouldn't turn on... and will give error messages...

It could still be the PSU that failed. It may be giving enough power to run those lights but not enough to actually boot.

Also with no memory you will not get a boot. Just error beeps. If the memory is bad you will get the same result.

The video card might have gone bad too. Test it in another system if you can.

What motherboard, CPU, PSU, Graphics are you running?

It could be the motherboard/CPU too
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May 7, 2012 10:23:40 PM

No overclocking.
The PSU is only a few years old, but my system does run 24/7 so I can't rule it out.

Without pulling more out of the case or digging in deeper:
- An Antec PSU, 800 or 900 I think
- MSI K9N2 SLI Platinum MB
- AMD Opteron
- MSI Geforce NX8800GT (currently disconnected and using built-in graphics)

It's not posting or beeping, so I don't have anything to go on except manual observations.

I also just tried resetting the BIOS- no change.

Right now I have my CPU in but memory removed. Under proper circumstances it *should* be beeping at me, right?
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a b V Motherboard
May 7, 2012 10:36:27 PM

I'd just put at least one stick of Ram in at a time...
Then you can swap the other with it.
That way you can tell if it was the RAM

PSus go out sometimes...

Look on your motherboard for Bulging Capacitors

Capacitors look like little cylinders and the tops should be flat. If the tops are split or have a domed appearance it means they crapped out...
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May 7, 2012 10:55:03 PM

It occurred to me that the internal LEDs might not just be decoration, and they're not. They're status indicators which also serve to point towards errors...

And according to them:
SystemPowerON
The D-LED will hang here if the processor is damaged or not installed properly.

So the motherboard is blaming the CPU. I take that with a grain of salt since I imagine power/MB problems could both lead to a false positive there, but it's the only lead the hardware itself is giving me.

Advice on whether I should assume it's the CPU, or go with your guys' gut that's the PSU?
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a b V Motherboard
May 7, 2012 11:09:22 PM

I always blame the PSU first... based on experience. I keep an extra known working PSU in the closet to test my theory and I am usually right.

If it is something else you usually need to have extra parts around to test each individually...

I have an extra video card for testing too but that is irrelevant unless you have the Bios set to ignore the onboard GPU. In that case I'd recommend resetting the Bios to factory via a hard reset.
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May 8, 2012 12:42:37 AM

pacioli said:
If it is something else you usually need to have extra parts around to test each individually..


Heh, would be easier if they didn't change form factors every couple years. AM2 being so obviously outdated now, I just ordered a new AM3+ board and CPU. If it turns out the power supply is still bad after that then, well... guess I'll get a new one of those, too.

The trend of my luck, I usually have one of the MB or CPU go every few years. A short enough span of time to be annoying, and just long enough to make it hard to buy a replacement for just the broken piece. So we'll see. At least I'm getting 4 more cores out of the deal.
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a b V Motherboard
May 8, 2012 1:04:52 AM

pacioli said:
I always blame the PSU first...

I tend to do that too...

- PC won't boot or gets into a periodic reboot loop - dismantle PSU expecting leaking junk caps and turns out to be the case ~90% of the time
- external HDD has trouble spinning up - dismantle, usually find bad caps in built-in PSU
- LCD displays have a hard time turning on or seem to stop responding - take 'em apart and find leaking caps on their 3.3/5/18V PSU outputs

Under-rated or otherwise crappy caps seem to be everywhere. Thankfully, nearly every device I have found bad caps in worked good-as-new (if not better) after swapping caps with models featuring much higher AC ripple current ratings. (Most caps I am replacing are rated for less than 1A RMS, my replacements are rated for more than 2A)
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