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I have an Intel board, and I really do not know which board it is, I built the machine for a relative, but he forgot to keep the documentation.

Long story short, the computer was disconnected during a lightning storm, but a lightning strike travelled in via the ethernet cable (It was directly connected to a power brick commonly seen on those long distance ISP Wireless transmitters), and the motherboard was shocked. I am attempting to get this PC going.

The problem is as follows: The computer will randomly reboot, just in the middle of anything as it pleases. May load to EFI (or whatever BIOS is nowadays), may load to bootloader, may even get to the OS. But before 5 minutes is up, the system will always die. Out of curiosity, I plugged my voltmeter in to a molex connector. On the 5V side, it gets a good, consistant +5.13V. On the 12V side, it fluctuates, as follows: Upon immediate startup, it soars to 12.11-12.13V. It will now do one of two things: it will immediately jump down to 12.04-12.05V, or hover for about a minute at 12.11-12.13, then jump down. It seems the longer the voltage stays at 12.11-12.13, the shorter the machine will stay running.

Also, post codes, whenever the machine locks up, but does not die hard, seem to be between "AA" and "AC". Does this make any sense to anybody? Do you all think this motherboard is salvageable? It was an expensive bugger, and I'd prefer to not replace it.

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It is almost certainly toast. –  KCotreau Jun 25 '11 at 23:49
    
Thank you very much, if not for good news, you got it through my skull the same lesson an engine rebuilder has: Free stuff is quite often, not free. –  Stetson RDT Jun 26 '11 at 0:11
    
This situation reminds me of this post (you did unplug, which is good): superuser.com/questions/287709/… –  Randolf Richardson Jun 26 '11 at 0:17
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It is very reminiscent, we just completely forgot to unplug that. Either that, or we forgot about the power brick. I believe my relative there has bad luck with forgetting, he learned the lesson to unplug his PC last thunderstorm. –  Stetson RDT Jun 26 '11 at 0:21
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Make sure it not a coincidence, check the capacitors on the mobo for swelling. The surge may have put them over the edge. They can be replaced if you have soldering skills, just did my HP, replaced 9 of the buggars, cost me 5 bucks, up and running like a champ. –  Moab Jun 26 '11 at 1:33

1 Answer 1

up vote 4 down vote accepted

Try two things (I'll start with the no-cost option first):

  • Unplug everything, press the power button (in an attempt to turn it back on), then plug everything back in and power it on again; this is a "deep power cycle" and I am guessing that the extra power that might have traveled over your network wiring may have overcharged some of your capacitors (or other such components), and I'm hoping that all you'll need is this deep power cycle to reset things and get it all working normally again.

  • Replace the power supply (they can fail without notice, and subtle outputs may not be detectable with a general purpose volt meter).

I hope this helps you.

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Just out of curiosity: It did rather deep cycle, I had it offline for about a month, before I hauled it out of storage and tried to start it without power, then plugged it in and started it. It ran for 10 minutes straight, then all of this above started in. Could the power supply have cooled itself out enough, or is it just a happy characteristic of a PSU to be subtle? –  Stetson RDT Jun 26 '11 at 0:26
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Thank you very much. I'm probably not going to go with the PSU, as it is showing very steady power most of the time, and I'm just kidding myself hoping elsewhere. Many thanks for a second great answer from you, it was quite kind! –  Stetson RDT Jun 26 '11 at 0:46
    
Having the computer offline for an extended period of time is not the same as running a deep power cycle as I described in my answer. As far as cooling is concerned, that doesn't normally take very long, and the power supply's fan should be more than sufficient to prevent it from overheating. If the deep power cycle doesn't resolve it, then from a cost-perspective I'd try ruling out the power supply before replacing the motherboard (which would be my third assumption of where the trouble is coming from and is in agreement with @KCotreau's comment). –  Randolf Richardson Jun 26 '11 at 0:46
    
You're welcome. I hope your stuff doesn't get hit by lightning again. –  Randolf Richardson Jun 26 '11 at 0:48

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