Motherboard lightning victim dies hard

5

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 firmware 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.

Stetson RDT

Posted 2011-06-25T23:46:27.760

Reputation: 110

3It is almost certainly toast. – KCotreau – 2011-06-25T23:49:09.947

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 – 2011-06-26T00:11:18.390

This situation reminds me of this post (you did unplug, which is good): http://superuser.com/questions/287709/is-it-bad-to-leave-your-computer-on-during-a-thunderstorm/287711

– Randolf Richardson – 2011-06-26T00:17:49.790

1It 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 – 2011-06-26T00:21:33.313

1Make 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 – 2011-06-26T01:33:23.547

Thank you. That's an interesting idea, but I did take a look at the motherboard, and there was no visible damage (As a redneck, that's often what I look for first.) It appears that it was a lesser hit, but just as lethal to the system. However, thank you, that would be amazing if that were to be the problem! – Stetson RDT – 2011-06-26T05:36:26.787

Answers

4

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.

Randolf Richardson

Posted 2011-06-25T23:46:27.760

Reputation: 14 002

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 – 2011-06-26T00:26:05.650

1Thank 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 – 2011-06-26T00:46:32.787

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 – 2011-06-26T00:46:33.100

You're welcome. I hope your stuff doesn't get hit by lightning again. – Randolf Richardson – 2011-06-26T00:48:12.583

Asked: 2011-06-25T23:46:27.760

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