Problems with PC after power surge

Posted on 2006-06-22
Last Modified: 2008-01-09
A non techy mate's pc 'stopped' working after a power surge at his home, he asked me to have a look as it would not boot without hanging and could not enter BIOS. He brought it round to my place and plugged it into my kvm switch, it booted enough for me to initiate a scandisk which revealed:  "first allocation unit is not valid" errors. Scandisk fixed these. I then run the machine, rebooted etc on and off for 24 hours with no problems. I checked it with his mouse and keyboard, and other than an apparent fault with the ‘del’ key not working (hence could not get into BIOS) it seemed fine. Apparently fixed I gave it back. When he got it home he said ‘it was the same as before’ still had errors and he had had to turn it off at the plug. He brought it round to mine where, once again I connected it to a kvm switch, turned it on, allowed it to go through its disk check (its FAT32 so it would scan after a switch off at the mains) where it found one "first allocation unit is not valid" error and then worked fine. He took it back only to bring it straight back saying that he was getting a message ‘no support’ and a press F1 keyboard error. I tried it with a different keyboard but get the same error message. Seemingly the keyboard controller on the motherboard has decided to give up the ghost.

That still leaves me wondering where exactly the fault is and whether I should recommend a whole new pc, new motherboard, motherboard and PSU or what?

Any ideas?

Question by:PeteMulford
LVL 69

Expert Comment

ID: 16963222
A power surge is a non-trivial event to a PC.  It is likely that his power supply and/or motherboard were damaged and now must be replaced.  If he knows that these things happen fairly often, he should get a UPS to protect his equipment.

Author Comment

ID: 16963794
The surge apparently through the main trip in the house, dont know what caused it. So is it likely to be just the PSU and mobo, or could it also have damaged the memory and cpu? I'm concerned about recomending a simple mobo replace only to find something else like the cpu dies in a couple of days.

LVL 69

Expert Comment

ID: 16965459
The most probable outcome is that both the PSU and motherboard were affected.  In some cases, hard drives and video cards connected to the PSU were also damaged, but I can't guarantee that RAM and CPU were unaffected, they are just less likely to have been affected.
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Expert Comment

ID: 16965686
Just out of curiosity, does he have any USB devices plugged in at his house that you don't there?  
LVL 13

Accepted Solution

Watzman earned 500 total points
ID: 16965719
PC power supplies are very good at isolating surges, but there is often damage to the Power supply itself.  First thing I'd do is try a different power supply.  Also, you didn't mention it, but in my experience power surges almost always take out the modem, and I've seen more surges come in on the phone line than on the power line (but the modem is often damaged regardless), so if there is a modem card, PULL IT, at least for now.

Frankly, I wish you had not used Chkdsk to "fix" the hard drive.  A power surge won't change data on the disk drive (which isn't to say it can't destroy the drive outright, that is indeed possible), and it's more likely that the REPORT of the disk problem was buggy than that the disk data itself was bad, but using Chkdsk in such a situation can create a real problem where none was actually present (of course, this assumes that the hard drive wasn't physically damaged, and also if the computer was running when the surge occured, then damage to the disk structures is more likely than if the computer was off).

Beyond that, if the damage did get to the system beyond the power supply and modem, then every component of the system is suspect and you just have to test each piece one at a time (in my experience, damage is more often than not limited to the PSU and the modem, but certainly it can get out to the motherboard, memory, disk drives, etc.).

The final comment, of course, relates to the value of a UPS, which will generally prevent power line surges (and modem surges if the UPS has such protection (most do) and if the phone line is run through the UPS' phone line jacks (most users don't, even when the UPS has such protection).

LVL 14

Expert Comment

ID: 16966714
check the hard drive in another computer, if it still has problems there, it is more than likely bad & needs to be replaced

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