Another Puked 'Puter- PSU failure.

No, this time it's not mine!

My parent's computer puked up the old "Disk Boot Error" yesterday.

Now, i've warned them every time I visited them that their power supply was falling pretty low on the voltages- +12V was at 11.5, +3.3 was at 2.8, +5 was at about 4.5 etc.

Now, I Warned them that when a PSU blows it can damage *everything* so I'm also prepared for broken memory and drives. The question is, can an undervoltaged hard drive become physically damaged because of this?

(Yeah, i know, it's more likely the PSU blew and forced a crapload of V through the system at that point, too.)

Just wondering weather its worth repairing or should I just say that it's likely been damaged?

> can an undervoltaged hard drive become physically damaged because of this?

Most definately if the voltage dropped while the HD was writing, and the head may not have parked properly. However, more often than not the HD will simply have had its master boot record fried and be fine after a re-format, so don´t panic just yet.

Anyway, if the PSU is gone, swap it out (dead easy), and fire it up. If windows has been fragged, best thing to do is try to reinstall XP (or whatever) and try and format the HD. If it formats ok the HD is likey going to be fine. XP´s formating is fairly sensitive/flakey and pukes up errors at the drop of a hat.

Getting a "Disk Boot Error" is not evidence there is a problem with the PSU, and neither is multimeter voltage readings that are slightly off what's expected.

Those voltage readings sound fairly typical, and unless you have a good quality, calibrated multimeter, it is likely to not be more accurate than that anyway.

What, beside the low multimeter readings that you've been seeing for some time, leads you to believe that the PSU is even part of the problem?

The voltage levels have noticably dropped over a period of a few months, and during that time the system stability dropped too. This machine used to be one of my own a few months back, before I moved to the flat.

At one point the voltages were showing as particulary low (+3 was at +2 etc) and the system would just turn off- sometmies failing to turn back no again.

I agree it's unusual for a PSU to do this since when it starts to fail, normally the voltages will rise :)

Either way, I can and will fix it, i will change the PSU anyway, I just don't want to have to bother with a hard drive again- but if I must then I must. *sigh* Yet another XP reinstall!

[edit]

Aparently, their computer is working again now.

What you are describing could be something overloading the power supply.
Try (with power off, of course) disconnecting the PSU from the motherboard (so it has no load), and check the voltages then.
If the readings seem more normal then, try reconnecting the motherboard, but disconnecting everything else. Keep at it one thing at a time.

It might not be this at all, but it certainly could be either simply too much draw on an undersized PSU, or one faulty device that is draining current from an otherwise perfectly fine PSU. If this is the problem, the above tests should help identify the source.

Good luck!

Mark.

Heh it's a 250W PSU. Youch!