Very strange power problem

jimmynaetroots

jimmynaetroots

jimmynaetroots

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Joined
18 Oct 2002
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Hi guys,

one of my colleagues asked me to take a look at his PC tonight and I am completely stumped. It is based on an ABIT AN8 Ultra Mobo and the problem is this:

When you do a shutdown, the PC shuts down as normal and all the power goes off - however, it then after anything from 2 to 10 seconds makes clicking noises, and powers itself up again... I have NEVER seen anything like this before and google is no help - anyone any idea what the problem could be??

Thanks

G.
 
Probably the board, possibly the psu.

When a pc is off its not really off unless you turn it off at the wall, its in standby, and theres some logic on the board which can give a signal to the psu to start up. Presumably this logic is broken.

Have you checked the bios for anything that might cause this?
You can set some pcs to come on at a certain time from the bios so its definately possible that some setting in the bios could start it up.

The clicking noises are a bit wierd. Do you still get clicking noises if you switch it off at the wall as soon as its shut down?

Are you sure its actually shutting down and isn't getting stuck waiting for the disk to park its head or something? This seems possible and would explain the clicking.

Can you open it up and locate the source of the clicking noise?
 
Joe42,

Thanks for the reply. I have been through the BIOS and disabled all the things that could boot up the PC with no success. I opened it up and the clicking seems to be coming from the hard drives. It is definitely powering right off, everything goes completely silent, and after anything from a few seconds to several, the clicks start. Usually there is one click and it powers on, sometimes there are 5 or 6 clicks. There are 2 drives so I will try disabling one then the other and see if it makes any difference.

Wsa thinking it was the mobo myself but thought I would ask on here before I recommend him to shell out for a new mobo!!
 
Try swapping the disk thats clicking. I reckon its failing to park the head. Although why that would cause it to start up again beats me.

Another thing it could be i suppose is a dodgy harddisk controller... but that doesn't control head parking i don't think.

Does anyone know what the exact procedure is before the bios/board shuts the power off?

I'm guessing there must be something like a reverse post where it waits for the disk to report that its head is parked before it sends the signal to the psu to shut off power... so i suppose in the event that the disk does not return that signal it must not cut the power because that could mean the disk looses data, so i suppose it must be programmed to keep power and then do a restart.
If i was designing some logic like that i would have it emitt a beep code if the head didn't report that it was parked after a certain timeout period, rather than restarting... are you sure it doesn't emitt any sort of beep code before it starts booting up again?

Of course this is all just guess work and some logical thinking... ;)


I'm pretty sure you're going to have to get your hands dirty and swap some stuff around i'm afraid.
 
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