weird PSU issue today

suicidal_monkey · May 31, 2007, 03:42:32 PM

I've had one of those mornings... :g:

Decided to swap out my 9800pro AIW for my new passive 6200 (edging it further towards media centre duties) and got to tidying the cables and whatnot as they were a bit of a mess. Managed to unplug/plug-in the psu without unplugging it from the mains which briefly started the psu up. Anyway, no bright flashes, no hysterics of any kind ... but the pc wouldn't start up. :blink: Took the psu out, tried starting it up with a paperclip, nothing happens, though it does kind of make an electrical whine type noise. Then I ram a u-bent piece of paperclip across the green/black wires, plug it in and it starts up. I reconnect it to the motherboard, and although the psu is running and the fans are spinning the pc isn't booting. hitting the reset button causes the pc to reboot, I reset the BIOS...

But still the psu did not respond to the power button (via the motherboard). unplugging the mains, shorting the terminals with a paperclip and then re-plugging in the mains started the psu up though I had to hit the reset button to get the mobo to boot up, windows was fine, shut the pc down - fans carry on spinning as the paperclip is still shorting the grn/blk wires.

Not exactly sure what I did but I managed to acheive the right combination of shorting the grn/blk wires to get the psu going, shutting the pc down and removing the shorting-wire without messing anything up.

Seems to be okay now but I'm scared to open it up again!:doh:

Is there such thing as control logic in a psu that can get confused?

Gone_Away · May 31, 2007, 04:31:29 PM

dude you're mad.. There's no way I'd be messing with my PSU. If it's broke I'd get a new one.. not worth burning the house down for a couple of hundred quid..

delanvital · May 31, 2007, 04:40:50 PM

Oi that is weird. Basically, by attempting a jump start - but connecting wrong cables - you switched reset and power? Or something? :blink:

Anonymous · May 31, 2007, 04:42:23 PM

I always use one of these:

http://www.scan.co.uk/Products/ProductInfo.asp?WebProductID=391645

suicidal_monkey · May 31, 2007, 04:56:00 PM

actually I used one of these to check the voltages and button connections and suchlike having jump-started the psu before plugging it back into any of the pc parts.

It wasn't that the psu seemed broken. No loud bang, not even a quiet pop, no burnt smell or smoke, not even a satisfactory spark or proper electrical buzzing. Just a faint high-pitched whine as if one of the transformers in the switching circuitry was going a little haywire at worst. It just suddenly refused to co-operate with the motherboard (and vice-versa). It seems fine now - almost as if some circuit/capacitor got gently zapped and sort of "forgot" it was supposed to respond to the motherboard (or the motherboard needed to reset its power control or something)

Also it's not a normal ATX psu being a flat htpc-like case, though there's room enough to attempt some modding on that front at a later date if need be.

PSU is fine now, still don't know what tripped though

Anonymous · May 31, 2007, 05:02:35 PM

Sometimes unplugging the power supply from the PSU and then turning on your PC will drain all stored charge and "reset" things. Its worked for me more than once and is a darn sight safer than paperclips

suicidal_monkey · May 31, 2007, 05:32:21 PM

paperclips work fine so long as you know which pins to use, don't slip, don't drop aforementioned paperclip ont o the motherboard, ...okay not quite so safe

. I'll try remember to do all the simple things first next time

Perhaps my new pc won't have a weird psu size...

suicidal_monkey · June 03, 2007, 04:48:16 PM

managed to sort of re-create the psu problem.
If I unplug the mains from the psu for a while it then fails to respond when I've plugged it back in.
Maybe it's the bios/battery on the motherboard?

Anonymous · June 03, 2007, 05:18:53 PM

If it is the BIOS battery then all of the existing settings should be back at default when you do get the PSU to power up. If it is retaining settings then its not the battery. i can think of 2 things either your PSU has been damaged or your PSU has damaged your MB when it went pop.

suicidal_monkey · June 03, 2007, 10:16:20 PM

If I unplug the mains from the psu for too long the problem returns. I have to unplug the psu from the mains, put a short in place from the green-to-black, plug the mains in. This fires up the PSU and starts providing power, though it doesn't seem to boot the motherboard (that could have been the gfx being dodgy as per the other thread though - bad things come in threes right?).

In order to get things running:
unplug mains
put a short across the green and black
plug in mains (psu/fans/etc power up but no boot afaik)
cleverly hit reset and remove the green/black shorting piece (or something similar)
then everything runs okay until I next unplug the mains for too long.

I think I got bad BIOS checksums after this but whether it's the battery or a buggered BIOS...hopefully just the bios being bad but would that really prevent the motherboard from starting the psu etc when the "on" button was pressed?

One problem half-got-round, one (or two?) more to go...

While the psu is plugged into the mains and the motherboard and has ben got going everything functions as per normal. The on switch turns it on, off, etc. No issues.

Anonymous · June 03, 2007, 11:43:37 PM

but if you leave the power out do you have to reset your BIOS? if not then the battery is fine.

Most BIOS you can reset to default values by booting up with either INSERT or DELETE keys depressed (usually INSERT).