General hardware question

  wotbus@ 08:11 16 Jun 09
Locked

Fault finding a completely dead computer.
At what point do the fans come to life?
The PC on/off switch shorts two pins on the mobo which, I think:
Routes power to the FANS?
Can anyone post me a link to a step by step event sequence of events for nomal boot up?
Final question: Will a PC boot without a CMOS battery?

  ened 08:17 16 Jun 09

If the fans obtain their power direct from the psu and the psu is working then yes the fans will start up as soon as you hit the power button.

They will also start if they are controlled from the mobo so long as ther mobo is working.

I have never tried to boot without a cmos battery; I would imagine it is possible but you would have to reset the bios on every boot!

  Fruit Bat /\0/\ 08:24 16 Jun 09

If no fans / leds / hard drive noise, then check:

plugged in
cable / socket ok
fuse ok

then PSU dead.

  wotbus@ 09:02 16 Jun 09

Thanks all.
I have confirmed the PSU is dead by trying it on a good PC.
I have fitted a known good PSU to the dead PC and still completely dead.
I suspect the mobo is dead, given the owners description of what happened:-
"I opened the case and saw a wire hanging and thought it had dropped off so I plugged it into the nearest place which looked correct"...
The lead was a power (flat 4 pin of the type which powers some PCI cards) and had been plugged on to the mobo at a USB port connection.
I can understand this frying the mobo but would it ace the PSU at the same time?
It seems the PC had been playing up before which is why the owner decided to open the case.
I have already ordered an upgrade kit and PSU and will re-build his PC for him (the HDD is OK as is the VGA and Sound Card).
Fruit Bat /\0/\ - do you mean domestic fuse or is the PSU fused somewhere?

  Quiller. 09:06 16 Jun 09

Yes.

I have an old P111 desktop that I have never got round to put in a replacement cmos battery. I took out the old one to put in another machine and never renewed it.

  wotbus@ 09:13 16 Jun 09

Thanks BSOD. Most of my questions are acedemic as the computer will be re-built, but I really like to know and find out things :-)

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