[Tfug] Power Problem (slightly OT)

[Choprboy]

On Tuesday 22 January 2008 12:52, Jim Secan wrote:
> I had to power down my server to recover from a lock-up (long story).
> Once it was powered down, nothing I did would entice power to come back
> on.  No sparks, no burning wires, no noises, just no power to anything.
> Tried all combinations of switches and plugging/unplugging with no change.
>  Tried new power cord, different outlet, no change.  OK.  Just went
> through the joy of replacing the power supply.  Same behavior.  I'm at a
> complete loss as to what's going on.

Well.... given that it is an ATX powersupply, the front power button may not 
actually do anything other than send a signal to the motherboard BMC which 
should always be powered off the +5Vsb rail. There are really only 2 possible 
components at fault; the power supply itself has died (possibly kaput or the 
+5Vsb rail is dead) or the motherboard has a problem (died completely or the 
BMC is locked up).

I would first start by completely removing the power cord and let it sit for a 
few minutes to discharge, then plug it back in. If the BMC is locked up, that 
should reset it (as it never otherwise powers off).

Second, I would check the +5Vsb rail with a voltmeter, I think its the purple 
wire, but don;t remember off the top of my head. That should have +5V on it 
at all times (when plugged in), if it doesn;t then the PS is kaput.

Third, and finally, if the above all checks out, then I would momentarily (a 
second or so) ground the PSON wire (green I believe) with a paperclip to one 
of the black PS ground wires. This should cause the ATX power supply to turn 
on. If it does turn on, then it sounds like the motherboard has lost its 
magic smoke (which might coincide with your lockup). If it doesn't turn on, 
then your PS has a fault.

Adrian