The thunder storm broke my media pc...

[Simon Ryley <simon.ryley@xxxxxxxxxx>]

Hello all,

Had a lovely thunder storm in the Midlands on Saturday night, which
caused a power cut in our area overnight.

The following morning my media pc refused to turn on.  It's usually in
S3 standby, and a quick prod of the power button wakes it up so I can
watch Freeview through its tuner cards.  Even unplugging the power lead,
leaving it 5 minutes and plugging it back it failed to wake up.  (Which
it should do, as the BIOS is set to boot the machine automatically after
a power failure)

Last night I had a chance to look at it.
The ATX power supply in the machine is providing some juice, as the two
red leds on the back of my freeview cards turn on when the PC is plugged
in (as they should)
The power switch checked out ok with a continuity test across the pins
on the motherboard.
Following a google on power supply testing, I shorted out the green and
a black wire on the 20 pin power connector, and everything turned on.
It booted ok, and was perfectly happy.  Until I unplugged it to put it
back by the TV.  When it refused to turn on again (After I had put all
the covers back on as well!)
The only way I could make it wake up was to short out the green and
black wire again.

I did some more testing, and everything works ok, it will reboot,
standby etc as long as the power cable is not removed then plugged back
in.  If it is, I can only start the pc by shorting out pins in the power
connector.

Obviously something is wrong, but I don't know where to go next.  Is it
likely to be the motherboard or the power supply?  The power supply is a
custom Antec one to fit the case, so its not a simple job to replace it
with another standard ATX power supply.

Can anyone advise any further testing before I start buying new
components.

TIA,

Simon