On Oct 28, 8:55*am, UCLAN wrote:
Al wrote:
I have got a mobo here that is dead. I have done all the usual stuff
like trying new PSU, bench testing etc. Its dead - as in no fans, no
nothing when you hit PWR button - PSU doesnt even come on.

I connected the ATX molex from the PSU and shorted Green (PWR ON) with
GND on the molex and the PC came on. All seemed fine.

I think there is a IC on the motherboard between the PWR BTN headers
from the power on switch and the ATX header on the mobo that tells PSU
to start up.

The MB circuit only tells the enable circuit inside the PSU to let the
PSU turn on. To what voltage does the PWR_ON (green wire) fall when you
push the ON/OFF switch? The MB must pull this wire lower than 1.5v for
the PSU to turn on. I have seen enable logic failure modes where, for
example, 1.2v would not turn the PSU on, but 1.0v would. Check that
voltage level before replacing any ICs on the MB.

When I hit the pwr button that voltage level doesnt change.....(and
the switch is fine)