Re: Computer turns on and then just dies

s|b <[email protected]> wrote:

> I've got a computer I haven't used for some time. I took out a hdd (D:)
> and left it alone. I'm trying to get it to work again, but it just dies
> on me. I've reinstalled the missing hdd and replaced the BIOS battery.
> 
> When I flip the switch of the power supply the standby power led on the
> motherboard (ASUS F1A75) turns on, stays on for a bit and then dies. If
> I then try again, nothing happens. I have to turn off the power switch
> (power supply), leave it off and then try again. I can get in the BIOS
> shortly (all fans are blowing) and then power's gone again.
> 
> I checked all cables and they should be fine. What could be causing this
> and how to solve?

After replacing the CMOS battery, did you reset the CMOS table (to avoid
corruption of its settings, and restore them from EEPROM)?

When you apply power, do the fans spin, especially the CPU fan?  Or do
they just wiggle a little, and stop?  Or not spin at all?

Used air cans to dust out the inside, like the heatsinks on the CPU and
GPU?  If those are filthy, or not well secured to the CPU and GPU, or
the thermal paste has dried out, the heat from the chip cannot get
dissipated from the heatsink (which needs air blowing over it to remove
the heat fast enough).  Thermal protection will shutoff the computer if
temperatures of the chips get too high.  If you have any cables in the
way of air flow over the heatsinks, you need to move the cables out of
the way.  Cooling requires drawing inside air, so the inlet of air into
the case is needed.

When powering up, also check the PSU fan spins.  If not, it also has
thermal protection.

If this isn't a really old computer using an AT-style PSU where the
Power switch was hardwired into the PSU, but is an ATX-style PSU where
it still supplies some power (3V standby) to the mobo to power the
onboard logic for powering on, and to where the Power switch goes to the
mobo, have you tried shorting the PS-On signal on the mobo header to
where the Power switch connects?  For ATX, the Power switch goes to the
mobo instead of the PSU.  It drops the PS-On line to ground which
signifies to the PSU it should come fully on.  On the cable going to the
mobo from the PSU, the PS-On signal is the green wire.  With the PSU
cable connected to the mobo, you can use a couple sewing needles to
press into the backside of the cable connector, and cross the needles to
short the PS-On pin to a Gnd pin.

https://en.wikipedia.org/wiki/PS-ON_Signal
https://www.smps.us/atx-pinout.png
Pin 16 (green) = PS-On
There is a ground on both sides of the PS-On pin.