PC won't turn on but not a power supply problem? Please Help....

[vladimir.mcbadger]

I'm completely stumped by this one - I have 2 old pentium III 1ghz
computers and I wanted to swap the power supplies over as one was
quieter than the other.

The only difference between the 2 power supplies was one was the new
one had a total output of 135w and the old one was 125w. I swapped
them over and it turned on and booted up for about 25 seconds but then
the screen went blank, the fan on the CPU stopped spinning and the only
activity was a green LED on the motherboard.

I turned the PC off and then it wouldn't turn on at all. I checked the
new power supply and the fan doesn't spin when I put the power cable
in, thus indicating I may have managed to kill it.

I have now put the old working Power supply back in and the fan spins
when power is attached but the pc won't turn on. Is there a fuse on
the motherboard I have may have blown? or have I blown the whole
motherboard? Any suggestions on what I should do?

Thanks in advance

Andi

 

[Mike T.]

I'm completely stumped by this one - I have 2 old pentium III 1ghz
computers and I wanted to swap the power supplies over as one was
quieter than the other.

The only difference between the 2 power supplies was one was the new
one had a total output of 135w and the old one was 125w. I swapped
them over and it turned on and booted up for about 25 seconds but then
the screen went blank, the fan on the CPU stopped spinning and the only
activity was a green LED on the motherboard.

I turned the PC off and then it wouldn't turn on at all. I checked the
new power supply and the fan doesn't spin when I put the power cable
in, thus indicating I may have managed to kill it.

I have now put the old working Power supply back in and the fan spins
when power is attached but the pc won't turn on. Is there a fuse on
the motherboard I have may have blown? or have I blown the whole
motherboard? Any suggestions on what I should do?

Thanks in advance

Andi

OK, after donning my protective body armor, I think it's safe to point out
that it's quite common for a power supply to die and kill a mainboard in the
process. If it's any consolation, the power supply would have died soon
anyway, so you didn't kill it. -Dave

 

[vladimir.mcbadger]

Is there any way I can check if the motherboard is still alive before I
bin the lot?

 

[DaveW]

There are NO fuses on a motherboard. Either your PSU or your motherboard
has expired.

 

[Robbie McFerren]

There are NO fuses on a motherboard. Either your PSU or your motherboard
has expired.

While you are right, there are no fuses in the main power lines, I must
correct you for the record, USB ports have a special type of fuse. They
are polyfuses which will heal themselves (an overcomplicated
self-resetting circuit breaker). Other devices will have fuses also.

 

[Dave]

Is there any way I can check if the motherboard is still alive before I
bin the lot?

Yes, but you've already tried a known good power supply. Unless you screwed
up a connection somewhere, the mainboard should boot. -Dave

 

[vladimir.mcbadger]

As this is an old P3 motherboard am I correct in thinking that the
mainboard should boot as long as the big 24pin connecter is attached to
the motherboard? I didn't mess with the actual power button connector
so that should be ok - I can't see anything I have missed - could there
be something I have missed?