PC will not power up

[Frank]

A client brought his pc in for routine cleaning. When I plugged it in and
pressed the power button nothing happened. I checked the following:
checked the outlet / replaced the cord / swapped power supplies / removed
all cards / reseated the power supply plugs on the MB / removed the MB and
attempted a power up / jumpered the power switch pins on the MB.

Here is the kicker: I reinstalled the MB let it set for about an hour then
it booted up. When I shut it down the same no power issue came back. Any
ideas?

 

[R. McCarty]

Maybe a cracked trace or run on one of the internal layers on the
motherboard. If you remounted it that might have applied enough
pressure to force it closed. However, after powering up the heat
would cause it to re-open. I'm assuming you tested the front panel
switch or manually shorted the header Pwr-Switch pins.

 

[ron]

Do you own a Multi Meter?
If so try measureing some voltages to see where you are
losing the mains volts.

You may have to even look inside the power supply.
Careful....there are 400 volts in there.

Tech's just replace.....not repair any more.......
Its a throwaway world.................sigh............Ron

 

[jonah]

A client brought his pc in for routine cleaning. When I plugged it in and
pressed the power button nothing happened. I checked the following:
checked the outlet / replaced the cord / swapped power supplies / removed
all cards / reseated the power supply plugs on the MB / removed the MB and
attempted a power up / jumpered the power switch pins on the MB.

Here is the kicker: I reinstalled the MB let it set for about an hour then
it booted up. When I shut it down the same no power issue came back. Any
ideas?

Sounds like a MOBO failure to me, dry joint, cracked tracks something
similar. Can you try the MOBO in a known working PC just to boot up
and rule out the rest of the components? It does not have to run just
prove it will power up or not.

Taking it out and putting it back in probably jiggled it back into
action temporarily but on shutdown something as minor as the fans
stopping can cause enough shock to screw it up again. One thing you
could try is an aerosol freezer, sprays liquid nitrogen onto a circuit
board and temoporarily fixes dry joints and cracks, crude but it can
prove a faulty area of a board, but even if you get lucky and find a
fault the odds on you being able to fix it without causing even more
damage are very slight.

Jonah

 

[Frank]

Thanks for the replies on this. I suspected a MB problem from the start.
Just wanted other opinions.

 

[-rwxrw-r--]

Do you own a Multi Meter?
If so try measureing some voltages to see where you are
losing the mains volts.

You may have to even look inside the power supply.
Careful....there are 400 volts in there.

Why would he? He already stated that he swapped the power supply with the
same results.