PC will not power on at all

[slhardware]

I have a PC with an old Abit KT7-RAID motherboard that doesn't power on at all when I press the power button. The PC worked fine before I shut it down when I went on a 3 week vacation, and then when I got back it wouldn't power on at all. I found that the CMOS battery was dead, and I replaced it, but it still won't power on.

I have removed most of the components from the motherboard. The only things plugged into the motherboard right now are the PSU, 1 stick of RAM (removed the other 2 sticks), the CPU, and the CPU fan. Touching the 2 power switch pins with a screwdriver isn't doing anything - nothing powers on.

I have tested the power supply with a PSU tester so I know that's not the problem.

On a few occasions a few days ago, pressing the power button resulted in the motherboard powering on for 1 second and then shutting down. But now it won't even do that anymore.

What should I try next? Would I be able to hear any POST beeps if I removed all the RAM and also the CPU?

Is it worth removing the CPU heatsink and applying new thermal paste? It's been several years since I did that. I hesitate in doing that because this particular heatsink is difficult to remove and put back on - I destroyed a CPU once doing it.

Should I remove the motherboard from the case and test it?

 

[thx1138v2]

I would break the entire machine down into its component parts.

Remove the motherboard before removing the CPU. That should make it easier to remove/reinstall the CPU/cooler without damaging it.

While the mobo is out and the CPU is off also remove the chip set fan and redo the thermal paste there.

While it's apart blow out the case and all of the connectors with canned air.

Take the cover off of the PSU and clean the inside. I know you said it's working OK but if it's old you might have a problem when you fire it back up under load.

Clean all circuit boards with +90% alcohol including the back of the mobo.

I'm not familiar with that specific mobo but some motherboards require grounding to the case to work properly so remount the mobo in the case, the CPU, and the RAM module before testing. I did have an ABit a long time ago that required the case grounding to work but it wasn't that model.

You should hear beeps if you have a case speaker attached and you power it on without RAM. If not, it may have finally died.

Look for any bulging and/or leaking capacitors on the mobo and PSU when you are cleaning them. If you know how to use a soldering iron, they are usually easy to replace but you have to have the same capacitance and the same or higher voltage rating.

https://www.google.com/search?q=bulging+motherboard+capacitors&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwjB27mayq_VAhUi6oMKHYKaD2IQsAQINA&biw=1024&bih=644

 

[slhardware]

I did all that and it still won't power on.

There are no bulging capacitors, in fact, 11 years ago I sent this mobo to badcaps.net to have all the capacitors replaced.

So either the mobo or the CPU died, but how do I know which one?

 

[thx1138v2]

I did all that and it still won't power on.

There are no bulging capacitors, in fact, 11 years ago I sent this mobo to badcaps.net to have all the capacitors replaced.

So either the mobo or the CPU died, but how do I know which one?

You have to use a known good CPU to test the mobo and a known good mobo to test the CPU. But it could be both.

Sorry for the delay replying. Vacation.