Computer won't turn on Part II

[dredd2929]

OK, I celebrated too early.

I went to turn on my PC today, and again, nothing. The eerie thing about this is that it will be working just fine and then out of nowhere it won't turn on. The last time I used the PC was Saturday and as I said, no problems. The motherboard is brand new (ASUS P5Q), which is what I identified the problem to be last time this happened (last MOBO was ASUS A8N SLI Deluxe)...but maybe that wasn't the problem??

Any ideas?

 

[dredd2929]

The plot thickens.

I just got the PC to turn on, but I'm afraid of letting something go unresolved. I unplugged my PC from the APC battery backup and plugged it directly into the wall. I pushed the power switch and nothing happend, except for a faint clicking coming from inside the case. I turned the switched the switch on the back of the PSU off and on, and the computer turned on! This APC unit is old (+ 3 years), so I'm thinking maybe the motherboard (or PSU?) didn't like something about the current it was getting from the APC.

What do you guys think?

 

[Flipped Gazelle]

Try another PSU?

 

[dredd2929]

I just tested the PSU and it works fine.

The computer was on for a while, and I walked out of the room for a few minutes. When I came back the computer was off, and the power LED on the case was blinking (which I thought was really weird). I pushed the power button again, and the computer turned on, but no display came up. I turned the computer off, and tried turning it on again, and now it won't turn on at all.

That's where I'm at right now. My PSU is a PC Power and Cooling 510 SLI.

I had this exact same problem about 1 month ago. I tried stripping the PC down to just the motherboard and PSU (and CPU and RAM). The PSU tested good, so I assumed it was the motherboard. I replaced the motherboard (along with a new CPU and RAM since my previous board was a socket 939 and new one is a socket 775). The new build worked perfectly for a month. Then this morning I go to turn the computer on, and exactly like before, nothing happens.

I tried shorting the pins on the motherboard that the power switch connects to, and it didn't turn the computer on, so I don't think the switch is bad. The only explanation is the MOBO is bad, at least that's the only think that makes sense to me. I just can't help thinking there's something else going on that's causing the motherboards to go bad.

I was thinking it might be my APC battery backup. The battery is over 3 years old, so maybe its starting to feed some noisy current to the system. I assumed that PSU would filter it, but maybe it only filters to a certain degree that is insufficient to prevent a failing battery from damaging the motherboard.

Does any of this make sense?

 

[Ileader36]

Try an entirely different PSU, I had a Antec Smartpower 2 500w on my old system, worked perfectly.
In the new system would occasionally get no boot at all, and the more I oc'd the cpu the worse it got.
Vrails were good too, new PSU fixed it.
Borrow one if You don't want to buy a new one straight away.

Can You see what the capacitors look like in the PSU, if bulged or leaky then it is no good.