shutdown or power supply?

[jsilveira]

Hi,

I recently noticed that a few times when I pressed the power button on my pc, nothing happens. At first I suspected it to be my power supply, however I turned everything off, change outlets and rebooted, everything worked fine. Then I opened my pc, and realized I had not cleaned it in ages, there was alot of dust accumulated everywhere, including my video card fan. I would like to know whether this might have over heated the mobo, and by default caused the computer shut down? Or could be a faulty power supply?

thank you.

 

[torandson]

hi,
I don't know if this is relevant to your case or not, but it is food for thought.

Recently the power suppply on an aging e-tower system began to emit a terrible screech. So I went to a local computer store and bought a replacement power supply. That power supply was made specifically for e-tower machines and is much smaller than a standard AT power supply, so it is significant here that the supply was presumably compatible with my system.

But after I installed it that proved not to be the case. The first time I turned it on it worked fine. The following day, when I hit the power switch, it did nothing. I repeatedly hit the power switch, plugged and unplugged, it and eventually, it came on, so I backed up my system.

Then I turned it off to see what would happen. Again, pressing the power switch did nothing. This time, repeatedly pressing it did nothing. So I reinstalled the old power supply with the noisy fan and the machine powered up instantly when I hit the switch.

I took the replacement back to the store, and it was tested to be good. "But it doesn't work in my system" I protested and got a refund. I bought a 99 cent fan at a local discount store and filed its plastic housing till it fit (backwards to get the air flow in the right direction) in my power supply, and put my old power supply back in my system. It works fine.

The lesson is, I believe, that the voltage which is detected by the front panel switch determines whether or not the power supply comes on. I had been told by the tech who insisted that the power supply he had sold me was perfectly good that my motherboard was bad and needed to be replaced. However, I am writing this possibly useful tale to you on the very system with that very same motherboard and old power supply working just fine. No hardware problems here at all.

I believe there is a question of the voltage at which the motheroard detects the power switch, and the voltage that the power supply feeds to that detection circuit. In my case I have proven, at least to myself, that two components both of which are operating reliably in specs as designed, may not be in agreement about what the front panel button is doing, and age is a likely source of change in electronic components and voltage levels.

The voltage from the wall socket, the power supply, and a motherboard resistor are all prime suspects. Replacing the power supply might be a good idea. A bad power supply is a disaster, and the system is not worth trying to save money in that area. Having said that, though, my solution was a 99 cent part. Go figure.

--torandson