ROBOT.LK

I have problem with my PC. I will try to explain it as good as I can.

Suppose that I have left my computer off(not connected to mains) for about 8 hours, and then try to turn on after providing mains. And after turning on mains supply from UPS, when I press power button on computer the power LED turns on and then turns off instantly. Then for few seconds, computer does not turn on for few seconds (about 10 seconds) no matter how hard I press the power button. After about 10 seconds it turns on. I tried to check the power good signal with multimeter because i am worried that it might be just wired to the +5V lane without having proper monitoring circuits since my power supply is a cheap one.

But power good goes to +5V after pressing power button. I am thinking of buying a Cooler Master power supply. But I am not sure if this is a problem with the motherboard.

One of my friends had this kind of problem. We had to keep it in the sunlight to heat up in order it to boot (a loose joint for sure).

I am just writing because i want to know if there is anyone with similar experience.

I will try to check it again tomorrow with multimeter, but I have a question. Is it supposed for the power good signal to be 0V when the computer motherboard is off(provided that power to PSU is supplied, motherboard LED is lit up).

Another thing to mention is that I heard another capacitor explosion sound from the computer. But could not find any exploded capacitor on the motherboard,sound card or the PSU. And I am not quite sure if this problem started after that sound.

First thing you should do is to remove dust on the motherboard and power unit using a blower. In the rainy season, the dust that are stored inside the power unit used to get wet and spark between the casing and power source. You might have heard this sound. So clean the whole unit first. Secondly disable any power management setting on the BIOS to be sure that there is nothing set in there. It would be better if you could use Load BIOS defaults to be sure on that.

I do not let the computer to gather dust inside. I apply pressured air with the blower about once a fortnight, and regularly clean the fans, vents, heat sinks etc. There is virtually no dust on the motherboard. No dust on the RAM or sound card.

But cleaning the power supply is less often because it requires more screws to be removed.
There is no any thermal issue with the computer, CPU is running cool, the NB and SB too. Anyway this is a four years old computer. And this is the first sign of problem I am having with it except the graphic card I removed about 3 months ago.

Anyway I will try cleaning the power supply today. However I am to throw that cheap metal away soon and go for a Cooler Master 550Watt or 650Watt. Just wanted to figure out what is wrong with this thing.

I cleaned the power supply. Removed dust from top and bottom sides of the power supply. But the problem still exist. To reproduce the problem, I do not need to wait 8 hours. Seems like 1 hours is enough.

I saw that the PWR_OK wire is attached to a LM339. So it is not just attached to +5V rail. So my guess is that there should be some problem with stabilizing the voltage of the PSU. Also I saw two capacitors with rounded tops.

According to your description, it seems you need to change the power supply. Further usage might even damage the motherboard. So better change it soon.

I am going to buy one next month. This time a good one. Now I am on the laptop with MeeGo. .Cool OS by the way.

The problem is gone away after removing the CMOS backup battery for few minutes. I am not sure if it was due to any power setting. Who knows. This motherboard takes about 1minute to POST if I leave my USB web cam connected during POST. I am really sick of this motherboard. It is from intel, by the way.
Buying a good one from ebay is scary. I have fried 3 motherboard by tinkering with them. But got all three covered under warranty.

It would be better if you could use Load BIOS defaults to be sure on that.

If you have done this as I said before, you would have made it working without removing battery.
Anyway lucky that you finally got it working.

Anyway thanks for the ideas.I still do not have any idea about the fault. Could be some corrupted configuration setting.

I am going to move to an Intel Sandy Bridge when AMD releases its Bulldozer. Intel might cut the sandy bridge prices. They are very energy efficient. If I could get hold of a Bulldozer, i will go with that. And graphics also from AMD.
My target is to build a computer system that would use about 50Watts when idle(without monitor, hope to go with an 18Watt LCD). This PC is drawing lot of power.

Even after clearing CMOS settings, the problem came back after few days. I bought a new power supply today. This time it is a good one considering the old one. It is a Cooler Master RS-460-PCAR-D3, a 460Watts power unit. Now the problem seems to be gone.
http://www.coolermaster.com/product.php?product_id=3686
Only thing is that it does not have PFC. Do not have much money to spend on a power unit. I think they are expensive since shipping charges are high. The power unit i bought is lot heavier than my old no-name one.