Computer not starting - help needed



So I have put together a computer for my father. It’s a P4 Prescott, socket 478, Abit IC7-G mobo, 400W Mercury PSU, 1x NEC DVD-RW and 1x WD1600JS, with Radeon 9550, 2x 512 MB RAM. Now this computer worked flawlessly till the summer 2007. Then I took it apart and set up a new computer for me in the same housing. I have basically put together my old computer but as soon as I press the switch it does nothing.
If I remember correctly there was a red LED that went on when the mobo got power. I can’t see that anywhere. I was checking the voltage of the battery and it’s 3.00V. I really don’t know if that’s normal. All power supplying units (in this case batteries) have a bit higher voltage that labeled when they are new. Should I get a new battery? Can a computer still boot with battery? The battery should be CR2032H 3V.

I also tried to clear the CMOS and it does not help. I have cleaned most of the dust on the mobo and PSU so that couldn’t be that much of a problem.

I also checked the PSU’s voltage on +12V (yellow) and COM and it reads 0.14V which is somehow confusing.

Any help? Please! My old man is really looking forward to start browsing and googling. :slight_smile:


I also forgot. If I turn the PSU on and after a while I switch it off there’s that silent ‘buzz’ almost like normal mobo would do, but sounds thinner and quicker. This of course is not happening if I unplugmain ATX power connectors from the mobo. So power goes somewhere but why am I not able to turn the PC on?


Reading your question is confusing which computer are you referring to having the problem #1 or #2 or #3??? Did you make sure you follow the directions to plug all the right connectors in the right spot and make sure all connections are seated correctly? Some PS have on/off switch on them.


Are you sure that you that you have all the wires connected right?

Download the manual and make sure.




You might want to tear the whole system down again and put it back together. Before locking the cpu lever put a good amount of finger pressure on it, then lock it down.


I’d say that you either have a short circuit, bad PSU or have killed one/some components. :wink:


We are talking about computer #3 all the time.

The mobo and the CPU (along with the cooling unit) was not taken apart. I have stored that assemled on antistatic bags in my closet. I just put the mobo back into the housing and reconnected the wires (I have Abit’s layout sticker on the housing panel so I am pretty sure I have connected everything right).

If CPU was bad or not in order, the mobo should start anyway. Unless you have power and a mobo I should at least hear a click or something.

One of my friends pointed out it could be a bad PSU.


MAke sure the power switch connector is correctly connected to your motherboard (use platinumsword’s link for the manual), and make sure that the power supply has 5v standby voltage when the power supply is on (even if the computer is off and the power supply hasen’t powered up).


Well I tried that now. When the connector is unplugged (PSU switched on) it reads 5.1V between purple and ground. When connected to motherboard the voltage is around 1.7V between these two. I don’t think that drop is normal.


It sounds to me like either something is shorted on the motherboard, or most likely, a bad power supply. You are right that it shouldn’t drop like that.



Actually is really silly to say this. After 18 years of dealing with computers and fixing numerous of them I couldn’t help mine! So I took it apart and threw the mobo out and there it was! One mobo spacer too much and it shorted!

I really don’t know how did I miss that one. I was pretty sure to check the layout twice last week when I was putting all together.

The PSU works fine. The short was right behind the power switch connectors. I jammed that lower portion of the mobo when I was measuring the voltage 10 minutes ago and suddenfly the small led flashed on the mobo and fans turned half way. Then I realized what went wrong.

Thank you guys for pointing out great solutions and info! You sure saved me a lot of time in future. :slight_smile: