Weird MoBo problem

I have been working on PC's for 18 years. I have my A+, MCSE, and Network+ certs and I have NEVER seen (or heard [read below]) this problem. I turn the PC on. The POST screen comes up and tests the memory fine, finds the drives,etc. About 5 - 7 seconds after it finishes POST the keyboard locks up and if you have the case off you hear this high pitch whine, first in a medium tone, then it goes up a bit in pitch that last 2 - 3 seconds and the system shuts off. You can flip the power switch off in the back of the PC and back on and the push the power button on the front and the PC comes on again and repeats the same process. I first thought that the Hard Drive was going bad so I unplugged it and it did the same thing. I have removed and re-seated ALL cards, the processor, and RAM, plus cleared CMOS, but no change. Are there any ideas on this problem??? Or is the motherboard shot, because it is brand new, just replaced.

Thanks

Jerry

 

At the risk of being too obvious, but I can't hear the sound :

Sounds like a fan that is catching. The higher the whine, the smaller the fan. Possibly on the video card or inside the power supply?

 

If you are looking for confirmation, I think you have nailed it pretty accurately. Capacitor can or something similar - keep flipping it and it'll blow or burnout completely.

 

Thanks

I am gearing toward the MoBo. I have turned the PC on without the fan plugged in and I , obviously, can hear the whine and it is coming from some where on the board, not the PS. I was trying to hopefully get a different scenario fromm some other techs because this MoBo is for a customer who has NEVER gotten to use this PC since he bought it in January. The day he go it the processor overheated and burnt out and now this.

Thanks

Jerry

 

Yo xbot.

If a key on the motherboard was stuck when you were booting would it fill up the keyboard buffer and beep and with a continuous key input the beep would be so fast it would sound like a high-pitch whine. It might also prevent the bios from continuing to boot. The keyboard input routines in the bios are probably not that elaborate. I'm not sure if the bios has a keyboard buffer or not or if it is a function of the keyboard control chip. Probably doesn't look for keys until after the POST. Keyboard would seem to lock up too. Fits. Easy to try another keyboard. Just a shot in the dark.

 

Got It

Hey. Thanks for the help but I have found the problem (I think). I called my business partner and asked him if he had every heard this "noise" and he said yes. One or more of the capacitors on the board is bad. They are over charging and that is producing the noise. I have never heard of this but I suppose it can happen even though the whining was followed by a "pop" sound when it happened to him and I am not getting the pop.

I put another board in the case and hooked it up with no problem. The power supply is fine, good voltage.

Thanks again,

Jerry