Need Help. Getting current from case and KB

Im working on an older PC for someone and whenever I plug the PC in, regardless of whether or not the power is on, there is a current running through the case and the metal bottom of the keyboard. I've tried running it on a different circuit and I've already swapped out the power supply (250w AT) and it still does this.

Any clues?

Thanks

Adam

 

Hi raistlinneo, welcome to TSG.

Can you explain a little more....are you getting shocked when you touch the metal?

Is the monitor still plugged in? Sometimes a modem will do this also if it's connected to the phone jack.

 

it's only when i touch the metal, either the back of the case, or the bottom of the keyboard. the monitor is plugged in and turned on. The only other things connected are the mouse and keyboard. There is no modem, and the NIC is not connected.

The machine runs perfectly fine in spite of this, but I dont want to give it back to them like this.

Thanks Again,

Adam

 

If definitely sounds like something may be shorting against the case....you might try checking the standoffs below the motherboard to be sure nothing is resting against the metal case....also do you have any stray power cords from the power supply touching the case?

 

I agree with you you, I would not want to put anyone in danger. When I unpluged the Compaq the Final time, it was torn down for learning, and recycled to the local land fill. Even at 70 volts I was not sure where it came from so it was a danger. Because of the cheap stand offs used by Compaq for the motherboard, I learned to do what ever it took to mount the motherboards very carefully in all the cases. I still think that the motherboard in the Compaq was shorting even though I did not see any contact areas. If I still had it then I would replace the snap in metal stand offs with plastic ones. Marturo

 

i checked the systemfor possible short-out points, and found none. I even replaced the motherboard standoffs as Marturo suggested, but I still get a current. Unless one of the drives is shorting out to it's case and from there to the system case, I have no more ideas. So I'm gonna try that and see what comes up.

Thanks again for all the help

Adam

 

You need to verify that the electrical outlet is in fact grounded. This problem sounds like a "floating ground" meaning the electrical system is not grounded, you have a bad power cord or there is a bad neutral either in the electrical system or recepticle.
The MB operates on low voltage DC, if you have AC or high voltage (house current) on the case then the problem is on the high voltage side of the power supply (the power cord or house wiring). I would suggest you have a licensed electrician look at your wiring.