Minor shock when connected case to monitor

May 12, 2011 at 15:20:00
Specs: none, 512 MB
while working on a pc, i noticed i was receiving a minor shock from the case. this only occurs when a display is plugged into the vga port. happened with 2 monitors. also its causing the pc to shut down and boot on its own (shorting power pins). pc is sitting on a grounded steel workbench but is on rubber feet with no contact to the steel

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#1
May 12, 2011 at 15:40:51
If it was just a static shock (like touching a doorknob after walking across carpet), then you don't have a lot to worry about (but you could still easily damage the PC with ESD). If it's a consistent shock (like holding on to a bare lamp cord) then you have a serious wiring problem either in the machine, monitor(s) or building you're in (like a faulty ground). This potentially could kill someone if not corrected. I have an isolation transformer on my workbench to help prevent any such problems; perhaps something you may also want to investigate.

"Channeling the spirit of jboy..."


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#2
May 12, 2011 at 15:59:47
Well i did some tests. Turns out there is 60v coming from the part of the cable that hugs around the connection on the motherboard. I moved both the monitor and case off of the workbench onto a dry concrete floor and there was still 60v AC going through the case. I know for a fact that the receptacles are not grounded. but why is there 60v going through that cable? and it was on two different displays. this has never happened with either display before. and i think it just started because i was not feeling anything earlier. Ill take the isolation transformer into consideration but i would still like to find out why this is happening at all. thanks

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#3
May 12, 2011 at 17:37:44
Okay I found out whats wrong. The part of the cable that was carrying a current is connected to the monitor's earthground connection. the reasong there was a current was because the earthground is carrying 60v. both the monitors and cases earthgrounds were electrified and when the cable came in contact with the case, it was completing the circuit. the issue is isolated to this receptacle. i will definatly fix this tomorrow. luckily, the amperage was low enough that i didnt get hurt. and im glad i found this before someone got a serious shock. thanks for your help!

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