Electrified Computer issue

Arch Guru XX

So today I was setting up a wireless router in my apartment. When I removed the Cablem Modem -> PC cable from my PC (so that I could hook it to the router, and then connect the router back to the PC) I noticed that the back of my PC seems to be holding an electrical charge. If you touch the sides of the case, or the front, nothing happens, but the back of the computer - where all the various ports are, so I'm figuring that something back there might be aligned incorrectly or something - causes light tingling in my fingers if I touch it. The effect is worst around my video and sound card, but still noticable on the rest of the rear panel, with the exception of the fan grill. I did not get a good sense of exactly where the worse location is, because I don't want to accidentally kill myself (this is also why I did not touch the PSU).

The thing is, the charge remained even when I turned the PC off and flipped the switch on the PSU so the PC could not be turned on (I tested this by lightly brushing the rear panel with my pinky finger).

How do I approach this? The comptuer seems to be working fine otherwise, but I have difficulty believing that an electrified rear panel is a good thing. But if the charge remains while the computer is off, I'm not real excited about rummaging around inside the PC.

Does anyone have any ideas about what might be causing this, what to look for, and how to handle the situation without electrocuting myself?

Meiz

Other then removing the power cable from the power supply and checking it every couple of hours, there's not much else one can say.

Look for any exposed wires touching the metal as well.

See if you can shoot lightning out of your fingers to eliminate yourself as the cause.

blincoln

Usually problems like that are related to a grounding issue, like the outlet you have it hooked up to isn't properly grounded. You're not using one of those ghetto 3-to-2-prong adapters or something, are you?

mspencer

Does that PC have a telephone modem? The only time I've ever felt that kind of shock was while working on a PC with a modem. (I think this was 1997 and I was only 20 then.) I removed the modem with the phone line still connected, and when those needle-like pins on the underside of the card touched my hand I felt an almost-kinda-painful shock that made my muscles in my hand feel weird.

Other than that, I don't know what to tell you except be careful.

Were you touching two parts of the computer at the same time, perhaps both the card slots on the back and the top of the case? Or were you otherwise grounded, touching a metal pipe or other ground source? (If you felt a tingling, then either current was entering your body at one point of contact with the computer and leaving your body at another different point of contact with the computer; or it was entering your body where you contacted the computer and leaving someplace else, like where you're touching a pipe or other ground source.)

Aside from bare wires touching the sides, motherboards also have lots of bare metal on the bottom, suspended a few mm from the metal case by some plastic or metal standoffs. If there's something wrong with how your motherboard is mounted, some of those metal contacts might be touching the case. That would likely fry your motherboard or power supply before you had a chance to notice any tingling sensations.

capnrico

mspencer wrote:

Does that PC have a telephone modem? The only time I've ever felt that kind of shock was while working on a PC with a modem. (I think this was 1997 and I was only 20 then.) I removed the modem with the phone line still connected, and when those needle-like pins on the underside of the card touched my hand I felt an almost-kinda-painful shock that made my muscles in my hand feel weird.

Other than that, I don't know what to tell you except be careful.

Were you touching two parts of the computer at the same time, perhaps both the card slots on the back and the top of the case? Or were you otherwise grounded, touching a metal pipe or other ground source? (If you felt a tingling, then either current was entering your body at one point of contact with the computer and leaving your body at another different point of contact with the computer; or it was entering your body where you contacted the computer and leaving someplace else, like where you're touching a pipe or other ground source.)

Aside from bare wires touching the sides, motherboards also have lots of bare metal on the bottom, suspended a few mm from the metal case by some plastic or metal standoffs. If there's something wrong with how your motherboard is mounted, some of those metal contacts might be touching the case. That would likely fry your motherboard or power supply before you had a chance to notice any tingling sensations.

That was because phone lines carry a charge, the jolt you felt was the actual voltage on the phone line, most likely unrelated to this guy's issue.

mspencer

capnrico wrote:

mspencer wrote:

Does that PC have a telephone modem? The only time I've ever felt that kind of shock was while working on a PC with a modem. (I think this was 1997 and I was only 20 then.) I removed the modem with the phone line still connected, and when those needle-like pins on the underside of the card touched my hand I felt an almost-kinda-painful shock that made my muscles in my hand feel weird.

Other than that, I don't know what to tell you except be careful.

Were you touching two parts of the computer at the same time, perhaps both the card slots on the back and the top of the case? Or were you otherwise grounded, touching a metal pipe or other ground source? (If you felt a tingling, then either current was entering your body at one point of contact with the computer and leaving your body at another different point of contact with the computer; or it was entering your body where you contacted the computer and leaving someplace else, like where you're touching a pipe or other ground source.)

Aside from bare wires touching the sides, motherboards also have lots of bare metal on the bottom, suspended a few mm from the metal case by some plastic or metal standoffs. If there's something wrong with how your motherboard is mounted, some of those metal contacts might be touching the case. That would likely fry your motherboard or power supply before you had a chance to notice any tingling sensations.

That was because phone lines carry a charge, the jolt you felt was the actual voltage on the phone line, most likely unrelated to this guy's issue.

Indeed. I guess I could have said that explicitly -- I assumed people already knew that. Sorry.