Electric Shocks

[relaksuah]

[tt]Have you ever tried touching the PC casing only to get a mild electric shock? I get this kinda often and it gets real irritating when troubleshooting. Tried to feel whether the heatsink got warm, even that gives a shock. Anything metallic that I touch in the casing, even with the PC turned off, gives me a mild shock. Sometimes, even with the power turned off. Due to this I had to take the plug off the wall just to facilitate any handling of the parts inside.

I dont have any carpeting, just a ceramic tiled floor which I put my feet on. I work on my PC on the floor (My table's a sorry mess).

I work in a school, taking care of the 200++ computers there. I never get this kind of shock at my workplace at all.

My question is : what might be causing all this electric shock? It's mild, but irritating. Any help? BTW, this is also the same happening to my second PC, and other previous PCs which I've built at home too.

 

[G0AOZ]

The first thing to say is DON'T TOUCH IT! Get a qualified electrician to check out your installation. You need to establish if this is a mains electrical fault or just good ol' plain static. I would not suggest that you go and check this out again but try and recall if the shock was there constantly every time to touched the equipment whilst you were standing stock still. If yes, then I'd say you definitely have a fault in the mains installation. But if it was a one-off, and repeated touching of the case or earthed parts produced no further shocks, then you have a static build up, and you need to use a proper earthing wrist strap before starting any work on the computer.

If you are in any doubt whatsoever, get it checked out professionally. If the fault suddenly goes nuclear, so do you...


ROGER - G0AOZ.

 

[ANFPS26]

Check your wall outlet for proper grounding. The PC case should be grounded to an "earth" ground for safety. Here is some info on grounding outlets. This is for 120v outlets, but 220v outlets have to have a safety ground also.

http://www.handymanusa.com/articles/ground1.html

Jim

 

[chaps]

Normally you should have D.C. Voltage of approximately 3v, 5v and 12v, the +2.45V
Reading that you have is a little low. That might indicate that the power supply, or the on board power regular is not putting out the proper voltage. However software driven voltage-monitoring utilities are sometimes inaccurate. If your system seems to be working well then it probably is. You should use an anti static strap when working on the CPU. Static will normally build up with in the human body under any and all conditions. The body’s electrical system runs on approximately 1 volt, any walking or movement will increase static charges.

Mike

 

[edfair]

You can get the problem from wearing the wrong kind of underwear or clothes, from sitting in a chair with the wrong kind of covering, from working in an building with an excessively low humidity, and from various other reasons.

You might want to get an outlet tester to make sure that nothing is crossed in the building wiring and use an ohmmeter to verify that the grounding lead of the power cord is not broken. These checks are just to be on the safe side and probably won't show any problems.

When it gets partitularly bad at my house I use a penny as the device to take the hit as the static flow is through a larger area holding the penny than the small point that normally is the conduction path. And I have had it bad enough in the winter that the computers will sometimes reboot when touched.

Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[relaksuah]

[tt]OK, alright. I've just taken to note the differences between A/C shock and D/C shock. (God I just had to have to experience it today) It seems my PC is leaking D/C voltage. Now I just need to find out how the leak occurred and how to ground it.

 

[edfair]

If you will describe how you figured that your machine is leaking DC we might have a chance to answer the quextion.

In general, the 0v from the power supply is tied to the frame of the machine via the grounding standoffs that support the motherboard. And if any DC is leaking it is partially shorting the power supply and leads to the power supply shutting down.

Static shock is DC shock. And having static shock doesn't mean there is leakage.

Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[franklin97355]

I don't think he's talking about static but more like a ground fault where voltage is getting to the case of the computer.

 

[tviman]

For voltage leaks to the case from the computer, look for dust balls and screws under the motherboard.

relaksuah, you haven't indicated that you where a grounding strap when you work on your equipment or whether you use an anti-static matt. If you're working on the floor, both of these are must-have items to prevent ESD damage.

Your tile floor is probably glued to a concrete floor which in turn is in direct contact with earth. If the soil drainage conditions are poor, the concrete substrate could be soaked with moisture which would also cause the tile floors to hold excess moisture. Any electrical ground could be leaking right back into the building via the floor.

A friend who runs a computer repair firm spent thousands in electrical upgrades - just to prevent what you're going through. (It never occured to him to check his licensed electricians work). The business next door was a laundromat that had been having drain problems for years. Their electric service box (440 volt, 3 phase) was grounded to a copper rod in the ground. Years of maintenance and remodel developed a short to ground in one circuit that effectively turned all the grounds in the adjoining buildings "hot". My friend cooked 2 PC's and suffered a severe shock to himself before he discovered this.

There's always a better way. The fun is trying to find it!

 

[GSFDigital]

HEY. two things to check before you call an expensive electrician. first I assume you have a telephone line plugged into the modem, try shutting it down, disconnecting it and touch the case to discharge the static buildup, then repower without the phone line attached and see if it occurs. Frequently a bad ground on your phone line will produce low voltage buildup. that's why they generally clamp the line to a copper ground stake in the yard or attach it to metal plumbing pipes.
Second if you use a cable modem or tv card the same thing applie, make sure the line is grounded.
last...don't go poking around inside of a case that has known issues with electrical discharge, that's the quickest way to turn it into toast.
Hope it helps.

GSFDigital