Fun with static electricity

I

ilikecake

Gawd
Joined
Feb 20, 2006
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759
Hi

I am having an interesting problem. I have the Antec Fusion case for my secondary computer. The reason I mention this is that it has a metal front. I was using my secondary computer yesterday to try to find a way to fix my primary computer. I was burning a CD, and when I went to press the button to close the CD drive, the computer shuts down. Thinking this was odd; I turned the computer back on, and proceeded to try several things to get my primary computer to work again. A few minutes later, I need to use my secondary computer. I go to touch the case, and again it shuts down. This time, I hear a spark of electricity go from my hand to the computer.

Overall this happened about five times. I have never had a static problem (that I know of). I thought the outside of the case should be earth-grounded. Why then does it kill the computer when I shock it?

Both my computers are plugged into A UPS, though they are plugged into different ones. Could this be causing a ground loop between the computers? Is the earth-ground from the UPS isolated from the real ground? Will the shocks cause permanent damage to my PC?
 
Do you have a voltmeter? Does it report continuity between the ground pin of the power plug and the front of the case?
 
I once touched the front panel USB on my Sonata II, got a slight shock, and Windows froze (no BSOD). It could happen to you, too.
 
Thanks for the replies

unhappy_mage said:
Do you have a voltmeter? Does it report continuity between the ground pin of the power plug and the front of the case?
Click to expand...

I checked a bit with my DMM:

-There is continuity between the ground pins on the UPS and our house's earth ground.

-There is continuity between the ground pin on the UPS and the steel part of the Antec Fusion

- I cannot read continuity between the steel part of the case and the aluminum part of the case (the front).

However, for some reason I can't seem to read any sort of continuity for the front of the case. Even if I touch both plugs to the front of the case. Am I missing something here? I am almost positive the front of the case is aluminum, and it doesn't look like it has been coated.

That mystery aside, I can't see how the front of the case could possibly be isolated from ground. Is there some other possible reason for the reboots?
 
Well, at least it's not as bad as the computer I tried to fix which gave me a jolt of 120 when I touched the power button. I thought it was just bad static so I hit it again. It demonstrated that I was wrong. So, a couple hundred bucks of rewiring by an electrician later, machine magically started working better.:rolleyes:
 
Hehe, I suppose I should count my blessings. At least it is me shocking the computer, not the other way around. Nevertheless, the problem is annoying. It doesn't seem to be doing it anymore. so maybe it was an isolated incident? I don't see how this is possible, but there are a lot of things about electrical wiring that I don't know jack about.
 
May sound a little weird, but you might think about your clothes.

I have a pair of shoes that will help build static electricity... after killing an automotive computer with a static discharge, I have banned them from my office. LOL.

I also have a few nice warm fuzzy shirts that build static... those too are banned from the office. I've killed more than my fair share of flash eproms with static.
 
I should probably also get rid of the carpet in my room. :D However, that is not really my primary concern. I know I will build up static, but touching the computer case should dissipate the static to the earth ground provided by the power supply. However, in doing so, it shuts down my computer.

I thought that the earth ground would be isolated from the electrical grounds, and therefore this sort of thing shouldn’t happen. Is this not the case? Should I look for shorts inside my case? I don't see anything obvious, but I may have missed something.
 
I get a funny shock whenever I touch the case of my computer + other electronics.
Favorite example was hand on the case and RCA connectors on the VCR
And my obvious best experience was USB hard drive + computer = pop sound + new motherboard
:eek:
 
Shouldn't earth and electrical ground be connected to the same stake?

But yeah, I'd look for shorts inside the case. Maybe the mobo is touching the chassis or a wire got stripped?

ilikecake said:
I thought that the earth ground would be isolated from the electrical grounds, and therefore this sort of thing shouldn’t happen. Is this not the case? Should I look for shorts inside my case? I don't see anything obvious, but I may have missed something.
Click to expand...
 
You should be reading continuity between the front of the case and the gound on the UPS and outlet. If not the front of the case is not grounded and the static is not being drained to ground, but rather most likely drained into your components.

And yes the earth ground and electrical ground are connected per code giving no difference in potential. Potential = voltage. Check to see why the front isn't grounded. It may be the manufacturer designed the front to be grounded thru metal to metal contact versus a "ground wire".
 
I'd report this to Antec, the FCC, and the Consumer Products Safety Commission, and I'd connect the metal front to the chassis with a #18 wire attached to eyelets.

All but one PSU I've seen had the earth and electrical grounds connected together. The exception was a high quality Delta, but in a couple of other brand PSUs, including Antec SmartPowers, their circuit boards were designed to keep those grounds separate if a jumper wire wasn't soldered in place (it always was). But separated grounds will tie together through the computer chassis, unless it's made of plastic.
 
I will check the continuity again when I get a chance. I find it hard to believe that the front of the case and the sides of the case are not electrically connected, seeing as they are both metal and probably attached with metal bolts. However, it is certainly a possibility, and I will examine it further. I will let you know how it goes.

Is there any reason why the front of the case should be isolated from the rest?
 
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