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Static discharge on the case?

F

flexyjerkov

n00b
Joined
Apr 27, 2010
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I'm perplexed by the problem that i'm having at the moment, it seems when I touch my case or run my hand across it I can feel what can only be described as static. Yet placing another metalic (Earthed) item on the metal stops this. Now I know this is not a good thing but cant for the life of me think where to start. I've checked mains plugs etc and loose connections or splits in the cable and found nothing...

What can I do?
 
First best guess is the power supply has a leakage current to its own chassis that is energizing the case. This is not susposed to happen. And if severe enough a mains cicuit breaker would blow. The PSU is grounded through the mains and the ground in the PSU should be connected to the PSU chassis which grounds the case by the mounting screws of the PSU. (Not to mention the ground wires going to the motherboard, motherboard ground, ground pads around the mounting screw holes, mounting screws, metal motherboard standoffs, case.)

So you have a short to ground through a high resistance that is energizing your case with fairly high voltage (cause you cant normally "feel" the +5 or +12V the power supply puts out, so its on the mains side of the PSU before it gets transformed to DC and why it feels "staticly" because its AC) but the high resistance is preventing sufficient current to flow and a breaker or fuse to blow.

Check that your power supply mounting screws are biting through any finish on the case so they make good contact.

New build ? Or this just start happening.

What I am trying not to say, is there should be zero leakage current to ground and the only component in the computer that can generate a voltage that you could feel is the power supply. And it apparently is defective or failed. And your grounding is wonky somewhere as you have discovered.

Get rid of that supply, you can fix the ground perhaps and make the symptoms (energized chassis) go away but the underlying problem will remain.

Thats the only reason I can think off off hand for what is going on. Hopefully someone will have a less costly idea/solution/insight.

Its a deathtrap.

I really hope I am wrong.
 
Well the case itself is a new build and i've ensured all the screws are in place as they should be. I'll check the PSU over tonight and check for anything out of the norm. The PSU is a corsair 640 watt I think?, cant remember off hand. So hopefully if thats the case they'll swap it for me.
 
Your chassis should already be earthed. Wall outlet -> green wire in power cord -> IEC recepticle on PSU which is bolted to power supply housing which is bolted to your chassis.

1. Something is wrong with the power supply, very unlikely due to the way IEC receptacles and power supplies are designed.

2. Your outlet is wired wrong, or the outlet's integrity has become compromised (the green wire inside of it has come loose) Also unlikely, but more plausible. Try a different outlet, such as the outlet your getting the different earth from?
 
What case do you have? I heard stories of the new Coolermaster CMS Advanced II having grounding issues but i'm leaning towards the PSU in your case.
 
It could also be the other way around:
You're the one that's being charged by grinding against the chair, the carpet, or whatever. Then you will discharge into the computer, no matter if it's grounded or not. (In Sweden, where I live, it's very common to have wall sockets without protective earth in all rooms that aren't "wet".)

Cheers
Olle
 
flexyjerkov said:
but cant for the life of me think where to start.
Click to expand...
If you have multimeter remove PSU's cord from wall and measure resistance between plug's safety ground contact/pin and metal part of case near PSU.
If resistance is about zero fault is in building's wiring if there's high/"infinite" resistance then fault is in between these measuring spots.
 
Get a multimeter out, set it to ac voltage and measure the voltage between your case and the ground or neutral(larger side of a polarized outlet) on a wall outlet. If its anything like ~120vac(more then likely, will be lower than 120, probably ~90-100vac due to resistance and such on the case itself) then you have live ac current leaking from the power supply.
 
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