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Shocking chassi?

A

Acedia

Junior Member
Hey everyone I've got this small problem with two of my computers.. well they've become shocking 😉

Everytime I touch the chassi of the computer I get electrocuted, does anyone know why the chassis get conducting.. it's damn anoying.

Does anyone know what I can do about it? Or why they do it?
 
Sounds like a grounding problem, it could be back at your circuit breaker panel. There's a little tester that you can use to make sure the outlet is wired correctly and has the correct power and ground configuration.
 


<< On the contrary, I have been electrocuted by 120VAC a few times. It's not static and I'm still here 🙂 >>

Are you 100% positive? 😀
 


<< Yup, I can wave my hand and turn on florescent lights now. >>



lol 😀 I've been electrocuted once... in shop class - miswired my lamp 😉
 
A capacitor doesn't hold an AC charge.

...if timed right and if it has no ESR or series resistance (only theoretical) a 120VAC outlet could put a 340VDC charge on it (based on Vpp)
 
If it's like static, it's probably harmless, but if you feel a buzz or numbness, it's probably 120VAC and has to be taken care of. At the very, very least, get a GFCI or GFI (ground fault circuit interrupter), and plug everything into it or you could be killed. There are portable versions that plug into wall outlets, priced anywhere from $3 to $30.
 


<< Hey everyone I've got this small problem with two of my computers.. well they've become shocking 😉

Everytime I touch the chassi of the computer I get electrocuted, does anyone know why the chassis get conducting.. it's damn anoying.

Does anyone know what I can do about it? Or why they do it? >>



This is perfectly normal on an ungrounded case. Switching power supplies have ceramic or film capacitors bewtween hot-ground-neutral and very slight current flows through case to ground through capacitave coupling. Capacitave coupling is unique to AC circuits.

When the case is connected to ground, the potential difference is almost zero, but in absence of ground bonding it can go up to 120V AC(and max current of a few hundred micro amps)

You can VERY carefully connect the case to neutral side of 120V AC. If you turn the plug around or misconnects it to hot, your chasis will become 120V above ground though.
 
120v is nothing. You'd have to really lock on down onto a 120 rail to hurt yourself. As a small child first time under 5, second time 8-9 ish, and again at 11 I've been got by 240v. (Well can't be sure I was zapped when I was 5 as I was more scared by the bang as the sparks, but I was putting the nail into the extension cord!)

Yes, electricty can kill. No, most people who get electrocuted do not die. It also takes current. I've zapped my sister with a few thousands of volts as a young spirited youth. She is still alive to tell about it as it was with microamps. Got a decent scream out of her 🙂

It is equally (perhaps more) likely that the chasis is grounded, and you are the one charged up. Walking acorss a carpet, weraing lots of nylon clothes. As long as the computer is plugged into a working grounded outlet, the PSU will be grounded, which is conected to the chasis. You'd have to work to unground the computer.
 
What the grounding issue might be is this:

In a normally wired house, there is three wires going from the panel to the outlet: Hot, Neutral, Ground. Normally the neutral is connected to ground in the panel. In a GFI setup if the current is flowing through ground instead of neutral it kicks it off.

In your situation the ground might be disconnected somewhere.
 


<< This is perfectly normal on an ungrounded case. Switching power supplies have ceramic or film capacitors bewtween hot-ground-neutral and very slight current flows through case to ground through capacitave coupling. Capacitave coupling is unique to AC circuits.

When the case is connected to ground, the potential difference is almost zero, but in absence of ground bonding it can go up to 120V AC(and max current of a few hundred micro amps)

You can VERY carefully connect the case to neutral side of 120V AC. If you turn the plug around or misconnects it to hot, your chasis will become 120V above ground though. >>



Cool, now I know what it is when it does happen.


And no, 120V doesn't kill very easily. I've been shocked about 6 times by 120V. The last time was the worst though. I had an AT Power Switch in my hand and turned it on. Apparantly, the plastic covers on the terminals were not in place and my hand clamped down on the switch for a good 20 seconds. I'm not sure how I released it - it was in a position that it could have stayed electrocuting me pretty easily. The burn marks took about a month to heal, but no permanent scars.
 


<< 120VAC will zap you but won't kill you.
You will be hurting in the morning. >>



You won't always be hurting. I stuck my hand in a switch box one time and got zapped. My hand just buzzed a little and felt odd for a few mins, but that was my only problem. 🙂
 


<< Yes, electricty can kill. No, most people who get electrocuted do not die. >>



Most people who are shocked by electricity don't die, but all people who are electrocuted do.
 


<<

<< Yes, electricty can kill. No, most people who get electrocuted do not die. >>



Most people who are shocked by electricity don't die, but all people who are electrocuted do. >>



yeah yeah, technicality 😛. "electrocuted" means you were zapped to death, shocked just means you got a (usually non-lethal) jolt 😉

Anyway... is this case giving you the buzzing kind of shock, or the static kind of shock? if its vibrating/buzzing, thats not a good thing.
 
I "think" i was shocked once by a 120V wall plug. I can't tell if that was what it was.

I was plugging in a TV into a wall plug that was behind a bed. The damn prongs on the wire wouldn't go into the plug. The prongs were acually into the plug far enough to be conducting electricity (i think) but i kept trying to make the plug go in all the way. My hand slipped off the plug and my thumb came into contact with one of the prongs. It was only for a second or less. It felt like i had pinched my finger VERY badly and it was sore for a few minutes. But after that nothing.

So did i pinch my finger or get zapped? Who knows....
 
well, maybe a spark, maybe you pinched it. in my experience AC makes your muscles contract 60 times per second so it feels like a vibration. either way... I dont recommend trying it again to see 😉
 


<< well, maybe a spark, maybe you pinched it. in my experience AC makes your muscles contract 60 times per second so it feels like a vibration. either way... I dont recommend trying it again to see 😉 >>



Try 120 times per second. The waveform oscillates the full 360 degrees per cycle, therefore two voltage peaks (-ve and +ve) per cycle.
 
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