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Bizarre accident lan cable contact with circular vent causes shock

Last response: in Components
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January 21, 2011 4:58:19 AM

Hey community,

I am dealing with a very bizarre accident which occurred to me. My internet was having some issues so I wanted to directly plug in the lan cable from my modem directly into the PC (instead of via the router as a middleman). In the process, I accidentally scrapped the outside portion (circular vent) of one of the fans with my lan cable and there was this large blue electric current shock with the accompanying brrrrrrr sound of electric current. I'm running a dell xps 9000 - I don't believe the specific specs of my computer are important as this happened externally at the chassis.

There is some residual burn scorch marks that were left at the circular vent. Links: 1) http://i417.photobucket.com/albums/pp258/whatsntomake/p... 2) http://i417.photobucket.com/albums/pp258/whatsntomake/p...

Here is the damage to my lan cable (there are 2 scorch marks): 1) http://i417.photobucket.com/albums/pp258/whatsntomake/p...) http://i417.photobucket.com/albums/pp258/whatsntomake/p...

How exactly did this happen and why was there an electric current? I did not know a lan cable could actually do that. My computer chassis was not open and no internal parts were sticking out at that time. I unplugged everything afterwards and opened my computer. There was no visible damage to the internal components so far as I could see. As this is a very unusual case - I doubt this has happened to many people before - is there anything I should watch out for?

Thanks,
a b ) Power supply
January 21, 2011 6:06:55 AM

There would have to be a short somewhere. Either the cable modem or the PC would have to have a poor or missing ground.

A big static charge might do the trick I suppose... but that kinda points back to the poor/no ground thing.

So you have a poor/no ground issue and a mystery source of power. I think your PC has a Flextronics 475W PSU? That might be bad I suppose. Or a short elsewhere in the PC.

Suppose you had a free molex (PSU) connector that had fallen onto something... say an unused motherboard standoff, in such a way that is was making contact with one of the pins inside the molex connector.

An Ethernet cable does carry a small amount of current, but not enough to produce that on it's own.

I would be checking the case with the PC running for voltage, using a multi-meter.
I would also check the line from the modem for excessive voltage. Shouldn't be more than 2.5V I think.
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January 21, 2011 6:22:46 AM

Actually I would take that machine into a good service center as it is clearly an electric shock and or fire hazard. Leave it unplugged and take it in lest the next burn marks be on you.
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January 21, 2011 5:58:44 PM

A bad power cord to the power supply with a bad ground connection could be the cause. As also stated the power supply could also have a problem with the ground. Do you have access to a digital volt meter? You could diagnose where the problem is with one.
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January 21, 2011 6:39:58 PM

Something isn't grounded properly and has a floating ground. You need to check chassis to ground voltages on all of your equipment and see which has a chassis ground that doesn't measure 0 volts (or really close to it). This can be caused by defective equipment (that isn't grounding properly and has an energized chassis). That isn't a static discharge, that'a AC, and with a substantial amount of current I might add.
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January 23, 2011 9:21:32 PM

Thanks for the responses,

I ran a multimeter around my outlets and made sure they checked out. I ran one around the line for the modem and found nothing out of the ordinary. I also ran the multimeter around the my desktop case with the power on and running and found values of mostly 0 on the side of the computer. On the backside of the computer I had values of mostly 0 and some within the 1-4 volt range near the pci express slots (the removable ones you can take out on the backside)
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