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While arranging cables tonight to prepare to plant a new workstation, I got an electric shock from the VGA cable (that was hooked up to a seemingly good, yet older LCD monitor).

Of course, when the monitor was powered off, it didn't happen, but when we plugged it back in, I got the same jolt, and decided to trade monitors before electrifying a brand new workstation.

Does anyone know exactly what goes wrong inside an LCD monitor to cause this? I know older CRTs were shock-worthy, but I never expected it from newer technology.

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3 Answers 3

up vote 5 down vote accepted

There's an electrical fault in the monitor. I hope it's under warranty.

It is NOT the signal for the picture, which is extremely low voltage and high frequency and cannot be felt. It's probably a short in the monitor which has put real voltage on a cable meant only to carry a signal. Unplug it, leave it unplugged, and either get it fixed or dispose of it.

Nothing to do with "new technology" here--the problem isn't in the technology, it's a wire making contact with the wrong part.

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What I meant to say is I would have expected a milder shock from an LCD than a CRT. –  CoffeeBean Sep 26 '09 at 19:47
    
Actually, both CRT and LCD use high voltage inside. CRTs need high voltage for their electron beam, which LCDs don't use. But LCDs usually use a cold cathode backlight, which also needs around 500-700V. However in both cases this voltage should never get near any of the connector pins. So it's certainly a device failure. –  sleske Feb 25 '10 at 9:44
    
@sleske newer LCDs often use LED backlight. –  kinokijuf Sep 1 '13 at 19:36

but I never expected it from newer technology.

Why not?

Somehow the signals needs to be transferred from a to b, in order to do that they need energy of some sort. Electricity is the way to go..

Wherever Electricity comes into play, there always is a chance to get shocked, however mild or severe.

In order not to be shocked, Electricity need to run into the earth, thus the technical term "to ground". If you get shocked it's mostly due to faulty grounding.

Faulty grounding results in YOU being the medium it (the electricity) needs to run into the ground (a complete circuit), thus shocking you.

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The shock is due to electrical signals (from the monitor) flowing through your body. The signal is always present(when monitor is on), just that it needs the circuit to be completed. Normally when you connect it to a workstation, the circuit is completed by the workstation. But when you hold it, its you who complete the circuit & hence the shock :).

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Aren't all voltages produced by the graphics adapter? I doubt that the monitor will "power up" its side of the connection. –  innaM Sep 26 '09 at 9:21
    
No, this is not correct. As explained in CarlF's answer, the regular VGA signals are too weak to be felt. –  sleske Sep 2 '13 at 6:51

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