test screwdriver lights up at 15-pin monitor input cable

Nov 26, 2006 3 Replies

Hi,



While assembling a computer I noticed that my test screwdriver, which is supposed to indicate hight voltage (more than 200V) lit up when touching the 15-pin connector coming from my monitor (which had power). I had somebody do this to his computer monitor with his screwdriver and the result was the same. The pins are safe to touch.



What's an explanation of this?



Mihalis



PS: Please e-mail me at snipped-for-privacy@gmail.com as I am not monitoring the group frequently.



You are coupling some of the high voltage from the picture tube but it is at such a low current level that your body pulls it down. You can see the same kind of thing with a digital meter connected to just about any long piece of wire.

Thanks for your explanation.

Would you mind being a little more detailed in "You can see the same kind of thing with a digital meter connected to just about any long piece of wire."

Mihalis

snipped-for-privacy@aol.com wrote:

Digital meters have a very high input impedence so the "antenna" effect of a long piece of wire will cause you to get erattic voltage readings. Any small load will make them dissapear. Plenty of do it yourselfers and even some experienced electricians get fooled by this "phantom voltage".

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