actually, no. the voltage will not discharge through the ground terminal on the power cord, it will discharge between the chassis (because it is connected to the outside, conductive coating of the crt which forms the "ground" plate of the capacitor) and the internal layer, or "dag" of the crt which is the "hot" terminal of the capacitor.
best actually to connect the alligator clip as near the crt as possible on the chassis to avoid getting anything else in the current path. also best to do it with the machine unplugged to avoid the mistake of doing it with the machine on or bumping it on accidentally. the "earth" "ground" has nothing to do with the storage or discharge of high voltage on the crt. the crt is made to also be a capacitor by coating the inside and outside of the tube with conductive films, with the glass in between. this is a most excellent and essentially free way to get the needed high voltage capacitor. the charge is stored entirely on the two conductive films (technically on/in the glass as well), and they are what need to be shorted together. the big red wire connects to the inside layer, the outside layer connects to the chassis ground, which just happens to be earth ground when it's plugged in if the outlet is grounded. note that most computers will operate just fine without a proper earth ground, though i don't recommend it. the only way to get it to discharge through the power cord (and you should never try this!) is to connect the alligator clamp to a ground on the outlet or some similar foolishness when discharging the crt. it's also best not to discharge the crt when you don't need to, the very high current surge you produce is hard on the conductive coatings and can eventually damage them, that's why some manufacturers suggest using a resistor in the discharge path. in practice, i've always used the screw driver and alligator lead method. you do have a problem if the chassis is loose and not properly connected to the crt "ground", in which case you can zap parts on the board. the truly optimum place to discharge to is one of the crt mounting screws (at the front or face of the tube) or the metal band at the front of the tube, or on larger monitors to the bare wire stretched across the back of the tube, said wire being used to make the "ground" connection. chassis ground and earth ground are often very different in practice. of course, if the clip lead should come loose, pull back the screwdriver immediately, before the loose lead zaps something on the machine or possibly you (if you are touching the chassis). you also want to use a screwdriver with thick plastic, one that is not antistatic (as they inherently conduct), and one that is clean, it doesn't take much dirt on the plastic to make it conductive to high voltage. in any case, be careful of the neck of the crt, they are rather thin and delicate, and the smallest crack will let air in and ruin the crt. if you hear a sucking noise, it's done. (i've done this once myself). Mark Ginn wrote: > > The best tool (IMHO) for discharging any CRT is a flat blade screwdriver > with a alligator clip attached to it and the chassis, while the unit is > plugged in, but turned off. This way, the voltage will route thru the ground > terminal in the power cord. --------- -- "Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure, or nothing." - Helen Keller, American Blind/Deaf Author & Lecturer... -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> The FAQ: <http://macfaq.org/> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
