clive@drutx.ATT.COM (Clive Steward) (11/09/87)
in article <2853@batcomputer.tn.cornell.edu>, eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) says: > > This may give you sweaty palms the next time you open your Mac II case. > If and when you go inside the case, it is wise to have the > machine grounded (plugged into a grounded outlet), to put it on a ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > conducting grounded surface, and to keep a grounding strap on your body (I > run a wire with alligator clips from my metal wristwatch band to the chassis). ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Julian, forgive the caps, etc., but you're giving me sweaty palms just thinking about it. Both of these are VERY dangerous. First of all, you should NEVER put your hands inside of any electrical equipment with the plug in the wall. ALWAYS, unplug it. Standard safety practice, for obvious reasons. And not even always sufficient, as some circuits can store enough energy to hurt you (such as the deflection/anode potential generator in any tv set, terminal, or non-MacII Macintosh). Second, you MUST not ground yourself with a low-resistance path. If you come into contact even with the leakage current some legal plug-in devices have, you're at least going to get a nasty 'bite', and perhaps damage yourself or something else pulling away. If you happen to hit something live, or the case of a device which has failed internally (or was designed prior to certain standards), you can very easily get a FATAL shock. The commercial wrist-straps are designed to guarantee a high (I think it's in the vicinity of 100 kilo-ohms (for non-EE types in the crowd)) resistance to ground, to avoid this hazard. This is still enough of a ground to bleed off static quickly from the ~100 pf capacitor your body offers. Let's just not offer your body, ok? Clive Steward