scott@max.u.washington.edu (11/28/89)
In article <5126@tekgen.BV.TEK.COM>, stephenc@tekgen.BV.TEK.COM (Stephen Coan) writes: > In article <10936@max.u.washington.edu>, scott@max.u.washington.edu writes: >> ... >> (At this point, go to the bathroom or kitchen and touch >> your hand to the faucet to discharge yourself of any static electricity). >> ... >> Sincerely, >> Scott K. Stephen > > Please NOTE! DO NOT go running around your house to discharge yourself. > This only works if your computer is AT the location where you do the > discharge. On the way back, you are going to acquire a charge again, and > this may be worse than the one you had when you started out. > > Best Bet. After the case is opened, touch the top of the large metal > sheild covering the VIC II chip. This IS GROUND, and will safely bring you > and the computer board to the same potential. DO NOT touch any other parts > first, as a discharge anywhere else will likely do some terrible damage. > > Steve Coan > tektronix!tekgen!stephenc (503) 627-1794 Hmmm.... I thought grounding was bringing one's static level equal to that of the circuit that you are going to be working with, so as to avoid a sudden large voltage/current exchange with yourself and the circuit (and thus consequent damage to the circuit components). Grounding oneself by touching the circuit-ground seems to be conflicting with the very thing that you are trying to avoid - trying to be at equal charge level as the circuit without sudden current/volatage exchange. Since it is more likely that the computer has been connected to the power supply recently, and the ground of the power supply is the earth, I think that grounding one self by touching the faucet (which is the earth ground) will bring you to a static level equal that of the circuit without any sudden charge exchange between you and the circuit. And also one does not acquired static charge that easily and that quickly. Unless you're deliverating trying to creat static, like some vigorous rubbing of cloth or brushing your hair, there will be no built-up of static after grounding. What is more, if you have built a static charge on your body (and if you do not continue to do the thing that you did to build up the static charge) that charge will dissipate away in few minutes. Aside: For those who are interested, this dissipation occurs because the water molecures in the air (humidity) steals or donates electrons from the object that is chargely inbalance with the surrounding thus bringing that object to a neutral level (learn that in physics :) ) So, because of this almost everything around you is at ground level. In fact, being still for five minutes or so before touching a circuit will be not a bad idea either (too make doubly sure that you are at a proper ground level)....but then who would want to do that. This is why I touch the faucet for my grouding. I don't know whether or not this the proper way to do it, but so far I never had any static charge damage problems. But then Mr. Coan could be right.... Any other comments on how to ground oneself before working on the circuit? :) Sincerely, Scott K. Stephen
jgreco@csd4.csd.uwm.edu (Joe Greco) (11/29/89)
In comp.sys.cbm article <11128@max.u.washington.edu>, scott@max.u.washington.edu wrote: ]Hmmm.... I thought grounding was bringing one's static level equal to that ]of the circuit that you are going to be working with, so as to avoid a ]sudden large voltage/current exchange with yourself and the circuit (and ]thus consequent damage to the circuit components). Grounding oneself by ]touching the circuit-ground seems to be conflicting with the very thing ]that you are trying to avoid - trying to be at equal charge level as the ]circuit without sudden current/volatage exchange. The ground plane is "relatively" immune to static discharges, although I would not try creating a large static charge and then dissipating it on the ground plane. Static is extremely detrimental to MOS logic circuits, and you are really trying to avoid discharging into an actual logic circuit. As I recall, it is easily possible to blow certain kinds of MOS chips with the charge from just a few steps on carpeting. Since most people service their units on a workbench, it is probably most logical to ground your unit to earth ground and get a wrist strap type grounding gadget and ground yourself to earth ground. You should be very safe, but such extreme measures probably are not needed unless the air is very dry and you are in a bad environment. Me? If I'm worried, I touch an outlet and then the ground plane of the unit. ]And also one does not acquired static charge that easily and that ]quickly. Tell me that when you've just blown a 25 MHz 80386 processor or one of the 'x87 coprocessors. You'd rather not risk the methods you mentioned. Static is a sneaky enemy and will kill you when you least expect it.. :-) -- jgreco@csd4.csd.uwm.edu Joe Greco at FidoNet 1:154/200 USnail: 9905 W Montana Ave PunterNet Node 30 or 31 West Allis, WI 53227-3329 "These aren't anybody's opinions." Voice: 414/321-6184 Data: 414/321-9287 (Happy Hacker's BBS)
scott@max.u.washington.edu (11/29/89)
In article <1239@uwm.edu>, jgreco@csd4.csd.uwm.edu (Joe Greco) writes: > > Me? If I'm worried, I touch an outlet and then the ground plane of the > unit. Just to clarify the above statement.......I believe what he meant when he said "touch an outlet" was to touch the ground of the outlet which can be the screws holding the outlet (in three plug outlets it can also be the center hold), but the screws usually have a coat of paint so sometimes it is hard to make a good contact. I think you will be way better off if you just go the bathroom and touch the faucet which is the same ground as the one at the outlet; besides while you are in the bathroom you may want to do other things before starting work on a complicated circuit project. :) > ]And also one does not acquired static charge that easily and that > ]quickly. > > Tell me that when you've just blown a 25 MHz 80386 processor or one of the > 'x87 coprocessors. You'd rather not risk the methods you mentioned. > Static is a sneaky enemy and will kill you when you least expect it.. :-) Couldn't agree more....with such delicate components like a 80386 or a 80486 (I had the pleasure of holding one, a broken one that is :) ) wearing a grounding wrist-band and working on a grounded metalic bench is always a good idea. But for some of us and in some circumstances that is not possible, and in those cases touching the faucet (and then the ground-plane of the circuit, if you can find it) is the next best thing, and for working on the C64 I believe this is more than adaquate. > jgreco@csd4.csd.uwm.edu Joe Greco at FidoNet 1:154/200 Sincerely, Scott K. Stephen
slangner@clmqt.marquette.Mi.US (Stickster) (11/30/89)
I used to work on integrated circuitry in the Air Force, and among the many training sessions I was exposed to was the simplicity of picking up a static charge. Merely walking, without scuffing your feet can load you up with a couple Kv of charge. Your best bet is to have a GOOD earth ground within arm's reach while you work on your computer. Make sure it is gounded, preferably not through the power supply, but with a grounding wire from a ground path on your computer to the earth ground. Ground yourself frequently, especially before touching anything else inside your computer. This should help prevent you from zapping a critical chip. -- ============================================================================== | Steve Langner-Stickster-Commodore SIGOp | rutgers!sharkey!clmqt!slangner | | Enterprise Info. System, Mqt. MI, USA, Terra, Sol | slangner@clmqt.UUCP | ================== "It's dead Jim, but not as we know it." ===================
kentsu@microsoft.UUCP (Kent Sullivan) (12/02/89)
In article <1239@uwm.edu> jgreco@csd4.csd.uwm.edu (Joe Greco) writes: >Since most people service their units on a workbench, it is probably most >logical to ground your unit to earth ground and get a wrist strap type >grounding gadget and ground yourself to earth ground. You should be very >safe, but such extreme measures probably are not needed unless the air is >very dry and you are in a bad environment. > >Me? If I'm worried, I touch an outlet and then the ground plane of the >unit. Thought you-all might find this article interesting--it's from comp.sys. mac.hardware, where a very similar discussion is winding up: ------------- From uunet!snorkelwacker!think!samsung!uakari.primate.wisc.edu!ames!ncar!boulder!rieman Fri Dec 1 11:56:12 PST 1989 Article 570 of comp.sys.mac.hardware: Path: microsoft!uunet!snorkelwacker!think!samsung!uakari.primate.wisc.edu!ames!ncar!boulder!rieman >From: rieman@boulder.Colorado.EDU (John Rieman) Newsgroups: comp.sys.mac.hardware Subject: Re: Memory Questions Message-ID: <14328@boulder.Colorado.EDU> Date: 29 Nov 89 08:20:29 GMT References: <cZMlnuG00WB404Z0cv@andrew.cmu.edu> <4129@phri.UUCP> <3122@jarthur.Claremont.EDU> <5671@umd5.umd.edu> <3231@jarthur.Claremont.EDU> <381@fsu.scri.fsu.edu> Sender: news@boulder.Colorado.EDU Reply-To: rieman@boulder.Colorado.EDU (John Rieman) Organization: University of Colorado, Boulder Lines: 25 [a series of articles suggest grounding yourself to various household objects...] Like outlets, cold-water pipes are only theoretically safe. Water utility folk and plumbers are taught to exercise extreme care with water pipes, since a faulty appliance can turn the cold-water pipe "hot." Even if the pipe is a good ground, wiring yourself to it while you open up a 110V device is less than smart -- it's too easy to get caught up in the excitement and plug the Mac back in, just to see if it's gonna run. Then when the bomb appears, you figure you'll just wiggle a board and... PZZZZT! Anyway, as I understand it, what you want is not (necessarily) an absolute "ground." You just want the potential between you and the machine to be zero. If you're both floating at 500 V relative to some Platonic ideal ground, no problem. The recommendation I've read, which I've seen VAX, Apple, and various other professional computer service people follow, is just this: Unplug the machine, snap a grounding strap around your wrist, and clip the lead from the grounding strap to the machine's chassis. For board-level work, such as installing chips, try to find a metal desk or table, and ground yourself and the equipment to that. (Don't wear polyester and don't shuffle your feet -- probably good advice in any case.) - john ----------- What John says is very important: you don't need an absolute ground, but rather a ground where the *potential* between the machine and you is zero. The ground strap is a very effective method. Kent Sullivan Microsoft Corporation The opinions expressed in this article are my own and do not necessarily reflect those of my employer.