grege@gold.gvg.tek.com (Greg Ebert) (12/04/90)
You Gaussed it, dude ! You need to degauss your tube. Try taking it to a local TV repair shop, and ask them to do it. If they want more than $5 for a 30 second task, tell them to [obscenity deleted]. Don't worry ! You havn't done anything permanent.
archer@stlvm2.iinus1.ibm.com ("Gary D. Archer") (12/06/90)
Ref: Append to PC-HDWE USENET (ARCHER) at 23:27:38 on 90/12/04 The 1304HG does have a built in degauss button, it's the power switch. When you turn it on cold you'll hear a ker-chunk, thats the degausser. It only operates when the monitor is cold, so quickly cycling it on/off doesn't work. Gary ---------------------------- Append follows ----------------------------- ----- PC-HDWE USENET appended at 23:27:38 on 90/12/04 GMT (by USENET at ALMADEN) Subject: Re: Magnetic burn on VGA monitor From: schwalbe@pinocchio.Encore.COM (Jim Schwalbe) Date: 4 Dec 90 18:52:28 GMT In article <33951@netnews.upenn.edu> mfontana@eniac.seas.upenn.edu (Mark A Fontana) writes: > Help! I've just had an accident with my Super VGA monitor >(a Sony CPD 1304). [Deleted explanation of how he exposed his monitor to magnetic field] No need to worry. I don't think you did any permanent damage. I think you just need to degauss the tube. I guess I'm kind of disappointed to hear that the Sony 1304 doesn't come with a degaussing button (or did you not try it). I'm thinking of buying that monitor. Many good color monitors do come with degaussing buttons or switches. If it doesn't have a degausser, then I'm not sure how to do it but I'm sure it can still be done. Someone else will probably know. .---------------------------------------------------------------------------. : Jim Schwalbe .----------------. "Half of what I say is : : Hardware Research Group .--+-------------. | meaningless; but I say it : : Encore Computer Corp. | | E N C O R E | | so that the other half may : : Mail: | `-------------+--' reach you." : : schwalbe@encore.com `----------------' - Kahil Gibran : `---------------------------------------------------------------------------'
kenw@col.hp.com (Ken Wyatt) (12/07/90)
I missed all the previous explanation on how this crt became magnetized, but allow me to relate a possibly similar experiance with my EGA monitor. One day I tried running a magnet around in front of the crt while observing all the fasinating color changes. Of course, when I removed the magnet, the most of the "color changes" remained! It took about two months of use before the built-in degaussing coil could finally remove all traces of the residual magnetism. I suspect that the process could be greatly speeded up by using a video tape demagnetizer. Turn on the demagnetizer, holding it a couple of inches from the face of the crt. Slowly (with a circular motion) move the demag. around the crt face, keeping the distance about two inches away. Once the entire face has been treated, SLOWLY start to move the demag. away from the crt surface WHILE KEEPING THE DEMAG. POWER APPLIED. When you get about three feet away, remove power to the demag. You should now be left with a fairly clear screen. Any residual problems will likely be fixed by the built-in demag. coil (which is located around the perimeter of the crt face). I caution you that I have not personally tested this technique, although it has worked very well for color televisions and is a standard procedure used by service persons.
berger@anomaly (Mike Berger) (12/07/90)
mfontana@eniac.seas.upenn.edu (Mark A Fontana) writes: >Read on, MacDuff... one further lesson that MAGNETS and COMPUTERS > just don't mix! *---- Your color purity should return with a bit of degaussing. If your monitor is working correctly, the built-in degaussing coil should come on for a few seconds when you turn the monitor on (after the thermistor has cooled). If you've done enough damage, it might take a week or two of normal use before the CRT is completely degaussed. An external degaussing coil would speed things along. They're about $ 20 - $ 30 at electronic supply shops. -- Mike Berger Department of Statistics, University of Illinois AT&TNET 217-244-6067 Internet berger@atropa.stat.uiuc.edu
cgordon@vpnet.chi.il.us (Crash Gordon) (12/15/90)
<stuff about magnetized CRTs> It's not actually the TUBE that's magnetized. Nor is is the PHOSPHORS. There is a piece in the color CRT called the "shadow mask". (Monochrome CRTs don't have a shadow mask.) The shadow mask is a perforated sheet of foil stretched just in back of the phosphors; the electron beam passes through the shadow mask just before striking the phosphors. What has happened is that the shadow mask has become magnetized, and is deflecting the beam as it passes through. The "neato" effect is caused by a magnetic field deforming the electron beam. This can be a lot of fun to play with, but do it with a cheap TV, not your PC monitor!. Most (if not all) color monitors include a degaussing coil, since CRTs tend to magnetize themselves slightly during normal operation. Since this normal residual field is weak, the degaussing coils are also pretty weak. But they can take out a heavy field if enough cycles are used. The coil is activated through a thermistor, so that the appropriate type of magnetic field is produced. (Degaussing requires an alternating magnetic field with a slow decay.) The thermistor shuts down the degaussing coil as it (the thermistor) heats up. This means that simply cycling the power to the monitor won't force more degaussing -- you must leave the monitor off for a minute or two to allow the thermistor to cool. Probably, your monitor problem will clear up in a few weeks, as the internal degaussing coil does its thing. The bad potential is that if the field which caused this problem was strong enough, it may have actually bent the shadow mask. In such a case it would be time for a new CRT. I doubt that yours is such a case, since an accidentally magnetized ruler probably wouldn't produce a strong enough field. ----------------------------------------------------- Gordon S. Hlavenka cgordon@vpnet.chi.il.us