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To: techknow@collusion.org
Subject: [techknow] De-gaussing
My 27" TV has psychedelic coloration around the edges of the screen. I am assuming the shadow plate has become magnetized (most likely by the "shielded" surround speaker that was set on top of it). Does anyone have a de-gaussing coil I could borrow or know a cheap source of magnetic wire so I can make my own?
Response:
magnetic wire can be a bitch to find to make a coil,you can get a coil from twobits.com for 45 bucks - which is fairly reasonable if you want to do it quickly, or you don't want to shell out the cash and have some time to kill, use a large refrigerator magnet or old speaker coil -
First try the internal degauss circuits of the monitor by power cycling a few times (on for a minute, off for 30 minutes, on for a minute, etc.) If this does not help or does not completely cure the problem, then you can try manually degaussing
consist of a hundred or so turns of magnet wire in a 6-12 inch coil. They include a line cord and momentary switch. You flip on the switch, and bring the coil to within several inches of the screen face. Then you slowly draw the center of the coil toward one edgeof the screen and trace the perimeter of the screen face. Then return to the original position of the coil being flat against the center of thescreen. Next, slowly decrease the field to zero by backing straight up across the room as you hold the coil.
When you are farther than 5 feet away you can release the line switch.The key word here is ** slow **. Go too fast and you will freeze the instantaneous intensity of the 50/60 Hz AC magnetic field variation into the ferrous components of the CRT and may make the problem worse. It looks really cool to do this while the CRT is powered. The kids will love the color effects. Bulk tape erasers, tape head degaussers, open frame transformers, and the"ass-end" of a weller soldering gun can be used as CRT demagnetizers but it just takes a little longer. (Be careful not to scratch the screenface with anything sharp.) It is imperative to have the CRT running when using these wimpier approaches, so that you can see where there are still impurities. Never release the power switch until you're 4 or 5 feet away from the screen or you'll have to start over. I've never known of anything being damaged by excess manual degaussing though I would recommend keeping really powerful bulk tape erasers turned degaussers a couple of inches from the CRT.
I have even degaussed with a permanent magnet but this is not recommended since it is more likely to make the problem worse than better. However, if the display is unusable as is, then using a small magnet can do no harm. (Don't usea 20 pound speaker or magnetron magnet as you may rip the shadowmask right out of the CRT - well at least distort it beyond repair. Use something about as powerful as a refrigerator magnet.
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