49 Magnetic Fields and Degaussing
Description
This article is from the comp.sys.ibm.pc.hardware.video Frequently Asked Questions, by Michael Scott with numerous contributions by others. (v1.0).
49 Magnetic Fields and Degaussing
[From: Sam Goldwasser ]
Indications of need for degaussing are small or large areas of the screen where the colors are not correct or where color balance has suddenly changed. There are other possible causes - both electronic and mechanical - but stray magnetic fields is numero uno on the list.
The shadowmask or aperture grill of the CRT - the fine mesh just behind the phosphor screen - is normally made of a material (steel or InVar) which is easily magnetized. This can happen just by rotating the monitor on its swivel, by moving it from one place to another, by switching on or off some piece of electronic equipment near the monitor, even by a local lightning strike.
Since any stray magnetism affects the color purity and convergence, it is important that the CRT is demagnetized before use.
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