Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!gatech!purdue!tut.cis.ohio-state.edu!cs.utexas.edu!usc!ucsd!brian
From: brian@ucsd.EDU (Brian Kantor)
Newsgroups: sci.electronics
Subject: Re: TV degauss problem
Message-ID: <1921@ucsd.EDU>
Date: 26 Aug 89 15:27:32 GMT
References: <6939@rpi.edu>
Reply-To: brian@ucsd.edu (Brian Kantor)
Distribution: sci.electronics
Organization: The Avant-Garde of the Now, Ltd.
Lines: 28

Most consumer TV degaussing circuits consist of a coil of magnet wire
around the front face of the tube, and a simple analog timer circuit.
The idea is that every time the set is switched on, a moderately heavy 
alternating current is run through the coil and is gradually reduced to
nearly nothing over the space of a few seconds.  This has the desired
effect of demagnetizing bits of metal that may have picked up a slight
magnetic "charge" from the Earth's and other ambient magnetic fields.

Your experiment with the magnet could easily have place more
magnetism into the TV set than this weak degaussing system can cope
with.  If you're lucky, a degaussing coil (such as the ones Sun
ships with their color workstations, or which can be bought at
large electronics suppliers or maybe even Radio Shlock) is a much
more powerful degausser and may, properly used, be able to clear
the problem.

If the magnet you were fiddling with was strong enough and you got
it close enough, you may have bent or misaligned the shadow mask
in the CRT, which would cause the electron beams to land off-register
with the colour phosphor dots on the tube face.  There is no cure
for this problem except to replace the tube.  However, if the
misalignment is not large, you may be able to tune it out with the
convergence controls in the set.  This is a complex procedure that
takes more patience than I normally possess, so I don't recommend it.
Don't even TRY it without a copy of the manufacturer's alignment
procedure in front of you - and you'll need a bar/dot generator.

I wish you good luck.  You're going to need it.