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From: barry@hprmokg.HP.COM (Barry Fowler)
Newsgroups: sci.electronics
Subject: Re: TV degauss problem
Message-ID: <10040020@hprmokg.HP.COM>
Date: 28 Aug 89 16:29:18 GMT
References: <6939@rpi.edu>
Organization: HP Networked Computer Mfg. Operation
Lines: 57

brian@ucsd.EDU (Brian Kantor) Writes:

etc, etc....


>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
 ^^^^^^^^^^^

WRONG! WRONG! WRONG!

>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.

In all due respect to Mr. Kantor, the convergence controls DO NOT
have an effect on this described problem.  The convergence controls 
control red, blue, and green SHADOWS in varous portions of the screen
and DO NOT have an effect on COLOR PURITY, which is the problem created
by the basenote writer holding a permanent magnet to the CRT.

NEVER hold a permanent magnet hear a color CRT.  You will often permanently
magnetize the shadow mask of the CRT, creating the problem described in the
basenote.  My suggestion is to purchase a degaussing coil from a TV
parts supplier.  With the coil turned on and the set turned on (actually
the set doesn't really have to be on but it provides feedback), 
rotate the degaussing coil, first close (around 6") in overlapping circles
in front of the CRT.  Continue while slowly distancing the coil from the 
CRT until you are about 6 feet away from it.  Then turn the coil 
perpendicular to the CRT and shut off power to the degaussing coil.
This should remedy the problem IF the CRT isn't permanently ruined.

If you are a "technical type":

There are also two "purity rings" on the neck of the CRT.  These also have
an effect on color purity.  To adjust them, turn the color level to minimum
color intensity.  Adjust the red screen control (G2) to the screen is 
a full red raster.  Rotate the purity rings independently until the non-red
shadows on the screen go away and the only color on the screen is red.
Then, reset the G2 controls for a good black and white picture.

If the above procedure seems too complicated and you aren't sure of what
you are doing, DO NOT attempt to do it.  You will create a whole bunch more
work for the serviceman and will be charged, rightfully so, an additional
amount for goofing things up because it takes LOTS of time to reconverge
the set properly.  I often had this task and it ain't fun....

Good luck,

Barry


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