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Thread: Degaussing issue? Moving dark/purple tint on WG CRT

  1. #1
    Armored Scrum Object

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    Degaussing issue? Moving dark/purple tint on WG CRT

    I have cabinet with an older 25 inch Wells Gardner monitor in it that has developed an issue a while ago with some strange discoloration. Monitor is probably at least 20+ years old.

    I noticed the bottom corner of the monitor had an area about an area with the colors a bit off, a bit dark and the reds had a purple tint to them (similar to how a CRT acts when close to a magnet). This was most apparent on KoF '95 where the POW meter is in red, the 2p side was visibly purple instead of dark red. Cab is in a room in my basement with nothing around it that should cause interference and hasn't been moved around for years.

    I noticed when rearranging cabs the spot would move, depending on what position the cab was facing or where it was at in the room it would vary in intensity or placement on the screen.

    Ideas? Could this be something fixable with a degaussing wand or coil?

  2. #2
    N00b of Syougi
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    Just going off my experience with Sony PVM's and Consumer TV's here, but yes, the built-in degausser could be getting a little weak so an external degausser could fix this....however I've never had that completely fix this problem on any CRT I've tried it on (even bought a powerful pro style degaussing wand).

    Moving the yoke back into position (they can shift over time as things loosen or glue breaks down and gets brittle, the wedges shift, etc) fixed this more often than the above. ...those yoke's can be a bitch to break free sometimes so a strategically placed magnet can sometimes eliminate like 90+% of the discoloration – I find this to be a much easier solution with pretty good results. I've used the little neodymium magnets you can pickup 50 packs of for cheap off Amazon (there's supposedly professional grade proper magnets to use, but I've never found a place to by those from. Those are the type what the factory possibly used when the monitor was made and tuned and can also fall off through age).

  3. #3
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    ChuChu Flamingo's Avatar
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    What you are experiencing is the earth's natural magnetism affecting your picture. That is why you notice it changing depending upon what direction it is facing (NSWE etc). This is why technicians would often calibrate in the exact spot where the crt would stay. Reason being is that you could get the crt dialed in perfectly convergence wise/geometry, but once it moves due to the earth's magnetism it could shift ever so slightly.

    Another cause for the yoke moving over time is also due to 15 Khz vibrating over years. I thought that was interesting when I read up on it.

    What Dochartaigh said is sound advice. I would first start with some magnets to do some convergence correction and if that doesn't work do a yoke. Just make sure when you loosen it you don't let it move too far ahead or else you have the fun of doing convergence by hand.
    Last edited by ChuChu Flamingo; 02-27-2018 at 03:10 PM.


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