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14933Re: [midatlanticretro] OT: CRT Rejuvenation

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  • Mr Ian Primus
    Oct 28, 2009
      --- On Wed, 10/28/09, Joe Giliberti <Starbase89@...> wrote:

      >Does anyone have any experience rejuvenating CRT screens? How is it done? I >have a really nice Sony TV monitor from the late 80's that has developed >some picture issues. I don't want to toss it, as I want to use it for c64. >Mainly, a purple spot has formed in the corner, and the picture is no longer >as sharp as it once was.

      I don't think this is really a weak tube problem. The purple spot is more than likely a simple magnetization issue. All color sets have a degaussing coil that fires when the set is turned on from cold. If your degaussing circuit has failed, the shadow mask inside the tube won't be demagnetized when you turn it on, so any residual magnetic field can leave it slightly magnetized and cause this issue. It's also possible that it got slightly too magnetized - and the small coil in the set can't cope with it. The earth's magnetic field affects CRT's too. It's also possible that the purity has slightly drifted, but that's pretty rare - I'd try using a manual degaussing coil first.

      The focus issue can also be related to the tube going weak, but it can drift due to other component aging as well. There is a focus control on the flyback transformer, you probably just need to adjust it slightly.

      I wouldn't think this is a weak-tube problem at this point. If the tube were really weak, the colors would get dim, and one color usually gets weaker than the others.

      If you haven't fixed it by the winter party, bring it along, I can look at it for you. I've got a CRT rejuvinator, but, again, I don't think this is your problem here.

      -Ian
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