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Re: [midatlanticretro] OT: CRT Rejuvenation

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  • David Gesswein
    ... People have mostly answered this. Rejuvenation is done to cure low emission which makes the picture dim. When you can t turn it up enough or the picture
    Message 1 of 9 , Oct 28, 2009
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      > Does anyone have any experience rejuvenating CRT screens? How is it done?
      >
      People have mostly answered this. Rejuvenation is done to cure low emission
      which makes the picture dim. When you can't turn it up enough or the
      picture gets too fuzzy due to the high brightness setting is when you
      need to rejuvenate. They also sold little transformers to increase the heater
      voltage which also increases emission. I have used my rejuvenator on a
      VT100 terminal screen. You hook it up to the connector on the back of the
      tube.

      > Mainly, a purple spot has formed in the corner, and the picture is no longer
      > as sharp as it once was.
      >
      Like people have said this is likely a magnitization issue. Some (large?)
      monitors/tv's have internal degauss coil around the tube. If yours has
      that and the drive has failed manually degaussing it will only work for a
      while. If you heard a buzz for a few seconds or on turn on or the picture
      shaked for a few seconds it had a built in degaussing coil. If it didn't
      it may not have had one or they did a better job of it than some of
      my monitors. A friend had a large TV the coil drive failed on and it
      got the funny colored spots.
    • Mr Ian Primus
      ... 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
      Message 2 of 9 , Oct 28, 2009
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        --- 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
      • Brian Schenkenberger, VAXman-
        ... DEC used the Sony tubes in most of their larger video monitor offerings such as the VRT21. Even with the degaussing coil in tact and functional, these
        Message 3 of 9 , Oct 28, 2009
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          Mr Ian Primus <ian_primus@...> writes:

          >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 mas

          DEC used the Sony tubes in most of their larger video monitor
          offerings such as the VRT21. Even with the degaussing coil in
          tact and functional, these tubes would experience magnetization
          of the shadow mask. It can be very difficult to get residual
          magnetization that is causing the color bleed neutralized when
          this happens. I have one such tube with this issue that I was
          able to minimize but never completely annihilate. I just live
          with it as it's not all that pronounced now.

          If your system needs an RGB/sync-on-G or RGB/V&H monitor, there
          are RGB-to-VGA adaptors. You can then use a modern display as
          your video monitor -- even an LCD flat panel. Imagine just how
          much less your Watt-Meter will spin and how much less you'll be
          donating to your power company each month. ;) Much less heat
          in the summer months too.

          --
          VAXman- A Bored Certified VMS Kernel Mode Hacker VAXman(at)TMESIS(dot)COM

          "Well my son, life is like a beanstalk, isn't it?"
        • Dan Roganti
          It also make a difference if you had moved something recently close to the TV. Something which is magnetic(or creates magnetism), a speaker, metal case, floppy
          Message 4 of 9 , Oct 28, 2009
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            It also make a difference if you had moved something recently close to the TV. Something which is magnetic(or creates magnetism), a speaker, metal case, floppy drive, any power supply, etc before you try to degauss it.

            =Dan
          • Joe Giliberti
            I actually haven t used the set regularly for a few years. When it was in use, it was not used for anything other than TV and playstation
            Message 5 of 9 , Oct 28, 2009
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              I actually haven't used the set regularly for a few years. When it was in use, it was not used for anything other than TV and playstation

              On Wed, Oct 28, 2009 at 1:29 PM, Dan Roganti <ragooman@...> wrote:
               


              It also make a difference if you had moved something recently close to the TV. Something which is magnetic(or creates magnetism), a speaker, metal case, floppy drive, any power supply, etc before you try to degauss it.

              =Dan


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