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RE: [midatlanticretro] OT: CRT Rejuvenation

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  • Brian Schenkenberger, VAXman-
    ... A degaussing coil. That was a common footprint in the Sony tubes. Be carefull of the high voltages inside. The focusing screen is in the tube. Try
    Message 1 of 9 , Oct 28, 2009
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      >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.

      A degaussing coil. That was a common footprint in the Sony tubes.

      Be carefull of the high voltages inside. The focusing screen is in
      the tube. Try cleaning the entire unit. Blow all the dust off of
      all of the wiring leading to the tube. Be very carefull NOT to move
      the deflection coil. Realignment can be tedious. A TV repair shop
      may be able to refocus the tube for you for some $$$.

      --
      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
      Dan Roganti wrote: Joe Giliberti wrote: Does anyone have any experience rejuvenating CRT screens? How is it done? I have a really nice Sony TV monitor from the
      Message 2 of 9 , Oct 28, 2009
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        Dan Roganti wrote:
        Joe Giliberti 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 have one here, but I'm too far for you I think -- Pittsburgh :)
        I could always bring to the next vintage computer workshop



        I overlooked a couple of things in your message - I haven't finished drinking my coffee here yet.
        On the purple spot - it really sounds like you need a degausser.
        The bigger the better depending on the size of the tube.
        I have a 16" here that would help too.
        On short notice, you can also you the magnetism generated from a 100W solder gun.
        I've done when I was without my tools, it has a smaller mag. field but you can still clear it up.

        About the sharpness, there's a focus control on the flyback that will adjust this.
        When you can't get it completely in focus, it sounds like the Flyback is wearing thin - it'll be time for a change soon.

        =Dan



      • 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 3 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 4 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 5 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 6 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 7 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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