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Thread: Just to confirm:

  1. #1
    Join Date
    Feb 2015
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    Default Just to confirm:

    Working on a Model 4 that had seen better days: The top half of the chassis had been off before but I had to go in again to replace the keyboard and upgrade the drives and add hi-res video. I removed the top and as I did so I heard a soft whoosh. Never heard that before. When the top was all the way off I noticed the small board (electron gun) at the end of the tube had come off the tube.

    I assume that I have pooched the CRT. I haven't applied any power since; I don't know what would happen if I did, but if there is any diagnostic I should perform before looking for another tube please let me know.

    Thanks,
    -CH-

  2. #2
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    Default

    Ouch. That sucks. Literally.

    I'd carefully inspect the gun end of the tube to look for any cracks in the glass. There is often a little glass bit at the center the pins that can break easily. If anything is obviously broken, then don't even bother powering it on again, it's hosed.

  3. #3
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    Unfortunately, it's easy to break off the tip of the evacuation tube "nipple" in the center of the socket. If that happens, you've let the pixies out. When disposing of CRTs, this is about the safest way to relieve the vacuum in a CRT about to be trashed.

  4. #4

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    If you heard the obvious swoosh then sorry to say that it’s likely game over for the tube.

  5. #5
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    Default

    I can probably help with replacement parts, contact me.

    If you heard a woosh.....its toast.

  6. #6

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    It might be worth hanging onto in case the early television museum ever gets their crt rebuilding service running.

  7. #7
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    Default

    Yah, I knocked off the end nipple and bent the pins. What an idiot; I knew better.

    If someone anticipates a possible repair I will set it aside and donate it; otherwise it will go where all my other mistakes wind up...

    The tube is marked Philips 12VCMP31. I have begun the search for a replacement.

    Thank you for your responses.

    -CH-

  8. #8

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    isn't is possible to re-evacuate them?

  9. #9
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    Yes---but it's not a procedure for a layman. The rebuilders generally replace the whole gun assembly, bake, evacuate and burn-in.

  10. #10
    Join Date
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    Default

    Here’s how it’s done.

    https://www.earlytelevision.org/crt_rebuild.html

    Whole neck is cut off the tube and replaced in this example. I suppose in theory if you *just* wanted to evacuate one through the broken nipple and re-seal it then maybe you could somehow jury rig it with garage-workshop level equipment, but my guess would be you’d leave enough gas inside that the electron gun would die a premature death, among other things.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

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