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12" CRT Monochome Display

Discussion in 'Troubleshooting and Repair' started by vintageibm, Jun 7, 2010.

  1. vintageibm


    Jun 7, 2010
    Hello, I have a very old IBM 5151 12" monochrome CRT display. Built in 1981. It was working fine when I left the room but when I returned I found the text on the screen to be pulsing in and out (getting bigger & smaller). It would also be waving/quivering/shaking. It did it pretty much all the time but would stop for a short amount of time maybe less then a 1 min and work normal. Info for this display can be found here then clicking on IBM 5151. I am a collector so I simply don't want to just replace the display. I don't know much, so try to keep your answers on the simple side. I have a very limited knowledge. I can test parts if someone tell me the location and how to test them on a DVM. I don't have a scope. Thanks
    Last edited: Jun 7, 2010
  2. Tesla


    May 10, 2010
    There are some very dangerous voltages inside this CRT (actually any tube monitor or TV) that could easily kill you.

    Definitely not a project for a beginner. Even an experienced technician should have training on high voltage appliance repair before attempting such a repair.

    If your overall end result is to have a working vintage IBM 5151 monitor, your best bet would be to:
    1. Buy a used one from eBay or computer salvage
    2. Find a TV shop (that still does board level repair) and see if they can fix it for you.
  3. vintageibm


    Jun 7, 2010
    Hi, yes I am fully aware there is 10,000 plus volts inside the display and were the high centers are. I would still like to trouble shoot and repair this display! Can anyone help me?

  4. shrtrnd


    Jan 15, 2010
    I agree with Tesla, dangerous inside if you don't know what you're doing. Wanted to say I've seen this problem repeatedly in very high humidity places. I live in the desert with an evaporative cooler in the summer. If you have high humidity, when you turn on the CRT, you can get some pretty wild problems (like you described), for a while, until the moisture evaporates when the CRT warms up. Consider that as a possible source of your problem, if you're in a wet environment.
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    I once worked on a very dusty mine site. Even though everything looked clean, the moment it got humid all sorts of weird electrical faults showed up. Inside most electrical equipment was a thick layer of almost conductive dust that became far more conductive as it got more and more humid. The first fault-finding technique was to clean out the dust first :)
  6. Resqueline


    Jul 31, 2009
    When the image of an CRT zooms in & out it's a sign that the High Voltage is unstable. Less voltage = bigger (& darker) image. Flakey HV transformer maybe?
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