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Thread: Commodore PC 20 III works after 15 minutes

  1. #1

    Default Commodore PC 20 III works after 15 minutes

    My Commodore PC 20 III does not work after turning on. The monitor shows nothing. When I leave it on for about 15 minutes, turning it on again works fine.

    Supersoft / Landmark Diagnostic ROM's software also doesn't work at first, it freezes in a random place. After about 15 minutes, the test passes correctly.

    Where to find the problem?

  2. #2

    Default

    I know about computers stopping to work because parts run hot. But computers that first have to warm up before it will run ???

    What I can think about is a bad connection, between an IC or even inside an IC, that expands a bit when warming up, thus creating a good connection. Hoe to find it? Use some cooling spray to cool various parts. If the computer stops, you have found the bad spot. Of course no guarantee at all that this idea will work.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  3. #3

    Default

    I know about computers stopping to work because parts run hot. But computers that first have to warm up before it will run ???

    What I can think about is a bad connection, between an IC or even inside an IC, that expands a bit when warming up, thus creating a good connection. Hoe to find it? Use some cooling spray to cool various parts. If the computer stops, you have found the bad spot. Of course no guarantee at all that this idea will work.
    With kind regards / met vriendelijke groet, Ruud Baltissen

    www.baltissen.org

  4. #4

    Default

    Yes, my computer needs to warm up

    Watch the video on first run:
    https://photos.app.goo.gl/qUbWJH8JoMamCNuc6


    Watch the video after a few minutes:
    https://photos.app.goo.gl/x5h8sJNfwKyR88vAA


    See how it starts up after several minutes:
    https://photos.app.goo.gl/o3EmwYbPPc7AzR5T8


    I'll try your idea in a few days.

    Maybe someone else will suggest something?

    I still have a PC 10 III. I moved all the ICs from the second computer (the ones in the sockets) and there was no improvement. I updated the bios to the latest version.

  5. #5

    Default

    Partially repaired.

    A few years ago, I removed the batteries. Now I have looked closely. I fixed two connections. The computer starts right away.

    However, I get the error "Bad ram at 8075D = 00h, expected = 00h".

    About this next topic.

  6. #6
    Join Date
    Oct 2016
    Location
    Dutchess County, New York, USA
    Posts
    324

    Default

    I had a PC that failed to boot completely when first powered up, sometimes took 2-3 attempts to get to POST. It was early sign of a pending video card failure. Problem went away when I replaced the totally failed video card.
    Crazy old guy with a basement full of Pentium 1 laptops and parts

  7. #7
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    7,040

    Default

    Quote Originally Posted by dippaolo View Post
    However, I get the error "Bad ram at 8075D = 00h, expected = 00h".
    I have replied in the thread that you started about that.

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