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Thread: Amiga 1200 2B Mainboard - Data bus high

  1. #1
    highpuff's Avatar
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    Oct 2012
    Västra Götaland
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    Default Amiga 1200 2B Mainboard - Data bus high

    Got an issue here that is harder than I expected to fix. The problem is that after a while, depending if the PCB is cool or not, all data bus'es gets high after a while. No picture is ever displayed.

    Things to know:
    - The PWR-led stays dimmed.
    - This happened when the owner tried to upgrade from 3.0 to 3.1.
    - I'm using the Dialoga 2.0 ROM's that I verified a few times during my tests that they work.
    - The Caps button works a few pushes then stays off/on.

    I have done the following:
    - All clocks are checked and has the correct frequencies
    - Checked all traces from U6A and U6B
    - Checked for shorts
    - Removed both U7 and U8 (CIA A-B)
    - Removed the 68EC020 CPU and used a working Blizzard 1220

    Any ideas? I cannot see any damage at the ROM sockets but will remove them tomorrow and see if there is something there. Maybe I will try to replace the MPU as well.

    For a short period of time I was suspecting that it could not read from from the ROM's. The exact same behaviour occurs when I remove U6A or both of the ROM's and power on the Amiga.

    Thanks in advance

  2. #2
    Ministry of Retr0bright and Street Judge VIP
    Merlin's Avatar
    Join Date
    Nov 2007
    38 (100%)


    Thread moved to AmiOracle as a more suitable place to get a response.
    The future's so Retr0bright, I gotta wear shades.....

    As rkauer said:-
    "Retro computers seems like an orgasm: it is always better to have a real one than fake it".

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