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Thread: Osborne 1a Help

  1. #1

    Default Osborne 1a Help

    Hello everyone!

    As per usual, I picked up an Osborne 1a and it doesn't work. Before powering it on, I rebuilt the power supply completely and tested it with a load. No ripple on my oscilloscope.

    The symptoms are the same as most of the older posts here on VCF; those being a mess of characters on the screen and non-boot with the speaker making a continuous beep.

    The only thing that is different with my machine is that I discovered that if I grip the BIOS chip by the pins, I can get the Osborne to boot to the welcome screen and it remains stable for several minutes before it gets corrupted again. I re-seated all the chips but no change.

    I read that the 4116 dynamic ram chips go bad but probing and piggybacking all the ram chips yielded only a single faulty one. I'm not sure what to look for but all the ram was showing similar activity amongst each of them.

    Is it possible that the BIOS CMOS chip is bad? I will be posting a video on Youtube that shows the problem shortly.

    Any thoughts?

  2. #2

  3. #3

    Default

    Hello,
    it is possible to have issues with bad sockets or broken trace. Try to check continuity with a multimeter . You check the signal on address and data bus on Z80? Best Regards.

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