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Thread: Compatible CPU for Kaypro 2X?

  1. #11
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    If you're talking about the 40 pin DIP above marked PIO (on your photo as the MK3884), it's a Z80 SIO chip, otherwise known as a Z8440, or in CMOS, as a Z84C40. The Mostek part number is a second-source ID.

  2. #12
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    Quote Originally Posted by durgadas311 View Post
    The PIO provides an interface to the RTC and modem, and usually it's absence doesn't prevent CP/M from running (boards were left with PIO, RTC, and modem un-populated for the "economy" versions).

    I don't think I have a description of what problems you are seeing. Can you describe what's wrong?
    I just get a blank green screen with diagonal lines going down it when I turn the machine on, the same problem I had with a TRS-80 Model 4 I briefly owned actually. I don't even know where to start with that.

  3. #13

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    That sounds like either the video (analog) or else the CRT controller IC(s). Hard to say which without seeing the pattern. The analog circuitry is probably repairable, and CRT controller chip might be replaceable, but the custom-LSI CRT chip is probably only replaceable by cannibalizing another Kaypro.

  4. #14
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    Quote Originally Posted by durgadas311 View Post
    That sounds like either the video (analog) or else the CRT controller IC(s). Hard to say which without seeing the pattern. The analog circuitry is probably repairable, and CRT controller chip might be replaceable, but the custom-LSI CRT chip is probably only replaceable by cannibalizing another Kaypro.
    It's really hard to see because the CRT is so dim (and doesn't respond to the brightness knob) but there's kind of a big green box with lighter horizontal lines going across it.

    D1j6LblWoAETfgt.jpg

  5. #15

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    I'm no expert in the area of video, but that could almost just be the normal raster of a blank screen, with brightness set to maximum. Still, blank screen means nothing (software) is running. If the brightness knob does nothing, that might imply something wrong with the video circuitry. It's probably going to take old-fashioned detective work, and an oscilloscope, to track down what is wrong. I guess the good news is that there is a raster, so some clocks are still working.

  6. #16
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    Yup, looks like a blank raster to me also.

  7. #17
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    Quote Originally Posted by durgadas311 View Post
    I'm no expert in the area of video, but that could almost just be the normal raster of a blank screen, with brightness set to maximum. Still, blank screen means nothing (software) is running. If the brightness knob does nothing, that might imply something wrong with the video circuitry. It's probably going to take old-fashioned detective work, and an oscilloscope, to track down what is wrong. I guess the good news is that there is a raster, so some clocks are still working.
    I don't own an oscilloscope, time to find someone who does I guess...

  8. #18
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    Quote Originally Posted by durgadas311 View Post
    I guess the good news is that there is a raster, so some clocks are still working.
    I don't know how good the news is though. If I recall, I was also getting this screen on my 2/84 which turned out to be the bad custom chips. Hopefully it's not that on his, but I'm not sure if this is enough to know if it's bad or good news yet.

    Generally I find that computers that don't power on at all make me the most optimistic that they can be fixed since it's usually just a power supply issue... Things like this (similar to the Commodore "black screen") could be just about anything.
    -- Brian

    Working Systems: Apple IIe/II+/Mac+/Mac 512k, Atari 800/520STFM, Commodore 64/Amiga 3000/SX-64, IBM PS/1 2121-B82, Kaypro II, Tandy 1000 SX, TI-99/4A, TRS-80 Model 4 GA
    Project Systems: Amstrad PCW 8256, Kaypro 2/84 (Bad Chips: 81-194, 81-189).

  9. #19
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    I do have a multimeter at least so I could probe the custom chips and see if they're getting correct voltages and such, granted, I don't know what said custom chips are...

  10. #20

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    it could also be the rom chip... some went bad or lost info from rom.. mine is a x2..

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