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Thread: Unique S-100 computer (Z-80/Vector Graphic/Micropolis)

  1. #171

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    I would normally start looking on the drive PCB first, but your drive cabinet has a single board that controls two drives instead of a board per drive. I only have schematics for the latter. Have you found and downloaded schematics for the PCB in your drive cabinet? If so, point me to it and I’ll download a copy.

    Mike

  2. #172

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    Yes I believe this is it:
    http://www.bitsavers.org/pdf/micropo...nual_Feb79.pdf

    The board pictured in 4-3 is very similar to mine. There are some differences with connector positions but its the closest I've found. The schematic starts on page 132.

    Here is a closeup of my drive cabinet board
    20200522_205335.jpg

  3. #173

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    Actually, before we look for a write issue, have you looked at the 60hz strobe lines on the hub disc? How is the drive speed?

    Mike

  4. #174

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    Actually I just realized I hadn't tried something after my adjustments.. I was never sure which head connector went to which drive on the internal board. Every test previously I'd swap the connectors around in case they were backwards. So now I swapped them and I was able to get a successful write! It said the disk was created at the end. I wrote the 56k "Vector CPM for Micropolis.vgi" image. However, I am unable to boot from it using the 'B' monitor command. The disk drive engages but just spins and nothing happens.

    How would I check the strobe lines? The speed seems ok but how can I measure it? The belts do seem a bit loose.

  5. #175

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    Look on the hub pulley. Is there a strobe pattern printed on a white disk? Just watch in a room with (ideally) fluorescent lights. It should appear to stand still while the motor spins. Most likely it will appear to move forward or backward slowly. You can then adjust a pot on the board in the drive cabinet as detailed in the manual you posted the link for to make the pattern stand still.

    Mike

  6. #176

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    Quote Originally Posted by nullvalue View Post
    However, I am unable to boot from it using the 'B' monitor command. The disk drive engages but just spins and nothing happens.
    The manual you posted has the connector information so you can know for sure in future.

    If PCFLOP was able to write and verify the disk, then it should boot unless you have RAM problems. Use the monitor to test RAM from 0000 to DFFF and let it run for a while.

    Mike

  7. #177

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    Quote Originally Posted by deramp5113 View Post
    The manual you posted has the connector information so you can know for sure in future.

    If PCFLOP was able to write and verify the disk, then it should boot unless you have RAM problems. Use the monitor to test RAM from 0000 to DFFF and let it run for a while.

    Mike
    Yes, very odd that I could run the disk creation but that I couldn't boot. How long does boot from disk typically take? Just a few seconds, right?

    I let the memory test run for over an hour. From what I can tell, I got 0 failures: 20200524_095448.jpg

    Yes there is a white disk with a strobe pattern. I will attempt the speed test.

  8. #178

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    So I put the drive under florescent light and attempted the speed test. There is just a blur of the wheel, no appearance of a slow spin or standing still. I adjusted the pot (tried both the top and bottom) and no adjustment seemed to make any difference whatsoever.

  9. #179
    Join Date
    Dec 2005
    Location
    Toronto ON Canada
    Posts
    7,338

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    It has to be a 'real' oldskool fluorescent, not a newfangled compact fluorescent (CFL) bulb, or you could try an LED powered from a low-voltage AC power brick through a resistor.

  10. #180

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    You can pick out the pattern even with an incandescent bulb. Not as obvious as fluorescent, but it’s there.

    Mike

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