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

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  • nullvalue
    replied
    Awesome, will do - is the track 0 signal simply asserted by that switch, or is there more involved than that?
    Last edited by nullvalue; May 13, 2020, 08:32 AM.

    Leave a comment:


  • deramp5113
    replied
    Great progress! Use a scope and see if the track 0 signal on the interface cable (pin 26) is getting asserted (asserted = low). Look at the signal on the drive PCB and then on the floppy controller PCB and see where it is failing. Trace backward as required to its origination on the drive PCB, and/or forward to it's final destination in the latch on the floppy controller end.

    Mike

    Leave a comment:


  • nullvalue
    replied
    So I decided to go through and give everything another good cleaning. Let the ribbon cable soak with some DeOxIt on the leads and cleaned up the connectors on the drive PCB. Making some progress! Now the solenoid engages and the head snaps down. The worm gear engages and moves the head all the way to the outer edge of the disk. I can see once it reaches the edge, the 0-track switch does get engaged. However, the application is still saying "Seek to track 0 failed". Same thing happens for both drives. But now at least I can see the head only engages on the correct drive when I enter 0 or 1.
    Last edited by nullvalue; May 13, 2020, 07:18 AM.

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  • nullvalue
    replied
    Yes they only start spinning once they're selected, and stop spinning after about 5 seconds. I only hear the sound of the hub spinning, no head loading sounds at all.

    Leave a comment:


  • deramp5113
    replied
    Do your drives start spinning only when they’re selected and then stop after 4-5 seconds, or do they run all the time like an 8” drive? When the drive is selected by PC2Flop, do you hear the head load?

    Mike

    Leave a comment:


  • nullvalue
    replied
    Originally posted by deramp5113 View Post
    Sounds like you'll have to start diagnosing drive operation then. Now that you have the unit open, do both drives spin when either drive is selected? With power applied, can you still rotate the worm gear on each drive with your fingers or does it feel like it's being held in place now?
    Yes if a disk is in the drive, both drive hubs spin regardless of which number I enter. Yes, when power is applied, I can no longer move the worm gear.

    Here are some pictures of the inside of the drive - if that helps any:

    20200512_175012.jpg 20200512_175021.jpg 20200512_175233.jpg 20200512_175042.jpg 20200512_175100.jpg 20200512_175154.jpg 20200512_175914.jpg
    Last edited by nullvalue; May 12, 2020, 03:02 PM. Reason: Added pictures

    Leave a comment:


  • nullvalue
    replied
    Originally posted by exidyboy View Post
    Through rough handling in the past the leadscrew can actually pop out. Perhaps imagine a dislocated joint. Can you see that it is seated correctly at both ends. If you send the right signals you might get a tiny amount of movement when it is in that state.
    I'm pretty sure it's in the right position. I took the whole thing apart, cleaned and regreased everything.

    Leave a comment:


  • exidyboy
    replied
    Originally posted by nullvalue View Post
    Edit: The head mechanism is not moving at all. Belt & disk spins, but no head movement. Occasionally I hear a squeaking/squealing sound like something is trying to move. Could the stepper motor be seized?
    Through rough handling in the past the leadscrew can actually pop out. Perhaps imagine a dislocated joint. Can you see that it is seated correctly at both ends. If you send the right signals you might get a tiny amount of movement when it is in that state.

    Leave a comment:


  • deramp5113
    replied
    Sounds like you'll have to start diagnosing drive operation then. Now that you have the unit open, do both drives spin when either drive is selected? With power applied, can you still rotate the worm gear on each drive with your fingers or does it feel like it's being held in place now?

    Leave a comment:


  • nullvalue
    replied
    Thankfully, the hubs do seem to spin freely and smoothly, I don't feel any binding or grinding. With power off, I can rotate the worm gear using just my fingers fairly easily. I tried with a disk in both drives, 0-3, no options produced head movement on either drive. The squeaking sound I hear may just have been coming from the hub. On closer inspection, I don't really sense the stepper motor engaging in any way.

    Leave a comment:


  • deramp5113
    replied
    I have not had much problem with the stepper motors (head movement) in the Micropolis drives, but it could certainly be stuck or have failed. How hard is it to manually rotate the worm gear and move the head on each drive (with power off)?

    Note that the hub motor will typically spin on both when either drive is drive is accessed. The hub bearings in those Micropolis drives are often bad. Remove the belts and see how freely the hub spins on each drive.

    Mike

    Leave a comment:


  • nullvalue
    replied
    This may be helpful to know but this system was found complete with everything except for the FDC board. That I had to purchase on eBay (vintage computer museum). I have no idea as to it's condition or what system it was pulled from. It was really odd - the ribbon cable was just dangling inside the chassis. The dual drive was there - but no controller.

    Yes I have the Micropolis 1053-II, which has two 5 1/4" drives. '0' spun the top drive. Curiously, '1' also spun the top drive, not the bottom as I would have expected. '2' and '3' also spun the top drive.. I will open it up and try your experiment.

    Edit: The head mechanism is not moving at all. Belt & disk spins, but no head movement. Occasionally I hear a squeaking/squealing sound like something is trying to move. Could the stepper motor be seized?
    Last edited by nullvalue; May 12, 2020, 05:18 AM.

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  • deramp5113
    replied
    The CPU speed is set by jumper area A on the COU board. Both 2 and 4 MHz use the 8 MHz xtal. But if this was all working before as a system, most likely the CPU is at 4 MHz like the FDC is set.

    With power off, manually rotate the head worm gear so the head is clearly not at track zero. Then run the program. Does the head move at all after you select the drive in PC2FLOP? Do you have more than one drive? Did you try both drives as an option in PC2FLOP?

    Mike

    Leave a comment:


  • nullvalue
    replied
    Originally posted by deramp5113 View Post
    Send me a picture of the 4mhz jumper area shown here: https://deramp.com/downloads/vector_...%20Jumpers.jpg

    What speed is your CPU running?

    Mike
    Here is the speed jumper area:
    20200511_194127.jpg

    The crystal attached to the Z80 is 8mhz.

    Leave a comment:


  • deramp5113
    replied
    Send me a picture of the 4mhz jumper area shown here: https://deramp.com/downloads/vector_...%20Jumpers.jpg

    What speed is your CPU running?

    Mike

    Leave a comment:

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