Image Map Image Map
Page 1 of 4 1234 LastLast
Results 1 to 10 of 35

Thread: Repair of MPI 51M

  1. #1
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,026
    Blog Entries
    2

    Default Repair of MPI 51M

    I've got two MPI 51M 5.25" drives in my Osborne 1. Drive A: does nothing but spin when a disk is put into it. Drive B: will pull the head all the way to the back, and then sort of 'rubber band' it where it's like it tries to go forward a little and then bounces back. The head seems to move fairly well along its rail if I do it manually so I don't *think* it's a sticking issue.

    I'm wondering if there are any adjustments I can try with these without the special alignment disk and so forth? I've done a Qtip with iso alcohol but no effect.

  2. #2
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,026
    Blog Entries
    2

    Default

    I'm going to revise what I said. Suspicious of the boot disks I'd made, I opted to remake them on a different set of disks. I also picked one-step rather than double-step in the ImageDisk settings. That produced a boot disk that drive B can read. Drive A still cannot though. And when I put anything in Drive A and then move over to Drive B to reset and test again, Drive B suddenly won't read the disk. I ended up having to remake the boot floppy to get Drive B to use it properly.

  3. #3
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    29,949
    Blog Entries
    20

    Default

    How's the terminator situation? I've got a couple of what I believe to be 52Ms, but the labels have dried up and fallen off long ago. They're 100 tpi.

  4. #4

    Default

    Disk drive have logic failures, just like anything else. The fact that the B drive can work tells me that it is unlikely the controller. It sounds like the A drive has got a failure that is causing it to turn on the erase heads or write head. It could also be just a static DC current through the heads as well. When reading there should be no current through the heads.
    Dwight

  5. #5
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,026
    Blog Entries
    2

    Default

    Are these things something someone like me can fix? Or do I need a pro? I did see a website somewhere... not sure how current it is... offering to rebuild these things.

  6. #6
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,026
    Blog Entries
    2

    Default

    I tried a format on the non-working drive. It runs through the format without any problem. When I try to do a directory though, it just gives me a BDOS error. However, if I move the 'formatted' disk to Drive A.. it just gives me a no file message (since nothing is there). So the faulty drive can format, it seems, but not read or write files?

  7. #7
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    29,949
    Blog Entries
    20

    Default

    Er, formatting is writing. However, many CP/M third-party formatting programs (DRI never provided one, since it's controller-dependent) don't bother to verify (read) after the format pattern is written. So you don't really know that the drive is writing anything.

    Even among those that verify the format, what is done with bad sectors doesn't follow any particular convention.

    Strange, but true.

  8. #8
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    4,026
    Blog Entries
    2

    Default

    To do my test, I took two disks that was formatted with a PC. I verified the good drive could read neither of them. Trying to read them produces a bdos error.

    So I formatted one in Drive B (the bad drive), then moved it to the A. Now instead of a bdos error I get NO FILE. I don't know CP/M well... but I thought NO FILE meant it could read the disk and simply didn't see anything on it?

    I need to learn how to copy with cpm from one disk to another with a single drive. Hoping that's possible. That way I could see if I could copy a file onto the disk the bad drive allegedly formatted.
    Last edited by falter; February 4th, 2019 at 11:06 PM.

  9. #9

    Default

    I believe there is a onecopy program. In any case, one can load it into memory and then write it back to a file. I forget the commands but recall doing it in the past. I think the LOAD command writes it to 100H but forget the command to write it back to disk. Maybe it was in the debugger.
    Any way, I know it can be done.
    Dwight

  10. #10

    Default

    When you said you formatted it on the PC, do you mean you formatted it as a DOS disk or formatted it as a CP/M disk? Is it MFM or FM?
    Also your post are confusing about which drive is which. Earlier you said you could read in the B drive, now you say it is the bad drive?
    Dwight
    Last edited by Dwight Elvey; February 5th, 2019 at 07:16 AM.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •