Image Map Image Map
Page 3 of 8 FirstFirst 1234567 ... LastLast
Results 21 to 30 of 76

Thread: Tandy 2000 FDC chip question

  1. #21
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    35,746
    Blog Entries
    18

    Default

    FWIW, you can also use CopyQM in "blind" mode.

  2. #22
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    5,176
    Blog Entries
    3

    Default

    I successfully made a new boot disk just on 5.25 media.. but same deal. It just does this over and over again until the head is as far as it can go.

    https://youtu.be/78c7SAXtDzc

    I'm becoming more doubtful that this is a drive problem and more likely a floppy circuit problem somewhere. I will probe the circuit tomorrow and see if things on the read circuit look normal.

  3. #23
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    35,746
    Blog Entries
    18

    Default

    Does the floppy drive seek to track 0 upon boot?

  4. #24
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    5,176
    Blog Entries
    3

    Default

    Quote Originally Posted by Chuck(G) View Post
    Does the floppy drive seek to track 0 upon boot?
    I don't think so. I think it just starts moving from wherever it happens to be.

  5. #25
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,249

    Default

    I vaguely remember you recently got a Tandy 1000 working, I think it’d be worth it, just for the heck of it, to install the Tandy 2000’s drive as drive “b” and see if you can run it through its paces. (Remember, it won’t automatically double-step so it won’t read your normal disks, but you should be able to format 40 tracks on it and do read and write checks, or a full 80 tracks if you boot DOS 3.2 or higher and use the apropos driveparm command in config.sys.)

    Does the drive *ever* step backwards, or is it always unidirectional?
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #26
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    35,746
    Blog Entries
    18

    Default

    Hmmm, that's not right. The 765 should be issuing a "recalibrate" as part of its reset sequence, as the software needs to know the actual position of the drive head--and the only reliable way to do that is to step out until the track 0 sensor kicks. Check the status of the "direction" line (pin 18 ) at the drive. It should go high when the drive is stepping away from the hub. If it stays low, the drive will always step toward the hub, no matter what.

    If pin 18 goes high but the drive steps toward the hub, it's the drive that has the problem. If pin 18 stays low, check the 7416, U40, pins 1 and 2 and the 74LS241 that feeds it..

    Note that the "step" sequence involves 2 signals, pin 18 (direction) and pin 20 (step). The sequence is that direction is set than a high-to-low transition on pin 20 triggers the actual stepping.
    Last edited by Chuck(G); November 28th, 2020 at 09:48 AM.

  7. #27
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    5,176
    Blog Entries
    3

    Default

    Yeah I don't see the head really move backwards or seek Track 0 at all. If you watch the video you can see it does slightly move backwards after each lurch forwards but that could just be tension release or something.

    I'll try it in my 1000 and see if it'll read anything there. I've even put a couple of other drives.. one a 360k and the other a 1.2mb into the 2000 and they all behave like this.. so I think the drives themselves probably aren't at fault here. I think it's more like what Chuck suggested.. we're gonna find something not flipping to change direction or seek track 0.

  8. #28
    Join Date
    Jan 2011
    Location
    Vancouver, BC
    Posts
    5,176
    Blog Entries
    3

    Default

    Okay so neither drive reads anything on the T1000, but they do seem to try to seek Track 0.

  9. #29
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,249

    Default

    Quote Originally Posted by falter View Post
    Okay so neither drive reads anything on the T1000, but they do seem to try to seek Track 0.
    Did you try formatting a disk with a 2000 drive as B: after booting from A?
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  10. #30
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    35,746
    Blog Entries
    18

    Default

    Does the 2K use the PC drive-select convention? That is, are both jumpered to the second drive select and the cable uses a twist to differentiate them? Or does the 2K use first drive=DS1, second drive=DS2 and no-twist cable?

    I'm too lazy to look that one up.

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
  •