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Thread: Tandy 2000 and 3.5" floppy conversion

  1. #21

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    I will look into the IC tomorrow. The existing 5.25” drive works but it could be how it’s jumpered, too, masking a problem with that chip. Right now it all works with my new cable. Maybe the sub-version of the 3.5” is odd since it was an IBM OEM version.

    Thanks again for all of the help. Great way to end the day

  2. #22

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    Interesting thing. The 1.44MB drive on the PC can read the disk directory but the geometry is all off so it's not usable for cross-platform, yet. The 800.COM program doesn't help. Need to do some research.

  3. #23

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    Using the ZAPMID program to twiddle the FAT_ID is required to make this work. Now cross-platform. Yay!

  4. #24
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    Now on to the GOTEK.

  5. #25

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    Quote Originally Posted by Chuck(G) View Post
    Page 90 of the 2000 Service Manual says that pin 16 is the usual MOTOR ON/.
    Page 130 has the schematic of the floppy section. Note that MOTOR ON/ is driven by U140, pin 8. Perhaps there's a problem in your cable, if this pin goes low.

    INUSE/ (pin 4) is merely an activity indicator driven by the HDL output of the 8272--note that it's an input to the drive. I wouldn't bother with it--the drive LED will come on when the drive is selected.
    Chuck -- if I could revisit this for a minute. U140 us a 7416, a high current open-collector hex inverter/driver. Right now I have MOTOR_ON grounded at the drive because that seems to be the only way that it is able to work. I don't see any pull-ups on the U140 side and without a schematic of the floppy drive, I have no idea what's happening there. It would seem that grounding it would be OK because there are no pull-ups anywhere but I wanted to get your thoughts on that.

    Thanks.

  6. #26
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    Yup, I wouldn't leave it that way permanently, but the 7416 is open-collector, so grounding the MTR ON/ pin won't hurt anything (i.e., the 7416 can only pull down toward 0V; there's no active pullup). The usual (i.e. recommended) interface is using 7438, which has a somewhat higher output current rating, but if it works, it works.

  7. #27

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    Excellent, thanks Chuck.

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