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Thread: 3.5 inch floppy drives - repair or not?

  1. #11
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    Exactly.

  2. #12
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    OK, let's put it this way; some of the drives have information that allow you to do what I need to do (lock a drive into Mode 1) but most don't and just removing the HD sensor doesn't do it. Apparently, the DD mode (1) needs a high from the sensor (for some reason). I could tie that line high, and it might work, but, I really don't have time to experiment with it unless someone wants to buy one.

    With some early Panasonic JU-257s, there is a row of slide switches along the back edge of the logic board that allows you to accomplish this very easily and some have nice little diagrams on the logic board that tell you how to do it.

    In no case does any of it require messing with the HD detector.

    The big problem is that I don't have any of the drives that I have the instructions for and I have a LOT of drives with no instructions. Everyone seems to build their drives differently, so there is no one-size-fits-all solution to faking up a 720K drive from a 1.44M drive, especially in devices that are smart enough to just format with the 720K parameters.
    Legacy Computers and Parts

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  3. #13
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    If you're really curious, I can post a photo of how to restrict the drive to 2D.

    Personally, I use either FD235F or NEC FD1035 drives for that.

  4. #14
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    Always curious, Chuck. It tells me I'm still alive LOL. Yup, and I don't have any of either of those drives.

    Quote Originally Posted by Chuck(G) View Post
    If you're really curious, I can post a photo of how to restrict the drive to 2D.

    Personally, I use either FD235F or NEC FD1035 drives for that.
    Legacy Computers and Parts

    Sales of, parts for, and repairs to, Vintage and Legacy computers.

  5. #15
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    If it doesn't slip my mind, I'll get one out and take some photos as I work through it. I assume that you also want pin 34 = READY?

  6. #16
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    Quote Originally Posted by Druid6900 View Post
    OK, let's put it this way; some of the drives have information that allow you to do what I need to do (lock a drive into Mode 1) but most don't and just removing the HD sensor doesn't do it.
    If you can find a fixed or switch-selectable DD drive, great, but FWIW all the 1.44 drives I've ever worked with use switches instead of sensors, so it's pretty trivial to either cut or short a trace to lock them in DD mode.

    With some early Panasonic JU-257s, there is a row of slide switches along the back edge of the logic board that allows you to accomplish this very easily and some have nice little diagrams on the logic board that tell you how to do it.
    Some models without the switches use the same board, so you can install jumpers instead.

    The big problem is that I don't have any of the drives that I have the instructions for and I have a LOT of drives with no instructions.
    I'm familiar with that problem...

    m

  7. #17
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    Some 3.5" HD drives (especially the earlier ones), used the so-called "PS/2" signaling, where the host called out the density. It could really be a problem because you'd get 1.44M data on 720K floppies--the system was blind. In the later years it got worse, as some PS/2s would use the same system for ED floppies, so you could get a 2.88M recording on a 720K floppy. Eventually IBM came to their senses, but I still occasionally have to drill a hole in a 720K floppy to read it.

    Spec sheets can be very hard to find. Only recently, I came across the OEM manual for the Teac FD-235HG "3-mode" drives. Apparently, there was even a USB version of the 235HG with an added-on USB adapter board.

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