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Thread: Restoring borked 3.5" floppies

  1. #1

    Default Restoring borked 3.5" floppies

    I have a couple of 5.25" floppy drives I want to use, but I have no idea how to get them working. The one I'm most interested in is a Teac FD-55GFR.

    I think my main problem stems from jumper settings. For the most part, I've just been throwing jumpers at it with the guidance of a couple of old scanned manuals. I think I got it to do something once, but it wouldn't read. The disk spun up and it did little else.

    The other drive is an Epson SD-600. I'm not especially excited about this one, partly because its aesthetic (bright white face with curved corners and edges) really doesn't fit any of my machines. I know even less about the Epson, especially the jumper settings. Also, the disk latch lever thingy takes an unusually large amount of force to get it to latch.

    I'm also confused about which drive is which in the BIOS. One of the machines I want to get a 5.25" drive in is a somewhat obscure Netram desktop with a PII-333. The other is a Compaq Deskpro 2000 w/ a Pentium 166 that I rescued from a recycler. Both support a 5.25" drive, but I don't know which connector on the cable corresponds to which drive letter. I think the cable in the Netram has a connector for a 3.5" drive, and the other drive can be 3.5" or 5.25". The one in the Deskpro has a 3.5" connector and a 5.25" connector.

  2. #2
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    The "PC standard" (for lack of a better term) is that all drives are jumpered as drive 1 (DS1). The cable has a twist between the first and the second floppy connector, so that any floppy drive connected to the first connector (before the twist) is drive 1 and any drive connected to the connector after the twist becomes drive 0. Some BIOS'es allow drive remapping, but apart from that drive 0 = A:, drive 1 = B:.
    Torfinn

  3. #3

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    Leaving the jumpers in their original positions is always a good place to start.

    If you're going to play the jumper game it would help to enumerate which jumpers are currently closed.

    Using a head cleaning disk is also a good procedure as any fouled heads will prevent even a properly configured drive fro being able to read any disk.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

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    I'll repeat what tingo just said and add a bit to it.

    With a few exceptions, the "flat" part of a floppy drive cable connects to the "B" drive and the part after the "twist" uses the "A" drive. As mentioned, the PC convention is to set each drive to the second drive select, however it's labeled. There are also some oddball controllers that support 3 or 4 drives with unconventional cables and/or jumpering.

    I have a Compaq Deskpro server where this is reversed, probably for reasons that the space for the cable is small. But it will still support two drives.

    Some systems (particularly later ones) support only one drive. This is mostly a matter of LPC peripheral chips supporting either two floppies and no parallel port or one floppy and the parallel port. There simply aren't enough pins on the package to do both.

    The original purpose of the "motor on" line on 5.25" drives was to provide a way to save the motor brushes. 8" drives with AC line powered spindle motors used a head-load mechanism that allowed the motor to run all the time. Since induction/synchronous motors don't have brushes, their operating life is very long.

    When Teac introduced their 5.25" drives with brushless spindle motors, they bragged that now it was possible to let the motor run continuously. But by that time, the PC had made its choices, which is why head-load solenoids on 5.25" drives (they were originally on early 3.5" drives also) pretty much vanished from the scene, or became a rarely used option.

    The problem was that the motor-on line was pretty much just an addition to the 8" interface and there was only a single common line for all drives. The idea was that if one drive was spinning, they were all spinning. Because of the small power supply on the 5150, IBM didn't want both floppy drive motors spinning at the same time, so they contrived the cable "twist" scheme that allowed the same cable to be used for both drives, but gave individual motor control. You sacrificed two of the four drive selects in the process, but that was never in the cards for the PC anyway--no space to put four full-height drives.

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