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Thread: 26 to 34 pin question. Does the Compaq portable 486c have non standard floppy pinout?

  1. #1

    Default 26 to 34 pin question. Does the Compaq portable 486c have non standard floppy pinout?

    Ive been tinkering with my Compaq Portable 486C that has a bad floppy drive.

    I ordered one of those gotek floppy emulators like ive seen others use in various vintage computing sites.

    I also ordered a 26 pin to 34 pin adapter like this one

    https://www.ebay.com/itm/1pcs-34-Pin...d/322560136186

    the floppy emulator came in today so i pulled the machine apart, looked on the non-functional floppy drive for pin 1 and also on the ribbon cable as well as the connectors arent keyed.

    plugged the 26 pin into the adapter (matching pin 1) then plugged the 34 pin connector into the floppy emulator and also hooked up the 4 pin power connector from the adapter to the floppy emulator.

    powered it all up and the floppy emulator cooked itself (let the smoke out) and the PC wouldnt boot.... damn.....

    i took the floppy emulator apart and the 3.3v voltage regulator fried.

    i double checked with a meter the adapter and it matches the adapter pinout in this chart

    http://www.martinruss.com/sy99adapter.html

    i plugged the old floppy in and rebooted and it recognized it no problem. still wont read disks but it doesnt appear that killed anything permanently.

    i tried a 34 pin regular floppy with the adapter as well and it nuked that thing as well but that one i didnt care about cause it was flaky.

    ill try replacing the voltage regulator and test the emulator in another machine that still has a floppy connector.

    UGH. any ideas?

    did compaq use a weird non standard floppy? is their ribbon cable pin 1 mislabeled?

    i dont want to cook anything else nor break the machine.....

    thanks

    Brian

    PS, im going to poke around the old broken compaq floppy drive and look for power and ground pins on the board. those should be easy to find and would tell me if i had a connector backwards.

  2. #2

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    doh... it is an non standard 26 pin.

    i know now.......

    Brian

  3. #3
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    The martinruss adapter looks to be suited to the Teac FD05 floppies, but there were other schemes using 26 pins; e.g. Sony. The brand and make of the original 3.5" floppy might be helpful.

  4. #4

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    Quote Originally Posted by Chuck(G) View Post
    The martinruss adapter looks to be suited to the Teac FD05 floppies, but there were other schemes using 26 pins; e.g. Sony. The brand and make of the original 3.5" floppy might be helpful.
    oops.

    its a Sony MP-F17W-P3

    compaq spare 82084.

    i believe its pinout is similar to the floppy in this thread

    http://www.vcfed.org/forum/showthrea...+floppy+pinout

    i did some probing with a meter and the power and grounds appear to be what is defined in that thread.

    Thanks

    Brian

  5. #5
    Join Date
    May 2011
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    To get the drive to properly work, the DENSITY and DRVRDY pins on the drive side both have to be tied to any ground pin.

    (Grounded DENSITY gives the proper 1.44 MB capacity, while grounded DRVRDY will allow the computer to use the drive anytime you want.)

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