Attempting to Fix a 3.5″ Floppy Drive and a New 5.25″ Drive

The start of the year is a time when I am usually visiting family, but is also a time for cleaning out old junk and rubbish at work. This year I did a little cleaning out whilst visiting family and found an old 3.25″ floppy drive from our original old PC. Upon returning to work we took the opportunity to do some serious cleaning before things get busy again, and in the process found a 5.25″ floppy drive basically unused and still wrapped in plastic. Two old gems having sat on a shelf for at least a couple of decades.

First up lets take a look at the 5.25″ drive, it is a FZ-506 made by Chinon in 1987 (I think). Whilst this is probably the first Chinon drive I’ve owned myself, these were fairly common drives back in their day. This example is basically pristine, it shows no yellowing, the lubrication seems in good shape, and it operates like brand new. It even still has the cardboard in the drive, for protecting the heads in transit. Quite a lucky find indeed.

The 3.25″ drive is a Panasonic (made for them by Matsushita) and is of an unusual design. This particular example was in our old Twinhead 386sx machine, it was one of the first upgrades my Dad bought for it. This drive saw many of our games, homework and home-made software from my teenage years, so it has a little sentimental value. It was very well used, so it’s no surprise that it’s not working.

When I hooked it up the drive seems to think it is working, but it failed to seek, and the spindle speed didn’t seem quite right. With many old drives (of any type) it’s often simply a case of mechanical components being seized and requiring lubrication. A little bit of light machine oil freed up the spindle motor and seemed to free up the head actuator.

Testing with Image disk revealed that the disk speed is now correct, and that it can read tracks on a disk, but it still isn’t able to seek properly. The actuator seems to not even be trying to move. This makes me suspect the control board, and looking at the connector I suspect it may be as simple as a dry solder joint.

Unfortunately I’ve run out of time this month, although I’ll be keeping it on my work bench because I think I have a good chance of repairing it. I should have some repair result next time.

3 Responses to “Attempting to Fix a 3.5″ Floppy Drive and a New 5.25″ Drive”

  1. March 16, 2021 at 6:29 am


    Stumbled upon your post googling about 386sx and its floppy drives. Coincidence, but a day ago I was fixing laptop very similar to Twinhead 386sx and one of many problems it had was floppy not reading any disks. Managed to fix it by replacing leaked electrolytic capacitors (http://asknotes.com/2021/03/15/fixing-epson-smd-1000-floppy-disk-drive/). Yours, even if a bit different model fdd, probably will have similar issue.

    As You are familiar with Twinhead 386sx, maybe you now what is its key combination to enter Phoenix bios setup? As on mine I can get into bios setup only by disconnecting hdd or fdd or cmos battery, then I get a F2 option. Otherwise, I did ctr+alt+s and couple other combinations, but it seems that only ctr+alt+s does something, but this something is just a restart, any ideas ? Thanks!

    • March 16, 2021 at 8:43 am

      ctrl+alt+S is supposed to the key combination to enter the BIOS on those machines from memory, but you may have to press that combination during the POST or before DOS boots to get it to work. My Dad had one of these machines when I was a kid.
      Also another key combination that may work for you is ctrl+alt+ plus/minus to toggle the turbo speed on and off, that should work all the time. I believe that most machines with a Phoenix BIOS respond to these key combinations regardless of who manufactured them.

      I’m working on this drive at the moment, and have found that the connector for the stepper motor had lifted away from the board, which will hopefully be the cause. If I can manage to reconnect the motor maybe it will work again. I’ll check out the caps just in case.

      • March 17, 2021 at 12:23 am

        Then it is going to be an easy fix for you, good luck 🙂
        And ctrl+alt+s worked at the end of the day, its just somehow you have to be really precise when to press it.
        Nice blog by the way, will be visiting once in a while 😉

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