Was it installed in the same 486?
Try a different cable or connect it to the other edge connector.
Try it with a (different) I/O controller.

Ok so make things clear (my brain is foggy 🤣): you tested the floppy drive on a test bench and it worked fine. You installed it and it does not.
Did you use same motherboard, same controller, same cable, same everything on the test bench as the build you put it in ?

SodaSuccubus wrote on 2020-07-17, 23:07:

Hi, me again with another question 😜

I just got in a Toshiba ND-0801AG 1.2MB Floppy Drive. I only have a few stacks of disks with me atm, but i managed to write and format a shareware copy of Wolfenstein 3D to one. Installed off the disk too.

This all worked fine when it was on the testbench. When actually installed into my 486, the drive refused to recognize any files on my freshly formatted Wolfenstein disc. It displayed nothing, not even the label. Like the disk was empty. Formatting disks will result in a "Unable to write to BOOT, Format terminated!".

I had a similar problem with 2 such drives recently when trying to use them. It would format, but result in that error message at the end.

I did a few things which seems to get it working again
1: I cleaned the heads with isopropyl alcohol. Be careful when you do this. I used an isopropyl alcohol soaked q-tip and rubbed gently back and forth (not side to side).
2: I moved the heads manually up towards the center of the disk when idle and let the drive move them back when seeking. They may have been out of alignment.
3: While running IMD disk, I gently picked up the top head while reading and let it back down gently.

Now this isn't the best way to treat a drive, but for some reason, it worked. I suspected an alignment issue, that maybe the heads weren't sitting right in the middle of the trakc.

As for the test disk, they are specially manufactured, you can't just download an image and write it to a blank disk.

BoraxMan wrote on 2020-07-18, 12:15:

2: I moved the heads manually up towards the center of the disk when idle and let the drive move them back when seeking. They may have been out of alignment.
3: While running IMD disk, I gently picked up the top head while reading and let it back down gently.

physically moving the heads around randomly would never fix an alignment issue

alignment is controlled by tiny adjustments on a cam screw, if it gets out of whack you can't just shake it back into place 🤣

maxtherabbit wrote on 2020-07-18, 13:50:

BoraxMan wrote on 2020-07-18, 12:15:

2: I moved the heads manually up towards the center of the disk when idle and let the drive move them back when seeking. They may have been out of alignment.
3: While running IMD disk, I gently picked up the top head while reading and let it back down gently.

physically moving the heads around randomly would never fix an alignment issue

alignment is controlled by tiny adjustments on a cam screw, if it gets out of whack you can't just shake it back into place 🤣

It probably wouldn't but something about doing that fixed two drives. I'm not sure what it did, but I had one drive suddenly do this twice, and both times I did this, it fixed it. A another did this once. Playing around with the position of the head, moving it up and down did SOMETHING. Could be a coincidence.

I just faced a similar problem and it was the I/O controller.
I have three 5,25" drives that refused to work properly. The PC recognized the drives but behaved erratically while reading disks. Sometimes it worked fine, other times it couldn't read anything at all.
I cleaned them, lubricated them, recapped them, no change.
I already gave up on them when I decided to try them in a different computer and they turned out to be flawless.
It was I/O controller incompatibility because it worked fine with 3,5" drives.

BoraxMan wrote on 2020-07-19, 09:55:

It probably wouldn't but something about doing that fixed two drives. I'm not sure what it did, but I had one drive suddenly do this twice, and both times I did this, it fixed it. A another did this once. Playing around with the position of the head, moving it up and down did SOMETHING. Could be a coincidence.

oh I believe you that it did something, just not changing the head alignment

it could have just unstuck something in the stepper, sled, or head tensioner spring assembly

maxtherabbit wrote on 2020-07-19, 14:32:

BoraxMan wrote on 2020-07-19, 09:55:

It probably wouldn't but something about doing that fixed two drives. I'm not sure what it did, but I had one drive suddenly do this twice, and both times I did this, it fixed it. A another did this once. Playing around with the position of the head, moving it up and down did SOMETHING. Could be a coincidence.

oh I believe you that it did something, just not changing the head alignment

it could have just unstuck something in the stepper, sled, or head tensioner spring assembly

Yes, I think that is most likely.