Floppy disks not working on other Macs?

[dv-]

So I’ve cleaned and lubed a few floppy drives now, and I’m running into a weird issue.

I have a stash of old floppy disks (1.4MB and 800k) but all of them show this so I think it’s the drives. (?)

Basically if I format a disk it’ll work on that drive. I can copy data to and from it, etc. But if I try to bring that data over to a different machine, the computer won’t read it. I can reformat the disk on the second machine and… it won’t be readable on the first.

I’ve got five machines going now, and there are a couple that are OK with each other, but no three of them are cross-compatible.

So… what did I break when I was cleaning/lubing the floppy drives, do you think?

 

[ironborn65]

the heads of your disk drives have different alignments with respect the track 0.
I'd try to make cross-tests and see which Macs, assuming you have more than one, can properly see the same floppy.
Maybe only one has a non-standard alignment. Or you can find an original floppy or a known working one from someone else and use it as a reference.
This is quite normal.

PS: I hope you did not remove the track 0 sensor from the rail, this would cause your issue. Finding the right position will be a long succession of trial and errors.

 

[dv-]

PS: I hope you did not remove the track 0 sensor from the rail, this would cause your issue. Finding the right position will be a long succession of trial and errors.

No, I didn't - almost every video I watched on Youtube before I set about my first attempt warned specifically against doing that.

Although some of the drives have been through multiple hands so I guess I can't guarantee somebody didn't.

I'll do some more methodical testing and try to isolate which drives may need to be realigned. I can do "long succession of trial and error" if it means I can actually sneakernet the occasional printer driver or something.

 

[Franklinstein]

Back in the day there were specific test jigs from Sony that the service data instructed you to use. Obviously if any of those still exist they're in the hands of specialists or rotting in the back of a closet somewhere and so you're not likely to find one.

The other option is to use a reference floppy and do incremental tweaks to the head stepper motor and/or track-0 sensor until it reads the disk correctly (see Larry Pina's excellent set of Macintosh repair books for more info on this).

Where do you get a reference floppy? Sometimes commercial floppies (i.e., an install disk for SimCity 2000) can be used - if your drive won't read it, adjust it until it does and it should be in compliance, but this does put extra wear on the disk and you'd probably want to avoid that since they don't exactly make them anymore. Other times, as with modern audio or video alignment tapes, you make them yourself with a known-good reference drive. The problem is: how do you know which of your drives is actually the good one? It's tricky. I guess you can see which of them reads the most disks without errors, then format a disk on that drive to use to realign the other uncooperative drives. Or maybe you can buy a test disk from someone here or there's a seller online who offers them.

 

[ironborn65]

this might help (I did not do it)
it uses a different technique, but it's a nice document and well explained