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MP-F75W wont write to disks/initialize disks
Posted by: feltel on 2023-06-04 02:55:39
Another part in my SE30 journey. I assembled the machine and tested it. A few days ago I cleaned/lubed the floppy drive, a Sony MP-F75W, as per https:// www.youtube.com/watch?v=2LWfjsvc8OA. In the assembled machine the drive worked at first. I could read data and write data, initialize disks an so forth. Out of the blue I no longer can initialize disks. When I want to initialize a disk the formatting starts but when it switches to "verifying ..." there is an error stating that the initialization has failed. Also I cannot copy any data to a known working disk. Reading disks works as before without any issues.

I took it out of the machine and re-cleaned the heads, but this doesn't cure the issue. What went wrong with the floppy drive?
Posted by: zefrenchtoon on 2023-06-04 09:38:51
Did you check the sector zero probe ?
Posted by: feltel on 2023-06-04 09:49:15
Do you mean the photoelectric barrier next to the floppy cable connector? I didnt clean it after the write errors. I'm sure I cleaned it initially. I'll check.
Posted by: zefrenchtoon on 2023-06-04 10:23:46
I mean this:

800K Floppy Drive Head Issue — Track 0 Misalignment?

I have been exchanging dialog with a viewer of my YouTube channel who has been servicing his 800K drives in conjunction with my video on that subject. In particular, he has two 800K drives which show the head moving all the way to the back but then the heads stay there. If the head is then...
68kmla.org 68kmla.org
Posted by: volvo242gt on 2023-06-05 03:09:51
Another link, on the other forum: https://tinkerdifferent.com/threads/superdrive-floppy-maintenance.549/ Talks about adjusting the Zero Track Sensor. Been able to get my drives working after doing this.
Posted by: feltel on 2023-06-05 04:18:47
Okay, thanks. But could be a mis-aligned Track Zero sensor be the cause for not writing at all? I would assume if the sensor is mis-aligned wont read at all. Mine does read without problems. If I interpret https://tinkerdifferent.com/threads/superdrive-floppy-maintenance.549/post-5984 correct a mis-aligned Track Zero sensor would result in a non-working drive at all.
Posted by: volvo242gt on 2023-06-05 11:00:31
If it's slightly off, the drive will read a disk, but won't write to it. So, it may still need adjustment.
Posted by: feltel on 2023-06-05 11:06:46
Okay, than I have to do the inevitable. I'll follow the linked PDF and hope for the best not to make things worse.
Posted by: jmacz on 2023-06-05 12:40:04
Aligning the zero track sensor is time consuming and super annoying. I went through it on one of my machines that could read known good disks from my other computers but could not write (error), or could write but resulted in floppies that my known good drives could not read. Took a while finding the sweet spot but eventually I got it resolved. I think I spent hours on it.
Posted by: arroz on 2026-10-03 10:56:24
Hi

I’m having exactly the same problem. Did you solve it by aligning the sensor? It’s strange to me that’s the cause of the issue. I would understand if it could not read floppies from other Macs (it does) and other Macs would not be able to read disks written on this floppy, but I don’t see why it can’t write/format at all.

Thank you!

Miguel Arroz
Posted by: feltel on 2026-10-05 08:44:30
Unfortunately not. Back then I came across a battery bombed Classic and I took the easy route and swapped its drive into the SE/30. It is working since then.
Posted by: bibilit on 2026-10-05 10:08:08
Probably not an issue with the head, as you are able to read but not write, maybe an issue in the board.

It will be interesting to swap the board with a working unit and troubleshoot the problem afterwards.
Posted by: arroz on 2026-10-06 07:23:32
Hi

I ended up fixing it today, and it was indeed a Zero Track Sensor (ZTS) alignment issue. That was a pain to get right, but eventually I did.

I still don't understand exactly why it behaves the way it does. In my view, the sensor being off would justify disks formatted and written by this drive not being readable by other drives, and vice-versa. Yet that's not how it works. If the sensor is misaligned, the drive simply cannot format disks. Unless the last (inner) track is already being written outside of the magnetic zone (which I doubt, and the symptoms I saw seem to disprove that, especially step 4 below), it seems it should work.

Even weirder, the tolerance seems to get lower as the tracks approach the centre of the disk. What I did was:

1. Format a disk on a different Mac;
2. Insert the disk on the affected drive. If it's not read at all, move the ZTS a "large" distance;
3. If the disk is read, start writing files to it;
4. Somehow (and I truly don't understand why*) the amount of files I can write (aka, how far the files are being stored from track 0) depends on the fine alignment. If it starts failing at about 500K capacity, the sensor is very off. If it fails only in the last 100-200K, the sensor is almost right.
5. Do this repeatedly until I can fill the drive all the way to the last track (0K of available space, it's good to have a very small file and keep duplicating it).
6. Do the final test: format the disk and see if it survives verify. Also make sure the first tracks to be verified don't take too long (meaning the drive got read errors and it's trying again).

This is incredibly painful because when you get it right, the simple fact of tightening the screw will move the sensor a fraction of a mm and break the alignment. So you need to unscrew, move, screw it again, all with the machine on (be careful to learn when the drive will move or not, you do NOT want it to move while the screwdriver is on the screw, as it will be hit by the plastic tab) so you can test repeatedly. In fact, the last steps were literally just tightening and loosing the screw about 1/8 of a turn without even moving it until it could format correctly and without the first verified tracks taking longer. Ideally use a plastic screwdriver, if not, be very careful to not touch the wrong thing and cause a short.

* Why I don't get what's happening in step 4: the head position over each track is obtained by the number of steps the step motor turns, starting at track 0, detected by the sensor. There is no cumulative error. Meaning if you turn, say (made up number, there are a lot of steps per track, but let's assume 1 step per track for simplicity) 50 steps from track 0, you know you will be at track 50. So either all the tracks are right, or all the tracks are wrong. Of course, if the head is just outside the tolerance, it's possible some tracks are right and some are wrong because physics. But why does it seem to get worse, consistently, from the outer to the inner track? I don't know, and would really, really love to understand this.

Regards,

Miguel Arroz
Posted by: shirsch on 2026-10-06 07:30:45
Just a WAG, but you may be getting tripped up by residual data from previous misaligned runs. To be rigorous it would have been best to bulk erase the diskette after every adjustment.
Posted by: arroz on 2026-10-06 07:40:45
True that. That would make the process even more painful, but me more accurate for sure.

BTW another thing I forgot: I don't know if all drives do this, but this drive emits a "click click click" sound when it's idling (even with no disk inside), about a click a second. I never noticed it before, although most of the times I am cleaning drives, it's for an LC or so, with a loud fan. No idea why, it doesn't seem to be anything mechanical. I replaced 4 of the 6 caps (I don't have caps small enough of the correct values to replace 2 of the front ones).
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