2x Chinon FB-354, wrong cylinder number

[8362r8]

Hello,


I tried to do extended research before writting here but it seems that I am not getting anywhere.. Maybe there's one out there having a hint which would bring light into the darkness..


Involved drive Models:
3x Chinon FB-354 REV E (1x working, 1x buggy), 1x Chinon FB-354 REV A (buggy)

Description:
- The buggy drives won't read any floppy disks. The reading process doesn't start when a disk is inserted. There's only a 4x click sound audible (see below).
- The clicking sound without a disk inserted is normal.
- Amiga Test Kit Signals + Ami Alignment System Tests : WPR TK0 RDY are OK, Motor rotation is OK, Steps from 00...79 are OK, but cylinders number are not 80!
Everytime when re-initializing the drive there's another number (68, 32, 50 etc.)!
- When inserting a floppy disk it will be recognized but the step motor behaves strangely: Mostly it steps 2 times back and then attempts to step forward,
also 2 times but with no luck. It could also happen several times more. That depends on the insered disk.
Instead of that behaviour, sometimes the step motor brings the heads in the middle of the spindel (around cyl 40) and remains there.
- Formating of a disk (X-Copy) works well without any errors, but the same disk can't be read (Checkdisk shows up Errors 1, 2, 5 on some tracks) with this same drive.
The same happens when a disk from gotek/ADF is copied to this drive- no read afterwards.

What I did so far:
- cleaned the drive properly including heads, spindle, contacts etc.
- on the spindle I did apply grease again
- the disk insert & write protect micro switches I did bypass by an external switches to exclude that cause
- I replaced the 4 caps by new ones.

I have the same problem with two drives (one Rev E, one Rev A)! On the Amiga/controller side is everything well, another identical drive (Rev E) works fine.
I am thinking of the track 0 sensor, but without unmouting it I see no more options to clean it other than using compressed air and a tweezer + paper + IPA.
I don't think that misalignment is causing the problem, as also disks written on the particular drive won't be read.

Any ideas where to look at?


Thanks to anyone having a look at this one.

[solarmon]

If it was alignment issues, then normally, formatting a disk and reading it back on the same drive is OK. But here you are saying the reading back the the formatted disk is not OK?

[8362r8]

Yes exaclty. It doesn't matter if any disk or a disk written by the failing drive itself.
I wonder especially about the fact, that the cylinders won't be recognized correctly..

[solarmon]

It sounds more like a read issue.

Did you try the disk alignment test in ATK, which a known good disk - preferably an original Workbench or magazine coverdisk?

[8362r8]

Yes I did so.

Not with an original WB Disk or cover disk but with a) a trusted Disk wirtten on a well working drive, which is working well on various other drives and b) a Disk written on this particular drive.

The result is with both Disks more or less the same : Reading is not possible. Doing the ATK Read Test will result in red erros showing up "B" or "-".
Doing the alignment Test ATK reports on Cylinder 0 for both Sides "okay" (.), while Cylinder 40 and 79 are ending up in missing or -low Cylinders (X and -).

Can anything be inferred from this?

[solarmon]

Are you using latest ATK version - you can move between tracks in the alignment test now.

Make sure you clean and regrease the track motor worm gear, as well as the guide/glide rails.

[8362r8]

I was using version 1.16- now updated to the latest 1.18. Regarding that there seems to be no difference. With the alignment test tracks/cylinders 0, 40 and 79 may be adressed but not every single track. Or do I miss something?

In the meantime I had a huge progress with those drives: the clue was your hint "...as well as the guide/glide rails".

The breaktrough came with a thorough cleaning of both parts, spindle and guide rail/axis. For that I removed the PCB as well so that I had proper access. It looks like that especially the re-greasing of the guide axis was doing the trick. With that the sound of the stepper motor is now much smoother and the reading issues seem to be gone. I will have some more extended testing, but i'm quiet sure those two drives are back!

Maybe interesting for others is that not only the reading issue disappeard with the procedure, also an 3rd drive which reported "Track 0 sensor not found" was working again after a proper cleaning and re-greasing.

[8362r8]

That brings me to the next two drives:

The 3rd one I mentioned is one of two which suffered once from a bad disk. I never had a closer look to them until now. It happened back then, that I inserted an original driver disk in both the drives to make a copy from it. The disks seems to be evil as both drives started to make grinding sounds as soon the motor was spinning.

Both drives are Chinon FB-354, Rev A from an A2000. I went with both drives through the same procedure (proper cleaning & re-greasing). All signals are fine and also the stepper motor is now moving smoothly on both drives, but unfortunately the issue with the grinding sound remains. In fact, as soon a disk is inserted the upper head starts to scratch the upper surface on the inserted disk which is dead afterwards.
I tried to have a close look to the those particular heads and compared them with the one from a well working drive but I can't see any difference. The head doesn't look broken or crumbling. Even the position (disk inserted or not) seems to be identical with the reference drive.

Acutally it's quite a shame, those two drives are appart from that in an excellent condition and I would love to bring them back to live as well...

Any ideas about that?

[solarmon]

Regarding ATK. It is actually a test build that has the alignment improvement. I had forgotten that Keir hadn't released it in a stable release yet. See:

https://github.com/keirf/Amiga-Stuff/actions

I'm glad you got your drives working again. Yes, people often forget to regrease all the mechanisms, which can cause problems if they cannot move freely.

For your other two drives - on some drives you can adjust the spring that holds the head down. Maybe you can adjust it to not push down so much. Also make sure there isn't anything that is making the floppy disk sit at an angle on the fly wheel

[8362r8]

Thanks for clarification and for your efforts solarmon, very appreciated!

I took an even more detaled look at those two drives. On the Chinon FB-354 there is a spring which holds the upper head. There are 3 positions where the spring may be positioned. I can see that this position varies over drives. I assume this was done while manufacturing and may be an adjustment for the spring load. Does this know somebody more detailed?

As the head is touching the surface of the floppy disk it may have an impact of the abrasion of the disk and even the head.

In this case it didn't change the behaviour of those two drives.

The cause for scraping disks was still existing leftovers of the evil disk which I used ones on those drives. Actually I was cleaning the heads of both drives several times. Really! I was thinking I did it very well but I was wrong.

I headed over to Herb's retrotech website - which is an amazing and reliable resource for all retro computing questions hence also floppies : http://www.retrotechnology.com/herbs...ean_disks.html. After reading there more or less everything about floppy drives and disks I deceided to give a cleaning disk a change. Actually I was always doubtfully of using cleaning disk- but it was my last resort.

With enough IPA on the inlay of the cleaning disk I firstly ran ATK's Read disk. This was still not enough. I then used the Signal Test whichs moves the head back and forward while the motor was spinning. I repated that approximately 7 times - and - wow - that made the trick!
Both floppy are not anymore scraping disk and are now working flawless! In fact I was very surprised and still impressed how thoroughly a cleaning of drives heads may be necessary to get remains of a bad disk really off.

I thought to describe is as accurate as possible so that it may be helpful for others.

My lessons learned
- always check unknown floppy disk visually before putting them into a drive. S magnifier and really good light may be needed
- never trust "original" disks. If there are any scrapes, spots or blur visible, clean - if any possible - the disk first if you really need this paritcular disk, otherwise don't put that disk into any drive
- it that happens clean immediately the heads. clean them well. clean them very well. clean them even better!
- cleaning disk are not that evil

To make this lines little bit more colorful I attached a picutre of the drive, the evil disk which originated the story, one afterwards killed disk and the lovely cleaning disk.

http://www.retrotechnology.com/herbs...ean_disks.html
http://www.retrotechnology.com/herbs_stuff/drive.html

[solarmon]

Maybe I should have suggested to clean the heads again, and again. I always clean and check the heads, especially after a disk has made a lot of noise and/or got scratched. But I don't use cleaning disks as I like to manually clean and inspect the heads.

Glad you managed to get it working!

[8362r8]

Not your bug - you mentioned it and I was actually quite sure I cleaned it already well; hence I did misdescribe it accordingly...

What I still wonder- how do you inspect the head visually? I was trying to do this, I even have a small mirror tool to do it. Also on the used cotton buds I couldn't see any dirt, but it had to be there..

The head pictured here is one of those which are now definitely clean again.

[solarmon]

I usually just inspect by eye. Sometimes you need to keeping angling it to see it in different lighting and reflections. Sometimes I also use a USB microscope for more suspect drives.