Floppy drive alignment

[olivier.jan]

Recently one of my colleagues asked me if I could help fix a floppy issue with his STE.
Some floppies were not reading properly and he didn’t know what caused the issue: the floppies, the smd-380 drive or the computer.

This weekend I first tried the floppies, and as I was lazy I simply used a greaseweazle with a known good Mitsumi floppy drive and imaged all 4 floppies.
All were ok without any error and the generated images were perfectly usable with Hatari. Good.

Next, I cleaned the Epson smd-380 floppy drive and tried the same method but it stated spitting error for side 1. I cleaned again but no luck.

I then proceeded to get raw images from greaseweazel and looked at it using HxC floppy emulator software. I never really used the analyzer function of this software before, but it’s really great for this kind of troubleshooting :

It clearly showed me garbage for the first two tracks of side 1 while side 0 was perfectly fine. Moreover, when looking at track 2 (the first track properly read from both heads) the TRACK_ID was 2 for side 0 but only 0 for side 1.
So clearly head 1 was misaligned by 2 tracks compared to head 0.

To fix it, I simply repeated the following operation:
- Unscrew and move head slightly, screw.
- Raw image tracks 0-4
- Use HxC software to compare data from both side and check track ID
- repeat operation until Data is properly read on both side and track IDs are the same.

After 10-15 mins, I managed to get it right, I then did a full disk image and tested it in Hatari with success.

So clearly this method is not perfect as the heads might not be perfectly aligned, maybe just enough to read the few disks I tried. I would need to use a scope to fine tune the alignment.

On the other hand if I had used the scope directly, I’m not sure I would have detected a 2 full track misalignment easily.

As a conclusion, a simple and cheap Greaseweazle can help save old floppy drive without the needs for an oscilloscope (even though having both is better).

[exxos]

Maybe you can post the image of the screws which you adjusted as it may help others in the future :)

I think I looked into head adjustment Some of the older drives, don't remember which ones now but it was a while ago, but there was simply no way of doing it IIRC. Heads were just simply spring-loaded and that was it.

[olivier.jan]

Here is a picture with the red arrows pointing to the two screws securing the top head.
On the smd-380, both heads are mounted on a tray which is moved by the stepper motor. The bottom head is fixed to the tray and cannot be adjusted.
Only the top head can be adjusted to align it with the bottom one, or at least I haven’t found any other way to do it.

IMG_0824.jpeg