Atari ST drive in Amiga 500, no disk change

[Vaeltaja]

Hi everyone,
yesterday my Amiga's floppy drive broke permanently so I had to start to look for a replacement drive. I have a Panasonic 257A427P for pc, but that's impossible to mod for Amiga since it doesn't even have a jumper plate to solder to change it to DS0. Anyway, while searching for information I came across some board where someone said that you can replace Amiga's drive with Atari ST's drive. Since I had broken STFM I decided to try it and it works but with one big problem: It doesn't recognise disk change.

The Atari ST drive model is Epson SMD-480L, which I believe is similar to SMD-400 which was used in some Amiga models I think. I know that Atari and Amiga has disk recognition in the same pin on the drive connector, but it seems disk change is different.

Does anyone know how to solve this problem? I've tried to search information for hours but without any luck.

My knowledge is quite limited and I just recently started to use Amiga again for the first time since 1990s, so there's a lot that I've forgotten and even more that I didn't know in the first place.

[amiman99]

Most commonly you would jumper pin 2 to 34 to give a ready signal or disk change signal.
More info here: http://eab.abime.net/showthread.php?t=30944

[Vaeltaja]

Thanks, I forgot to say that I'm aware of that method. Only problem is that I'm not quite sure are those pins the same in the ST's drive. For example according to this thread on Atari-forum if you want to replace Atari's floppy drive with pc drive you have to make changes to pin #28.

Weird thing is that Amiga's drive started to work but only if the Amiga itself is placed in a certain way on the table/self - it's kinda hard to explain how it sits there, but I'll post picture of it later. Because of this weird behaviour I think there's two choices for what's wrong:

1. PSU's cable or connector is somehow damaged, since in this position the PSU's cable that goes to Amiga bends more than it does when Amiga is placed normally. Actually now that I think, before this behaviour started that cable was more bent but then I arranged it differently so it wouldn't bend so much and after that drive stopped working properly.

2. Disk detection switch doesn't work properly/can't reach the bottom. I've cleaned the switch couple of times and first time it helped but after that it didn't really make any difference. In this new position front right corner of the Amiga comes over the table and sits on the air. Could it be that detection switch is too short and that little imbalance helps it reach the bottom?

When Amiga is placed on the table normally, disk drive just gives two times that noise when it tries to detect disk. I've tried try different positions but this is the only one that works. I also noticed with ST's drive it had problems with some disks that work with Amiga drive, and I know for sure that ST drive is in good condition. I also tried STE's floppy drive that is even better and it had problems reading those same disks (read/write error), but Amiga drive reads them right in this new position. I haven't tried those Atari drives in this new position but I'm 100% sure that their disk detection switches are working properly since they work normally with STE.

At the moment I don't dare to move the Amiga since I finally want play something with it.

[amiman99]

I would fix the cable first, before trouble shooting the floppy drive.

Maybe you can consider Gotek drive, virtual disk drive, uses USB and ADF floppy images.

[Vaeltaja]

Things have taken interesting turn: I've found that the problem is either floppy drive or PSU. Instead the reason is my crt-tv.

Amiga and the tv are placed on metallic storage rack with plywood shelves. First, when the drive was working normally, the tv was about 20-25cm above Amiga. The problem with this setup was that the tv was little bit too high to view comfortably when playing, so I decided to lower it (I can adjust height of the shelves) and that was when the problems started.

Today I started to experiment by changing Amigas position on the lower shelf. After a short while I realized that when the Amigas floppy drive was under the tv it didn't work, but as soon as I moved it away from there it started to work. I lifted the tv shelf to the height it used to be and now it works. But I noticed that it still causes interference, for example if I play Lost Vikings the 2nd disk doesn't work unless I move Amiga further from the tv.

I think the tv creates some sort of electromagnetic field that messes up the signals or something for the floppy drive. I really can't move the tv any higher or Amiga any lower, so my question is: Can I make some kind of shield under the tv that would block that interference and if so, what material should I use?

That crt-tv has a place for battery so it can be used as a portable tv, so that might have something to do with this whole thing. But I'm not really an expert and my knowledge is limited in these things too.

[Vaeltaja]

So far I managed to stop the interference with metal tray. Now everything seems to work like it should. It's been an adventure...