exxos's Atari, Amiga & retro forum

I dug out a couple of old 1.44 floppy drives that were salvaged from PCs about 10 years ago.

I gather they should work in the Milan so I gave them a clean and plugged in. They responded correctly with the light going on and off but nothing was read. So I tried a 720k formatted disk and that worked.

I suspect that the hd detection "switch" isn't working, it looks like it's an IR one.

One drive is labelled Citizen and the other isn't labelled but looks identical.

Is there any fix for this ?


I started using my ST again recently and it might have the same issue. Although I remember that the 1.44 upgrade didn't work in TOS2 or Magic, it was one of them.

OK, so a few things to unpick here. If you already know some of this that's fine, but I don't know where you're at with this si I figured it's worth mentioning.

Firstly a 1.44MB FDD will work with an ST but only as a 720KB drive. If you want to use a 1.44MB drive with HD then you need this: 1.44MB FDD Board

TOS 2.06 on an STE does in fact have a jumper block that enables the HD floppy code in the OS, however it still requires the above board to work in HD mode even with the jumper enabled. I can't recall how HD formatting is selected for non STE hardware though.

Next up is the drive ID. IIRC PC drives are set as ID1 and the ST needs ID0 for both internal and external FDDs so that will need addressing and the drives may well have their ID jumper soldered. Some do have a jumper block but most I've seen are soldered. I don't know if the Milan requires ID0 or ID1.

In terms of the HDD detect switch, it may just need cleaning, and possibly you may need to re-cap the drive to sort things out.

I am using these drives in the Milan to keep things (PC) simple although my STfm does have an HD upgrade that I fitted in the 90's. The power and ribbon connectors are labelled jp2 and jp3 so there might be a jp1 but I couldn't see it. This is not relevant in the Milan and they work with 720k floppies.

I did give the detect sensor a quick swab with some ipa and a cotton bud.

Copilot reckoned that the IR sensors can go cloudy and I expect that if this is the case then there isn't much of a solution except perhaps hard wiring it to 1.44MB, if that is possible.

"Citizen Z1DE‑58A uses an optical HD‑detect sensor, and that sensor is almost certainly the reason 1.44 MB disks fail while 720 KB disks work. "

It suggested shining a torch into the sensor to see if it triggers hd mode.

Note that "PC" floppy drives use DSKCHG (Disk Change) signalling rather than READY on pin 34. The ST requires the latter.

DSKCHG signalling just sends a pulse on the line when a new disk is inserted and turns it off when the drive gets a SEEK or MOTOR-ON signal. READY signalling has the line set low whenever there's a disk in the drive. So when using the PC drive the ST may think that the floppy disk has been removed directly after it access it for the first time.

Amigas also need drives with READY signalling rather than DSKCHG.

The sensor is a telecopic plastic rod, it could be an IR sensor but I have a feeling it is a switch. I gave it a dab of contact cleaner in any case.

With the 1.44 HD floppy mod on my TOS v3.06 equipped STacy, I use a small AUTO
folder program to enact the format HD floppy option from the drop-down menu.

Contact cleaner didn't make any difference. It still only reads 720k floppies.