1.44 floppy upgrade issue with DD disks

[Cwiiis]

I got and fitted the 1.44 v7.1 floppy upgrade board on an STE - no issues with fitting and 1.44MB disks work great, but now 720K disks are no longer working.

I tapped a line that I identified as the HD select (gets pulled to ground when a DD disk is inserted, otherwise is high at about 4.63V) to the D0 point on the board. Should this work, or does it expect something else/have I got something wrong? Given that when the point is disconnected it works as an HD drive, I assume pulling to ground is the correct behaviour. Is there anything I can do to debug this?

[exxos]

Might be best to post images of how you have it all wired up.

Assuming you followed the install guide ?

https://exxosforum.co.uk/atari/last/flo ... ex.htm#HD7


With 0V it should switch to 8Mhz. I'd suggest scoping the 1772 clock to confirm the switching is working.

[Cwiiis]

So, to test that theory I connected the board to ground directly from the PSU and now 720K disks work, so I guess there's something wrong with the ground it's getting from the drive somehow - I'll of course double-check continuity, that would be the most obvious thing, but I don't think it's that, I did check that before...

I did indeed follow the guide and I'm pretty sure I have it correct, it's this D0 line where the issue appears to lie, and given connecting it to ground on the PSU works using the same point, my issue must be somewhere on the drive/the connection to the drive.

[Cwiiis]

Ok, problem identified - when connected to the board, it hovers at 3.3V instead of ground... Now that I know that, I've no idea what I can do about that though... Any ideas?

[exxos]

Just to confirm you are using a MPF920 drive ?

[Cwiiis]

I'm not using an MPF920, I understand that that may not be a supported use-case but it seems like it's very close to workable. I've attached a photo of my setup for reference. This drive (a TEAC FD 235-HF) came already fitted with the machine when I got it, you can see the exposed copper where they'd tied the density select to ground to force the drive to treat all disks as DD (not really sure why they did this given how easy it is to just put some tape over the hole, but there you go).

IMG_20230925_113821.jpg (359.64 KiB) Viewed 1927 times

[exxos]

You need to solder to the switch. All it should do is connect the wire to 0V when a DSDD is inserted. That's it. Looks like you solder a wire to some logic part of the drive. But I can't really comment on those drives as I have only really used the MPF920.

[Cwiiis]

You need to solder to the switch. All it should do is connect the wire to 0V when a DSDD is inserted. That's it. Looks like you solder a wire to some logic part of the drive. But I can't really comment on those drives as I have only really used the MPF920.

Thanks, I guess I need to take the shielding off the drive and find where the switch actually is - I was hoping I could just use this point but it's clearly not suitable. If I find it I'll report back as I think this is an extremely common and easy-to-find drive and otherwise works great.

[exxos]

I think this is an extremely common and easy-to-find drive and otherwise works great.

I do remember testing the TEAC FD 235-HF 20+ years ago. Was expensive back then. IIRC I had nothing but problems with it, even with standard formats. Maybe I had a bad drive, no idea, but I don't think it supported extended formats even ?

[Cwiiis]

I think this is an extremely common and easy-to-find drive and otherwise works great.

I do remember testing the TEAC FD 235-HF 20+ years ago. Was expensive back then. IIRC I had nothing but problems with it, even with standard formats. Maybe I had a bad drive, no idea, but I don't think it supported extended formats even ?

It seems there are a multitude of different versions of it that vary pretty wildly, but the one I've got works great as both DD and HD - I just need to get access to this bloody switch! Managed to strip one of the screws so just seeing what I can do about that at the moment...