exxos's Atari, Amiga & retro forum

I was looking around the forum, and found something about an STF Buffer
I dunno if this would do anything. Or has already been succeeded by a better fix.

I believe this is the thread icky mentioned the Nasty DMA from.


https://www.exxosforum.co.uk/forum/viewt ... 110#p13231

DoG wrote: 16 Sep 2020 16:00 It isn't as simple as the floppy disks going bad then? If two drives behaves in similar way? Got a gotek?

I really should get a spare gotek for these purposes to be honest. I did try my spare floppy drive though. I have also tried different disks. The issue was reproducible over two different floppy drives and disks. Also the aspect that the drive can format/write perfectly but has issues on the read, so far all of this is pointing to the DMA (especially after all the things I've tried already) Even though I have tried a brand new WD chip from exxos store which made no difference, I've put an order in for the VL1772 version just to be sure. I'll also try a new floppy belt just to make sure.

I'll update the thread again once I've got all this done.

AtariFox wrote: 16 Sep 2020 16:03 I was looking around the forum, and found something about an STF Buffer
I dunno if this would do anything. Or has already been succeeded by a better fix.

I believe this is the thread icky mentioned the Nasty DMA from.


https://www.exxosforum.co.uk/forum/viewt ... 110#p13231

That is just for the H4 remake board unfortunately, not something for STFMs

Steve wrote: 16 Sep 2020 16:07

AtariFox wrote: 16 Sep 2020 16:03 I was looking around the forum, and found something about an STF Buffer
I dunno if this would do anything. Or has already been succeeded by a better fix.

I believe this is the thread icky mentioned the Nasty DMA from.


https://www.exxosforum.co.uk/forum/viewt ... 110#p13231

That is just for the H4 remake board unfortunately, not something for STFMs

Bugger. Looked promising too, since the prototype was on a STM, lol.

I think diagnosing step by step is the best approach as you have been doing thats what I had to do on the ALPHA by testing two versions of the 1772 chip and two versions of the DMA chip to see which combination worked. Thats how I ended up figuring out it was a DMA chip that was causing my issue.

The 1772 buffer board can work on an STFM (I have one on my STFM) but as mentioned above I would just get the machine working normally first.

The 1772 buffer should work on any machine.. But if the 1772 has been swapped a couple of times already.. Then I would assume that is not a issue.

Its starting to make me wonder what can be wrong now :lol: :roll:

It does sound sooo similar to my Nasty DMA issue.

I would socket out the DMA and try another one to see if that is the case.

Sounds almost like these issues https://www.exxosforum.co.uk/forum/viewt ... 221#p49221

Though again, the MFP is involved and some TTL logic chips if you look at the schematic...


EG on the H4...

Thank you for continuing to offer help and advice all.

Socketed DMA, tested new DMA chip, no difference!
In desperation, decided to do an extremely thorough floppy service, not just a head clean. Full swab with IPA, remove old rail grease, apply new innox PTFE machinery grease, clean heads again & replace all caps on the power circuitry.
And this seems to have solved the problems. Not sure exactly what the issue is after all that...

Video of drive working: