AtariFox STFM service blog

[AtariFox]

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

[Steve]

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.

[Steve]

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

[AtariFox]

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.

[Icky]

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.

[exxos]

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:

[Icky]

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.

[exxos]

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...

Capture.PNG

[AtariFox]

Thank you for continuing to offer help and advice all.

[Steve]

Socketed DMA, tested new DMA chip, no difference!

IMG_20200920_124046.jpg

IMG_20200920_124159.jpg

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.

IMG_20200920_130642.jpg

IMG_20200920_132111.jpg

IMG_20200920_133246.jpg

IMG_20200920_134728.jpg

And this seems to have solved the problems. Not sure exactly what the issue is after all that...

Video of drive working: