AtariFox STFM service blog

[Steve]

One small anomaly I just noticed is this: On the STFM KIT DUAL TOS kit that is installed (with ube chip) The ube has not been connected to pin 16 of CPU, the bank select jumper is on bk2, but TS is bridged! Which according to your instructions, could mean the ube chip is damaged. I know this probably has nothing to do with the floppy. But I might unsolder the TS blob, and test the other TOS bank.

The UBE chip isnt used nor connected.

It reads ToS 1.04 and has done since i first got the upgrade, i' have not needed to mess with it as i just want it to run 1.04 and i just switch the jumper if i want tos 1.02.

Okay I added a DMA sip 10k resistor pullup and it's a little better. Managed to load yaart off floppy. Will do more testing tomorrow.

So you think i must have done something to the DMA chip? I can't believe I caused so much of an issue with just the soldering thing i messed up with.

I must have really buggered up something for it to need all this.

Don't worry I'm not connecting or enabling the UBE chip, I just noticed that TS was bridged, which according to the installation instructions could blow the UBE chip. I just mentioned it in the blog in case it was relevent to the floppy issues.

As for the DMA chip pull-ups, reason I did this is because the DMA is intrinsic for floppy and ASCI operations, and on this forum it has helped others with similar issues in the past.

[Steve]

END OF SERVICE BLOG
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Unfortunately I have been unable to completely solve the floppy issue, but I have improved it somewhat. I have managed to load Gembench and YAART to run through testing, but it seems to be inconsistent and other times it won't load. But economically for AtariFox I cannot spend more time on the unit, as I've already spent quite a few days trying my best to solve the problem, I have to call it a day.

* Socketed & installed WD chip & resistor mod
* Tested new WD chip
* Installed DMA resistor pullup mod
* Replaced 6 x bus data resistors on motherboard
* Cleaned floppy heads
* Re-flowed solder on floppy header connector
* Re-flowed solder on major chips on the board
* Pulled, cleaned and re-installed both PLCC chips & sockets
* Direct wired ram bypass to 4700 cap
* Replace c68 and test

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[PhilC]

Nicely done @Steve . Just a thought, have you tried floppy head alignments?

[exxos]

Don't see if you actually tried a different floppy drive ? Most of the original ones are pretty busted these days

[Steve]

Nicely done @Steve . Just a thought, have you tried floppy head alignments?

Don't see if you actually tried a different floppy drive ? Most of the original ones are pretty busted these days

Phil: I actually don't know how to do that to be honest
Chris: The only spare floppy drive I have is my TT's Epson SMD340. It is a high density drive but I figured it would just work in DD mode if I tried it out. I did try it and it worked as well as his stock DD drive, same issues.

[AtariFox]

Thanks so much for all your hard work @Steve

I dont know if the drive is misaligned, since you used your Atari TT 030's one and it did the same thing.

I might buy a new DMA chip then, I can buy one of those and do it, if you'd socket the existing chip for me. or up to you if you want to outright replace and see.

Otherwise, thank you so much for the time and effort in doing all this amazing work on it for me.

[Steve]

No worries I'm just sorry I couldn't completely solve the problem. I don't know whether replacing the DMA would help, usually with digital systems they either work completely or not at all. That's the thing though it can become an endless rabbit hole of fault finding.

[exxos]

Maybe just a bad cable ? You could put a socket there instead.. But of course more work...

[Steve]

Maybe just a bad cable ? You could put a socket there instead.. But of course more work...

True true... I will put it to him see what he would like to do.

[AtariFox]

Maybe just a bad cable ? You could put a socket there instead.. But of course more work...

True true... I will put it to him see what he would like to do.

You mean a new socketed floppy cable? I mean i guess you could try that.