AtariFox STFM service blog

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Steve
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Re: AtariFox STFM service blog

Post by Steve » Mon Sep 14, 2020 4:47 pm

PhilC wrote:
Sun Sep 13, 2020 10:09 pm
Watching with interest as I got this far with one of my Megas
I read your thread and our issues seem to be slightly different. This machine can successfully format a floppy disc 100% of the time. It just has difficulty reading data. The issues on reading data seem to be quite random, where a certain program on the floppy will load one time, but then not after.
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Re: AtariFox STFM service blog

Post by derkom » Mon Sep 14, 2020 5:18 pm

Steve wrote:
Mon Sep 14, 2020 2:53 pm
Can anyone give me advice on this, I can't seem to find anything when searching forums. I've soldered in the header, but then noticed all PC floppy cables have a blocked hole. So it won't plug in to the header unless I remove a pin, also the same with the Atari disk drive as all of its pins are populated:
You can also make a new hole in the plug by heating a pin with a lighter and then jamming it into the plastic. :)

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Re: AtariFox STFM service blog

Post by Tomswork » Mon Sep 14, 2020 6:36 pm

The octal buffers on megafile maybe bad and sorting the dma port

Tom

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Re: AtariFox STFM service blog

Post by AtariFox » Wed Sep 16, 2020 2:11 am

A real unfortunate pain in the ass this thing is. I really don't know what what's caused it. If only i hadn't tried to solder the wd pullup myself, none of this would have happened. I have floppy cables without the blocked hole, but, since it's already been removed, it's fine.

The only thing that keeps bothering me is the scraped lacquer exposed trace i did. I dont know if there's even an issue on the underside of the board.

Did find this service manual, does bring up some of the issues being had.
http://www.atarimania.com/documents/ata ... manual.pdf

But, Even with a recap, and Steve got to test with a new Exxos PSU, it still did'nt fix it.

I don't /really/ want to spend more on it, It's already quite more than i thought it would be (i live on benefits unfortunately) and i'm not sure what else would be wrong with it. Unless more people here have further suggestions to do, things to solder and such.

But from what i can gather. There's something messing or broken with the chips or even traces that control the read data from the floppy drive and feed it through. It must be on the WD1772 trace lines because thats the chip all the read and write data has to pass through, then to the dma, then to the cpu.

I've never even gotten to use the stupid thing other than buy a ToS switch and a ube video adapter. Never got to play games or even get to see if the megafile i fixed works either.

I may call it quits if nothing else aside from a dma replacement works, pick it up and shove it in the cupboard.

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Re: AtariFox STFM service blog

Post by Steve » Wed Sep 16, 2020 11:19 am

I understand your frustration. The traces you mentioned are fine, I tested them all with a multimeter. I also checked all traces on the DMA. I have a feeling that your attempt at soldering the bus resistor didn't cause the problem. Like it was suggested a couple of posts up, I have a feeling that this started when you began testing the megafile. As you know having it plugged in stopped the floppy entirely, and unplugged it seemed ok, but I'm wondering if you thoroughly tested the floppy in-between this incident and the bus resistor attempt.
Tomswork wrote:
Mon Sep 14, 2020 6:36 pm
The octal buffers on megafile maybe bad and sorting the dma port

Tom
If this is true then perhaps it is possible that the DMA chip could be damaged.
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Re: AtariFox STFM service blog

Post by Icky » Wed Sep 16, 2020 11:33 am

Just a thought could this be a DMA chip issue. I was seeing similar behaviour when building the STFM Alpha Remake and the DMA chip appeared to be working but with floppy issues. After replacing the DMA chip it worked correctly.

That’s why we ended up calling it the Nasty DMA as it took us a while to figure out the DMA was at fault as it seemed to be behaving.

I know this doesn’t help your STFM but @exxos with the remake has improved buffering on the ACSI and the Floppy bus to reduce these types of issues such as plugging things in etc.

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Re: AtariFox STFM service blog

Post by exxos » Wed Sep 16, 2020 1:34 pm

DMA issues.. Has so many complications.. Noise on A1 can FUBAR the DMA ... Bad PSU... Even working 1772 chips can cause DMA malfunctions...may well be a blown DMA chip ..
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Re: AtariFox STFM service blog

Post by AtariFox » Wed Sep 16, 2020 3:35 pm

Well i spoke with my father and he said he'd still help out with cost.
I honestly dont want to give up on it because i'd love to enjoy the system.

What about all those resistors behind the asci port? Would any of them being bad cause it too?
exxos wrote:
Wed Sep 16, 2020 1:34 pm
DMA issues.. Has so many complications.. Noise on A1 can FUBAR the DMA ... Bad PSU... Even working 1772 chips can cause DMA malfunctions...may well be a blown DMA chip ..
Another bad WD1772 chip even new could be a thing? Sheesh. He got to test it with one of your Powerunits and the issue still persisted.

So A1 and or DMA then. Honestly I think doing as much as possible to fix the thing would be nice.
Icky wrote:
Wed Sep 16, 2020 11:33 am
Just a thought could this be a DMA chip issue. I was seeing similar behaviour when building the STFM Alpha Remake and the DMA chip appeared to be working but with floppy issues. After replacing the DMA chip it worked correctly.

That’s why we ended up calling it the Nasty DMA as it took us a while to figure out the DMA was at fault as it seemed to be behaving.

I know this doesn’t help your STFM but @exxos with the remake has improved buffering on the ACSI and the Floppy bus to reduce these types of issues such as plugging things in etc.
Thank you for your input icky, that does raise my hopes that it is a bad DMA all this time. Since the ASCI goes through that chip too.
Steve wrote:
Wed Sep 16, 2020 11:19 am
I understand your frustration. The traces you mentioned are fine, I tested them all with a multimeter. I also checked all traces on the DMA. I have a feeling that your attempt at soldering the bus resistor didn't cause the problem. Like it was suggested a couple of posts up, I have a feeling that this started when you began testing the megafile. As you know having it plugged in stopped the floppy entirely, and unplugged it seemed ok, but I'm wondering if you thoroughly tested the floppy in-between this incident and the bus resistor attempt.
Tomswork wrote:
Mon Sep 14, 2020 6:36 pm
The octal buffers on megafile maybe bad and sorting the dma port

Tom
If this is true then perhaps it is possible that the DMA chip could be damaged.
Thank you steve, Put things at rest in my head to the traces issue. What does it look like on the underside?

As for the floppy. It had no problems really, other than when i made a bad disk. I used those tools to make images to floppies and it would read and execute without a problem for what i ended up testing it for. It's read cubase from a overwritten atari system disk, and would read the ones i made when i first got it. Then the ones I made to get the megafile going, megafile on > no floppy > megafile off >floppy ok.

Before i did the resistor thing, and touched the chip, it'd read and write disks, i cant really explain anything else

So if the buffers on the megafile i fixed are bad..That means i shorted something on the atari when i plugged it in? Or?

I don't think Steve's done anything with the megafile. It was Icky's before i got it, then i soldered/fixed all the wiring and got a MFM drive.

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Re: AtariFox STFM service blog

Post by Steve » Wed Sep 16, 2020 3:40 pm

We will try a new DMA and.. if all is well, then it will likely be that there is a problem with the Megafile. This is why I haven't touched the Megafile yet as you gotta solve the system issues before moving outwards. If the floppy comes back to life I will definitely not plug the Megafile in as it could blow things again. It would have to be looked at by itself. Stay tuned for another episode of AtariFox STFM adventures, hopefully the last episode :)
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Re: AtariFox STFM service blog

Post by DoG » Wed Sep 16, 2020 4:00 pm

It isn't as simple as the floppy disks going bad then? If two drives behaves in similar way? Got a gotek?

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