AtariFox STFM service blog

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Steve
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AtariFox STFM service blog

Post by Steve » Sun Aug 30, 2020 7:27 pm

Hi, this STFM is having issues where the floppy stops working when the ASCI HDD is enabled. User had trouble doing the DMA resistor mod and worried the floppy controller might be dead.

Motherboard: C070789-001 REV.D1

I can see where the client had trouble
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As I'm not sure whether the WD chip works, I'll fit a socket with the pullup resistor (I could have installed it underneath too I guess)
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Nice and clean, checked traces, all good.
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Socket fitted ready for WD chip.
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Chips ahoy!
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A marpet ram upgrade is installed and had those red tweaser connectors, I removed them and soldered the ram bypass for better connection.
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tzok
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Re: AtariFox STFM service blog

Post by tzok » Sun Aug 30, 2020 8:11 pm

Steve wrote:
Sun Aug 30, 2020 7:27 pm
Ouch, looks like that big CAP on the PSU is about to go POP!
I may assure you that it is completely fine! The plastic insert on the top has that hemispherical shape. I had the same, decided to replace it. But when removed, it measured perfectly fine (ESR, leakage, and capacity). I have removed the plastic wrapping, and discovered that this is only a protective insert, not the capacitor's can.

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Re: AtariFox STFM service blog

Post by exxos » Sun Aug 30, 2020 8:50 pm

Just to clarify, Heat from the cap can warp the plastic top, but its not a definitive indication that the cap is perfectly OK. Also as I keep saying, ESR meters can give you indication of a caps values, but even tested OK , it still cannot be assumed the cap is healthy. Such meters can lie to you!
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Re: AtariFox STFM service blog

Post by Steve » Sun Aug 30, 2020 10:47 pm

Cheers tzok I did not know this :)
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Re: AtariFox STFM service blog

Post by Steve » Mon Aug 31, 2020 4:07 pm

After doing these fixes the floppy drive still says 'Drive error data could be corrupted' when loading programs.

I then have done these:

Floppy 1k resistor 5v pullups
IMG_20200831_143913.jpg
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Data/address bus 2.2k sips
IMG_20200831_160623.jpg
IMG_20200831_160623.jpg (552.17 KiB) Viewed 411 times
Repairs & Servicing for Atari & Amiga machines (and any other retro computers) Located in the West Midlands UK. PM me if you require assistance.
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Re: AtariFox STFM service blog

Post by Steve » Mon Aug 31, 2020 4:10 pm

Still when loading programs from floppy, I see 'Drive error data could be corrupted'

I have also: cleaned floppy heads & tried known good floppy drive

Next I am thinking either: Ram test and/or PSU test.
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Re: AtariFox STFM service blog

Post by exxos » Mon Aug 31, 2020 4:20 pm

It may simply be because of the long cables on the marpet. They cause all sorts of screwy problems. Changing the bus resistors may solve it, but last motherboard I had here, I gave up with it. So you might have to try removing marpet to see if it solves the problem.
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Re: AtariFox STFM service blog

Post by Steve » Mon Aug 31, 2020 5:06 pm

Good idea, cheers.
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Re: AtariFox STFM service blog

Post by AtariFox » Tue Sep 01, 2020 4:03 pm

Hi there! Thanks for working on my atari.

It never had any actual issues reading or writing floppies even with the marpet plugged in and working when i got it. i did run extended memory tests on it when i first got it and it had no errors.

So the floppy works again without the megafile connected?

it sat mostly in the cupboard for a year or so till i managed to get the parts for the megafile @icky sent me. Though the ASCI Cabie may be damaged, i don't know, since i think icky said it was cut in half at some point. ?

But yeah, when i finally finished and installed the Megafile it would give the floppy cannot be read/data corrupted? issue. But when the megafile was unplugged it would work just fine.

At least it did before i messed up the soldering and i dunno if i burnt out that c68 resistor it's supposed to go to by the larger chip above it with too much heat.

has the megafile been tried on another Atari? Since due to the issue, i was never able to initialise the disk or anything.

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Re: AtariFox STFM service blog

Post by Steve » Tue Sep 01, 2020 4:16 pm

To be honest I haven't had a reason to check the megafile yet, as the ST itself has issues. I'll check out that capacitor.
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