Black vertical lines on ST

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Steve
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Black vertical lines on ST

Post by Steve »

Hey guys,

Just hoping for some pointers on this. At first I thought it was a RAM issue but the memory test passes fine on diagnostics and on YAART. Machine is an old rev B ST. Any ideas? Thanks

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czietz
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Re: Black vertical lines on ST

Post by czietz »

I recently helped solve a similar issue: https://www.atari-forum.com/viewtopic.p ... 63#p421063. (Of course, in your case it won't be exactly D10, but another data line.)
Steve
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Re: Black vertical lines on ST

Post by Steve »

Thanks @czietz I'll check it out!
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stephen_usher
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Re: Black vertical lines on ST

Post by stephen_usher »

Looks like a Shifter issue.
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czietz
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Re: Black vertical lines on ST

Post by czietz »

PS: Looking at the pattern on your photo, I suspect D3.
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exxos
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Re: Black vertical lines on ST

Post by exxos »

Machine would not boot like that if it was a RAM fault, you basically have one data bit low all the time. I would check out the databus to the shifter or re-solder it etc.
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PhilC
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Re: Black vertical lines on ST

Post by PhilC »

exxos wrote: Fri Sep 10, 2021 12:38 pm Machine would not boot like that if it was a RAM fault, you basically have one data bit low all the time. I would check out the databus to the shifter or re-solder it etc.
@Steve That makes sense considering the other stuff we found.
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Re: Black vertical lines on ST

Post by Steve »

Hi guys,

I've checked D0 to D15 going to U22/26/23/27 pins, everything seems to be connected fine (buzzed them all) I also swapped out all chips U22/26/23/27 with different ones. I also swapped the shifter, still the same.. hmm what am I doing wrong?! :D

Here's a picture of the lines I've buzzed (highlighted in green spray paint) they all seem fine:

Screenshot from 2021-09-12 19-02-47.png
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PhilC
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Re: Black vertical lines on ST

Post by PhilC »

@Steve ok so all the lines buzz out ok, good. Now stick your scope on them one by one and one of them is likely staying low, hence the black line.
If it ain't broke, test it to Destruction.
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DoG
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Re: Black vertical lines on ST

Post by DoG »

Check other side of U22, U23, U26, U27.
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