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suspicious_milk

Dead simple 130XE video fix ONE WIRE

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This 130XE's video with its vertical lines has been driving me crazy. So I opened it up and started playing.

Not only did the lines on the left side of the screen vanish, but as an unexpected bonus - the video is now crisper and the colors look soooo much better.

 

To be fair, the "before" pic has the brightness and contrast on the display turned up little so the lines were more noticeable in the pic, but the "after" pictures brightness and contrast was NOT re-adjusted.

 

The fix is simply jumping one resistor to one pin on the ROM just below it.

 

My results are amazing and I hope this helps somebody, as most other solutions I've seen require de-soldering which I'm not ready for yet. YMMV of course, but I hope yours are as good or better than mine!!

 

post-32718-0-79252900-1485725460_thumb.jpg

 

post-32718-0-38009900-1485725439_thumb.jpg

 

post-32718-0-82252400-1485725475_thumb.jpg

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On my 130XE the only difference it made is dimmer characters, no effect on vertical banding whatsoever. Is this even safe for the machine, what's the technical explanation for this mod?

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Sorry, but I cannot offer the technical explanation you desire. I was going over a handful of various suggested fixes I've collected on these and other boards, trying individual steps of different fixes (not applying any "complete" fix). I don't have the skill to apply all steps in any of the solutions because I'm not skilled enough to de-solder, so was trying any and all steps that I could do and easily un-do. I hoped I would get lucky (but didn't think I would) and see some kind of improvement. Just an exercise to practice my solder skills and learn a little bit by reading technical details of existing solutions. Learning and experimenting. Any anecdotes about monkeys, typewriters, and Shakespeare are appropriate.

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Pin 11 of the CD4050 is LUM1 input.

Can't tell for sure but it looks like that resistor might be for the LUM0 output from the CD4050, would need to open a real machine and verify.

 

What would be interesting is to see a luma band display with this mod to see if it's adversely affected the luma output.

It could be that the display looks smoother because the picture is being posterized.

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The trace from that resistor goes to pin 6 of CD4050, opposite of pin 11, which is an output pin

Edited by gargoyle

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It's like I said - pin 6 is effectively being joined to pin 11 of the 4050.

 

ie - C (out) to E (in)

 

which on the Atari is LUM0 from GTIA to LUM1 from CD4050.

I don't know why you'd want to do that. I could understand tying together LUM0 outputs from GTIA and 4050 together which might smooth out the imbalance between the 2 chips but why tie LUM0 to LUM1 - the way I see it, the luma would be smoothed out to the point where there'd be loss of fidelity.

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