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Yet another Asteroids

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Nes4life View Drop Down
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    Posted: 24 Feb 2018 at 9:42pm
Got another Asteroids PCB on the bench - this time for @pjkram. It's a late revision with the blank column in the middle. All this means is that some ICs have shifted right one column.
  • Symptom: dead but some jibberish on screen (and then 2 low tones) when pressing on CPU
    • Pull out 6502, sand legs, reseat, and game boots!
  • Symptom: test grid shows four crazy figures of '8' (see pics below)
    • Replace LS157 at D/E10 (D/E11 on some revisions) and then LS157 at F/H10 (F/H11 on some revisions)
  • Symptom: test grid shows collapsed top and bottom
    • Replace LS157 at F/H10 (F/H11 on some revisions)
  • Symptom: tiny asteroids but not text
    • LS175 at M7 had outputs stuck low. It takes all 4 scales as inputs.
  • Symptom: Some asteroids have a dim diagonal line in the bottom right - as part of their design. On further inspection of the test grid, the brightness scales are wrong, with all lines at full brightness.
    • LS164 at K9 (K10) was iffy. No signs on the scope that anything was wrong but piggy-backing fixed the problem. 

As is usual for me, I tend to go to the last ICs passing signals to the DACs and work backwards. In this case I found low outputs on both LS157 but the inputs were fine. Interestingly, piggybacking only showed improvement on D/E10(11) and not F/H10(11). For the size issue I started at the LS273 at K7, saw the scale signals looked healthy and moved on to the LS175 at M7 where I found stuck outputs.









For the size issue investigation:


That brightness issue:

What is should look like:

 




Edited by Nes4life - 27 Feb 2018 at 10:46pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bonehead Quote  Post ReplyReply Direct Link To This Post Posted: 24 Feb 2018 at 10:19pm
Another nice fix and good write up on how you did it.

Keep up the good work.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pjkram Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2018 at 5:52pm
Looking forward to finally play this!
Great work Phill

Edited by pjkram - 27 Feb 2018 at 5:53pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote funhouse Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2018 at 6:11pm
Good stuff Nes4life.

When I finally get some arcade space this Spring, fixing my Asteroids PCB is up on my list and I know these posts will help. Smile
 




Edited by funhouse - 27 Feb 2018 at 6:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nes4life Quote  Post ReplyReply Direct Link To This Post Posted: 27 Feb 2018 at 10:44pm
And that's that! Brightness issue was a LS164 at K9 (K10). It's basically mastering the Z-out along with the scale signals. Now I'm going to soak-test it



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