Yet another Asteroids

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   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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Nes4life Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Senior Members Joined: 02 Jan 2014 Location: Ashford, Kent Status: Offline Points: 5213 Feedback: 5	Post Options Post Reply Quote Nes4life Report Post Thanks(0) Quote Reply Topic: Yet another Asteroids 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
	NES4Life ------------- Owner of ... too many cabs!

bonehead Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Senior Members Joined: 05 Jan 2013 Location: Bedfordshire Status: Offline Points: 10781 Feedback: 5	Post Options Post Reply Quote bonehead Report Post Thanks(0) Quote Reply Posted: 24 Feb 2018 at 10:19pm
	Another nice fix and good write up on how you did it. Keep up the good work.
	Always looking for a bargain. Wanted. Centipede uprigh, bezerk, mad planets.

pjkram Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Groupie Joined: 20 Aug 2015 Location: Kent Status: Offline Points: 135 Feedback: 0	Post Options Post Reply Quote pjkram Report Post Thanks(0) Quote Reply 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

funhouse Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Senior Member Joined: 28 Mar 2016 Location: West London Status: Offline Points: 6948 Feedback: 5	Post Options Post Reply Quote funhouse Report Post Thanks(0) Quote Reply 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. Edited by funhouse - 27 Feb 2018 at 6:12pm

Nes4life Members Profile Send Private Message Find Members Posts Add to Buddy List View Feedback Senior Members Joined: 02 Jan 2014 Location: Ashford, Kent Status: Offline Points: 5213 Feedback: 5	Post Options Post Reply Quote Nes4life Report Post Thanks(0) Quote Reply 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
	NES4Life ------------- Owner of ... too many cabs!