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.
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:
Nes4life2018-02-27 22:46:47
- 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:
Nes4life2018-02-27 22:46:47
