Archived from groups: rec.games.video.arcade.collecting (More info?)
I posted a question about this problem about a week ago. Finally fixed the
board today, and it was a toughie. Thought I'd post the information here to
save someone else a lot of time and work.
Board: _Ms. Pac Man_.
Symptom: No red sprites. (That is, no red color on any of the moving
images.) Red color is present elsewhere on screen, such as in the maze and
alphanumerics.
What I tried: Replacing color PROMs at 4A and 7F; character EPROMs at 5E
and 5F; 7489 RAMs; supporting TTL logic chips...
Solution: The culprit turned out to be a bad 74LS20 at location 3E. In
particular, the input on pin 2 was not responding. What was really
infuriating about this was I had previously removed that chip and tested it,
and it worked on the bench!!!! #*$%%#*. Replacing that chip cured all.
Whew!
Matt J. McCullar
I posted a question about this problem about a week ago. Finally fixed the
board today, and it was a toughie. Thought I'd post the information here to
save someone else a lot of time and work.
Board: _Ms. Pac Man_.
Symptom: No red sprites. (That is, no red color on any of the moving
images.) Red color is present elsewhere on screen, such as in the maze and
alphanumerics.
What I tried: Replacing color PROMs at 4A and 7F; character EPROMs at 5E
and 5F; 7489 RAMs; supporting TTL logic chips...
Solution: The culprit turned out to be a bad 74LS20 at location 3E. In
particular, the input on pin 2 was not responding. What was really
infuriating about this was I had previously removed that chip and tested it,
and it worked on the bench!!!! #*$%%#*. Replacing that chip cured all.
Whew!
Matt J. McCullar
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