Flashing “1” in corner of screen. Took a look at the Pac-Man troubleshoot by picture guide and that pointed me to “4R video RAM bad”. Swapped it, no good!
Tried swapping other RAMs, no change either. Started pulling all socketed chips and found a bent pin on the ROM at 6E! straightened it, and reinserted, Pac lives once more.
That will teach me to try the simple checks/fixes before the more complex ones…
Solution: Fixed bent pin on a ROM chip.
Game would boot normally, but would then start getting random lines/glitches through the screen after running for a couple of minutes; they did not otherwise effect gameplay. Immediately suspect video RAMs, start hitting ’em with the freeze spray and sure enough, got a bad one. Replaced it, and all is well!
Solution: Replaced bad RAM chip.