recently got a pacman, its a ‘pac 1/pac 2’ cocktail bootleg as detailed here;
http://lawnmowerman.rotheblog.com/#pac12Bootleg
fired it up and got a black screen
first things first, clock... and found no clock signal at z80 (pin 6)
used schematics to trace clock generation back to 74LS107 @ 8A. - inputs were pulsing but outputs were steady.
pulled chip, it failed test.
pulled replacement from dead board.
board then boots, cycles through self-check. says ‘memory ok’ then resets. continuous audio tone.
consulted troubleshooting guide , describes 8k missing will give same fault,
check 8k, outputs stuck high.
pull chip and it fails, replace and now boots to static garbage.
consult troubleshooting guide. mentions 139 at 7m giving this fault.
check it and its missing an input on pin 15 (floating pin)
use schematics to find the missing input is supplied by pin 14 of a 138 at 7J.
pull 7J, it fails test. replace and board boots
play a couple of games and then sound becomes erratic. hehe... to be continued.
schematics and troubleshooting guide used available here;
http://www.mikesarcade.com/arcade/manuals.html
