Ghosts'n Goblins
My favourite arcade of them all. Ghosts'n Goblins is famously merciless: six stages of demons, one knight, and armour that lasts about four seconds. I grew up feeding it coins alongside my ZX81, C64 and Amiga, so owning the real board was never really a choice.
The PCB I got runs on a Motorola 6809 and came with a personality of its own: an intermittent memory fault that only showed up when it felt like it. I ended up writing my own 6809 assembler test routines to corner it. It took a lot of bench hours, I must admit, but the fault lost ;) Sir Arthur now runs flawlessly on original silicon.
Commando
Capcom, 1985: one soldier dropped behind enemy lines, a helicopter that never comes back for you, and a vertical-scrolling run-and-gun that became an instant arcade legend. Through its home conversions it became part of a whole generation's DNA.
The plan was simple: buy two faulty boards, each a three-deck stack of 250 chips driven by twin Z80s, and make one good machine out of them. The boards fought back with a dead CPU, a stopped clock, flaky ROMs and stuck flip-flops, but chip by chip both came back to life. The third act is finished too: the complete 1985 schematic set rebuilt as interactive digital schematics, all 18 sheets walked IC by IC, with a written explanation of how every part of the machine works.
