Game did not boot, and seemingly no logic activity anywhere on the board. The clock circuit is the first place to start for this kind of thing. It mostly consists of a crystal oscillator, a few resistors/capacitors and a 74S04 in a kind of feedback loop.
I removed the S04 chip from the board but it tested ok – the actual problem was the crystal oscillator itself had failed. 20.160MHz is kind of an unusual value for arcade games, but a replacement was found and fitted and everything worked 100%.