Ok, calling this is a ‘repair’ is probably a misrepresentation as it was so easy. I bought this pcb from a junk pile and it arrived a bit dusty but not physically damaged in any way. It was missing all eproms (68K program, Z80 audio program, audio samples eprom) and the socketed PAL at IC58 (PAL16L8). The schematics show that IC58 generates monitor sync so it definitely wasn’t going to show anything without that..
Burned all eproms from the MAME set, and the PAL16L8 onto a GAL with thanks to the PLD images at http://www.jammarcade.net/pal-dumps/
And it worked! Well, almost – no sound and wouldn’t accept any coins. It seems this is due to the connector marked H on the board. I’d assumed this was a stereo sound output, but it seems 12V is required here in order to power the sound amp and coin IO. 12V from the jamma connector already runs here – so you have to jumper pins 1 & 2 together and 3 & 4 together to enable sound & coins. With this done the game worked fine.
Mystery 1 – why does connector H even exist, when 12V is already at the jamma connector!?
Mystery 2 – why did an operator strip a (presumably) working board just for some cheap eproms and a PAL? I guess something else more important at the time needed the parts.