I like a challenge like this too, which is why i bought this cabinet, it was something nobody knew anything about.
i cant make out the labling on the PR50 IC, so i dont really know how to dump it.. i didnt even realise it was a prom till you said it.
the control panels are original, they havnt been changed. however there are japanese control panels under the aluminium english overlays (i guess theres meant to be an english overlay over the start button panel aswel). the japanese ones are even more generic however, just yellow text on a black panel, and the aluminium is a high quality overlay that looks like it is probably a old as the cabinet.
I'm in australia, but the cab is definately from japan, apparently the rest of the world ran out of cabs while japan had extra or something, so alot of japanese cabs were converted to english and exported. (so i'm told)
that cocktail does look similar, not completely identical, but theres no question that it is a sega cocktail, so it's not suprising that there would be variations. it's probably a generic sega cab design, but i still would like to know what game it left the factory with.
I'll get some high quality shots of the instruction sheets when i get up to taking the glass off. i'm still trying to sort the pcb at this point.
I got the game running today, the 2101 ram came and now the game plays, i still have problems with sound though.. theres a constant white noise tone and background (alien) noise runs all the time from the moment the game is switched on. also fire and dying noises are missing... any suggestions?
the game has the namco logo at the game over screen.. not suprising really, it has namco set 2 character roms.
edit:
did some more fiddling, replaced some more ic's, and now the white noise is gone. also discovered the purple ships were turning red when diving and fixed that by cleaning up the legs of the 27ls00(i think) ram ic's. the fire and explosion noises are still not there, and i've replaced 7T, 7R, and 9L. i'm gonna replace some 555 timers tomorrow which will hopefully fix the background noise being on during game over.
also putting 5v on pin 7 of 9L triggers the explosion noise, but the volume is very low, just as it is for the background noise.. i dont really know where to look for this problem.. any ideas?
I've been using the midway troubleshooting manuals, and so far everything they've said has matched this sega pcb except for A11 and the components around it. i guess it uses a different amp design? (A11 is an MB3713, as used on many bootleg boards, but i dont believe this is a bootleg for a moment. are there any legit boards that use this amp?)
another edit,
the game works perfectly now, except purple aliens are a bit blurry, i've got new ram coming that might fix that though. the problems were caused by a broken pin on the eeprom we put in to replace the dead V eprom that came in it..
so many hours work and it now works!
still looking for info on the cab history though..