Have a sit-in Line of Fire with a custom chip error. The ls139 that selects the ic seems to be okay, but I can't figure much more out without a datasheet for the sega chip... which just won't happen anytime soon :\
The best would be a full at least semi-working board since there's also a botched s-ram replacement job on there which was jumpered all over the place already, and the nicely bent pins of the two ram chips pulled out three more traces when I tried to replace them... and they are just a -pain- to back-trace on these sega boards... (Whoever invented the trace spacing, thickness, and via/component leg hole sizes at sega in that period should have been shot in the testes just for that... I have yet to see -any- sega board from those times without jumpers after component replacement...)