I’m working on a Tempest PCB bought some months ago on ebay. It missed some PROMs and custom chips on the aux board.
I needed a little bit to find all missing parts and I tested the aux board using my working main so I’m sure it works.
So, plugging the boardset I can see this strange TEST screen:
all “0” are on the same line… They should be on 5 different lines…
Exiting fro the test the game resets.