Pinouts are here:
https://wiki.arcadeotaku.com/w/Sega_Blast_City_Wiring_Guide#Cabinet_I/O_Board
https://www.arcade-projects.com/threads/sega-model-2-and-model-3-filter-board-pinouts.1121/
2-pin connector is probably for the coin meter. You can leave it disconnected.
Triple check the power connections, everything else you are safe to mess up.
Thank you! Yeah saw a 2 pin connector on the Blast City IO board and it said "Coin Chute | Ground" not sure if that's kinda what you saw as well or if that is unrelated. I will leave it disconnected for now.|
Do I need to set the game to free play if the 2 pin cable left disconnected?