don't know if you know Sega's weird wiring color scheme or not, I was able to deduce it from the pinout on the power supplies on a few different games..
white is ground
yellow is +5
red is +12
brown is +3.3 (if applicable)
or if you don't believe me, just read your power supply or if it's been Americanized you can follow the usual red/yellow/black wiring back to a little power adapter board that takes power in from the power supply and then outputs it back out to the filter board on the PCB cage. try to get your readings at the power adapter board, since it'll be next to impossible at those micro connectors on the filter board.
5.25 is a good voltage to try at, since these are a little power hungry.