Having all the Sega Showcase or Sega Concave machines as i call them, i would be checking/replacing the starters. (shaped like any normal white little barrell shaped fluro starters)

Take them out n clean them, or just replace them altogether. Also when u put the new fluro in, jiggle the tube a little at each end as sometimes the contacts can be a little touchy. I note, that sometimes it can take 30 or 40 seconds for the fluro to light up. if it doesnt start straight away, give it another 20 or so seconds.

I would be having a serious look at how the power supply has been set up in the machine. it might be set at 220 volts, not 240 etc.

Brett,

From what Jeff has described I believe the transformer is jumpered correctly.

On your machines, I take it there is two wires (black & white) running from the ballast near the fluro tube, into the cab where a 2 pin molex connector connects a blue / blue from the transformer?
This should feed 120v to the ballast / fluro.
From what Jeff described, it appears that this was bypassed and the ballast was wired directly to the mains.