It's been ages since I have seen a stock Galaga, but aren't these different power supply boards? Honestly, if you don't have a power supply for your Gorf, then do yourself a favor and buy the switcher kit and install that. With this method the game will be working while you are researching which original linear power supply to install in there.
My Wizard of Wor mini, which has the same set-up and PS as Gorf, has an original PS that died and was replaced by a switcher kit. The previous owner did this, but the game has been rock solid since.
Scott C.