I don't know the pinout for System 9 games, but I'm guessing they use the same standard colors for Williams. solid grey being +5, grey-yellow for +12, grey-green for -5 or -12 (whichever they were using at the time). the +12 and -5/12 should be only for sound, if your +5 is sagging a lot then it's probably due for a rebuild.
I've seen some nasty stuff with those System 9 power supplies that get burned up.