My project
A consolized Neo Geo arcade system, crammed into an Xbox case. After taking it apart, I realised that I can simply use the existing powersupply...My problem, I can't seem to get the readings I need from the multi meter - I can get the basic 12v reading, but I'm picking that based on this pin out

That is the PSU that I have (some colours are different)
I need to bridge (trick) the psu into know it's on and to supply the correct voltage to the given pins.
Would that be right ?
Any help would be great.
Ben