Ask questions - Others that may experience similar issues will be able to follow the same process.

GI leaves the Power Supply board on all three connectors - Playfield, Headbox and Cabinet. There is also a relay on the power supply section that flickers the GI during attract mode and once the word "GALAXY" is completed.

So it could be the door lamp sockets, a playfield short or a shorted socket in the headbox.

question - Does the GI fuse blow when not playing a game ?

Simple isolation - If it is blowing, isolate by removing J1 (playfield) - then see if it blows the GI Fuse..

Remove the GI relay etc etc..