G'Day Johno - and welcome to the site 

F4 is your solenoid +43VDC. If it is blowing the moment you turn on the machine, then BR3 (Bridge Rectifier) has a short and needs to be replaced. You can confirm this if you remove J1 and J3 from the transformer board and switch on the game with a good 5Amp fuse. If it blows - it is BR3 - if not - you have a shorted coil..

try that as a starting point..