IF the power-supply board (with fuses) is on it's own, then pull out ALL cabling that go out to other boards...just leave the 240v mains into the power supply, then turn on the power and see if fuse blows again.
If it blows, something on your power board is shorting, more than likely a bad bridge-rectifier as suggested.
If your fuse doesn't blow, then it's definately an external board/loom/solenoid causing the problem.
(plug in cable/connectors 1-at-a-time onto the power board, to see WHICH board is causing the problem).
IF the power is part of a main driver board, at least remove all cabling that go from the driver/power board to other boards, and confirm if fuse blows (or not) again.
At least the fault will be on that board, or not...
Elimination......
