Boston ASW 250 Fuse Blowing

Hi, I have an ASW 250 subwoofer which blew a 800mA 250V fuse.
I replaced the fuse and blew as well. A 1A250V fuse also blows.
The only way the fuse won't blow and I get power with the green light is when the secondary.of the transformer is disconnected from the board.
I removed and tested the 4 main transistors from the board that it connects to and they all test ok.
No shorts between Emitter and Collector and base to collector or emitter values are fine.
Could it be the transformer or bridge rectifier closest to the connection of the transformers secondary wires connection point.
The transformer output measures 42V, 21V, 7.9V, 50V AC on the 4 pins if black lead is on the extreme left pin but the board it supplies has 15V in values as per schematic.
There is also an high frequency sound off the power supply board when the unit is on whilst secondary from transformer in disconnected.
The sound is present as soon as the power supply relay switches on.
Could it be a bad relay causing the fuse to blow when on load?