I would still recommend isolating the rectifier to see whether whether the fuse still blows. Disconnect the rectifier multiway plug and also temporarily remove the thick cable from the red terminal post just in front of the oil tank. It's a quick and easy test and will either point the finger at or exonerate the rectifier.
Must need my eyesight checking Andy
but having spent time searching for other end of the tenth red wire coded R80 on schematic, I found it immediately after your suggestion
.
Sincere apologies Vitaloni but it routes directly to voltage regulator of alternator. I'm pretty sure if you disconnect just this cable, which appears to terminate in a 10mm eyelet, you will find a dead short at the regulator/rectifier it connects to. A replacement 50 amp fuse shouldn't blow then by way of confirmation.
If so and given unreliability of this component, a full replacement with I believe the recommended HD unit is the way to go, even if it's found to be just chaffed wiring at regulator.
