Battery drain on 300tdi (Jap import)

I know this has been covered numerous times but wanted to ask specifically if my alternator is shot?
My battery drains within about 5-7 days, I've charged and drop tested battery which checks out fine, but there is a draw of about 0.3 amps constantly and I've noticed that when I connect the battery the double relay near the battery is powered up on both sides! But if I disconnect the alternator it doesn't do it and the draw reduces significantly. I have tried to test the alternator in situ on diode mode and it shows a reading of 500 units??? one way and nearly 2,000 units the other. I understand this is wrong and how the diodes work in the rectifier but does this categorically prove the alternator is knackered?
Incidentally, the alternator still charges at about 14.3 volts d.c. and is showing about 0.24 volts a.c.
Many thanks for any pointers, just don't want to shell out for an alternator if I'm barking up the wrong tree.

The alternator has 8 p/n junctions in the rectifier pack and if only one fails it will look normal with a multimeter but will have a drain, the only certain way to test it is with oscilloscope https://www.circuitspecialists.com/blog/testing-an-alternator-with-an-oscilloscope/ but if you dont have one better replace it's rectifier or the whole unit