Ok,
Thanks very much, at least I won't spend more days checking cables, grounding, isolation transformers and the schematic. That's why I did not understood why on previous ship it was Ok and this one is more crappy. Was about to think that the batch of DUs I have were all defectives.
I agree that you need one in JKF that works, very tight spots.
Anyway, pictures are still welcome if you have some.