I FINALLY got around working on the electronics of the jobo. I attached the motor to a power supply and it works perfectly smooth, sucking just 200mA. If I bypass the transformer and run it on the ext power supply it uses c.a. 240mA, which seems reasonable to me, but I would need to test that under load to see if it gets too high.
It seems the fuse connector was faulty - I changed that with a better one and the Jobo seems to run well now. But I'm not completely convinced: when running the TIP 3055 motor driver runs HOT, so hot that you can feel the warm plastic when the enclosure is in place. The 3055 is rated 15A, is this normal?
Also I'm scratching my head on the fuse: the schematic says 800mA, while the manual 1.25A. Which one is right? My jobo is very old, the electronics are "old style" as the repair manual states, but it is still a bit puzzling.
I also have a question: is it possible to re-grease the gearbox? After almost 40 years of life the grease that leaked outside seems just a sticky mess.
Thanks!