Sony DVK-2400 and DVC-2400 set

[MIPS]

Cautious experimenting yielded that in the end a regular 2N3904 would work as a substitute. After a bit of adjustment the 9v now present.

Going back to our more priority issue, we still do not have drum rotation. That I can tell from the documentation it should spin up the moment you put the VTR in standby with an intermediate circuit to handle the initial starting load. Instead it just sits there.



The diagrams say that the motor connects at points 1 and 4 on the DB board. Those two points when in standby read 11.5v so a voltage is present but weather or not it's what we're looking for might not be the bigger problem. Reading for a resistance across the leads from the motor and presumably its winding are infinite.

Either the lead to the motor has gone bad, the motor doesn't have a type of winding I'm expecting....or the winding has opened. Unless my observations are wrong that's the end of the line. Getting at the motor isn't at all easy and requires removal of the precisely aligned video head and surrounding mechanism which I do not have the tools to confidently realign.

Edited: The exploded view of the drum shows that there's an intermediate contact I forgot about. There's brushes or something similar inside. That's another potential fault point but again, it's located underneath the video head and cannot be removed form the underside.

Edited:
THREE BEERS LATER:




Well there's the problem. The motor brushes are pressed against the commutator with a thin metal bracket and foam. No surprise but after 50 years said foam has lost its ability to spring back, resulting in pretty much no contact. I'm not entirely sure how to proceed from here. Any ideas?