That's what I thought - I have a few days off work so have the time to try it.  The connections actually all look in pretty good order. I do still intend to order the mute relay and see if I can fix the original amp in the BC9000, but just in case that doesn't work, I have a backup.

While I was poking around inside the BC9000 I also decided to try to get the cassette mechanism out and have a look at the belt.  It's the Type 1 cassette deck; I've only replaced belts on the Type 2 before now. The cassette deck does work, but I also have a Beocenter 8500 which is the one I use, and the tape deck in the BC8500 can be a bit temperamental sometimes, so I want to put a new belt in it. My BC8500 also has the Type 1 tape deck, same as the BC9000. So, I thought I would take a look around the tape deck in the BC9000 (a restoration project) so I would know what to do when it came to replacing the belt in my BC8500, but I cannot figure out how the get the tape deck mechanism out!  There are three screws (two on the lower edge, and one above, next to the motor), but something still seems to be holding it in place at the bottom edge, that I can't see it. Has anyone here ever removed one?  What's the trick to it!? I have checked the service manual but it does not go into the level of detail needed, or not that I can see.