As long as it is not a very early one (pre Beo4 model) the answer is yes. However finding a STB-C will be tricky as B&O no longer supply this model.

I always use fully wired cables if possible - with ICE amplifiers, the chances of hum are much greater than the older speakers.

Simple things first - have you cleaned the heads? Interesting machine this though it is actually Japanese so parts are not as easy to obtain as most B&O. It ccould be that the azimuth needs adjusting - you will need the service manual and some knowledge!

What sort of Powerlink cable are you using?

Nice system - well worth £50. 1. Belt for the CD50 clearly needed but these are temperamental machines - I will be surprised if this works! 2. BC5000 - New belts again - much more likely to work! 3. May need the springs playing with. A little bend upwards wouldn't hurt! See if you can work out where the impact point is. Well worth fixing

They really went to town with the connections there! I think Alex is right though - you need a volume control. With mine, I run a digital output to the DAC from the Mac - single cable to the input - mine is optical though this looks like a straight electronic connection on yours. I then run the RCA outputs in my case to the AUX in of a receiver and

Looks fine - check it is fully working and that the cartridge is OK. These are very expensive to replace.

Lovely music centre - the speakers are worthless in this condition but the system will work with any normal speakers. The cassette needs new belts - they all do! The best record based centre that B&O made.

Never heard of a 3403 but the 3404 should be fine. Check it has a 7 pin DIN plug.

I use cotton buds and soapy water. Particular care should be taken with Beolab 5000s.