Yes, the contacts can be the problem.
You can diagnose this by looking at the display on the MCP;
If it lights up when rotating the wheel, the contacts are fine and vice versa.

If it lights up but doesn't actually change volume, the fault
lies elsewhere, most likely in the optical pulse readout
from the wheel.
Parts are available for this but err... not exactly as cheap as Chris'.

The contacts will have to be taken from a donor MCP, I suppose.

Martin

Exploratory surgery completed. The contacts look fine. But 2 of the 3 wires soldered to the thingy in the middle of the wheel had come loose. Can I simply solder them back together? Since I'm not very good at working with solid state components, is there somewhere I can take it to have the soldering done 'properly'? Is there a place that also sells the battery connectors for the Beolink? I'll start with whichever one is least expensive, just so I can adjust the  volume and make sure the whole system is working.

Marc

Found a dealer nearby who will repair everything.

Thanks to all for helping me to restore my beloved system!

Marc