I finally had time to check the FM board. What a hazzle to get it out. Removing 16 screws marked A – some of them quite hidden.
All the caps on the board test fine – that is the good news.
I am pretty sure that the fault lies in the square part 5105 which is just called ‘coil’ in the service manual. It is an IF can with a condenser, and it seems that the condenser in these dies for whatever reason. Since I don’t know the specification, I don’t know if a replacement part can actually be ordered from somewhere, or if it can somehow be repaired by replacing the condenser. Anyone has an idea?