Poking with a needle and fingers on the DIN connector should reveal the correct wiring. since the VU's will start to dance.
Manual machine has a schematic but you have to sign up ,you do get shown 2-"micro " Din sockets + a Din socket wiring but read-
Mini-DIN connector - Wikipedia
Manual Machine -
Uher 4200 Report Stereo IC Schematic
Mini-DIN connector - Wikipedia
Manual Machine -
Uher 4200 Report Stereo IC Schematic