Completely disconnected. Circuit is sitting on my desk. I have checked the voltages and I have 5.7v across the 5k pot and 12v across -ve MIN to +ve MAX pot - same as other controllers.
However, I checked VR3 (the pot coming off the wiper on the analogue pot) and it is not measuring any voltage across it's terminals whilst the on the other controllers it has a min 0.5v and increases with voltage from wiper. Maybe D9 has blown.