I have tried shorting the input and supplying 200-300 mv but there is no change. Thank you very much for the pictures! This is the model with the nixie tubes, right? I believe the schematic could be very similar. Could you scan the whole manual (you can use one of the smartphone scanning apps like Camscanner, no need for high quality), especially if there is a schematic. Also does somebody recognize the multi pin connector on the back? It looks like something similar to GPIB but it is definitelly not.