I picked up a 201A and it’s not receiving good on groups of channels 13-20 & 31-35 so I figu I would look at the synthesizer board. I removed and cleaned black channel control, removed a few crystals and they all checked ok. I also looked at the trimmer caps and they are all working. All the diodes tested good also.
When looking at voltages on Pin 1-12 I’m getting some voltages when I shouldn’t and some I should see are missing.
So now I’m thinking either this mod (clarifier unlock ?) is causing the voltages?
I took a pic of a sketch I did of S4 crystal / manual switch and where the cut wires go.
I also took an underside pic.