I have built 3 Piccolos, all stock. One of the Piccolos built for a friend has a problem.

No left channel at 20db gain setting, but otherwise A-OK. I am assuming the resistor at the 20 db gain position has a bad solder joint. So, I went to the schematic, but was unsure of the location. Could someone tell me the position of the 20 db gain resistor? Greatly appreciated!