Dod R-870 flanger/doubler rack unit channel not working.

Hello, long time lurker here, first time posting. The B channel on this DOD r-870 BBD Flanger/doubler only seems to have a little effect on it when I turn it completely to wet. From what I read, the B channel is supposed to have the inverted version of the wet signal along with the dry signal, while the A channel has the wet signal in opposite polarity as well as the dry signal. the B channel mix knob is third from the left. I havent used my soldering iron in ages, is it possible that one... Read more