I found the solution. There is a three pin header on the pcb near the Orig. knob that ought to have a pin jumper connecting two of the three pins to either 1) force a square wave on the incoming signal or 2) pass the original signal through. The jumper was missing from my module when it arrived. Without the jumper between the pins, the signal will not be controlled by the Orig. knob. I contacted the manufacturer and he suggested I take a jumper from a two pin header located behind the F/4 knob, which controls the AC/DC output. This jumper is not necessary for audio performance so I just slipped the jumper off the two pin header and used it on the three pin header as a work around. They are going to send me a replacement. Thanks for looking into it.
-FF