I didn’t have a schematic to hand, and to make matters worse someone had gone to the trouble of removing the lettering on the chips on the board, presumably to hamper copying.

No sound was coming through the effect, so it was simply a matter of tracing a signal through the circuit to find where it was “disappearing”. The large brown caps on the PCB are quite heavy to be held in place solely by the soldering to the PCB, and I soon found that the weight of the caps had caused a PCB trace break on one cap and a horrible dry joint on another.

Both this type of fault are common on PCB where the solder joint is mechanically stressed (think PCB mounted jack sockets), and fortunately are easy to repair. This repair demonstrates that the visual inspection is a most valuable diagnostic tool!