[MrFixr55]

Congratulations on finding the issue, Al! Yes, it was very common for a manufacturer to use "unoccupied" pins as interconnects instead of spending $0.02 on a terminal strip. By making a wiring error and then finding and correcting it, one learns so much more about the circuit and its machinations than merely replacing parts.

I bet this set really sounds nice. (Probably doubles as a pretty good guitar amp too.)