TouCans is back up and running! The culprit did in fact lie in the path between the power supply and ground in the PA chain. I didn’t see it coming though. Here’s the problem:

There was a cold solder joint on one side of the inductor. When KO6BTY and I measured the resistance across the inductor, it was infinite. When we remarked about this, 11 year-old Tawnse immediately said, that’s not what inductors are supposed to do. And yeah, she’ right. They’ supposed to conduct at DC.

Anyway, a few minutes later, we’d gone from this

Notice the magnet wire tint to the two wires whose solder joints are completely in the picture?

To this

    

Which, in turn, led to this later that evening.

The moral of the story for me? Always check the two terminal component first because they’re the easiest to fix.