Well, the problem with the volume control wasn't what I thought it was, and the problem was fixed by an unfortunate accident.
Instead of a burned spot on the resistive trace, it was where the terminal on the ground side was riveted to the phenolic board with the resistive trace. I didn't notice that a tubular capacitor that is on the end of a coax running to the wiper of the volume control was too close to a resistor. It arced through the paint on the capacitor while I was watching and made violent discharges in the volume control.
I expected the worst.
But, it turns out it just improved the connection so now the volume control tests and works perfectly!
John