[codefox1]

Looks like a tapped volume control, might be hard but not impossible to find a direct replacement. I'd try cleaning it with some deoxit, and measuring end to end and with wiper moving resistance with ohm meter, tap included. Work arounds with still obtainable controls can be done.

If the paper capacitors and ancient carbon resistors have been replaced, these should not be an issue.

Let us know.

Kind of blurry schematic here:
No cost version:

http://www.nostalgiaair.org/PagesByModel...013243.pdf

Better one (well worth it!) available at

http://www.nostalgiaair.org/PagesByModel...013243.pdf