[Eric T]

Here's the schematics for reference:

http://www.nostalgiaair.org/PagesByModel...013602.pdf

If your tone control (which I believe is R27) makes some noise on your speaker (meaning a little scratching, but otherwise silent), you may conclude that your speaker, audio output transformer, and 2nd AF amplifier are probably OK.

What happens next depends on what test equipment you have on hand.

Ideally you could trace signals with an O-Scope from tube to tube (output from plate of tube X to input grid of tube Y, etc.) When you lose signal, work your way back to where it was last good.

If you have a signal generator with an audio output, there is a test point under the chassis near the back labeled "AF Test" where you might be able to inject an audio signal to check the rest of the audio section. That will eliminate everything after that point, including the first audio amp and volume pot.

If all you have is a multimeter, you can check connections from component to component and resistors without parallel circuits, but Easter-egging like that wastes a lot of time.