I recently acquired this signal generator and am in the process of recapping and refurbishing it.

All the functions appear to work except the 0-15 Khz audio generator function. I am trying to get a better understanding of how it is supposed to work.

As I understand the descriptive narrative for this audio function, two RF signals are mixed, and the resulting signal is the adjustable 0-15 Khz audio output.

When I monitor the output port all I see is a RF signal that varies slightly when the audio frequency adjustment is turned.

Could it be that the fixed RF signal the one that is missing? Is one of the crystal oscillator signals used for the fixed RF signals?

Any advice on how to diagnose this?