The following circuit is from a commercial audio generator Heathkit AC-9, and evidently their assembly requires the use of precision components. It serves, however as a reference for possible repairs or recovery.
The circuit is a low frequency audio oscillator with outputs to attenuators.
Using two valves it has several settings bands whose component values are given in the table accompanying this article. The circuit also includes an analog indicator for signal strength. In Figure 1 we have the complete diagram of the generator.
Figure 1 - Full generator Diagram
The table below shows the positions of the controls and the values of R for different frequencies.
