[Vlad95]

Yesterday I tried to examine these resistors. I was surprised by the unknown design inside. The moving point does not directly contact the resistive plate, but is simply pressed against an additional contact spring that contacts the resistive layer at the desired point. Such a design should eliminate mechanical impact on the resistor and ensure a long service life.

But, unfortunately, this successful design completely failed due to the unsuccessful design of the resistive plate. It is made of cardboard with a carbon layer. As a result, the carbon layer oxidized, and the rating not only increased several times, but in some places the carbon layer of the resistor was completely open off.
I restored the tone rheostat. Not completely, the rating is higher than the original and is interrupted in the extreme position. But since this tone control is not important for functionality, and its rating is not critical, I can use this rheostat, restoring the carbon layer with a graphite pencil.

The situation is worse with the volume control potentiometer. It is the same in design, but with an added switch. The resistor condition is the same as above. In addition, the switch turned out to be unreliable. But the requirements for the circuit do not allow changing the resistor value and are sensitive to the quality of the contact. Unfortunately, in the case of the volume control potentiometer, it will have to be replaced with a new one.
I am currently buying both resistors online, but I will try to keep the original tone control but update the volume control.