I took this one apart:
I think it is from a ’70.
Here is the controller circuit board and a draft of the circuit:
I need to check for accuracy and draw a nice version.
(I’ll edit out this version.)
Warren, What is Q1? It is in the same case as Q2 and has
three wires, one is NC. I drew in a Zenier diode but it
probably acts as a temperature sensor. Can you please
write a description of the functioning of the circuit, my
skills are receding memory.
Best,
Grady