We found this circuit in a 1965 publication by General Electric. The zener is 8.2 V x 1 W and the table shows the capacitor values according to the number of cylinders in the vehicle.
This circuit was found in a Electronics Handbook (1989). The shown amplifier provides a few...
The SCR used in this 80's circuit depends on the load. The control is half wave and instead of the neon...
This circuit was found in Delco documentation from 1966. The components are from that time....