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 source, with slight variations, can be found in other articles in this section and on this...
This 45 to 90 Hz hum elimination circuit was obtained from a 1980s documentation. The operational can...
This simple 2004 circuit uses a common sensor used in television and other equipment. It checks...