This circuit, found in a 1977 documentation, indicates when the grid voltage goes through zero. Under these conditions, it produces an output pulse whose duration depends on the capacitor.
This circuit also appears elsewhere on this site, obtained from other sources. This is an 80's...
This ttransistor test was found in a 1987 documentation. It is a simple oscillator that allows to...
In the circuit of the figure we used a potentiometer of 1 k ohm. We can use a larger...