6SN7 Preamplifier (T1105E)

This preamp circuit has a typical configuration as found in a 1946 publication. Supply voltages are indicated.

Locked light alarm (CB6428E)
We found this circuit in an Electronics Now from the 1990s. The circuit crashes when light strikes the...
Semi-isolated Colpitts Oscillator (CB25554E)
This circuit was found in the February 1993 issue of Radio Electronics magazine. Some components depend...
LED photo sensor (CB6858E)
In the figure we have the way to use a common LED as a light sensor. The operational power supply...