Pentode voltage amplifier (T407E)

This circuit uses a 77 tube as a voltage amplifier obtaining gains of approximately 100 times. The circuit is from modern documentation on tubes.

Powerful current converter (CB5096E)
This circuit can convert an AC voltage signal into a current up to 1 A for powering a load. The...
Continuity Tester (CB4546E)
This continuity tester for low resistances was found in an English magazine from 1978. The circuit...
Liquid Level Control (CB5311E)
The purpose of this circuit is to maintain the liquid level of a reservoir between two values...