Filament source (T398E)

Despite being transistorized, this is a constant current source circuit for 1 V valve filaments such as the 1H4 tube.

Simple Transistor Tester I (CB18917E)
We found this simple transistor tester in a French publication in 1981. It uses a common analog...
Speed Game (CB22072E)
Who is faster? or reaction game are other names for this circuit that we find in old...
Photodiode Amplifier (CB4950E)
This circuit is from an 80's component manual. The components are from the time, but the circuit...