Filament source (T398E)

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

Galvanometer amplifier (CB21651E)
Obtained from a 1967 documentation, this circuit uses transistors from the time. The galvanometer can be a...
Linear Ohmmeter (CB10685E)
The circuit we present was found in an English magazine from 1980, but it can be easily assembled, as...
Light Comparison (CB4363E)
I found this circuit in a 1974 magazine, but it can still be easily assembled because the...