This battery-powered 3-valve circuit was found in American documentation from 1947; Two batteries are used, one high voltage and one low voltage for the filaments.
The circuits shown below consist of diode protections against accidental polarity reversal in the supply...
We found this circuit in the November 1994 issue of Electronics Now magazine. It doubles the...
The circuit presented is a simple MW tuner that can be plugged into the input of any audio...