Found in a 1949 Radio Electronics, this 4-tube circuit was fed directly from the mains with a half-wave rectifier.
This circuit was found in an American magazine 73 for radio amateurs of the 80s. It is an...
Found in American documentation from the 1980s, this circuit can be designed with equivalent...
This circuit is from a 1977 documentation. It is powered by the power supply of the circuit under...