This amplifier with the EL84 tube is a European commercial type from Corpim mounted on a printed circuit board. The diagram appeared in a September 1958 Radio Electronics magazine.
This simple half-wave control using an SCR, which may be TIC106, has been obtained from a US...
This circuit was found in a 90s Electronic Design. The circuit was designed to be powered by a 4 - 20 mA...
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...