This circuit is from an old Japanese publication of 1962. The circuit uses two batteries, one for the filaments of the tubes and the other one of high voltage for the plate circuits.
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
We found this circuit on an Elektor from the 90s. The frequency is given by capacitor C1. The...
This powerful regulator, shown in the figure is for 5V (TTL) is suggested by Motorola and makes use...