This circuit was found in the June 1980 issue of Radio Electronics magazine. The circuit uses an integrated circuit from time, and a power Darlington that must be equipped with a heat sink.
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...
This interesting source or isolation transformer also allows to vary the output voltage by...
In this circuit the CA3140, an operational amplifier, is used as a comparator with the zener diode...