We found this battery eliminator in a Radio Electronics magazine from August 1974. The transistor must be equipped with a heatsink and other voltages can be achieved by replacing the zener.
Found in Popular Electronics from the 1980s, this circuit can use more modern transistors such as...
This circuit is from a Radio Electronics from February 1970. The integrated circuit is an...
This is stage is transformer coupled and was found in na old publication of the year 1958. The...