This circuit is one of many of its kind that can be found on this site. This one is from a September 1987 Radio Electronics. The triac must be controlled according to the load.
This configuration from a 1976 technical documentation shows how to use a varicap in a direct...
In the figure we have a symmetrical power supply stabilized by a zener diode. Transformer and...
This MW receiver was found in a Raytheon circuit manual from the 1960s. Transistors are the first...