Found in a 1967 RCA documentation, this AC power grid contactor can be fitted with modern equivalent components. The SCR and the diodes must be according to the load current.
This circuit was found in documentation from the 70s. We can try current JFET transistors....
This is the power supply circuit for the amplifier in the previous circuit. The source is...
This bridge circuit is designed for 8-ohm speakers delivering a few watts of power. The circuit is from...