This circuit aims to replace a 90 V battery used in old tube radios. The circuit uses a transformer with appropriate voltage and the transistor can be any power one. Resistor R1 has values between 470 ohms and 4k7 depending on the transistor gain.

This circuit aims to replace a 90 V battery used in old tube radios. The circuit uses a transformer with appropriate voltage and the transistor can be any power one. Resistor R1 has values between 470 ohms and 4k7 depending on the transistor gain.