This PCB is the perfect solution to replace the selenium rectifier in vintage tube radios with modern silicon diodes, while maintaining the proper voltage drop. Since silicon diodes have a lower voltage drop than selenium rectifiers, a MOSFET and a trimmer potentiometer are used to provide an adjustable voltage drop. This allows you to fine-tune the voltage to match the original circuit specs, ensuring your vintage radio operates smoothly without over-stressing any components.

This solution is practical and easy to follow, whether you’re restoring a classic tube radio or simply looking for a modern and safe replacement for the selenium rectifier.

NOTES:

1. The Tab of the Mosfet is at the '-' potential, so the bolt connecting it to the PCB and then to the Chassis must be a nylon one if the chassis is not a common GND.
2. Before applying power to the board, set the Trimmer Pot to about half-way to prevent the Mosfet from being OFF when power is applied. This will prevent the circuit from seing the full B+ across it, which may damage the Trimmer Pot.

You can see the video on this project here: https://youtu.be/TMfBJIsDgkY