A DIY Tube Tester needs a lot of different power supplies to allow you to really test tubes correctly. You can set up these supplies independently, but a better solution is to build a single board that gives you all the voltages you need. This is it.

Using one single external transformer from an old tube radio, we supply the board with about 240 VAC (the transformer secondary voltage), and the heater AC voltage. What we get is:

• Two regulated High Voltage supplies, independently adjustable from 0 to 250VDC;
• A Negative Bias supply, adjustable from 0 to approximately -20VDC;
• A regulated 6.3VDC Heater supply;
• A Control voltage signal to activate relays or opto-couplers for the other elements in the circuit, like meters, etc.