Electronic – Why is the negative terminal connected to both transformers in this half-wave rectifier


I found the image below in an old book about vacuum tube rectifiers. Could someone explain why the negative terminal of the load is connected to the 6.3V transformer? I understand why it would be connected to the 350V transformer but not the other one too.

half-wave rectifier

Best Answer

The 6.3V supply is for the tube heater. The heater and cathode get surrounded by a cloud of free electrons. By putting the heater at the most negative point in the circuit you ensure that these electrons are not attracted back to the heater.