We will learn about tubes on this page.
Give us a little time and the fun will come, we are just starting up. You will need to know basic electronics. We will keep things as simple as we can.

Our first tube we will look at are called diodes or Rectifier tubes. A diode tube has two elements called the cathode and plate. The cathode has a heater elements that emits electrons and the plate collects electrons when it is more positive than the cathode.Take a look at the circuit, do we have AC, DC or what across the resistor? The next time we will look at this circuit.

5ar4 diode tube

The plate is made positive with respect to the cathode, it will attract electrons from the cathode (as you remember electron flows from negative to postive). Then current will flow through the resistor. When the plate is made negative with respect to the cathode, it will repel electrons (remember like charge attract and unlike charge repel) and no current will flow through the resistor. The plate cannot emit electrons under normal conditions, because it is not a source of free electrons. In our circuit we are applying a AC voltage to the tube and only when the plate is positive with respect to the cathode will we have current flow through the resistor. Only half of the AC cycle will flow and the other half of the Ac cycle will not flow in our circuit. We call this action rectification. Take a look at the example of what the voltage will look like: AC before being rectified , AC across the resistor after being rectified by the vacuume tube diode . The output of our circuit will not do much work, because it is pulsatiing DC. We must use filters to clean this up. The next time we will add a grid to the diode.

All the electrons flowing to the plate must pass through the spaces between the wire of the grid. If the grid has no electric charge it will allow the electrons to pass from the cathode to the plate. If the grid is made a little negative, in respect to the plate, then it will repel some of the electrons being attracted toward the plate. A strong negative charge on the plate can almost stop all of the electrons from being attracted to the plate and this will stop current from flowing thru the tube.