How do I know if a tube is weak? Why do the valves weaken and what happens because of this?
The tubes operate by the emission of electrons by a cathode that is covered with alkaline materials. For various reasons, such as the time of use, this material loses its properties of emitting electrons. When this occurs, the emission of electrons and hence the current through the tube is no longer as strong as when the tube is new. In other words, it loses its driving characteristics. For a power tube this means its weakening, that is, the decrease in power and for other types of tube can affect the ability to amplify or rectify and even oscillate. To check if a tube is weak there are devices that measure the current through it. In the photo a tube test. The sockets are for the various types of existing tubes. The instrument indicates the emission that must be on the green stop a good tube.
