Power tubes UX171 and CX371 can be charged in a set having 201A, 301A, 200A, or 300A tubes. Power tubes UX112 and CX112 cannot be charged. Neither can WD11, WD12, WXI2, C11 and CX12 tubes. Attaching them to the Charger, you will burn out the filaments. Curve Showing the Relative Amplifying Power Before and After Charging.
Tubes wear out with use.
The fact that they still burn is no indication of their ability to amplify the broadcast. After being in service for a period, the thorium atoms, on the surface of the filament, which carry the current to the plate, are consumed. There are more thorium atoms in the tungsten filament, however, which can be brought to the surface by charging. The chart above shows the difference between the amplifying power of a tube fully charged and operating at highest efficiency, and a run down tube. Charge your tubes once a month to keep them always at highest efficiency.