Bill while this is true, some of the surplus Russian tubes being purchased have failed -- since these tubes have been sitting on Russian shelves for over a decade. Here is a web page anyone buying surplus russian tubes!http://www.nd2x.net/tube-prep.html
Using tubes which have spent a significant amount of time, often years, "on the shelf" awaiting use! Due to the nature of physical materials, a certain amount of gases are always trapped inside the metals and ceramics, etc., used to construct each tube. A vacuum tube depends on a relatively hard vacuum to function without arcs and other undesired, often disasterously destructive, internal current flow. While in storage, a certain amount of the gases trapped in its materials is "leached" out into the vacuum of the tube. If one were to plug such a tube into an amplifier and apply all voltages and drive, the small amount of gas within the tube would ionize and provide said undesired internal conductive paths; such conduction often reduces an otherwise useful tube to trash. It is, however, possible to prevent these events from occurring by taking some rather simple measures to prepare such tubes for use!