Hi all,
A few days ago, someone asked "where is the getter on a thoriated
tungsten filament tube?" [as opposed to an oxide cathode tube...]
I just spent the morning with an expert in rebuilding of thoriated
tungsten filament tubes, and asked him that exact question. He told
me "it depends on the tube." Then he showed me a few examples: one
type was a small disc (zirconium) near the base of the filament
support pedestal; another was a zirconium wire helically wound on a
molybdenum pedestal at the center (coaxial with) of the filament
structure. He told me "it's almost always zirconium, because that
stuff LOVES to mop up gases, especially oxygen."
Then came what I consider very important knowledge:
"The getters are heated by their proximity to the filament structure.
That's why you should run the tubes at the full rated filament
voltage for about a hundred hours. Then you can reduce the filament
voltage a bit while still maintaining the desired output."
73,
George T. Daughters, K6GT
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