[Amps] Burn-in for Eimac?

[gdaught6@stanford.edu]

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