>
>>Filaments are not carburized when they are made. Even if the filament
>>were replaced with a new filament, the new filament would need to be
>>carburized with acetylene.
>>
>>>wereand grid structure and was about 50-75% the cost of a new tube.
>>>The less than reputable rebuilders used the acetylene method...
>>
>
>I find it rather interesting that Eimac's website, in its discussion of
>remanufactured tubes, notes that they replace filaments only when they
>cannot be re-used, and when they can be re-used, Eimac doesn't even
>discuss reprocessing them.
>
>Arlen
>
Carburization makes a 98.5%-tungsten/1.5%-thorium filament considerably
more frangible. Does it make sense that the filament would be carburized
before it is assembled into the tube? Maybe Eimac feels uncomfortable
discussing details, Arlen? . As I understand it, a filament wire only
needs to be replaced when one is broken. Otherwise, it can be
recarburized virtually indefinately.
I found it somewhat curious that during the ruckus at *QST* over the
Jan/1994 article "The Nearly Perfect Amplifier", Eimac's Mr. Reid
Brandon, W6MTF, told Paul Pagel and other *QST*-staffers that Mr. Willis
B. Foote was not authorized to inform me that a vhf/uhf oscillation
condition was determined (by Eimac's 8877 design-team) to be the cause of
gold-sputtering from the grid in 8877s, 8875s and other such tubes.
cheers
Rich...
R. L. Measures, 805-386-3734, AG6K
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