>Rich, you said;
>
>>IMO, damage allegedly caused by an 'internal arc' -- in tubes which
>>subsequently prove to have good vacuums -- is yet another 'old wives'
>>tale'.
>
>Am I interpreting you correctly that you are saying internal arcs CAN
>occur,
I believe that an internal arc can occur when a tube becomes thoroughly
gassy -- or when the anode cooler welds weaken, resulting in
misalignment, and the anode cooler subsequently becomes too close to the
grounded grid.
>...but rarely cause the major damage levels seen, such as bent
>filaments etc, when the tube is not gassy?
>
Not rarely cause. Can not cause... ...
- I do not believe that a 3-500Z filament can be bent by an arc between
the anode and the grounded grid. .
- I do not believe that an 8877's grid can be gold-sputtered by an arc.
- I do not believe that an anode VHF parasitic-suppressor resistor can
be damaged by an arc in the tube. Why not? Because such a resistor is
connected in parallel with roughly 0.09uH of inductance - which contains
little DC resistance.
- I do not believe that medium to large arcs can occur without leaving
a visable mark.
- I do not believe that there a type of gas which disappears when the
kaput tube is enroute from the tube socket to the high-pot tester -- even
if one of our amplifier "experts" {*QST*,
9/94, p.72} said so on numerous occasions hereabouts. .
Rich---
R. L. Measures, 805-386-3734, AG6K
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