>Jon Ogden wrote:
>>So why don't we see more extensive damage in 3-500Z's with bent filaments
>>if arcing is the real cause?
>>
>>I've asked this question at least twice and no one has responded to it
>>yet. So I am asking it again.
>>
>How much damage should you expect? I don't know.
>
>Nobody has come up with a real explanation of how the forces necessary
>to bend a filament are generated, applying the same principles as an
>electric motor.
So far, it seems that the grid current is large during a filament-bending
"big bang" event because 1A rated RFCs often have their copper-wire
melted by whatever it is.
>
>The other question that's still unanswered is what was the state of the
>filament just before the event? Was it properly centered in the grid
>cage... or was it already bent, so that even a small movement would
>cause it to touch?
In the new and near-new 3-500Zs I have tested, the cold filament-grid
withstanding potential typically exceeds 8000V. In a test I conducted
with horizontal operation, the withstanding potential decreased well
under 1kV per month.
>
>The same question can be asked about burned-out resistors etc: what
>state were they in, just *before* the event?
I have not seen totally burnt out suppressor resistors. I have seen
eyebrow-raising increases in resistance with little or no cosmetic
damage.
>
>I don't think anybody really knows, because even the "amplifier doctors"
>and "post-mortem experts" don't start looking until *after* something
>has gone wrong.
>
Good point, Mr. White.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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