>
>On Wed, 20 May 1998 18:16:48 +0100 Peter Chadwick
><Peter_Chadwick@mitel.com> writes:
>>We seem to be getting multiple threads again.
>>
>>There are three, I think, and muddling them up causes
>>misunderstanding.
>>
>>1. Are parasitic suppressors of nichrome more effective than those of
>>copper?
>>
>>2. Do parasitics lead to high enough currents to bend filaments?
>>
>>3. Can parasitics boil gold off grids?
>>
>>
>>I'd suggest that Rich has presented more than enough evidence to
>>suggest that the answer to 3 is YES.
>
>YES but as only one of the reasons...not the only.
Undoubtedly not the only reason, however, gold hardly boils easily.
>>
>>To 2, I am still totally unconvinced that you can get enough current
>>from the space charge and the filament in 3-500Z to do this. So I'm a flash
>>arc believer.
>
>I suspect that Rich is the only true believer of that idea Peter. Put me
>in the totally unconvinced column also.
As far as we know, Rich is the only guy in the [AMPS] group who autopsies
kaput 3-500Zs. . . In the beginning, I was unconvinced that the
filament could be bent that fast, that far during a "big bang" event.
However, I have seen numerous bent filaments that are arc-welded to the
grid, or touching the grid, sans-arc-marks anywhere - except perhaps on
the Tune-C. {photo of bent fil. on p. 15 in Sept-1990 *QST*} . . It
seems that whatever is bending the filament is simultaneously capable of
melting the copper wire in the 1A-rated grid to gnd. RFC in the TL-922,
yet doing so without leaving arc evidence in the affected tube.
>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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