>Rich,
>
>>Special, high peak energy-absorbing resistors are best,
>>although the cost is high.
>
>Have you any comments about using big solid carbon or metal film
>resistors - things like 50ohm, 50 watt metal film tubular resistors NOT
>spirally cut, as are/were made for dummy loads?
Spiral-cutting would reduce the voltage-gradient in the resistive
material.
>Similarly, the carbon
>things about 10 inches long and 1 inch diameter?
My opinion is try it. If the resistor does not fail during a test, it's
probably going to do the job of limiting peak fault current during a real
glitch. // Carborundum Co. made special high peak energy-absorbing
resistors before they were bought out by Cesivid [716 286 7610]. The
Cesivid catalog lists similar resistors. // To test a glitch resistor,
temorarily short the positive HV to chassis-ground. If the resistor
exhibits no sign of damage, you have a winner. If a glitch diode shorts
during the test, try replacing it with with 2 of the same type diodes in
parallel - or with a higher peak-current rated unit.
>
>Your comments on the failure analysis of the tubes you've looked at does
>suggest that maybe the glitch resistor is not as important...
IMO, the glitch resistor IS important because it limits peak current
during an intermittent oscillation condition. I believe that limiting
peak current during such an event can prevent the aforementioned types of
grid/filament failure.
> ... as has been
>suggested, because arcs per se don't occur. Unless of course, one
>postualtes that the VHF parasitic gets going, and the voltage swing
>achieved at the plate is enough to initiate an arc, leading to all the
>results..........I dunno
>
To be sure, it's a 'whodunit'. It seems likely to me that the arc is
external, and it occurs after the current pulse which apparently damages
the tube during a VHF oscillation condition. How else could the VHF
parasitic-oscillation resistor be damaged?
Rich---
R. L. Measures, 805-386-3734, AG6K
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