>? Semi-agreed. However, under full drive, the grid/cathode potential
>is typically110v-peak, or 78V-rms. Grid dissipation is approx. 0.15a x
>78v = 11.7w. The rated grid-dissipation is 20w.
>
>What part do you agree with?
>
? anode/plate current exceeded the manufacturer's limit.
>Does full drive mean 65W?
? An approx. value. Depends on anode supply potential.
> I had the impression that the tube was being hit
>with more drive than that (perhaps as much as the unfathomable 100W limit
>stated in the manual.) That would make sense, because the tube would not
>have loaded up normally at 65W if the plate choke was resonant on 17M,
>tempting the operator to increase the drive further and twist the load knob
>more. Wouldn't the excess drive increase the grid/cathode potential and
>grid-dissipation, perhaps fatally?
? I have run a 3-500z grid so hot it glowed, and no damage was done.
With no gold plating to damage, the grid will apparently stand a lot of
heat. As I recall, Tom Rauch made a similar observation.
>
>It's interesting that the hole in the tube was facing the plate choke. Did
>the choke's resonance on 17M have something to do with that?
? My guess is vhf did the melting. .
>
- later, Dick
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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