>
>It would seem to me that the operating parameters at the time of the failure
>do not explain the cause. ip was only 150 and ip about 500. Total key-down
>duration was no more than 20 seconds. This does not compute. Rich, I've
>seen you discuss VHF parasitics before. What would be the recommendation to
>eliminate them?
>
Reduce VHF amplification by reducing VHF Q. .
>Doug -- W4DXV
>
>
>----- Original Message -----
>From: Rich Measures <measures@vc.net>
>To: Dick Green <dick.green@valley.net>; Doug Person <w4dxv@ibm.net>; amps
><amps@contesting.com>
>Sent: Friday, June 11, 1999 6:48 PM
>Subject: Re: [AMPS] Finally - a real amp
>
>
>
>
>
>>? 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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>
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
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>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
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