>> From: Rich Measures <measures@vc.net>
To: <amps@contesting.com>
>> Date: Tue, 2 Sep 97 21:00:45 +0000
>
>> >1.) It has no grid protection circuit, making it possible to easily
>> >overdrive and damage the grid.
>
>> Over-drive is most likely to strip the oxide coating from the cathode.
>> [see photo in "Parasitics Revisited" (9/90 - 10/90 QST) ...
...snip...
>
>The grid dissipation is FIVE watts. Rated grid dissipation is reached
>at about 60 mA of grid current in the SB-230.
>
According to Eimac's constant current curves for the 8873/4/5, the
cathode-to-grid driving voltage is roughly 40V-peak, or 28 V rms.
28V*0.06A = 1.68W. . . It sorta looks like that in the Rauchian World,
P=3(I*E).
>Anyone in their right mind would know a 100 watt exciter could easily
>cook a five watt grid if the PA is underloaded. ...
SB-230s reportedly destroy the 8873 some time after being loaded
correctly.
>Anyone doubting that should ask Eimac,...
...snip...
Sounds like a good idea, Mr. Rauch. In 1986, I asked Eimac. . .
However, when you call Eimac these days, you won't be talking to tube
engineer.
Rich---
R. L. Measures, 805-386-3734, AG6K
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