Rich Measures wrote:
> If Pout drops when the amplifier is hot, tank component heating is more
> likely the reason than a problem with the 3-500Z.
This is a new problem that did not appear before. So I will check for bad
connections, burned switch contacts etc. However, the problem is that I can't
seem to get the 150 ma grid current with normal drive.
> - If you are able to get 400mA of plate/anode current with 65w drive,
> the tube is still good. // Note: The Eimac spec. is 400mA max.
It is harder to get 400 ma than before. The big difference is that it is hard
to get 150 ma grid current -- with normal loading it seems to peak at about 110
ma, even when I increase the drive way above 65w. I have a wattmeter in line
with the exciter, by the way; swr is reasonable and I can see the drive level.
I used to run about 410 ma plate and 150 ma grid with an output of about 800
watts CW on 20 meters (slightly more on lower bands, slightly less on higher).
Now I'm seeng about 700-750 watts at 400 ma plate and 110 ma grid current.
Any comments about which tube to get if I do end up replacing it?
Vic, K2VCO
Fresno CA
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