abnormallly high plate current

Lane Zeitler Ku7i at WORLDNET.ATT.NET
Wed Jan 5 22:19:11 EST 2000

I forgot to mention that I am getting the same readings with other known
good full out Eimac 3-500Zs so it is not the tube(s). Filament voltage
measured at the tube socket is 5.22 volts.


> Gents,
> For some reason I am getting higher than normal plate current in a single
> 3-500Z amp. On 160 meters with 400mA of Ip and 3500 volts under load the
> is only delivering 500 watts of output.
> On 80, the Ip is 400mA with 3500 volts on the anode and the output power
> only 600 watts.
> Seems that the efficiency is way way down. The other bands are similar to
> this. With 3500 volts on the plate at 400ma I would expect at least 850
> watts out if getting around 60% efficiency.
> What would cause this? The values of the pi output network C1, L, and C2
> very very close to what the formulas say they should be. I wonder if my
> plate choke is absorbing some of the power? Something is definately not
> right.
> Lane
> Ku7i

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