Ken Brown wrote:
> The logic seems sort of sound, except:
>
> If an amplifier is designed to work with 3-500Z tubes, that is it has
> the bias set to the proper voltage for clean linear and efficient
> operation with 3-500Z, and it has a output network designed to match the
> plate impedance of 3-500Z operating at the plate voltage and bias
> voltage the amplifier provides to the tubes, how can a tube that is also
> a 3-500Z operate differently and be more efficient than a 3-500Z?
3-500Z's are zero bias tubes, Ken. There are variations in the 3-500Z's
made by various manufacturers. The Amperex bottles drew less grid
current at idle for example, than the Eimac tubes.
> Seems like it is not exactly a 3-500Z, but rather a variant of a 3-500Z,
> and if it is dissipating less power than a 3-500Z, I would be suspicious
> that it actually needs a slightly different bias voltage to operate
> properly. If it is dissipating less power, I would suspect that it is
> operating more on the Class C side with current flowing in a smaller
> portion of the RF cycle. I would wonder about the linearity.
I draw a different conclusion: His old tired bottles were worn out.
They weren't capable of producing the same output as the new tubes with
the same amount of drive.
Dave Heil K8MN
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