> I am working on an older homebrew amp with a tetrode.
>
>
> ::What's the tetrode? What are the operating parameters (voltages applied
> to all tube elements)?
>
>
>
>
>
> The grid current is normal on 160, 80, and 40. As you begin to
> approach escessive
> drive, the grid current rises to 20 or 30 microamps. The grid current
> meter measures from 0 to 100 ua.
>
>
> ::Microamps? Microamps? Regardless of the meter scale, what's this thing
> really indicating?
>
> Screen current does not flow until the tube output increases -
> voltage is steady.
>
> ::What is the screen voltage? How do you know it doesn't change (under
> load)?
>
> Grid voltage does not change.
>
> ::What is the grid voltage? How do you know it doesn't change (under
> load)?
>
> I have tried several configurations of input circuits and they all
> act the same.
> Things that have been replaced or substituted.
> tube socket
> tube
> input circuit (but not the 50 ohm load resistor)
>
> ::What's the circuit? Where's the 50 Ohm load resistor?
>
> cathode circuit components
>
> ::What are they?
>
> I am somewhat suspicious of the tank circuit but unable to verify.
>
> I think fixing the grid current issue will help get to the root of
> the problem.
>
> ::Sounds like you're driving the grid, but then you talk about cathode
> circuit components. What is this circuit? Sounds like something
> "charging up" on the input side of the amplifier.
>
> ::WB2WIK/6
>
> Any ideas?
>
> Lynn, NO9Z
>
>
>
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