[Amps] unstable Ameritron AL811

Richard 2@mail.vcnet.com
Thu, 4 Apr 2002 08:11:32 -0800


>> Could this be caps reforming, gassed tubes, or the amp turning into an
>> oscillator (TPTG!)?
>
>Most common would be tubes and/or open grid resistors on the 
>tubes.
>
Not Invented Here syndrome? 
-  For the curious, it might be interesting to measure the resonance of 
the "grounded"-grid with a dipmeter.  If, perchance, the resonance of the 
grid is lower than the resonance in the plate/anode circuitry, the grid 
looks inductive at the anode resonant freq.,  a feedback path exists, and 
the VHF TPTG oscillator circuit is unfortunately extant  -- even though 
it does not appear on the circuit diagram.
> ...

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
end