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Joe's comments...
>>Your anecdote missed two important facts:=20
>>1) The amplifier was stable with the top cover on ... you made a=20
change, probably in the plate circuit stray capacitance when=20
you moved the top cover. That change "tuned" the parasitic=20
circuit.=20
>>2) The amplifier has "all voltages on" ... as such, there was=20
undoubtedly some residual anode current (all voltages could=20
not have been "on" if the cathode were completely cut off).=20
This allowed gain (and oscillation) if the feedback conditions=20
were "tuned" properly. =20
So Joe, you think it was an oscillation? ... sounds like it to me also.
Terry W6RU
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<DIV><FONT face=3DArial size=3D2>Joe's comments...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>>>Your anecdote missed two =
important facts:=20
<BR><BR>>>1) The amplifier was stable with the top cover on ... =
you made a=20
<BR> change, probably in the plate circuit stray capacitance =
when=20
<BR> you moved the top cover. That change "tuned" the=20
parasitic <BR> circuit. <BR><BR>>>2) The amplifier has =
"all=20
voltages on" ... as such, there was <BR> undoubtedly some =
residual=20
anode current (all voltages could <BR> not have been "on" if =
the=20
cathode were completely cut off). <BR> This allowed gain =
(and=20
oscillation) if the feedback conditions <BR> were "tuned"=20
properly. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>So Joe, you think it was an =
oscillation? ... sounds=20
like it to me also.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Terry =
W6RU<BR></DIV></FONT></BODY></HTML>
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