>
>A progress report and answering of some questions re:
>the oscillation in my AL-1500:
>
>The amplifier is a MFJ version.
>
>I called Ameritron tech. support today. Their only
>suggestion was to check the wiring of the cathode and
>heater -- I confirmed that the way it is wired is the
>way they say it is supposed to be wired.
>
>I tried a different tube -- it was worse, oscillating
>not only in the SSB bias position (as the original
>tube had done), but also in the CW position (where the
>original tube appears stable). [For those of you
>following along re: the low efficiency problems with
>my homebrew 6m amp, this 2nd tube came from the 6m amp]
>
>I checked the finger stock that contacts the grid, and
>everything seems well there.
>
>The Zener diodes are also ok.
>
>The two 50V bypass caps and associated diode on the filter
>capacitor board are all good (KM1H had asked about this).
>
>
>I made a parasitic choke from 3/8" wide silver plated strap,
>2 turns, 1/2" ID, shunted by three 150 ohm carbon resistors --
>no change.
>
>Any other thoughts lurking out there?
>
? What is the frequency of oscillation? Is the grid grounded through
an Eimac grid-grounding collet?
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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