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[AMPS] Re: AL-1500 Oscillation

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Subject: [AMPS] Re: AL-1500 Oscillation
From: (Rich Measures)
Date: Mon, 22 Feb 1999 12:54:17 -0800

>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?  


R. L. Measures, 805-386-3734, AG6K,  

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