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[AMPS] Re: AL-1500 Oscillation

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Subject: [AMPS] Re: AL-1500 Oscillation
From: (W7XU Arliss)
Date: Mon, 22 Feb 1999 19:07:03 +0000
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?

Thanks and 73,  Arliss

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