[AMPS] AL-1200 problem (self-oscillation?)

[Rich Measures]

>I'm having a new problem with my new AL-1200.  The tube seems to go into
>some sort of self-oscillation, even if you just turn the power on.  It
>makes some sort of clicky noise on 10M (as if it were arcing), and the air
>flow gets very warm.  If I try to drive power into it, the output power
>fluctuates wildly, from nothing to full power and everywhere in between.

[Twilight Zone theme]

>It doesn't always do this, and it seems to stop sometimes, and the amp
>works just fine as if there is no problem.  I tried reseating the tube and
>that had no effect.  I looked inside the RF deck while it was happening and
>didn't see any arcing.
>
>Does anyone know what might be going on?

Do you see anything unusual going on with the grid current, Jim?  
-  3cx1200a7s have about 7 times as much feedback C as an 8877, so they 
are not easy to tame.  
Rich....

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


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