Trouble with Ameritron AL-811H Oscillating!
 

My new AL-811H oscillates on the highest 3 band switch positions--20, 15 and
10 meters. This is without exciter drive. Plate current goes from zilch to
300 mA and grid meter goes NEGATIVE. This is a grounded grid design with
four 811 tubes in parallel. Power output as read on my tuner also shows RF
is being generated (what frequency, I can only guess). This problem seems
to be new after switching the primary to the 240 V configuration, which
incidentally boosted the plate from 1600 to 1800 V--perhaps too much for the
811 tubes?

I contacted Ameritron and hope to hear from them this week. Has anyone had
the same thing happen?

gibberdill wrote:
My new AL-811H oscillates on the highest 3 band switch positions--20, 15 and
10 meters. This is without exciter drive. Plate current goes from zilch to
300 mA and grid meter goes NEGATIVE. This is a grounded grid design with
four 811 tubes in parallel. Power output as read on my tuner also shows RF
is being generated (what frequency, I can only guess). This problem seems
to be new after switching the primary to the 240 V configuration, which
incidentally boosted the plate from 1600 to 1800 V--perhaps too much for the
811 tubes?

I contacted Ameritron and hope to hear from them this week. Has anyone had
the same thing happen?


The AL811H will run just fine on 120 volts

gibberdill wrote:
My new AL-811H oscillates on the highest 3 band switch positions--20, 15 and
10 meters. This is without exciter drive. Plate current goes from zilch to
300 mA and grid meter goes NEGATIVE. This is a grounded grid design with
four 811 tubes in parallel. Power output as read on my tuner also shows RF
is being generated (what frequency, I can only guess). This problem seems
to be new after switching the primary to the 240 V configuration, which
incidentally boosted the plate from 1600 to 1800 V--perhaps too much for the
811 tubes?

I contacted Ameritron and hope to hear from them this week. Has anyone had
the same thing happen?


The AL811H will run just fine on 120 volts