I did some testing of my 2 x 813, class-c grid-driven amplifier under HV for
the first
time today. After adjusting the neutralization (with HV off), I applied HV and
set the
bias for 50 ma ZSAC (there's a grid resistor to supply the additional class-c
bias when
drive is applied).
I connected a dummy load and set the plate tank for approximate resonance on
all bands and
diddled the grid tuning and loading to see if the amplifier would take off. I
didn't see
any flicker in the plate current, or any grid current. So I believe it is
stable, at least
under these conditions.
However, when I removed the dummy load, I was able to create an arc in the
plate loading
capacitor under some tuning conditions.
Note that all of the above was with no drive, fixed bias and screen voltage.
So it is possible to make it oscillate when there is no load connected. I
didn't determine
whether it was a VHF or HF oscillation.
The shield enclosure and bottom plate are not in place yet.
Here's my question: Should I bother with this oscillation at this point? Or is
it normal
to have instability when no load is connected to the amplifier?
I suppose the fact that there's no enclosure or bottom plate is also a cause...
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|