Hi Ted. I have a Centurion now and have had a couple of others in the
past. First question: how are you measuring the 600 watts? I suggest
using a constant carrier mode so there's no confusion about peak reading
or average reading wattmeters. The 6 pots on the display board that are
used to calibrate the meters are really poor and almost impossible to
adjust properly when calibrating the meters. I have replaced all 6 pots
with multi-turn Bourns pots - those are easy to adjust and unlike the
original pots they will hold the adjustment.
It's always a good idea to adjust the Centurion meter and bar LED power
readout using an external wattmeter of known accuracy. I use an
LP-100. The plate current and grid current meter scales should be
calibrated using the procedure given years ago on this forum. If you
can't find that, I can send you info and photos. That calibration is
done with no power to the Centurion.
You won't get any more power out than what you're seeing if driving
with 25 watts. To get to a KW out requires 50 watts on 160 meters and
gradually increases to 75 watts on 10 meters. Some use as much as 100
watts drive. Guess it depends somewhat on the tubes and of course your
skill in setting the load and tune controls. When you say "excessive
plate current", exactly what level do you consider to be excessive?
And, keep in mind that your plate current meter could be far out of
calibration. The stock adjustment pots will change settings with
vibration and shock from shipping over the years.
One other thing, adjusting some of the meter pots requires you to remove
the cabinet. Whatever you do, don't allow the high voltage safety
interlock lever to contact the HV terminal when there's still HV
present, even with the Centurion powered off. Doing so will likely
damage the bias transistors.
73, Floyd - K8AC
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