Ok, I confess...my lack of tube design experience is becoming real
evident to me! I might know something about RF, but the 4-1000A does
seem to be an animal.....
Yesterday I did some additional experiments on my amp. I put in a
different tube that I had gotten from someone and this tube had a lot
more gain. On 10 meters I was now able to put out at least 1200 watts
with AG6K's supressors. However, I decided to do the ol' stability check
on the amp with this tube. Guess, what, with my tune C at a minimum the
amp began to take off. The added gain of the tube was enough to make it
happen.
And when I added the cover to the amp, it would fly even easier.
I tried a couple of other things, but to no avail. Finally, I added a
third AG6K RL supressor in the anode line (just experimenting). This
took care of the oscillation. And I was down to about 1150 Watts now.
So then I went to 15 meters. Some odd things began happening. The load
C started popping and arcing. And the caps position changed as well. It
had been tuning up good with the cap at about 1/3 of maximum. Now it
wanted to tune up with the cap fully meshed. Previously the fully meshed
position was a false tune point. And still all kinds of sputtering. I
could move the cap just a hair and lose all output power. Strange
behavior.
Then I put the lid on and all heck broke loose. I keyed up and *BANG* it
went. As I said before, I've been using AG6K's suppressor ideas. He
suggests a 0.5 Ohm combination of resistors after the plate RFC. These
resistors are what went bang. I also blew 2 10 watt 10 Ohm current
limiting resistors (in series) on the supply side of the plate RFC. So
something REALLY happened yesterday.
So I am looking for suggestions from anyone. Perhaps I have a layout
problem. I seem to have a cabinet resonance problem, etc.
And I was hoping to get the thing working this weekend!
Tom Rauch has given me some good possible suggestions for the
suppressors. Perhaps I just need more inductance and a heftier R or
something. Anyone else care to chip in an idea?
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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