Hi Jim,
-
3-1000z's haven't been made in a while, chances
are you have a bit of seal leakage "air" inside. I had
a mucho similar problem with my BTI and an NOS
tube.
-
My "patch" was to do a procedure of long time
filament operation. There was a procedure
mentioned here on amps some time back to
preform a type of filament getting action, a search
through the archives might yield a copy.
-
I've also used the 3-1000z in other commercial
applications. It's my opinion it will oscillate as much
or more than almost any triode tube I've worked with.
I don't have data to prove it, but I've used the tube
quite a bit and it will sing without much prompting.
-
Solid parasitic suppression is a must. One unit I
worked on years ago had "suck out" tuned circuits
inside the final box.
The final box became a VHF cavity and the Engr
told me early units made some pretty wild "plasma
generators" Very similar to what has been reported
to occur in the many 3-500z amplifier layouts.
-
Add some large value degeneration resistors in the
drive / cathode circuit. Rich's web page shows
how.
If you made a G-G 4-1000z amplifier, the extra
grounded grid might hide some demons up to a
point.
-
cheers
skipp
--
--
From: JimMoci@aol.com
A problem for all the experts-
I Built a 3-1000Z monoband amp for 10 meters. I Sowly Variaced it up and
it
seems ok at 1500volts. Put 3KV on it and it will make a few watts of
power
without even putting RF to it. I heard a small RF type arc- kind of like
slight arcing in an air variable, (I have a vaccum cap) the tube glowed
red
and I quickly unkeyed it. I turned the load and tune caps a bit, tried it
again- it was quiet for about 2 or 3 seconds- then it did it again. I
have a
similar homebrew grounded grid 4-1000A amp and never had a problem- it
worked
great the first time I fired it up! I built the 10 meter mono-bander
because
I cant get the 4-1000A amp to work on to good on ten- but it works great
on
the other bands. Any suggestions?? Keep in mind- I have yet to even hook
a
rig to this- just a dummy load- I variaced it up, saw idling current, and
it
started to run away.
Thanks!
Jim
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