Once I solve this problem I will let you all know what stupid mistake I
have made with this linear....I have built more than 40 amplifiers over
30 years and this is the first one to give me problems...I guess I may
be getting old and maybe missing something in my dotage..(Grin)..
73.....Bob VK3ZL...
===========================================
The first mistake, continuing through every amp I worked on is that we
all are not taught that tubes were/are capacitors.
Anything connected to the cathode, plate or grid(s) will be inductive as
a wire, strap etc towards "ground". this makes a parallel resonant
circuit, which will make all bypassing impossible, as that is what we
thought was that lead-length towards the ground..
It manafists itself as extra harmonics, less swing of the tube element
bbefore saturation, arcing of components, real nice oscillations. Most
of these blow something up before we can find them, and so the fun goes.
My most difficult problem was one that blew the breakers upon
turn-on. We finally lined up enough big resistors to put in series with
the supplies, to limit the current so it would blow up something, yet
last enough that we could find out what frequency the oscillation was.
Lots of other things can cause lower frequency problems, just as
symptomatic.
Here is a tale of my first 10 KW transmitter fire-up, made to compete
against the collins 208-U10, the RF Communication's an/FRT 84. I still
Have a hate for a fellow who was amongst the crowd of 12 people, each
was assigned a corner of the chassis to watch as the power was applied.
This bastard poped a paper bag just at the countdown; really giving me
an mental shock which would have resulted in my similarilly cold cocking
him; he was saved by the presence of 12 witnesses, or was it
collaborators. Funny 40 years later...
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