>Anyone have some advice for me regarding the TX lock-up?
Usually, I have found, that a solid state PA maintains output (if the design
is decent in the first place) because either your exciter is still producing
some amount of output because of a bad input match or because you are
running the amplifier into a bad load, causing it to break into self
oscillation.
The RC network going from base to collector is present in nearly every solid
state amp, and also serves twofold purpose. One, is to maintain stability
(just because your amp has it doesn't mean it is an unstable design to start
with, it is considered good engineering practice), and also gives a flatness
to the gain across the band(s) the amp was designed for.
Before doing anything, I would run the amp into a non-inductive 50 ohm load.
I would venture to guess at this point that your amp is fine, and you will
see a load or feedline problem. Those are the most common problems I have
found on solid state PA problems you describe... Either with a 1 transistor
amp, all the way up to a 128 device 2SC2879 amp.
Hope this helps.
Toll_Free
73,
Ian ZS6BTE
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