>From reading the reflector, it would seem like owning an HF amp is an exercise
in frustration for anyone who wants to use it rather than fix it. I
discovered parasitic oscillations in my SB-221 and that lead me to Rich's
articles and subsequent taming of the amp. That was Heathkit, however. My
experience with Heathkit was that they were prone to shortcuts and often used
a hobbiest-like approach to engineering. What astonished me was that so many
(all?) of the amps on the market seem to have basic, fundamental problems with
their design.
When we spend our hard-earned money for an amplifier, is it too much to expect
an unconditionally stable product which does not eat expensive tubes for
lunch? If I were designing an amp (which I'm not), I would want to make it
"bulletproof" using any means at my disposal to protect it from the user. In
my "day job," we assume that if something can be done, the user will do it and
at the worse possible time. In fact we hire people that sit in front of our
equipment all day pushing buttons and turning knobs that they shouldn't be
pushing and turning. All in an attempt to protect the equipment from the
user. Why not the same approach with amplifiers? Is there anyone out there
who makes an amplifier who's design is not based upon TLC and the operator
never making a mistake?
Is it unreasonable to expect a tube to last 10-15 years in normal Ham service?
It would seem to me that any failed tube with less than 8,000 hours on it,
probably came out of an amplifier with an inherent design defect.
I hear very little about solid state amps on the reflector. Is that because
they are much more reliable than vacuum tube amps? It seems to me (keep in
mind, I'm not an RF type) that designing a tube amplifier to cover 1.8 - 30
MHz is a very tricky proposition, made particularly difficult by the demands
placed upon the output matching network -- a problem which is simplified with
solid state designs.
I will grant you this -- it seems like a tube amp is a lot easier to play
around with than a solid state amp. But for someone who just wants an amp
that works, is a solid state design a better choice? What are the tradeoffs
with a solid state vs. tube design? What gotcha's do SS amps have that are
not an issue with tubes? Has anyone ever seen a blown-up FL-7000? Are new
amp designs from the big guys (Icom, Yaesu, etc.) better engineered than those
made by Hams for Hams?
Chris, KF0FX
KF0FX@aol.com
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