Like N9WX, I am new to this whole AMP building thing. I am venturing forth
to build my first quasi-homebrew amp. Here's the story:
Back in 1994, I was given, by a very generous local DXer, an old amplifier
he had homebrewed in the 1960s. It was Class C, grid-driven. It had three RF
decks, each with two 813s, and put about 600-700 watts out 160m - 20m. (160m
and 80m shared an RF deck with band-switching while 40m and 20m were each
separate.) It was housed in a 5' rack cabinet, with a (4x) 3B28 HV supply in
the bottom, including a 3525v/2000kva transformer, regulated to 2750v by way
of a variac on the 117v primary, and a HUGE 1 Henry choke. Overall, this
amplifier was build in true homebrew spirit, requiring much maintenance over
the years. Due to several reasons, including some design quirks, it has
become less useful (read: still somewhat functional, yet not very
practical).
I have begun to disassemble it, and I intend to use the parts to rebuild it
into a 160m monoband amplifier, using four 813s in GG. I would like to be
able to operate SSB as well as CW, and would like to approach 1200w with a
modern exciter. I think this will make the amp more practical for me to use,
will force me to learn a thing or two, yet still will allow the spirit of
the original to live on ...
First:
Any general suggestions? I have read WB0NNI's intro to AMPS, ordered Bill
Orr's "Radio Handbook" and have been "thinking" about this for well over a
year. I also have some experience modifying and repairing my other amps
(AL-80, SB-220, 30L-1).
Second:
Where can I turn to for a crash-course (FAQ?) on transformers? Such as: how
to series and/or parallel transformers; when NOT to; how and when to
modify/rewind a transformer, etc. (You see, I need 10.0v at 20a (!) for the
filaments ... )
Feel free to reply off the list.
Thanks and 73,
Don Chisholm
K8BB
Pontiac, MI
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