I am new both to this list and to HF amps, so go easy on me please!
I have acquired a 1960's vintage Swan Mark I amplifier. The amp was
extensively modified prior to the mid-1970's including a complete rebuilding
of the rf-deck. The person I bought it from told me he never used the amp,
and it had sat in storage for at least ten years.
A DC check of the HVPS showed at least one of the old (date-coded 1966)
electrolytic caps as bad. So I replaced all of the caps, as well as the
equalizing resistors and rectifier diodes.
Before powering up the amp I would like recommendations as-to what else I
should do. As I said, the rf-deck bears little resemblance to the original
Mark I. The 3-400Z's have been replaced by 3-500Z's. A "penthouse" has
been added to the top of the cabinet to increase the clearance (for the
taller tubes, of course). Parasitic suppressors and heat-sunk anode
connectors have been added (yes, those silver-plated bands wrapped around
composition resistors that Mr. Measures loves so much). The tuning cap has
been replaced with a Jennings Vacuum variable and the coil and loading cap
do not seem to be original (I can't tell for sure since I have never seen
the insides of an unmodified Swan Mark I).
I don't know who did the modifications, but someone went to a lot of work.
There is a metal tag on the front panel proclaiming "Big Momma I Linear
Amp" and it is signed "K9STH/WA4MLI/WA5STI". I contacted STH/MLI/STI to
get some history on the modifications. He claims that he bought the amp
already (rf) modified in the mid 70's. He says he added the "penthouse" and
then sold the amp after having it less than one year.
So experts, what should I do with this boat-anchor? Keep in mind that I am
on a somewhat limited budget. New caps, diodes and resistors have cost me
less than $30 so far, and I can't afford to spend a great deal more, (no
vacuum relays in the budget!). This is my first HF amp. I hope to drive it
with an Icom IC-751 into a G5RV antenna tuned with a very large military
surplus (Collins) tuner.
If it would help I can take some pictures of the beast and email them to the
inquisitive. (Olympus C2100, 2.1 megapixels, 10to1 optical zoom, I like it
very much, thank you).