HI Folks,

After a long hiatus from HF and HF amps, (Just got back from an
incredible Arecibo Moon Bounce activation; a 60dbi gain antenna on 432
is a transforming exprience)

I am helping someone build a homebrew amp, a pair of 3-500Zs for a
friend in South America. First, I wonder if anyone (Preferably living
near Buenos Aires, or Montevideo, has for sale a 2 x 3-500Z amp
commercial, or hombrew? Even better, an unfinished one, or a
commercial "Basket Case" in the Heathkit SB 220, L4B or Kenwood TL 922
genre. I have most of the components for such an amp, here is W6
land, and can easily ship the lighter components, to the ham who is
building it. I would rather source locally, (Uruguay or Argentina, or
perhaps Brazil) the heavier components, the B+ Power Supply
transformer, and 30 amp 5V filament tranformer, etc, and maybe even
a chassis/Front panel.

Being a resourceful guy, I would also be willing to canvas the lower
power broadcast radio stations, finding engineers who are ham
friendly, with spares, storage rooms of things like Plate transformers
in the 2KW, 4000 volt class. I think I might be able to find those
engineers, through internet searches, of Broadcast Engineers in
Uruguay, or perhaps Buenos Aires.

The ham who wants to go QRO, lives in Uruguay, and the three major
metropolitan areas that might source hams, parts, or surplus
broadcast components, are Montevideo, Salto, and down the road a
piece, Buenos Aires.
I also have been out of the loop in HF amps, specifically 3-500Z
tubes. All my past experience with these has been with EIMAC tubes.
Are there quality Chinese or other maker 3-500Z tubes out there?
Which ones, are good value?

Also, the GS-35B used to be very cheap to reasonably priced powerful
tube. Maybe from a clean sheet of paper planning for a legal limit
amp, a GS 35B is a good choice for a tube, any suggestions? I have
seen relatively simple mounts for the GS 35B, basically a Clamp of
the grid ring to the chassis with a hole thru chassis to connect the
relatively low current Cathode/Filament supply. The Anode cooler is
impressive, and probably requires substantial pressure and flow, and a
teflon or similar chimney for full dissapation.

I dont have the specs or a schematic off the top of my head, but does
a GS 35B plate circuit have similar values of operating impedance as
3-500Zs at legal limit, therefore requiring similar Tune, Load, and
Inductance tank values? To get legal limit from a 3-500Z pair
requires higher than usual commercial design B+ voltages, perhaps
4KV. Is the GS 35B happy with 4KV on the plate, or is it happier for
full legal limit/100 watts drive, with higher voltage?

So.... just a few basic questions for this OT, who has been away for a
while.

BTW, several years ago, I sold a homebrew 2 x 813 Amp to a guy in the
mid west, whose call and name I dont remember, but I found the
schematics, and the original control wiring harness for that amp,
which I had misplaced at the time of pickup. If you recognize me, or
that 813 amp, get in touch, I can send you the wiring harness...
Thanks, best, 73,
Pat Barthelow AA6EG best email is