Steve WB2WIK/6 writes --
>Last time I built a tetrode amp I used a 4-1000A grid-driven and put +550V
>on Ig2, provided by a stiff power supply that had no electronic regulation
>whatever. Just a 400V, 200mA transformer, full-wave bridge, ~160uF
>filtering, and a 10k, 50W bleeder resistor dissipating 30W. Eg2 never
>varied by more than 1-2Vpk key up, key down, with modulation, without
>modulation, whatever. Seemed plenty stiff enough to me, and cost about $20
>for the entire circuit, including the transformer.
One concern is that the smaller ceramic tubes (i.e. not "tetrodes with
handles") are less forgiving than the 4-1000.
Another concern is -- there's been a lot of "put up or shut up" catcalling,
but the people calling the loudest really haven't provided any hard
documentation on their "facts," other than a reference to the 50-year-old
Eimac "Care and Feeding of Power Grid Tubes" and the information located on
Mr. Measures' web site, which is easy to locate in any search engine, or
via his standard email footer.
John? Tom? URLs? Bibliographies?
Personally, I'd like to see some different ways to control a screen before
I start blowing stuff up over here. Tom, especially -- all of us know that
it's damn near impossible for us to build an amp from new parts cheaper
than you can. It's nearly as hard to build one out of surplus parts for as
cheply as you sell 'em, once we're done building test fixtures and buying
replacements for the stuff with a smoke leak.
How about showing us how YOU do it?
I'm still working on my broadband input transformer xperiment, and will
post results as soon as they are available. I've been sidetracked by some
personal business.
Jim N6OTQ
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|