> 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.
>
::I guess I would have to ask, "less forgiving" in what way? My
other tetrode amps (homebrew projects) have been 4CX250B and 4CX1000A types,
used the same approach with those. Screen current goes positive, negative,
whatever -- mostly averaging "zero," and adjustable, to a large degree, with
the plate loading control -- but I've had the same pair of 4CX250B's in my
144 MHz amp since 1977 and they still work fine, and deliver 1kW PEP output
(2.2kV Ep, 350V Eg2, grid driven).
-WB2WIK/6
> 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
>
>
>
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