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-------- Original message --------From: jeff millar <wa1hco@gmail.com> Date:
3/3/22 10:15 AM (GMT-05:00) To: Steve Thompson <g8gsq72@gmail.com> Cc:
Amplifier Mailing List <amps@contesting.com> Subject: Re: [Amps] Modern Op-Amp
shunt stabilizator power supply (for tetrodescr Consider the arc as a zero ohm
resistor. The current peak is limited bythe glitch resistor and the impedance
of the HV capsjeff, wa1hcoOn Thu, Mar 3, 2022 at 8:35 AM Steve Thompson
<g8gsq72@gmail.com> wrote:> A while ago I breadboarded a screen regulator
supply with some> similarities to Jim's design. One of these was that the 'pull
down'> transistor could act as a clamp if there was a flashover to the
screen.>> I was fortunate enough not to test that function but I had a couple
of> questions which I never found answers for:>> How much current flows during
a flashover to the screen (assuming the> amp has a sensible glitch resistor in
the HV supply) and>> How long does a flashover last?>> Worst case guesses are
simple enough but I don't know how the physics> of the arc affects things in
practice.>> Steve G8GSQ>> On Mon, 28 Feb 2022, 21:37 Jim Garland,
<4cx250b@miamioh.edu> wrote:>> > Attached is the screen voltage regulator I
designed for my 160m/80m> > duo-band amplifier using three GU74B tetrodes. From
your msg, I suspect> > it’s similar in some ways to the circuit you’ve
described. The circuitry> is> > deceptively subtle, however, in that it
provides protection against> damage> > from grid-plate flashovers in the tubes,
which can be a problem,> especially> > with new (NOS) Russian tetrodes. I’ve
used this circuit for more than> five> > years and found it to be always
stable, with tight regulation. The> > circuitry mounts on a small file
card-sized PCB. The screen voltage is> > adjustable and I set it at a nominal
340V.> >> >> >> > If the attachment doesn’t come through (I’m away from my home
QTH and> have> > limited internet coverage, here’s a link to the complete
schematic> package> > for the amplifier. Pse email me if you can’t get any of
the diagrams to> > load!> >> >> >> >>
http://www.w8zr.net/160amplifier/images/Amplifier%20Schematic%20Package.pdf> >>
> 73,> >> > Jim W8ZR> _______________________________________________> Amps
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