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[AMPS] Screen supply regluation???

To: <amps@contesting.com>
Subject: [AMPS] Screen supply regluation???
From: ad5gb@yahoo.com (Randall DuCharme)
Date: Mon, 26 Nov 2001 16:23:43 -0800 (PST)

--- "Michael J. Tubby B.Sc. (Hons) G8TIC"
<mike.tubby@thorcom.co.uk> wrote:

> Not sure about the requirement for a bleed resistor
> id the design is
> a shunt-screen stabilisor since it will have the
> ability to both sink and
> source current. Does the design handle -ve current
> and remain in
> regulation?

Hmmm.... not sure about it's ability to handle
negative screen current.  It's actually a series
regulator so maybe this isn't the best design?  It's
bleeder strings pass about 15mA though.  

> 0.5% regulation sounds good but is this under static
> load or with
> a load that mimics the syabillic rate of speech? 

Well, first tests were static.  The latest test
involved powering my homebrewed guitar amp and playing
a little, with it's filter caps disconnected.  The amp
uses a pair of EL34s in the PA section and idles at
about 120mA.  Regulation was well under 1%. 

I'm not sure how to duplicate a negative screen
current condition without actually encountering it. 
Will an 813 amp encounter such a thing?   

The goal for this amp project is all-tube design, more
for educational value than anything. Solid state would
be easier to be sure.  The knowlege I hope to gain
with the screen/bias supplies and the experimentation
with different operating classes and modes I hope to
be able to use in future projects.  813s seemed like
the most forgiving candidates for my experimentation (
and inevatible blunders ) while still providing
something usable in the process.  ( All this just in
case you were wondering why I'm even bothering with
supplies on an 813 linear. )

Thanks again all!

Randy (AD5GB)





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