[ARC5] Circuit Help Needed

[Kenneth G. Gordon]

On 11 Feb 2017 at 0:22, Tom Lee wrote:

> 
> If the unregulated supply has very poor filtering, then setting the average value high indeed 
> helps, as then the worst-case ripple never gets close to letting the supply drop out of regulation. 
> That said, 700V does seem like overkill. Beefing up the filter capacitor and reducing the 
> unregulated voltage to, say, around 500V, would cut dissipation in half, which can't be a bad 
> thing (except, maybe, in winter),

Ha ha! :-)

> without affecting regulation in any significant way.
> 
> I no longer know what the cost of a suitable capacitor would have been at the time. Maybe it was 
> high enough to drive the design decision. Guess it's time to dig out some old radio mags to see 
> what the cost equation might have looked like then.

I would find that info interesting too.

I think that if I had Mark's power supply, I would 1) find a different, lower voltage, but 
current-capable transformer, and save the present one, then 2) Replace all the filter caps 
with more modern, higher capacity units where appropriate.

Thank you, Tom, for your help with this. I usually must flounder around until I figure these 
sorts of things out. Sometimes I takes me a while.

Once I properly diagnosed Mark's drawing, I found the circuit very interesting. I was not 
aware of a dual-triode cascade-connected control circuit in a regulated power supply before 
this, and this has been an excellent learning experience for me. The most common such 
circuits use a high-gain pentode. The circuit is simpler and works well. The Heathkit IP-17 
series is a good example.

BTW, "CasCode" turns out to be a contraction of "cascaded triodes having similar 
characteristics to a pentode" by the original designers, Frederick Vinton Hunt and Roger 
Wayne Hickman in 1939. Ha ha!

Ken W7EKB

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