Date: Sun, 20 May 2012 11:31:16 +0930
From: "Leigh Turner" <invertech@frontierisp.net.au>
Subject: Re: [Amps] The power of an oversized electrolytic capacitor /
pragmatism rules
Yes Peter, you won't go astray if you take your clues from what the leading
> commercial and professional vendors of the tube amplifier era did in their
> power supply designs; all based on pragmatic time proven sound engineering
> principles.
### leigh, those bozos are still living in the stone age. Wake up, it 2012..
not 1953. Just take a look at the henry 8k amp power supply. They use a 6000
vac sec + resonant choke + a pair of 16 uf oil caps. No load B+ is 6000 x
.9 = 5400 vdc The 5400 vdc sags down to 4800 vdc with just a 1250ma load on
it ! The correct size resonant choke from dahl just happens to be the same
size as the plate xfmr.. and in fact use the same identical core, and weighs
damn near the same as the plate xfmr itself ! Now instead of X weight, we
now have 2X for weight. It drops 600 vdc under a steady state load. Now
that's what I call fubar engineering. Its fubar cuz you need a 6000 vac
sec..with its real small ga sec winding. You also require a 300 W CCS bleeder
load as well, just more fubar.
## Ok, here is how I do it..for the same 5400 vdc NO load B+ supply. I use
a 3818 vac sec xfmr, plus a FWB, and a string of 16 x 2500uf @ 450 vdc caps.
Each cap weighs just 14 oz. Thats a total weight of 224 oz for the caps = 7
lbs. Thats also a total of 156 uf. Ripple is zero. Both static and dynamic
regulation are superb, and second to none. A single 100k @ 3watt mof across
each cap. Total diss = 18 watts for the 16 x eq resistors... and NOT 300W. In
both cases I just quoted, we are using a single phase, 60 hz plate xfmr. We
are NOT using a 3 phase plate xfmr, with the typ 208-360-480-600 vac input.
>
> There's no significant benefit (perceived or actual) to be gained in going
much beyond 60 uF or so in a single-phase FWB capacitor reservoir filter HV
power supply used in today's mainstream QRO amplifiers.
### again, you have no clue what ur talking about,simply cuz you have never
done it. On these rinky dink HV supplys, that use a doubler, using large
amounts of C is a great benefit. On any doubler, the caps get topped up only 60
times per second, if using 60 hz AC commercial single phase power. In VK land,
the same caps will only get topped up 50 times per second. On any FWB
circuit, the caps get charged up 120 times per second on 60 hz power.... and
100 times per second on 50 hz power.
## With any doubler, since the caps only get topped up half as much as a FWB
circuit... the caps in the doubler now have to hold their charge TWICE AS LONG
! To pull that off, you require DOUBLE the C right off the bat.
>
> Homebrewers with a parts junk box full of big electrolytics may wish to err
> on the large size with a 120 uF or so; but doing so will take you way past
> the diminishing return point.
### say what. BRAND NEW large lytics are cheap. It gets better. As soon as
you buy 25 of em, the price drops like a rock. Ameritron, et all, could easily
take advantage of this, I do.
BTW, Its all based on energy storage, not XXX uf. The caps in a 6kw amp need
to store quadruple the energy of the caps in a 1.5 kw amp, its that simple...to
get the same ripple under load. 1% or way less ripple is so simple to achieve.
Energy in joules = ... voltage squared x uf.... then divide that result by 2
million. 1 joule = 1 watt second.
Having a stiff / non-sagging AC mains feed and
> a "big" weighty core + copper HV transformer are more important factors in
> achieving good load regulation in dynamic SSB linear service.
## Old news leigh. Everybody in W6 land figured that one out back in 1968.
200A service panel + big ga cu wire, a short run, if possible, and a BIG
hypersil xfmr, like a 1 cubic foot 10 kva CCS pole pig, and you are almost
there.
## BTW, I just got 9 more emails from folks who stuffed big lytics into
existing HV supplys..and they all said the results were nothing short of
spectacular. That included everything from 811 amps to the typ 1.5 kw amps.
## Exactly how many B+ supplies have you built. I have done 23 so far. The
results I get are repeatable. If you dont believe me, Ill gladly send you a free
caseload of 2300uf lytics, + mating 100k eq resistors, and you can do the
experiment yourself. Same offer goes to KM1H.
later.... Jim VE7RF
>
> Leigh
> VK5KLT
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