[Amps] Alpha vs. Henry

[Jim Thomson]

Date: Sun, 3 Apr 2011 21:00:39 -0400
From: "Gary Schafer" <garyschafer at comcast.net>
Subject: Re: [Amps] Alpha vs. Henry


Not according to Collins. They say that the choke should be resonant at 120
Hz with minimum critical current, eg bleeder current, which keeps voltage
from soaring. 

As current draw increases the inductance of the choke will drop, going out
of resonance and increasing ripple voltage out of the supply.

73
Gary K4FMX

&&  resonant chokes schemes are steam engine  technology..and buy you absolutely ..nothing ! 
Resonate the choke at 120 hz... and the peak V across  both the choke and the resonating cap  will  be
through the stratosphere.   Both will  blow up, the choke will be ruined, and the cap will explode. 

&& To build em correctly, you have to suck one helluva lot of bleeder current.  At that point, the choke should
be resonant ABOVE 120 hz.   OK... now when you suck loads of plate current, the choke L  will  drop a bit...and
resonance will INCREASE.    IF the coke resonates  BELOW 120 hz...with just bleeder current... you are in trbl. 
When sucking plate current, the resonance will increase, and when it passes through 120 hz....Kaboom every time.

&&  It`s a stupid flawed design anyway, imo.   The 8 k ultra  runs  5400vdc  NO load.   To pull this off, they use a 
6000 vac plate xfmr.   .9 x 6000 = 5400 vdc no load...except for the 5 x 20k    at 100 watt ccs  wirewounds..all in 
series.   That`s  300 W CCS  of bleeder..which is a blast furnace !   Each 100w  resistor is dissipating 60 w...and they
run extremely hot.  OK,  now if just any ONE of those bleeders  ever open`s  up... watch out.    The B+  will soar  to
1.414  x 6000 = 8500 vdc.   At that point those failure prone oil caps used in the henry amps will become IED`s. 
The tube may well  be next, along with bypass caps, and everything else you can think of. 

&&  The regulation on the 8k is nothing to brag about either. 4800 vdc with just 1.25 A of plate current.  That`s a 12 %
drop..  It drops 800+  vdc   So much for the good regulation.    Both the plate xfmr and the mating choke are best seller`s when
dahl was still in business.

&&  Here henry used a 6000 vac xfmr....when a  3800 vac  xfmr + FWB  would have worked a helluva lot better. 
Even a  1900 vac  xfmr and a FWD  would have worked better.   A 6000 vac xfmr is a poor utilization of it`s
winding.  Then toss in the huge,heavy choke + heavy oil caps.   The classic resonant choke setup only filters 120 hz to boot. It won`t
reduce the ripple  at 240,360,480 hz.  So they still need a mess of oil caps. 

&&&  A simple 3800  vac hypersil xfmr, or similar... + a BIG C filter  will run rings  around the resonant  choke scheme.  Why
spend $$$  on plate xfmrs  with massive oversized sec  V ratings  = smaller ga wire used= low current capability....then toss in the 
meagbuck heavy choke = 1921 technology. 

later... Jim  VE7RF