[Heathkit] sb200/220 fan

[Jim Shorney]

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Hi Carl,

Thanks for your comments, they have been most interesting.

On Sat, 30 Nov 2002 18:04:10 -0500, Carl Huether wrote:

>> Not to get into a debate here, but much of what Rich says sounds
>> logical and reasoned.
>
>
>He does sound good with his spiel!
>So did P.T. Barnum


I've just spent several hours going over 250+ messages in Google Groups
on the parasitic debate.  It sort of reminds me of the 'transient
intermodulation distortion' furor that arose a few years ago in
audiophile circles.  While I note a great deal of passion on both
sides, I also seem to see a bit more passion on one side and a bit more
facts and figures on the other side.  Rich certianly isn't the best
diplomat in the world, but his creations do seem to have some merit. 
Perhaps his biggest problem was marketing; I'm developing the opinion
that he may have stumbled across a previously uninvestigated transient
phenomena, and developed a cure that (according to anecdotal evidence)
helps.  Simply calling it a 'parasitic' invited others to examine it in
a conventional framework, which quickly degenerated into a shouting
match.  Maybe he should have called it 'magic server pixie dust' or
something... :-)

What mostly interested me was a comment (not by Rich) about VLF
oscillations in GG amps (SB220 and L4B were specifically mentioned),
and a Collins service bulliten about 'detuning the grids' in one of
thier amps to eliminate this effect.  Search engines have turned up
nothing on this subject; do you have any knowledge?


>The trick is to quench the off resonance HV; see that little 10pf cap
>between the 40-20M contacts?
>Ive gone up to 15 pf on the 220 without problems. It does add to the Tune C
>but not enough to affect 10-15M.
>Trick is as old as the hills, just rarely used.


Ah yes.  Before I got my NCL, an old-timer advised me to check for the
presence of this very cap.  He told me that it was often removed when
it went bad, and not replaced (either because people didn't understand
what it was for, or it wasn't shown on the schematic).  Sure enough,
this cap was missing on my unit.  I replaced it before I even powered
up.  (side note: the HV interlocks were also removed by Navy techs - do
you have these parts?)


>If they (parasitics) dont cause a problem why look for one or even create another with
>half thought out ideas?


I'm not entirely sure that they don't cause problems.


>Do you use all the various automotive additives just because someone said it
>works?

Well, my dad was sold on STP, but I never used the stuff....


>Or are you even aware of the Slick 50 and other lawsuits over the last
>several years?


Seems like I've heard some muttering, but not using such items, paid
little attention.



>> Technology in almost every other area of radio electronics has improved
>> greatly over the last 50 years.  You're saying parasitic surpressor
>> technology hasn't, or can't improve?
>
>Yep.


Maybe you're right; I note Rich's reference to the 1929 Handbook not
that says low VHF-Q surpressors should be used... :-)


>Dont really need to, its good enough for the tube designers, its good enough
>for you and me.
>If there were a reason to change it would be an addendum to spec sheets, a
>tech bulletin or even a blurb in a magazine.
>Anything that would cut down on warranty failures would certainly not be
>suppressed (pun intended).


Can't argue with that logic.  Of course, logic isn't always employed in
the real world.


>I personally discussed the issue with Eimac engineers when the QST article
>first appeared. Since I work on amps on a regular basis I was concerned.
>Their comments are better left unsaid here, this is a family forum.


Everyone seems to talk to Eimac engineers in the course of this debate
(except me, of course).  I'll take you at your word on that.  Still,
I've worked with engineers enough to know that sometimes things happen
in the field that they swear can't happen.


>Funny looking magic parasitic cure-alls do nothing except generate
>revenue.;


I've seen that argument too.  It seems to me that if he were out to
make a buck, he would be selling beefy bandswitches....


>Rich got into a firestorm with the ARRL some years ago over his junk science
>theories.
>It continued on the Internet. Lets just suffice to say that several well
>respected amp and tube engineers had a jolly old time.
>Rich wouldnt back down an inch and got quite abusive. He is pretty much
>ignored by them these days.


So I see.  Although abusiveness and refusal to give an inch seems to
have been pretty common to both sides.  Maybe in 50 years or so we will
know the truth.


>If you like his stuff then by all means use it. I remove them from every amp
>that comes in for repair, then fix the causes.


The bottom line seems to be that Rich's surpressors do seem to tame
some unruly amps.  Will I order a set of these gizmos for my L4B?  I
dunno.  I haven't even had it on the air yet; we were going to use it
for Sweepstakes (long story), but the 8-pin Cinch PS connector flamed
out.  Literally.  The nice, shiney L4B almost started a fire, so I
brought up the rust-bucket NCL a good deal less slowly than I wanted to
on a variac (it hadn't seen power in over 10 years) and pressed it into
service.  That old, rusty NCL worked like a champ.


>A nice amp. Unfortunately it appears to have been designed by a committee.
>The RF and PS people never talked it seems.

I would like to hear more on this subject.  Off-list, if necessary.


>My day to day amp is a LK-500ZC. Its survived me since new as well as about
>6 years of very serious contest use by a guest op.
>Still has the original 3-500Z's.


I've heard tales of tubes lasting nearly forever if treated properly. 
The cost of replacements these days scares me...

73

Jim

- --
Jim Shorney      -->.<--Put complaints in this box
jshorney@inebraska.com
nu0c@amsat.org
Ham Radio NU0C
Lincoln, NE, USA
EN10PT
http://incolor.inetnebr.com/jshorney/
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