[AMPS] techno-babble

[Rich Measures]

>Hello gentlemen, and any others who may read this...
I smell smoke.  
>Generally I believe that ad hominem and other attacks, like several 
>examples in the following message, simply indicate that I've touched 
>a sensitive spot under a thin skin and don't deserve a response. 
N. B.:  Mr. Ehrhorn is not mad.  
>But IMHO 
humble?
>only a special sort of person spreads innuendos and rumors. And I submit
>that only a cowardly fool would deliberately spread vicious and false rumors 
>obviously intended to damage another and think that he can hide behind a
>self-incriminating disclaimer by labeling the rumor, "totally 
>unsubstantiated." 
The evidence suggests that some ETO amplifiers have had VHF parasitic 
oscillations.  You say that none has ever had one.  
>I leave it to you to decide for yourselves whether the above applies here, and
>I'm responding to a few items simply to illustrate once again how "careless" 
>"Mr. Masures" is with facts.
Sorry about the misspelling, Mr. Ehrhorn.  Your generosity is 
appreciated, and you might want to check your spelling of "innuendos".   
>----------
>From: 	Rich Measures[SMTP:measures@vc.net]
>Sent: 	Friday, November 28, 1997 8:59 PM
>To: 	'amps@contesting.com'
>Subject: 	RE: [AMPS] techno-babble
>
>.....
>
>Prior to 1988, there was no information in any ARRL publication on how 
>to design a VHF suppressor.
>
>####  In my recollection, every ARRL Radio Amateur's Handbook from
>before 1950 
1926 and 1927 were seemingly pretty good.  
>until at least the 1970's has quite a good basic description of
>parasitic oscillations, their origin, and methods for avoiding them.  ####  
-   If the available literature was adequate, the October 1988, March 
1989, and September/Oct. 1990 articles on vhf parasites in *QST* would 
seemingly not have been accepted for publication.  
>If you have knowledge on the subject, Mr. Erhorn, why not 
>write an article about it and submit the manuscript to *QST*?.
>
>####  You haven't been paying attention, "Mr. Masures." Your wish has been
>granted and raised one. If you will get out your 1995 ARRL Handbook 
OK
>and turn 
>to Chapter 13 on RF Power Amplifiers, on pages 13.27 - 13.30 
Got it.  
>in the section
>on Amplifier Stabilization you'll discover an updated and I believe 
>reasonably sound basic treatment of parasitics. 
The basics are there.  The description of the VHF resonant circuit is 
well-put.   What I don't see mentioned is the relationship between 
feedback-C and grid resonance.  This is the oft'-ignored link whereby 
regeneration takes place.  - -  Instead of the vague try this and that 
approach, it would be helpful to have an explanation of how increasing 
and decreasing Ls and Rs affect the VHF performance of the suppressor. - 
-  Your explanation of effect on HF performance is well-put.  - - An 
explanation of how a VHF suppressor achieves a Q-damping double-resonance 
effect might be helpful.  However, as I see it, the following paragraph 
is problematic.    
.................  
Quoting:
	"The parasitic suppressors described above very often will work without 
modification, but in some cases it will he necessary to experiment with 
both L and R to find a suitable combination.  Some designers use nichrome 
or other resistance wire for L, but there is no credible evidence of any 
fundamental difference in performance as a result.  Amplifier 
manufacturer W4ETO has never seen an HF amplifier using modern tube that 
could not be made completely free of VHF parasitics by using one of the 
simple parasitic suppressor constructions described above."
...................
Based on the kaput tubes I have tested that were awash in gold 
melt-balls, the last sentence doesn't wash.  

> Of course you must make 
>allowances for the fact that the Handbook is intended principally to help 
>amateurs in home-brewing and understanding amplifiers. 
>The information of how It probably isn't
>sophisticated enough to enlighten a real parasitic specialist.  #### 
There is nothing esoteric or difficult to explain about what takes place. 
 No calculus. Minimal algebra.  It's pretty much straight up AC circuit 
analysis, ohm's law and exorcism.  

>    How about you, Mr. Rauch?  Your friend Reid Brandon, who works at 
>Eimac, said he was not aware of any article on VHF parasitics.  Why 
>didn't he write an article on VHF parasitics? 
>
>#### Just exactly what is your point? And who cares?  ####.  
The point is that there were three articles on the subect in QST between 
1988 and 1990, and Mr. Brandon said he was not aware of any -- and he 
said so in a QST critique of the author who wrote the three articles..  . 
... and when does Editor Wilson get back from lunch, Mattie?   
 
>One of the gold-sputter damaged tubes shown in "Parasitics Revisited" 
>was removed from an Alpha amplifier.  Say it ain't so Mr. Erhorn.  
>
>####  It may or may not have been, "Mr. Masures." Who knows for sure?
I know.  Rus Healy (who copy-edited "Parasitics Revisited" {9=90 QST}), 
knows because it was one of the three gold sputtered 8874s that came out 
his amplifier - which is alleged to never oscillate.  
>We might be able to determine that, if you'd send me the S/N & date code 
>of the tube and of the alleged Alpha. Maybe our mfg files can match them.
QST kept the collection of parasite-damaged parts used for the photos in 
the article.    
>I think the more relevant question is, "Was it actually damaged in an Alpha 
>by parasitics?" In responsible language, my answer is that I believe the 
>probability it was NOT so damaged is greater than 99.9%.
But of course.  -  No amplifier that Tom Rauch ever designed has ever had 
a VHF parasitic oscillation, "because Tom Rauch designed them".  And no 
amplifier that Dick Ehrhorn designed has ever ... ... ... .  
>Can you prove to any reasonable certainty that the gold relocation did not
>result from a plate-grid DC arc? 
No arc crater on the grid -- gold boiled and blistered semi-uniformly 
around the circumference of the grid -- more gold missing from the 
grounded-end of the grid than from the other end -- prior to opening, the 
Funderberg gold-sputtering test indicates that the anode/grid leakage is 
due to loose gold, not due to ionized gas.  
>We all know that it's not uncommon for 8874, 
>8877, 3CX800A7, 4CX800A, and many other tubes to arc internally. 
Yes, indeed.  However, the anode to grid collet arc (anode to screen 
collet arc in tetrodes) results from loose, gold melt-balls landing on 
the ceramic anode insulator.  IMO, gold melt-balls come from gold plating 
boiling off the grid in thin layers due to an oscillation condition.  
Zzzzz, Zzzz, Zzzzzz.  

>With suitable surge current suppression in the amp, perhaps 99+ percent of 
such 
>arcs are self-quenching or are killed by the Ip overcurrent protection, 
>with no significant effect on tube life. 
Three of the 8874s in Rus Healy's Alpha had gold sputtering.  Does it 
make sense that all three tubes had bad vacuums, which produced arcs, 
that semi-uniformly evaporated layers of gold from the grids?  .  .  
About 2/3 of the kaput 8877s et cetera that I test suffered from this 
fate.  

Do you have the date-code span for 8877s that were manufactured with 
defective heat dams?  
  
>In my experience, probably less than 1% of 
>tubes experience severe dc arcs - usually when new or near end of normal 
>life - which are sufficiently sustained to (dare say "splatter" or 
>"sputter"?) enough gold from the grid to poison the cathode and kill the 
tube. We have 
>confirmed this phenomenon many times in a variety of tube types. 
Evaporated gold can be dislodged from the cathode and from the anode 
insulator by anode-up axial vibration,  partially restoring cathode 
emission and reducing the chance of another anode insulator arc -- 
provided that the tube is not inverted. . 

>When *QST* was copy-editing "Parasitics Revisited" for publication in the 
>9/90 and 10/90 issues, I received a hand-written inquiry from Mr. Erhorn. 
> According to our records, he placed order #1265, which was entered on 
>Wednesday, 4 July, 1990.  We sent him some parasitic suppressor retrofit 
>kits and a copy of the manuscript for "Parasitics Revisited".  
>Subsequently, I received another letter from Mr. Erhorn.  In this letter, 
>he said that he did not agree that 8877s, 8874s and the like were being 
>fatally-damaged by intermittent VHF parasitic-oscillations.   He said 
>that since Eimac replaced the kaput tubes he sent in, no questions asked, 
>the failure must have been due to a manufacturing defect.  .  Mr. Erhorn 
>said that if these tube failures were ETO's fault, Eimac would not have 
>replaced the tubes -- hence, Alphas do not have parasitic oscillation 
>problems. .  .  .  . 
>
>#### Not "hence..."  It's just further support for the other comments, 
>which I stand by 100% with respect to Alpha amps. 
Apparently, Mr. Ehrhorn's conclusions further support Mr. Ehrhorn's other 
comments. 
>BTW, we looked at the various
>kits and later cannibalized the resistors for some project or another. ####
If you had constructed the resistance-wire suppressors, instead of 
cannibalizing them, and had bothered to make some measurements, thou 
would have discovered whether or not resistance wire suppressors reduce  
VHF-Rp and VHF-Q *without* increasing the dissipation in Rs at 28MHz.  
Mr. Rauch assuredly deserves credit for bringing this to my attention via 
his somewhat hastily cancelled 28 November, 1996 post to the 
rec.radio.amateur.homebrew Usenet Newsgroup.  -  For example, in Wes' 
{N7WS} measurements with a Hewlett-Packard Model 4191A RF Impedance 
Analyzer, the resistance wire suppressor exhibited an Rp of 101 ohms at 
100MHz, while the copper wire (W8JI) suppressor exhibited an Rp of 166 
ohms at 100MHz, apparently giving the resistance wire suppressor a 40% 
advantage.  However, since the copper wire suppressor had the 
VHF-advantage (& 10m disadvantage) of using 9% more R and 33% more L, the 
comparison was probably weighted 15%  or so in favor of the copper wire 
suppressor.  .  .   And that's how, thanks to N7WS, F. E. Handy was  
proven right 70 years after he wrote:
 ."The combination of both resistance and inductance is very effective in 
limiting parasitic oscillations to a negligible value of current."   
.  .  {p.72, 1926 Edition of *The Radio Amateur's Handbook*}  

>I telephoned Eimac. An Eimac-engineer said that even 
>though Eimac engineers know about gold-sputtering damage, Eimac's 
>warranty dept. does not. When a returned, under-warranty tube shows any 
>kind of internal leakage, it is simply tossed into a scrap bucket and 
>replaced - no questions asked. I commented that it was nuts to replace 
>tubes that were damaged by a semi-stable amplifier design. He agreed and 
>explained that Eimac's warranty dept. does NOT talk to Eimac's 
>engineering dept.
>
>####  If you believe Eimac is foolish enough to give away new $300+ tubes for
>no good reason, I have a bridge you might like...  
Did Eimac manufacture 8877s with a built-in problem for a period of 1 
year?
Did Eimac manufacture 3-500Zs with defective anode-cooler spotwelds for a 
number years before it stopped making them?

> We often return defunct, in- or nearly-in-warranty tubes to Eimac for 
dissection and 
>technical feedback. 
>Do you really believe, "Mr. Masures," that dissections were done in the mail 
>room? 
Mail room?
>Eimac makes mistakes like the rest of us, but they aren't idiots. ####
I was told that the Eimac warranty dept. measures leakage with only one 
polarity.  Gas leakage can not be discerned from gold-sputtering leakage 
without using both polarities..    

>I got the impression that Mr. Erhorn has never taken 
>apart a kaput 8877, 3CX800A7 et cetera to see what's what. 
>
>####  Another bad impression. The carcasses are everywhere.  ####
Everywhere?  --  OJ told the LAPD that his fingers get cut everywhere he 
goes.  
  
>The totally-unsubstantiated rumour that I heard about why GE canceled 
>the contract went a bit different -- as in Not Invented Here syndrome.  
>################################################################  
>What can I add to this gem? Real facts about the saga of "1000+ defective 
>tubes failing at ~200 hours and the canceled contract" aren't hard to 
>come by.  But "Mr. Masures" didn't try because facts wouldn't support this 
pitiful, 
>weasel-worded attempt to damage reputations and credibility.
Bzzzzzzzzzzzzzzzzzzzzzzzt.  cough, cough.  Sounds like I'd better pick up 
some more 9v batteries.  .  .  Blaming all woes on Eimac is reportedly 
what damaged credibility with GE.  
>Facts? ETO lost a contract, 
>business dropped substantially... and today ETO
>sales are about double what they were before the lost contract. ETO remains
>the world's number one supplier of RF power to medical MRI systems houses. 
>Market share of the company that dumped us hasn't gone the same way. The
>power tubes in ETO MRI amplifiers are averaging about 18,500 hours lifetime, 
>and yes, that excludes 1000-or-so 8877's with defective cathode heat dams
>that caused grid-cathode shorts after only a fews hundred hours operation... 
>as happened to all the other users of 8877's during that terrible year.  ####
>
>Hmm.  The owner of a large company hand-writes letters.  . . .
>
>#####  Why do you suppose that makes "Mr. Masures" uneasy? Is it
>	really weird, or maybe subversive?  ####
Maybe sumthin's funny, what with all those tons o' money.  
...
>####  Yes, I know your name is Measures, Rich.   Mine's Ehrhorn.
yeah, yeah, but silent letters are kinda tricky, Dick.   
>73 all,
>
>Dick Ehrhorn   W0ID 

An appropriate suffix.  
cheers
Rich...


R. L. Measures, 805-386-3734, AG6K   


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm