>> I started to have this problem in 10th grade and the problem isn't going
>> away.
>
>The problem is rooted in false claims, poor technical advice, poor circuit
>behavior descriptions, and general misinformation. Unless the correct
>information gets out, the problem will continue. We should concentrate more
>on technical issues, and less on what we "imagine".
>
>> ** Interesting, Dave. I apparently assumed wrongly. My take on the
>> issue is that GE knew more about the 8877 failure problem in ETO
>> amplifiers than is assumed by some. GE's awareness of the VHF parasite
>> problem goes back to 1935, when GE engineer G. W. Fyler wrote about the
>> problem in "Parasites in Transmitters" in the Sept. issue of the IRE
>> Journal. // The first Eimac technical data sheet on the 8877 was
>> published in 1970. Eimac's W. B. Foote told me that the gold-migration
>> problem was discovered by the 8877 development team. Thus, they must
>> have known about the gold-migration phenomenon at least 16-years before
>> Foote told me about it in February of 1986.
>
>Neither the Foote letter nor GE said anything of the sort.
I have no idea what GE said to Dick E.
The Eimac Letter:
=======================
"VARIAN ElMAC, 301 Industrial Way
San Carlos California 94070 1 U.S.A. / Tel. (415) 592-1221 TWX 910
376-4893
February 18, 1986
Mr. Richard L. Measures
6455 La Cumbre Road
Somis, CA 93066
Subject: 2 pcs returned 8875 S/N G8AD-241 and F8VD-428J, for evaluation.
Reference: Your letter dated 21 January 1986; EIMAC RPA #SC-2303.
Dear Richard:
Your letter about parasitics is quite interesting, and it appears your
two tubes have had the same trouble. The emission was poor on test, and
consequently other test results looked bad. The tube engineer then cut
them both open for an internal examination.
Both have been badly overheated internally, the apparent result of an
oscillation condition. The grid in these tubes is gold plated and if
overheated the gold vaporizes off, of course, and some of it inevitably
lands on the oxide cathode, and that poisons emission.
Though your tubes are quite old (mid-1978 vintage) we will replace them
in the interest of good user relations. We will scrap the two you sent in
here, as we have to be sure they are out of circulation when we replace.
Good luck in your continued operation.
Sincerely, WILLIS B. FOOTE, Chief Specifications Engineer, Power Grid
Division."
------------------------------
** I take this letter to say that gold apparently evaporates during an
oscillation condition.
>
>Back in the 30's, tubes had long thin leads.
** Some still do. However, low L leads only move the problem higher
because the ability to oscillate also moves up.
>Nearly every amplifier was
>operating at the upper frequency limit of construction, components, and
>wiring. Becuase the amplifiers were operated near the limits, having very
>poor tubes, wiring, and components by today's standards there was no
>effective way to stabilize the PA's.
>
** G.W. Fyler (and F. E. Handy) came up with a simple idea that proved to
be fairly handy -- i.e., "the plate or grid parasitic circuits should be
damped with resistance". (GWF. Sept.1935)
>It was impossible, in the 30's, to get enough transfer from current in
>inductance to the dissipative resistance as the frequency of oscillation is
>approached because the operating frequency and instability frequency much
>closer than they are with devices even from the 40's and 50's.
>
** Say what ?
>Because of poor layouts and poor components amplifers had to be gain-reduced
>even near the operating frequency.
>Only a fool would think that has some universal meaning in modern systems.
>It would be like insisting jet engines use gravity-fed fuel systems, which
>worked so well in the early days of aviation. Vastly different systems
>almost always require different solutions, when looking for the optimum.
>
>> The story I got was that GE was concerned with the tube failure rate.
>
>The story I heard was you applied for a job at a major amplifier
>manufacturer, and your application was rejected.
** I was a metrologist who also taught electronics. Amplifier building
was just a hobby that started when I was 15.
>I was told since then, you
>have had a grudge against ETO and all manufacturers.
>
** I didn't know anyone who got cremated in a Ford Pinto or Crown
Victoria rear-ender.
>> plant. When I mentioned the 150 figure on AMPS a couple of years later,
>> Dick said I was going insane.
>
>I know you say some things here that you attribute to me that I never said.
** Like the letter I received from a person who claimed to be Tom Rauch
which threatened to sue me and QST if my Rebuttal to the 9-94 QST was
ever published in QST? If this person was an impostor, his timing was
uncanny since his letter arrived about a 10-days after I mailed a copy of
my Rebuttal to the real Tom Rauch.
>I always wonder how often you do that in "technical" discussions. Why not
>leave all the personal stuff about Dick
** Dick E. played the Insane Card and I said so.
>and everyone out, and stick to
>honest facts?
** Like when the smoke began to clear at the end the Grate Parasitics
Debate, when your faithful groupies were suggesting that I was probably
boinking the teenage girl who was filling suppressor retro-fit kit orders
?
>
Cheers, Tom
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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