>There?s an amazing amount of rumour and innuendo that
>goes on about the ETO amplifier for GE medical
>systems, the legendary 8877 problems, and ETO?s loss
>of the contract. It?s now been almost 10 years since
>I was personally involved, and 15 years since the
>incident took place, so the original players have all
>moved on. In fact the amplifier companies themselves
>no longer exist with the same structure or ownership,
>so I think some correcting of erroneous statements at
>this point won?t hurt anything. Besides, as I age,
>I'm finding it a lot harder to remain the strong,
>silent type... ;)
I started to have this problem in 10th grade and the problem isn't going
away.
>
>I speak from a somewhat unusual perspective ? I was
>the senior RF engineer at the company that was awarded
>the GE contract after ETO ?lost? it. Let?s nip one
>error in the bud right now.
>
>It has been said, ?GE Medical cancelled the contract
>years after Eimac fixed the heat dam problem.? This
>statement is wrong. The amplifiers which replaced the
>ETO amplifiers have been decommissioned for quite some
>time, and you can purchase subassemblies at hamfests.
>I did just that ? and the 300 watt solid state driver
>board which I obtained thusly has a date code on it of
>early 1988. Eimac has acknowledged that tubes
>manufactured from June 1986 to August 1988 were
>defective. So it would seem the replacement amplifier
>was in production while the cathode dam episode was
>ensuing and anybody who understands the engineering
>process will correctly surmise that the amplifier was
>under development even before the cathode dam episode
>began. The amplifier was, in fact, a custom, built
>for GE.
>
** 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.
>So, the loss of the GE contract by ETO very likely had
>absolutely nothing to do with the cathode dam episode.
Agreed.
> There are many, many reasons why a contract such as
>the General Electric MRI amplifier may be moved from
>one company to another, and technical performance is
>rarely the reason. The GE contract was a big one, and
>issues that were important to GE are of a magnitude
>nobody in the ham industry could probably come to
>grips with. It?s entirely possible that ETO did
>nothing wrong at all, and still lost the contract.
The story I got was that GE was concerned with the tube failure rate.
- After the QST article "Improved Anode Parasitic suppression for Modern
Amplifier Tubes" was published in October, 1988, I received a
hand-written letter from Dick Ehrhorn about the article. He concluded
that if kaput 8877s/8874s from Alpha amps had failed due to
gold-migration - as per the Oct. '88 QST article - , Eimac would not have
replaced such tubes under warranty because Eimac knew that gold-migration
is caused by an oscillation condition, Since Eimac replaced all failed
tubes, Dick assumed that the tubes failed from a manufacturing defect.
However, years later, Dick E. apparently began doing his own hi-pot test
for gold-migration using the W6IHA procedure. Subsequently, Dick sent me
an e-mail note about having 150 gold sputtered tubes on hand at his
plant. When I mentioned the 150 figure on AMPS a couple of years later,
Dick said I was going insane.
>
>Of course, ?we? (employees of amplifier company B),
>figured we knew why they lost the contract, but our
>likelihood of being right is not much higher than the
>likelihood of any comments on the AMPS reflector about
>the topic being correct.
>
I have tested a number of kaput 8877s from Alpha 77s, and roughly half
had loose gold inside the envelope. So, unless Dick E. lowered the VHF-Q
of the 8877's parasite suppressor for the 8877 MRI amplifier design, the
MRI version could also have had marginal VHF stability.
>
>The only fair thing to say about the GE contract,
>8877s, and ETO is that for the purposes of things
>discussed on this list, there is absolutely no
>relevant conclusion that can be drawn from the fact
>that GE switched vendors.
>
The track record of the Alpha 77 seems relevant since it was designed by
the same engineer,
>I can tell you this ? for the five years after that,
>when we went into competition against ETO for
>commercial amplifier business, ETO always had a
>technically solid offering. They were, without a
>doubt, a formidable competitor from an engineering
>standpoint.
>
One problem is that when I was taking electronic engineering c. 1960,
there was no course that covered parasites. The only information on the
subject in the department's library was apparently Fyler's obscure Sept.
1935 article in the IRE Journal.
>Since those days, I have had opportunities to interact
>with Dick Ehrhorn, W0ID
an appropriate callsign
>(founder of ETO). I found
>this ex-competitor of mine to be highly intelligent,
>extraordinarily capable of rendering accurate,
>well-researched engineering decisions,
According to what is taught in college engineering courses.
- However, Dick's decision to use 1w carbon-comp resistors to equalize
450WV electrolytics tells me that somebody at ETO did not bother to read
the resistor-mfg's V ratings. The same thing applies to ETO's use of RF
coupling/bypass type doorknob caps for tuned circuit applications. Not
only are bypass/coupling type caps temp-unstable, they are not nearly
able to carry the circulating current in a typical tank without hellish
overheating. (I learned that lesson by having a capacitor fire in the
"Plywood Box" amplifier).
>and what is most important to me, of utmost ethics.
I do not think it's highly ethical to toss out the "Insane" lable --
although, if I am nuts, I would probably be the last one to realize it,
so Dick just might be right.
> I would be more than pleased to have the opportunity to work with him.
Hubris tends to be not very pleasing.
In the words of McGeorge Bundy ?There is no safety in unlimited
technological hubris?.
>
thanks for the enlightenment, Dave
- R. L. Measures, a.k.a. Rich..., 805.386.3734, AG6K,
www.vcnet.com/measures.
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