>Rich...
>
>There's no doubt that heavy QSK users - especially contesters and other QRR
>types - wear out vacuum T/R relays. But it's not necessarily the contacts
>per se that fail. My experience with Jennings RJ-1As has been that after
>extensive use roughness tends to develop between the actuator and the
>contact arm where they move (slide?) with respect to each other. This leads
>to mechanical "sticking" with both N.O. and N.C. contacts open. The N.O.
>(transmit side) contacts will usually close when power is applied, but
>spring tension is insufficient to overcome stiction and close the
>receive-side contacts.
? I have seen something similar when residual magnetism builds up in the
armature. The fix is to reverse the polarity to the coil.
>Sometimes a sharp rap on the envelope with a pencil
>or small screwdriver handle will fix it temporarily,
? sounds familiar. .
> but once sticking occurs it can only get worse.
? indeed, until one reverses the coil to begin demagnetizing the
armature. Ten or so years later, perhaps another reversal will be
needed.
>
>Nonetheless, even most CW contesters get multiple years of service before
>it's necessary to replace the vacuum relay in ALPHA 77Dx/Sx, 78, and 91B
>amps. All our amps which use vac relays have interlock protection that
>prevents hot switching, which can kill contacts in very short order.
>
>The Kilovac HC-1, which looks virtually identical to the RJ-1A and has
>essentially the same specs, has a very different internal design which I
>believe is superior. We use the HC-1 in 91B and 99 amps because it has much
>better bounce characteristics and therefore a significantly longer lifetime
>in heavy duty, high speed QSK use.
? However, as I recall, it is rated for the same number of closures.
>
> Contrary to innuendo noted on this reflector some weeks ago,
>I've never seen "gold balls" in any power tube used in any ALPHA or ETO
>medical or industrial amplifier - not an 8874, 8877, 3CX800A7, 3CPX5000A7,
> 4CX800A or other tube.
? If one opens leaky tubes to see what's what, the warranty is voided.
> Neither I nor any other ETO/ALPHA employee so far
>as I know has ever learned of any such event from any credible source,
? There are some photographs of gold sputtered tubes in the September
1990 issue of *QST*.
>including our customers, tube manufacturers,
? The letter from Eimac's Chief Specifications Engineer, Power Grid
Division, Willis B. Foote, is not credible?
> and our own labs. That doesn't
>really prove that it has never happened, of course. But we've shipped
>roughly 25,000+ of those tubes in new amateur, medical, and industrial
>amplifiers. If even one of them ever developed "gold balls" or otherwise
>failed as a result of parasitic oscillations, we've heard about it from NO
>ONE but a single internet source well-known for rumors, innuendo, and
>agenda. The posting was flat-out false and defamatory.
? The photos in *QST* are fakes? // As I recall, you made a comment
on [AMPS] about having seen many tubes with internal leakage. When you
measure internal leakage, do you do it with one polarity or both
polarities? // I have three kaput 8877s that were removed from Alpha
77s. Two have gold sputtering. // Have you read the letter from
Eimac's Willis B. Foote regarding gold evaporation/sputtering from grids?
http://www.vcnet.com/measures/EimacF.html
// According to Paul Pagel, Eimac's marketing rep, Reid Brandon told the
QST-staff that Mr. Foote was not authorized to release information on
gold sputtering.
> What a surprise.
? ¿?
- later, Dick
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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