>Rich Measures said on July 2, 2001:
>"Low Rp parasitic oscillation suppressors apparently work. The Alpha
>86 & 87 does not use such suppressors. Around 40% of the 80-series Alpha
>owners I surveyed reported sudden failures that required factory repair.
>When Alpha founder Mr. Dick Ehrhorn was active on AMPS, he said that he
>had seen hundreds of tubes with gold-sputtering damage."
/\ I was wrong. I checked my notes and the quantity was 150, not
hundreds. However, I have autopsied enough kaput gold-sputtered 8874s
and 8877s that were removed from ETO/Alpha amplifiers to know that it can
happen -- but not as much as in amplifiers that do not use a parasitic
suppressor, such as in the SB-230 and AL-1500. A photograph of one
autopsied 8874 with gold-sputtering is shown in "Parasitics Revisited"
(September-October, 1990 *QST*). This tube was one of three that were
removed and tested from an Alpha 78. Two of the tubes had this problem.
>This didn't sound like a correct attribution to me so I forwarded
>the quote to Dick Ehrhorn to confirm if this is what he had said
>or what he believes. And this is Dick's reply:
>"Measures is simply unbelievable & evidently clean out of his gourd now.
>We had long exchanges on the amps reflector concerning tube failures. I made
>100% explicit that I had NEVER seen, or been made aware of by a credible
>source (i.e., Eimac or our lab), of even one 3CX800A7 (or any other tube
>type) failure which was attributable to parasitic oscillations in any ALPHA
/\ Eimac's Warranty Dept. does not specifically test for gold-sputtering
leakage. If any leakage is detected, the tube is replaced and the dud is
tossed into a scrap bucket.
>I just wanted to clear up this misinformation and misrepresentation
>of Dick's position on the issue.
/\ John - what kind of HF amplifier do you use?
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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