> Tom--
>
> Thanks for the clarification. I was not at ETO during the 8877
fiasco--but
> I was experiencing the same issues with the 3CPX1500A7s used in our
> 50 MHz wind profilers. Totally an EIMAC issue -- certainly not ETO's
fault.
The military had similar problems. It was not, as Rich tries to claim, a
problem with specific amplifers.
> Just a few years ago there was a problem with some 3CX800A7s. I kept
> hearing from Eimac that we (while I was at Alpha/Power) were the only ones
> having problems. Couldn't find any reason why ~30% of the new tubes
> would fail within about 100 hours of use. They just got OLD very fast
with low
> emission and high grid current. Fortunately (or unfortunately--depending
on
> your perspective) K1FO at Lunar Link was having the same problem and we
> started comparing notes. Steve did some excellent "CSI" detective work
> and discovered that the tubes that would fail early would also put out
full
> output
Ameritron was having the same problem during the same time period. Creeping
high grid current and short life.
The current problem is 3-500Z's
> much better. But this issue persisted for more than a year--resulting
> in Alpha amps working fine during their 48+ hour burn-in, but failing in
the
> field within weeks of being delivered.
Don't feel bad. 100 572B amplifiers were sold, all with defective Svetlana
572B's! Virtually 100% of the amplifiers failed.
I fully expect tubes to get worse, not better, as older engineers retire
coupled with a decreased demand making manufacturing a start and stop
process. Tubes are on the way out, all the signs are there.
73 Tom
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