Hi Steve!
> Out of interest, in what way were they too different?
Totally different date of manufacture, plate looked different (I don't
remember now what exactly was different), and when I tried them, one
would take most of the load, the plate getting incandescent even at
moderate drive.
> Did you get a
> chance to see if the problem tubes behaved the same in a different amp?
No. But I still have one of the problem tubes here. I kept it to mount
it on a wooden base! :-) So it's not too late to run any tests on it.
I suppose that a tube that arcs over - for whatever reason it does so
the first time - will get some metal evaporated from the arc, and this
might make it more prone to arcing in the future. I don't know if the
theory is right, but surely one tube that starts arcing, will keep doing so.
> Manfred mentions his experience being with a Kenwood amp (but not which
> one). Nichrome might not be a wonder cure, but Henry, Dentron and
> Measure's suppressors are all more effective than those fitted in a TL922.
Yes, the amp was a TL922.
So, you are proposing that the problem doesn't happen with the Chinese
tubes simply because they have less gain at VHF? I didn't even think
about that... I thought the Eimac tubes were just plain gassy! But you
may well be right.
Manfred.
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