> My last suggestion is to buy an Eimac tube. They are far superior to the
> Chinese tubes in my humble opinion.
Eimac blew it a couple times I know of. The Utah plant made 3-500s
that had graphite anodes spot welded to a cone that attached to the
vertical rod passing through the glass seal. Not sure what the cone
metal was, but those spot welds would fail if the anode got hot enough
which resulted in the anode hanging down and shorting to the grid.
Another problem I heard about but am vague on the details, had to do
with the gas used in Utah to deposit carbon on anodes. The tube
performance was inferior to those produced in California and at first
no one knew why. I don't remember what it was but eventually they
determined the gas in Utah had some property that was undesirable. I
don't know about the external anode tubes but most tube manufacturers
have committed mistakes on occasion. A good tube is a really hard
thing to make.
73
Rob
K5UJ
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