tubes age 147
when. Warming the tubes with a Zippo lighter will take the blue glow out. The
reason this works is, you heat the getter stuff and it gets some more of the gas.
At least enough of the gas is absorbed so the gas is not visibly glowing blue. In
old tubes not heated through use, the getter stuff can let some of the gas loose.
Very little gas and very long time (years) to get loose. Your NOS may not be
NOS but service pulls and stuffed back in the box. They could be victim's of old
age. If the emission is OK and the noise level below your acceptance use
them.
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Date: Mon, 19 Sep 2005 10:06:56 -0400
Subject: Re: [R-390] Tubes glow blue
Baloney. Beware, beware! There are two (three, actually, or more) kinds of blue
or other color of glow in tubes:
1) The thing is normal and operating properly. It is likely a beam power tube
and the electrons that don't get glommed by the plate whizz on by and hit the
inside of the envelope. The *glass* glows. This condition is recognizable
because the glow is ON the INSIDE of the glass envelope. This is not harmful
or indicative of any fault or weakness in the tube.
2) The tube has some gas inside (when it should not have much at all). The
electrons whizzing toward the plate hit the gas particles and the gas glows.
This condition is recognizable because the glow in AMONG the tube elements,
NOT on the inside surface of the glass. This IS indicative of a fault or weakness
in the tube. However, if you run the tube for a while, the heat *may* make the
getter material glomm onto the gas, reducing or eliminating the gas and the
glow goes away. Certain relatively new tubes (such as made by the Viac
company for
audiophiles) have special getters attached to the plate, which plates run so hot
as to heat up the getter device and activate it further to glomm more gas.
These unusual getter devices may be washer- or ring- shaped things that are
seldom seen in old tubes.
Notes on terminology:
"whizz" to travel at a high rate of speed. In the case of electrons travelling from a
cathode to somewhere else, accelerated by the electrostatic potential
difference between the electron and the somewhere else. "glomm" a special
term borrowed from the seller of the engagement ring now in our family, who
would sternly caution the Groom while He was examining candidate diamonds,
"Don't Glomm the Stone!" -meaning grab onto, cause the brilliant to become
dull, or otherwise mess up by attachment of dirt or whatever. Very used tubes
such as transmitting tubes, power tubes such as 807's, 6550s, KT-88's and
the like can sometimes be identified as being past their useful life because
(14 pages)
(10 pages)
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