tubes age 235
limited success. The trick was to leave the oven on for just long enough for the
getter to flash. Results ranged from "the tube was much better" to "it ruined the
filament" to "the tube burst". They had a pretty low success rate, but it was
interesting to see it did work for a few tubes.
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Date: Wed, 2 Mar 2011 15:11:21 EST
Subject: Re: [R-390] Gettering old tubes
The Toooob audio folks put a lot of value on the "Condition" of the getter flash
on the old premium audio tubes like the 6550 etc. I know that the getter is
flashed at some point in the assembly process by induction heating
(assuming it's already been rough pumped by mechanical means) and that
flash consumes most of the trace gasses inside the envelope. My question is
how much "Gettering" action takes place after the initial flash? I realize that
hard glass transmiting tubes use alloyed (coated?) getter material on their
anode structures that provide ongoing gettering provided the anode is heated
to a very high temperature (red plates orange plates white plates..... take you
pick)
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Date: Wed, 2 Mar 2011 17:39:12 -0600
Subject: Re: [R-390] Gettering old tubes
It is just an idea. I recall dissecting some of the tubes with the little metal halo
and found the metal that was left in the groove to be highly reactive (still). This
is the only reason I mention it. If we could inductively heat the getter halo then
some gas scavenging might still remain.
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Date: Wed, 2 Mar 2011 20:05:32 -0500
Subject: Re: [R-390] Gettering old tubes
Those strange audio geeks love NOS tubes but they cook the tubes for several
days on filament only without grid or B+. They swear the getter(s) do the job
90+% of the time on 50-70 year old tubes.
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Date: Wed, 2 Mar 2011 19:22:10 -0600
Subject: Re: [R-390] Gettering old tubes
I wonder what the grids look like after a couple days of filament-only?
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Date: Wed, 2 Mar 2011 20:31:21 -0600
Subject: Re: [R-390] Gettering old tubes
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