[ForSale-Swap] [Boatanchors] "burning" in tubes

[n griggs]

Burning in a tube is a great way to extend its life!  We have several amplifiers where I work that use C band transmit Klystrons.  We have two makes of amplifiers - one type is the replacement for the other.  On the older amplifiers, we keep the tube in standby which places a reduced voltage across the filament - normal voltage is 6.0 volts, reduced is about 5.7 volts.  On the newer units, there is an option called '1 Kv transmit".  These newer amplifiers have an option to adjust the beam voltage - between 6.5 Kv to 8 Kv or more depending on what the maximum voltage is for the tube.  This also reduces the filament voltage to the tube - from either 5.5 or 5.6 volts to 5.23 volts.  We have some tubes here that are over 8 years old and are still functioning with readings as close to new.  These will also put up to 3 KW of power if need be.
Neal KC4YCm

--- On Sat, 11/14/09, J. Forster <jfor at quik.com> wrote:

From: J. Forster <jfor at quik.com>
Subject: Re: [Boatanchors] "burning" in tubes
To: "RAY FRIESS" <rayfrijr at msn.com>
Cc: "boatanchors" <boatanchors at mailman.qth.net>, "FLBOATANCHORS" <flboatanchors at yahoogroups.com>, "glowbugs" <glowbugs at piobaire.mines.uidaho.edu>, "FORSALE" <forsale-swap at mailman.qth.net>
Date: Saturday, November 14, 2009, 2:22 PM

There is SOME rational for doing this. Tubes go gassy just sitting on the
shelf, especially if they have been sitting for decades.

Putting them in a circuit with filament/heater and B+ applied, but the
tube biased to cutoff, will help the getter scavange any gas molecules in
the tube.

Note, simply applying filament/heater power w/o B+ is NOT going to work,
because most getters scavange ions, NOT inter gas molecules. Do not leave
the grid floating either.

-John

=============



> A friend of mine says that now that I've put in a new pair of 572B tubes
> in my FL100B amp, I should let it sit, turned on, for 5 hours.  He says
> that burns in or breaks in the tubes before I put it in line on the air.
>
>
>
> True or just one of those old ham tales?
>
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