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

[n griggs]

I must have been having caffeine shortage when I typed my reply since some of it didn't make sense. (grin)  The '1KV transmit' does just that - it reduces both the beam voltage and filament voltage to extend the life of the tube.  The older amplifiers just reduce the filament voltage and have no beam current on the tube.  Also the older tubes use just the one voltage on the filament (-6 to 8 KV) with the collector at ground.  The newer units have multiple collectors - all depressed - with the maximum voltage at -6 to -8 KV.  The other collectors operate at approx -3 KV, -1 KV and -300 volts respectively.  Varian/CPI the manufacturer of the tubes we use (and amplifiers) agrees that the way we keep the older units in standby is a bit better than no filament voltage at all but it is not ideal.  That is why they added the 1 KV transmit option to the newer units.
Neal KC4YCM

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

From: J. Forster <jfor at quik.com>
Subject: Re: [ForSale-Swap] [Boatanchors] "burning" in tubes
To: "n griggs" <n_griggs at bellsouth.net>
Cc: "RAY FRIESS" <rayfrijr at msn.com>, "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, 7:56 PM

The gettering process is somewhat different for space charge tubes v.
magnetrons and probably klystrons. In the latter two, at least part of the
gettering action is due to sputtering.

When powering a maggie after long storage it is wise to pulse it at a very
low PRF until the vacuum has been cleaned up.

I would have thought to extend the klystron tube life, you would reduce
the filament and/or adjust the beam current, while keeping the beam and
reflector voltages constant.

-John

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



> 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?