I beleive that the only heat needed is the cathode heat, either direct or
indirect.
The 'getter' is rare earth material, and all it takes is heat from the
cathode to work.
If a tube is in use all the time, it will be doing it's job and keeping the
tube in good shape,
It will take a very very long time to wear out a tube uner ham radio use,
If the tube wears out for cathode, it is most likely because the filiment
voltage was on the high side of tolerence.
If you can put the voltage on the low side of tolerance, it last much much
longer, Maybee two or three life times....
Best wishes,
Rich
K5SF
>From: "Gary Hoffman" <ghoffman@spacetech.com>
>Reply-To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
>To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>Subject: Re: [TenTec] Centurion
>Date: Sun, 11 Dec 2005 22:06:48 -0500
>
>Hmmmm.....and I was just getting around to thinking about building a "test"
>socket setup.
>
>Are you saying that filament heat alone was enough to melt the solder ? I
>would have thought that it would take the red hot anode to get it that hot
>?
>
>Now as regards running them in the amp to heat them up, this I understand.
>However, it takes the anode heat to get a 3-500Z hot enough to activate the
>getter anyway, does it not ? So it seems to me that the only preventative
>for a 3-500Z type tube is to heat it often enough that when you do apply
>the
>high voltage, the gas buildup has not been allowed to get so bad that it
>causes a failure...right ? Otherwise, you would have to apply high
>voltage
>gradually, meaning you would have to install temporary resistors in the
>high
>voltage leads, as discussed elsewhere.
>
>If there is yet another way, I don't see it off-hand.
>
>73 de Gary
>
>
>----- Original Message -----
>From: "Robert & Linda McGraw K4TAX" <RMcGraw@Blomand.Net>
>To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
>Sent: Sunday, December 11, 2005 5:43 PM
>Subject: Re: [TenTec] Centurion
>
>
> > A couple of points and concerns expressed here are thus:
> >
> > The Centurion when turned on, applies filament voltage and HV at the
>same
> > time. The opportunity to run the tubes with filament only does not
>exist
>in
> > the Centurion. Same true for most other amplifiers using direct heated
> > cathodes and thus instant on tubes. For those tubes which have a heater
>and
> > a cathode, that's another chapter in the book and a time delay and warm
>up
> > is required for proper tube operation and life.
> >
> > As to running tubes outside of the amp, {for what ever reason} as long
>as
> > the filament pins and associated glass seals stay within their
>temperature
> > rating (base seal rating is 200 degrees C max.) then there is no
>problem.
> > However, exceed the temperature rating and the solder may melt out of
>the
> > pins and / or the seals expand such that outside air contaminates the
> > envelope. To that end, I have witnessed a fan failure on a commercial
>amp
> > using 3-500's. The solder melted out of one of the filament pins and
>thus
> > the tube ceased to function. These tubes operate at 5.0 volts, +/- 0.25
> > volts, nominal, at some 14.6 amps. Fortunately I was able to re-solder
>the
> > pin and save the tube. In order to prevent future failures, an airflow
> > switch was installed in the exhaust to activate the filament
>transformer
> > when adequate airflow existed. My CCA broadcast transmitter {4 x
>4-400's}
> > has the same feature.
> >
> > 73
> > Bob, K4TAX
> >
> >
> >
> >
> >
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> >
> >
>
>
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