[Milsurplus] Speaking of Rejuvenating tubes

[J Forster]

I doubt it.

In reading the patent, it seems to refer to a pulsed emission causing
the emitting electrode to vibrate and shake loose crud..

The reason the Gm of a tube goes down is loss of emission  of the
cathode, by loss of the Thorium, for example or poisoning of the
cathode. . Over voltage on the filament (overheating) causes more
Thorium to come to the surface and the emission to rise. It's a 50 year
old trick for TV CRT tubes. They sold little autotransformers that
plugged into the CRT socket for that purpose.

There were also "CRT rejuvenators" that connected the grid and other
electrodes together and ran the CRT as a diode at fairly high current to
clean the crud off  the cathode. I don't think they were really very
successful, long term.

As to applying voltage between the filament and cathode, indirectly
heated tubes (ones with cathodes) have heaters, not filaments. The
heater's function is to heat the cathode. It is not, of itself, an
important emitter. The heater is also on the wrong side of the cathode
surface to interact w/ the emitting surface much.

Over voltage on the heater or filament will usually increase the
emission for a while, but it is not a permanent cure.

FWIW,
-John

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

John Hutchins wrote:

> All -
>
> Any one have knowledge if this procedure to Rejuvenate tubes?
> http://www.wipo.int/pctdb/en/wo.jsp?WO=2007073517&IA=WO200707
> 517&DISPLAY=CLAIMS
>
> Sounds similar to Rejuvenate tubes article:
> http://www.antiquewireless.org/otb/rejuve.htm
>
> I wonder if a combination of methods would work;  over heating by 135%
>
> of rated voltage and  Pulsing with a low voltage to cause the filament
>
> to shake.
>
> 1. how much voltage potential would be acceptable between the filament
>
> and cathode since they are not physically connected.
> 2  what would be the frequency required to get the cathode and
> filament
> physically to shake a minute amount.
> 3. Reversing the voltage on the cathode put a positive on the cathode,
>
> Negative on one side of the filament, and plate would this help drive
> off impurities from the cathode.
>
> Hutch