[R-390] Testing tubes r392

[Charles P. Steinmetz]

randy wrote:

>The TV-10 can also be
>used to "beam" a tube (heavy current blast - to blow crud
>off the elements and expose fresh emitter areas).

Egad!  What a way to destroy tube cathodes.  Oxide-coated cathodes 
are not meant to have crud "blown off."  And apart from the direct 
damage to the cathode, anything you "blow off" it has to settle 
somewhere, and some will settle on the grid -- where it will cause 
grid emission (which often leads to thermal runaway).

Thoriated tungsten filaments (directly heated) can sometimes be 
partially rejuvinated by running the filament current up a bit, but 
with antique tubes you are much more likely to open the filament at a 
weak spot than to improve emission.

Bad, bad idea.

Best regards,

Charles