[ARC5] [Boatanchors] More and More "Gassy" Tubes

[Bill Cromwell]

On 04/21/2014 09:58 AM, J. Forster wrote:
> Tubes are not perfectly sealed, and some gasses (He especially) diffuses
> through glass. That's the bad news.
>
> The good news is many can be saved. That's what the getter is for. BUT,
> the tube MUST be operating for the getter to work. The trick is to power
> the tube without destroying it and let the getter to do it's job.
>
> Apply normal filament.
>
> Apply negative grid bias to ensure cutoff through a roughly 100k resistor
>
> Apply about 150 to 200 VDC to the plate through a current limiting
> resistor to limit current to roughly 1/2 max Ip.
>
> Slowly reduce grid bias, until Ip is about 20% of design Ip.
>
> WAIT. At least a day.
>
> The above an all be done on a tube tester.
>
> Retest for gas.
>
> -John
>
> ===================
>
I have done this and had about 95 per cent success. Obviously if the 
glass is visibly cracked or the getter looks like chalk or cobwebs it 
isn't going to work.

73,

Bill  KU8H