[Amps] Outgassing tubes.

[Will Matney]

Jim,

I should have added that those arcs, even though one might think minor, put's a quick surge to any power supply of several amps current similar to taking the B+ lead and quickly shorting it to ground and back off. This over time can weaken components like rectfiers and filters until one fails.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 10/2/05 at 1:31 PM Jim Reid wrote:

>Will wrote,  in part:
>
>> Plus with age, a small amount of atmosphere can seep in, 
>> especially on glass tubes and where the ceramic to steel 
>> meets on a steel tube. Though on any old tube that finally 
>> does start to do this more, one should think about replacing 
>> them sooner or later. They could end up damaging the power 
>> supply.
>
>Perhaps that is what happened to my little AL-811H.  
>My tubes were "only" about 10 or 11 years old, however.
>They were used very little over that time;  maybe they gassed
>up slowly from the atmosphere.  Would that account for
>the low transconductance shown,  see below?
>
>I sent the
>tubes over to KH6CDO in Honolulu.  He measured three of them
>at 800 umoh. Spec is supposed to be 900,  I think he said.  The
>fourth tube could not be tested.  The "glued-on" anode connector
>atop that bottle had come "unstuck" when I removed the plate
>cap connector.  Frank tried to file off some of the glue residue
>to get it conductive from the anode for the test;  he couldn't remove
>any of it;  I wonder if that tube ever participated in the amp,  hi.
>Or,  maybe it was the tube which arced?
>
>Anyway,  as Will suggests above,  it was the power supply
>where failure is now found.  Will see what it is in a few
>days or so.
>
>73,  Jim W6KPI