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
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