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
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|