|[AMRadio] Ever seen this?|
k4kyv at hotmail.com
Thu Oct 6 22:17:04 EDT 2005
I crank the VariAC down to 0V, apply
>excitation again, and "HOLY CRAP! WHAT'S THAT?" The recently installed
>250TH, with just 35 or so watts of grid drive looked like an 866 rectifier,
>under full load! A translucent 'blue glow' appears all around the inside
>of the glass envelope, with grid-drive applied.
>What causes that? Is the tube good?
>This 250TH hasn't seen air in about 5 years (since I got it) and appears to
>be brand-new. Can't tell that it was ever inserted into a socket, before
The 250TH is gassy. That's not uncommon with the Eimac type tubes that have
been sitting idle for a number of years, even if the tube has never been
used. If it is gassy enough to glow blue inside just from grid excitation,
it it beyond hope.
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