[AMRadio] Ever seen this?

Donald Chester 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.

Don k4kyv

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