[Boatanchors] More and More "Gassy" Tubes

[Jim Wilhite]

Dave, any breach of the seals would leak more than  gas into the tube.  That 
would include  Oxygen which would cause the filament to burn quite quickly.

You don't mention how you determined that there is gas in the envelope but 
there is always a very small amount which is the purpose of gettering the 
tube.  That gas will separate in a tube that has sat for a long time, but if 
you follow the directions of tube manufacturers, the getter will absorb it 
and the tube will be fine.

Most seal problems very well could be associated with the insertion or 
removal of tubes from the socket or dropping them when they are warm.  Even 
a short drop of a warm tube can cause the grid (s) to warp and eventually 
short.  The insertion/removal problems are most evident in power tubes that 
do not have supporting structure around the pins.

If you are referring to the blue glow on the envelope of the 1625, that is 
normal.  My first transmitter had that with new tubes (they had date codes 
of the late 40s and early 50s) and I was old enough to have a transmitter 
and license in the mid 50s.  Now if you see a blue glow inside the structure 
around the cathode/grid area, that is a different story.

Jim
W5JO

-----Original Message----- 
From: David Stinson


I'm starting to see more and more "gassy" and shorted
tubes lately.  Even the venerable 1625.
Not a lot- probably one out of  12-15, but that's
way more than I saw a decade ago.
You think these near-century-old envelope seals
have a "shelf life?"