On Sun, 03 Apr 2011 19:34:29 -0700, Jeff Liebermann wrote:

On Sun, 03 Apr 2011 20:09:10 -0700, David Nebenzahl
wrote:

So where does that purplish glow come from? I've seen it.

Impurities in the glass envelope or gas in the tube.

If gas, take an anti-acid tablet and you should be fine in a few
minutes.

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm Scroll down to:
C. Blue Glow -- what causes it?
for more details.

So even after a getter flash there is still a certain amount of
impurities? I've never seen a 6L6 that didn't have some blue inside
when in operation. It looks as though the blue only occurs where the
electron beams hit the inside of the glass. At least in new tubes.



--
Live Fast Die Young, Leave A Pretty Corpse