1 tube glowing blue?


I just replaced the SED 6550 tubes in my VTL MB450s. In 1 amp there is a tube that is glowing blue. Is there something wrong with it? Dont want it to blow.
Ag insider logo xs@2xpal

Showing 3 responses by pawlowski6132

Well, I knew that's what everyone was thinking. I just wanted to throw it out there.

;^)
Should be OK. Results from certain gasses appearing in the tube (i.e., not complete vacuum)
More specifically:

"The glow is caused by the electrons striking the plate, volatizing the surface, and dislodging atoms of nickel. High speed barium-strontium electrons from the filament collide with the atom, tearing off electrons, ionizing them and causing a deep blue color even in a well evacuated tube. The glow is a function of the plate voltage and the number of gas molecules in the envelope. In a good vacuum there are still billions of molecules. The electrons do not cause trouble because they all return to the positively charged plate. The size of the glow also varies with plate voltage and is not the same for each tube: it can vary from not discernable to very obvious even in daylight."