Blue glow in power tube?


I've got a ARC CA50 with new 6550C Svets that were professionally installed about 4 months ago. Each power tube has blue-ish hue streak inside. What does this mean?
viggen

Showing 1 response by trelja

Viggen, congratulations!

In the eyes of a great many hard core tubeophiles, the blue glow signifies a superior tube. Instead of worrying, look at it as your new favorite tube.