blue glow on power tubes

[bennieusmaximus]

Hey just a question to anyone who knows.I have a JMP that has the normal blue glow from the tubes.The amp is biased right.The question I have is that when I play the amp and watch the power tubes,the blue glow dissapears.then the blue glow comes back when I stop playing.Normal?These are KT88 tubes.

 

[MKB]

This is normal, nothing to worry about.

 

[NewReligion]

This is normal, nothing to worry about.

+1

 

[RiverRatt]

Yeah, a blue glow that clings to the inner surfaces is OK. If you see one where the gas in the tube fluoresces a purple or violet color, it's either losing it's vacuum and letting oxygen in or the getter didn't do it's job and left some oxygen in the bottle. Either way, the filament probably isn't going to last long.

Go to this site and read the article. You'll know more about tubes than you ever wanted to, including why tubes glow.

How Vacuum Tubes Work

 

[bennieusmaximus]

Yea I've read that the blue glow is normal expecialy on big bottle tubes,but i did not know it went away when playing,thanks for the help.