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"Blue Glow" in tubes! Advice needed!

post #1 of 5
11/23/10 at 7:09am
Thread Starter 

Well, I just got my Sylvania 6AK5 tubes for my Little Dot MKIII, but I noticed something interesting.

 

Every time I turn the amp on, there is almost like a "Blue Storm" all around the center edges of the tube. I call it a storm, because it actually is moving (sort looks like a plasma lamp). The thing is, after about 3-5 seconds, it just disappears and they are back to their orange glow.

 

(Although, even after disappearing, there is still a "Blue Streak" across one of my tubes. It's just a tiny one, and almost looks like a slight scribble)

 

Am I in trouble? Are these tubes about to fail? (They are brand new)

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post #2 of 5
11/23/10 at 6:52pm

Go down to part C

 

http://www.vacuumtubes.net/How_Vacuum_Tubes_Work.htm

 

What you have sounds ok

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post #3 of 5
11/23/10 at 6:59pm
I agree it's probably the harmless kind of blue glow listed in that article, and many pentode tubes exhibit this. BUT, as that article also says, THE ONLY RELIABLE WAY TO DETERMINE THE HEALTH OF A TUBE IS TO TEST IT ELECTRICALLY.
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post #4 of 5
11/23/10 at 7:18pm
Thread Starter 

That brings me great relief. Thanks for the article. (I suspected it was normal, but wasn't sure. Very interesting to watch indeed...)

 

I actually tried the stock GE 6AK5 tubes and they did the same thing. It's quite interesting, and only happens when I turn the amp on.

 

When I did try the stock tubes, I noticed one was glowing orange brighter than the other. Are the same tubes supposed to glow the same?

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post #5 of 5
11/23/10 at 7:21pm
No, there is no guarantee the oranges would be the same wink.gif
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