6H13C tube buzz and blue glow

[Jesse]

Hi

Yesterday i got a few Svetlana NOS 6H13C tubes.

After using it on my Crack about 2hours straight without any problems i took a little breather and turned off my amp.
1 hour later i turned my amp on again and started to listen it but this time after 5 minutes the 6H13C tube got two blue glowing spots on the glass either side of the tube.
One of the spots occasionally starts to flare up and down and everytime it does this i can hear buzzing sound from my right headphone.

Is this normal or should i swap tubes?
I did'n notice this phenomenon with 6080 tubes.

Before this i used a Sylviana 6080 tube and it has worked well at least 3 weeks.

--Jesse

[ALL212]

Remove tube...

I had a 2A3 that did something similar with a cool blue glow dancing in the top of the tube - I took video's of it.  But noticed the buzzing in the midrange on that side.  Swapped tubes - buzzing followed tube.  Replaced tube and buzzing went away.

Looks cool!!    Sounds bad... 

[2wo]

Tipicaly this is a little gas in the tube and will probably go away on its own. As the tube is run, the heat will allow the getter to absorb the gas.

I have a pair of 2A3's that had a pretty blue glow for awhile, I kinda miss it...John

[Jesse]

Blue glow  seems to be common phenomenon on 2A3 tubes.

Because i also have 4 2A3 tubes wich all have the blue glow, but i have never seen it move like that before nor heard any noises while it moves.

But should i just try to "burn in" the tube before i deem it lost cause or should i just deem it lost cause straight away?
I would like to try the "burn in" option but im afraid if the tub is faulty and could cause harm to my amp or my headphones.

Also yesterday i tried an other tube from the same set and after one hour in it had very dimm blue glow and this tube was also dead silent when amp wasn't playing any tunes.

[Paul Birkeland]

But should i just try to "burn in" the tube before i deem it lost cause or should i just deem it lost cause straight away?
I would like to try the "burn in" option but im afraid if the tub is faulty and could cause harm to my amp or my headphones.

You certainly don't want to run a gassy tube with your headphones plugged in!  You could try running the tube in your Crack for a while with no headphones plugged in, but there is some risk of damage to the amp.  Given the price of these tubes, I'd just toss that one in the trash. 

[Paul Joppa]

For what it's worth, there are two kinds of blue glow. One is florescence of the glass from electron bombardment and completely harmless. The other is glow near the elements, caused by traces of gas in the tube. This can sometimes be cured by running the tube for a few tens of hours; the heat activates the getter material which scavenges the gas molecules. Here's the article that came up at the top of google's list:

http://www.thetubestore.com/Resources/Matching-and-other-tube-info/Blue-Glow

[Doc B.]

I want to clarify this just a bit. The blue glow in the glass is a true blue. Blue glow from glass florescence does not make any noise. The "blue" glow from gas that might be around an element usually has more of a violet, sometimes almost pink color - that's from the argon in the air.  I think this difference is also mentioned in the article PJ linked.

If the tube's vacuum has gone a little soft from sitting for years and leaking around the pin seals (or right through the glass envelope) and the glow is very faint the getter may adsorb the gas and harden up the vacuum. If the tube has a bad seal leak or a crack and the glow is brighter, it's toast. If the getter is white rather than silver, don't plug the tube into an amp.

[Jesse]

Blue glow is definitely on the glass not on the element itself.

I think this tube is bad, because this blue glow is far from normal (at least i think so).

1. blue glow moves
2. you can hear noise (from headphones, not from the tub it self) while it moves
3. this i learned yesterday, blu glow it reacts when you touch the glass

I have 2A3 tubes wich all glow blue on some degree, but none of them has these three symptons.
I'm gonna discard this tube, but i'm stil very interested what could cause these symptoms.

So if you have more suggestions please post them.

[Doc B.]

If the blue glow is in the glass it is not related to the buzz and it is harmless. The buzz is most likely due to heater cathode leakage. If it is just buzzing you can try cooking it in for several hours and it might go away. If it is popping or spitting it more likely to have an internal short and should not be used.

[ALL212]

Here's the glow I had and I replaced the tube.  There was a midrange "grunge".  It's also quite possible the blue glow had nothing to do with the grunge, might have just been a bad tube.

[Doc B.]

Perhaps the glass glow indicates that the electron cloud is abnormally shaped. I'm just speculating, as I haven't really noticed a correlation of glass glow and noise myself. Might be worth compiling a history of people's experience with tubes with glowing glass.

[Jesse]

My blue glow isn't as intense as in Aaron Luebkes picture.

Mine is more like two dots on the glass 180 degrees of each other (in picture you can only see one and it looks more like line than dot).
I also think the blue glow isn't cause of the noise it's more likley a symptom.

[Paul Birkeland]

That blue glow isn't a problem in and of itself.