Hello, can anyone help me?
I've been reading lots of contradicting posts from a search on this forum, trying to find out about blue glow in one of my tubes.
Morgan jones says its ok inside the structure and normal for EL84's etc, but a sign of a 'soft' or gassy tube if its near the glass outside of the anode structure, as the blue glow is due to the collision of ionised gas molecules with the glass.
Well, I have only recently finished my stereo 2A3 amp, and only ONE of the two sovtek 2A3 output tubes shows a blue glow, just under the mica spacer at the top of the fattest part of the tube.
I've checked the HT, and bias voltages and they're ok.
I wasn't worried when my EL84's glowed, but I am now.
Can anyone actually shed anymore light on this, or should I send this tube back to the supplier?
I've been reading lots of contradicting posts from a search on this forum, trying to find out about blue glow in one of my tubes.
Morgan jones says its ok inside the structure and normal for EL84's etc, but a sign of a 'soft' or gassy tube if its near the glass outside of the anode structure, as the blue glow is due to the collision of ionised gas molecules with the glass.
Well, I have only recently finished my stereo 2A3 amp, and only ONE of the two sovtek 2A3 output tubes shows a blue glow, just under the mica spacer at the top of the fattest part of the tube.
I've checked the HT, and bias voltages and they're ok.
I wasn't worried when my EL84's glowed, but I am now.
Can anyone actually shed anymore light on this, or should I send this tube back to the supplier?
My Sovtek pair has been like that as you described (the blue glow and only one of the two) since I got them more than 2 years ago. They're still alive and sounds great - until I plug in my RCA 🙂
Well, if yours are still alive and well, I won't worry too much for now.
Thanks for putting my mind at ease.
I guess in a few years, it might fail, but then I'll know what to look for in the future.
thanks.
Thanks for putting my mind at ease.
I guess in a few years, it might fail, but then I'll know what to look for in the future.
thanks.
@ bobhayes
I know this may but contrary to what you have read, but I've never came across a good EL34 or EL84 (EL34's little brother) that did not have a "blue glow" near or "on" the inside of the glass envelope. When the tube is brand new the blue glow is usually "brighter" and then fades (dims) as the tube ages. I have observed EL34's that had no blue glow at all, but they were old and near the end of their life (weak). Now this from my 35 some years experience with this tube and all it's quirks.
Usually the glow looks like an "8" directly across from the grid alignment holes on the inner surface of the glass envelope. I believe that's were the electrons are streaming through the slots past the plate and striking the glass causing the glass to fluoresce. I've seen tubes such as a 6GH8 and other small pentodes, in TV's mostly, that had a blue glow that formed a ring around the tube opposite from the top or bottom or both mica spacers. Usually a badly misaligned tube or a "gassey" (glow floats around) tube. Now if you have a big blob that's floating around..., otherwise crack a beer, sit back, relax and enjoy the music!
Wayne ;D
I know this may but contrary to what you have read, but I've never came across a good EL34 or EL84 (EL34's little brother) that did not have a "blue glow" near or "on" the inside of the glass envelope. When the tube is brand new the blue glow is usually "brighter" and then fades (dims) as the tube ages. I have observed EL34's that had no blue glow at all, but they were old and near the end of their life (weak). Now this from my 35 some years experience with this tube and all it's quirks.
Usually the glow looks like an "8" directly across from the grid alignment holes on the inner surface of the glass envelope. I believe that's were the electrons are streaming through the slots past the plate and striking the glass causing the glass to fluoresce. I've seen tubes such as a 6GH8 and other small pentodes, in TV's mostly, that had a blue glow that formed a ring around the tube opposite from the top or bottom or both mica spacers. Usually a badly misaligned tube or a "gassey" (glow floats around) tube. Now if you have a big blob that's floating around..., otherwise crack a beer, sit back, relax and enjoy the music!
Wayne ;D
You were told incorrectly.
Blue glow inside the structure is gas.
Blue glow at the glass envelope is fluorescence. (cogsncogs is correct)
Look at it this way--aside from the metal parts, the cathode, grid, plate, etc, there's nothing inside a tube to glow...unless there is gas present. That's why they call 'em vacuum tubes, 'cause there's a vacuum inside.
Aside from testing the tube, a good indication of gas is when the getter starts turning white or disappearing, depending on the composition. The getter is the silvery, mirrored deposit on the inside of the glass. It's a combination of metals that react quickly with oxygen, removing it chemically. However, there's only a limited amount of getter, and when it's gone, the vacuum is going to deteriorate quickly.
Grey
Blue glow inside the structure is gas.
Blue glow at the glass envelope is fluorescence. (cogsncogs is correct)
Look at it this way--aside from the metal parts, the cathode, grid, plate, etc, there's nothing inside a tube to glow...unless there is gas present. That's why they call 'em vacuum tubes, 'cause there's a vacuum inside.
Aside from testing the tube, a good indication of gas is when the getter starts turning white or disappearing, depending on the composition. The getter is the silvery, mirrored deposit on the inside of the glass. It's a combination of metals that react quickly with oxygen, removing it chemically. However, there's only a limited amount of getter, and when it's gone, the vacuum is going to deteriorate quickly.
Grey
IS THIS EVER GOING TO STOP???
Hi,
On the inside, inbetween the plate and the grids, yes....Just about visible in the dark and that's it.
If you see more of it in power triodes or small signal tubes then that's not necessary something to lose sleep over but it sure as hell is a sign of badly pumped tubes and/or impurities in glass and/or various metal parts used.
To get rid of these remaining contaminants vacuum tubes have a getter (get it?) which is there to maintain and improve on the high TOR vacuum after it has been sealed of at the stem (top or bottom of glass, depending).
So, while this blue glow can be a normal sight with power penthode and tetrodes, it shouldn't be with a well made triode and, surprise, surprise, you'll hardly ever come across this phenomenon with good quality NOS tubes.
Why? Because QC was a lot better and the vacuum pumps were still doing a good job at sealing and pumping away gas. Simple as that.
Does this mean your tube stinks?
No, it does not....The getter will have to work just that little bit harder to burn away the gass and that's about it.
It should be noted however that the getter is the first thing to die in the normal lifespan of any tube under normal conditions so draw your own conclusions.
Now I've seen much abused penthode applications where just about any tube would show a blue glow in that circuit and not in a "normal" situation.
Guitar amp manufacturers seem to be great "artists" when it comes to finding ways to hammer tubes so don't be too surprised when you notice they die at least twice as fast there.
Should you see a blue glow close to the bulb of the tube and it's acting kinda funny then chances are the vacuum of the tube is losing it and you'll be losing that tube any day soon too...
Vacuum tube testers usually have a gas test so having such a meter or knowing someone who does is usually very helpful.
Having a few spares to check if they behave the same way can be telling too but not necessarily conclusive.
Watching blue glows dancing in tubes is about as cute as a cow watching a train go by. No offense to the cows.... 🙄
Cheers, 😉
Hi,
On the inside, inbetween the plate and the grids, yes....Just about visible in the dark and that's it.
If you see more of it in power triodes or small signal tubes then that's not necessary something to lose sleep over but it sure as hell is a sign of badly pumped tubes and/or impurities in glass and/or various metal parts used.
To get rid of these remaining contaminants vacuum tubes have a getter (get it?) which is there to maintain and improve on the high TOR vacuum after it has been sealed of at the stem (top or bottom of glass, depending).
So, while this blue glow can be a normal sight with power penthode and tetrodes, it shouldn't be with a well made triode and, surprise, surprise, you'll hardly ever come across this phenomenon with good quality NOS tubes.
Why? Because QC was a lot better and the vacuum pumps were still doing a good job at sealing and pumping away gas. Simple as that.
Does this mean your tube stinks?
No, it does not....The getter will have to work just that little bit harder to burn away the gass and that's about it.
It should be noted however that the getter is the first thing to die in the normal lifespan of any tube under normal conditions so draw your own conclusions.
Now I've seen much abused penthode applications where just about any tube would show a blue glow in that circuit and not in a "normal" situation.
Guitar amp manufacturers seem to be great "artists" when it comes to finding ways to hammer tubes so don't be too surprised when you notice they die at least twice as fast there.
Should you see a blue glow close to the bulb of the tube and it's acting kinda funny then chances are the vacuum of the tube is losing it and you'll be losing that tube any day soon too...
Vacuum tube testers usually have a gas test so having such a meter or knowing someone who does is usually very helpful.
Having a few spares to check if they behave the same way can be telling too but not necessarily conclusive.
Watching blue glows dancing in tubes is about as cute as a cow watching a train go by. No offense to the cows.... 🙄
Cheers, 😉
see my avatar 😀
It's the original 6V6 in my '71 Fender Champ, and it's been glowing blue for over a decade in my posession... Still works great.
It's the original 6V6 in my '71 Fender Champ, and it's been glowing blue for over a decade in my posession... Still works great.
As you can see, there are different schools or thought on this subject, which is nice for conversation.
I know not to worry about EL84's etc, but my question was specifically aimed at the 2A3 valve.
Thanks for all the input from everyone on the subject.
I think I will settle for 'this tube has some gas in it... not a lot but some.'
I guess the getter will work harder, probably go brown quicker than the other one, and will probably fail sooner, maybe in a couple of years or maybe in a couple of decades, where as the 2A3 showing no blue glow will probably last for ever... (figure of speech).
I think I'll stick with Morgan Jones and fdegrove on this one. It's gas but not that bad.
Thanks again.
🙂
I know not to worry about EL84's etc, but my question was specifically aimed at the 2A3 valve.
Thanks for all the input from everyone on the subject.
I think I will settle for 'this tube has some gas in it... not a lot but some.'
I guess the getter will work harder, probably go brown quicker than the other one, and will probably fail sooner, maybe in a couple of years or maybe in a couple of decades, where as the 2A3 showing no blue glow will probably last for ever... (figure of speech).
I think I'll stick with Morgan Jones and fdegrove on this one. It's gas but not that bad.
Thanks again.
🙂
I've read in many places that flourescence (blue glow near the glass that changes with the music) is actually a sign of an excellent vacuum. Is this a myth then?
Interesting question, hmmm what tube are you speaking of? First off no, it's not a sign of an excellent vacuum. I would say in a tube of excellent vacuum there would be very little blue glow observed between the grids of the tube and as the getter does it's work it would become less noticeable over time.
Now the blue glow on the inner surface (again an EL34) will fluctuate, brighten/dim, not "dance around" with "the music" as the current through the tube will change during musical passages, especially during strong bass notes such as a kick drum or a thump or rumble from a LP.
As I stated in my earlier post with a "new" EL34 the blue glow on the inner surface of the glass envelope (fluorescence) will be much brighter and slowly fade as the tube ages. I would guess to say a new tube has stronger cathode emission, therefore more electrons striking the glass causing the glass to fluoresce. I've also seen this fluctuation inside the tube near the grids which I believe is from the small amount of gas leftover from the pumping process. This will also diminish in a "good" tube as the getter does it's job.
Now this "8" pattern on an EL34 is sharply defined and is due to the grid alignment slots and the physical properties of the tube, grid spacing and alignment. Now I would dare say if you saw a blue "spot" on the inner surface of the glass say directly across from the mica spacer(s) tells me that the electrode spacing and alignment is not good and somehow allowing a stream of electrons "fly" past the plate and striking the glass near the mica spacer. gmarsh's 6V6 avatar shows quite a bit of it on or near the inner surface of the glass, hard to tell in that pic. Also the 6V6 came with a few different plate structures (shape), could there be a seam? Dunno. But looks awfully like plain ol ionized gas forced into it's shape by the electrostatic force of the anode. Just an "ignorant" guess on my part.
My rule of thumb: If the tube is strong and produces the power expected of it and the getter is black or silver, biases properly, does not produce pops or other funny noises, distortion within spec and does not have a "huge blue blob", don't fret.
Me thinks Frank is thinking I mean dancing blue glow is ok. Not so! It must remain stationary, always in the same place with a defined pattern and not move around with the music. If it moves around you have a bad tube and should be replaced. Purple glow is a definite sign of a vacuum leak and "must" be replaced! If I see a blue glow on my small signal tubes, triode or pentode, I will usually "toss" them.
Cheers
Wayne 😉
Re: IS THIS EVER GOING TO STOP???
Imagine, a tube maturing like a bottle of wine hidden away in the cellar.
Maybe also, sitting around all those years has given the getter plenty of time to do a thorough job even with tube internals cold.fdegrove said:
Imagine, a tube maturing like a bottle of wine hidden away in the cellar.
I've seen 6L6 tubes (I forget the European designation) in guitar amps glow for years and years. It's not, contrary to what was said above, a sign of impending death; just the glass fluorescing. While I'm thinking of guitar amps and tubes...actually guitar amps are far more conservative in their usage of tubes than stereo stuff. They have to be. Once a guitar/bass amp manufacturer gets a reputation for unreliability, they're out of business within a year. People don't pay bands who can't play. For stereo stuff it's almost a badge of authority to pop tubes.
Diminution of glow with age is a sign of wear and tear on the cathode. It no longer gives off electrons as readily. Of course, the tube's performance is deteriorating, too, but that's another topic.
Circlotron,
Actually, the getter works pretty quickly. Time won't give it that much of an edge.
There are two gas sources. One is the seal around the tube pins. The glass and metal both need to have the same coefficient of expansion so that no gaps develop as the tube heats up. Conversely, you wouldn't want the metal to expand faster than the glass and cause cracks in the glass.
The other is outgassing from the metal itself. It's worse if the power dissipation of the tube is exceeded, as heat releases more gas. I seem to recall that one particularly difficult gas is hydrogen. Can't remember offhand why it's in the metal or why it's so difficult to remove when the metal is being formed, but it's a booger to get rid of once it's in the tube.
Frank,
I'm curious...since you seem to believe that glow between the internal elements is not gas...just what substance do you suppose it to be?
Grey
Diminution of glow with age is a sign of wear and tear on the cathode. It no longer gives off electrons as readily. Of course, the tube's performance is deteriorating, too, but that's another topic.
Circlotron,
Actually, the getter works pretty quickly. Time won't give it that much of an edge.
There are two gas sources. One is the seal around the tube pins. The glass and metal both need to have the same coefficient of expansion so that no gaps develop as the tube heats up. Conversely, you wouldn't want the metal to expand faster than the glass and cause cracks in the glass.
The other is outgassing from the metal itself. It's worse if the power dissipation of the tube is exceeded, as heat releases more gas. I seem to recall that one particularly difficult gas is hydrogen. Can't remember offhand why it's in the metal or why it's so difficult to remove when the metal is being formed, but it's a booger to get rid of once it's in the tube.
Frank,
I'm curious...since you seem to believe that glow between the internal elements is not gas...just what substance do you suppose it to be?
Grey
Hi,
There isn't any...Same thing for the 6V6.
Some Euro types are close equivalents but not necessarily interchangeable.
Some manufacturers pick(ed) the toughest tube X from a manufacturer's catalogue to give them an edge over the competition.
When those NOS tubes are gone trouble starts with lower rated replacements untill enough power/money is gathered to upgrade a currently manufactured tube or the adapt the circuit to what's currently available.
Nowadays you only sporadically hear about problems like flakey 5U4Gs from Russia, there used to be similar transitional problems with 5AR4s/GZ34s from Russia, etc.
Either way, guitar players are your bread and butter customers when it comes to replacing tubes....
The other part of the business are paranoid audiophiles.... Ahemmmm.... (Sometimes for a good reason, but I digress)
Incompetent/ignorant "designers" + so so tubes = disaster waiting to happen.
I've seen literally thousands of 1960-1985 stereo amps running class A, AB and B with hardly any tube problem.
Most of them easily outperforming most newly made amps provided they're upgraded with top notch components and outfitted with good quality NOS tubes.
Did I give that impression?
No, it's gas alright. What else could it be?
What I did mean to say is that the blue glow seen between internal elements is quite common and pretty harmless with penthodes and tertrodes.
That is, as opposed to the blue glow you see all over the bulb which can be a sign of poorly outgassed tubes or an ailing getter...
Cheers, 😉
There isn't any...Same thing for the 6V6.
Some Euro types are close equivalents but not necessarily interchangeable.
Some manufacturers pick(ed) the toughest tube X from a manufacturer's catalogue to give them an edge over the competition.
When those NOS tubes are gone trouble starts with lower rated replacements untill enough power/money is gathered to upgrade a currently manufactured tube or the adapt the circuit to what's currently available.
Nowadays you only sporadically hear about problems like flakey 5U4Gs from Russia, there used to be similar transitional problems with 5AR4s/GZ34s from Russia, etc.
Either way, guitar players are your bread and butter customers when it comes to replacing tubes....
The other part of the business are paranoid audiophiles.... Ahemmmm.... (Sometimes for a good reason, but I digress)
Incompetent/ignorant "designers" + so so tubes = disaster waiting to happen.
I've seen literally thousands of 1960-1985 stereo amps running class A, AB and B with hardly any tube problem.
Most of them easily outperforming most newly made amps provided they're upgraded with top notch components and outfitted with good quality NOS tubes.
Did I give that impression?
No, it's gas alright. What else could it be?
What I did mean to say is that the blue glow seen between internal elements is quite common and pretty harmless with penthodes and tertrodes.
That is, as opposed to the blue glow you see all over the bulb which can be a sign of poorly outgassed tubes or an ailing getter...
Cheers, 😉
Blue glow on the inside surface of anode is common. I have 4 EL84s and all of them glows in the inside surface of anode. Glow between the elements is gas , that is bad.
well, i found this topic for another type of glow
It occurs in russian GU50 tubes.
(don't go "oh russian **** tubes" on me!)
These are VERY good tubes. They were used in MIG radar's, and no matter how stupid the majority of american forummembers think russians were, they could not afford blind migs flying around.
They are brand new, no getter wearing and not an awful lot of blue glow between the grids.
This indicates a good vacuum, however, i SOMETIMES get a very bright blue shine at the bottom mica spacer in 1 or two tubes. It looks strange, in the way that it looks like something reflected at first. I played around with my hand to see if it was something reflecting on the glass, but it isn't
Anybody any clue
(the shine is well outside the anode)
Bas
It occurs in russian GU50 tubes.
(don't go "oh russian **** tubes" on me!)
These are VERY good tubes. They were used in MIG radar's, and no matter how stupid the majority of american forummembers think russians were, they could not afford blind migs flying around.
They are brand new, no getter wearing and not an awful lot of blue glow between the grids.
This indicates a good vacuum, however, i SOMETIMES get a very bright blue shine at the bottom mica spacer in 1 or two tubes. It looks strange, in the way that it looks like something reflected at first. I played around with my hand to see if it was something reflecting on the glass, but it isn't
Anybody any clue
(the shine is well outside the anode)
Bas
There are two types of blue glow common in tubes. If there is a glow blue,pink, or purple in the space between the cathode and the plate, the tube has some gas in it. It is true that this is not common on old NOS tubes de to the better vacuum. A small amount of glow may not cause any problem, but it may lead to grid current problems.
A blue glow on the glass, a mica spacer, or other mechanical part is usully caused by the glass phosphoressing when it is being struck by flying electrons. This is harmless.
If you have a tube that glows like this your amp is already fried.
A blue glow on the glass, a mica spacer, or other mechanical part is usully caused by the glass phosphoressing when it is being struck by flying electrons. This is harmless.
If you have a tube that glows like this your amp is already fried.
Attachments
Hmm, I have a quad of Philips (Siemens maybe?) EL34's where all four have the flourescent glow. Been a while since I've used that amp so I can't say where exactly the glow was coming from.
Substituting a different quad of EL34's (1980's Ei's I think -- I say "I think" 'cause they're labeled Mullard!) gives no blue glow.
Both sets seem to sound and work fine (though I prefer the top end on the Mullards by far). The blue glow quad looks ace at night though. Lot's of approving comments from visitors! 😛
Substituting a different quad of EL34's (1980's Ei's I think -- I say "I think" 'cause they're labeled Mullard!) gives no blue glow.
Both sets seem to sound and work fine (though I prefer the top end on the Mullards by far). The blue glow quad looks ace at night though. Lot's of approving comments from visitors! 😛
i own a few sets of output tubes:
the JJ7027A and Svetlana(winged C) 6l6GC both give a kinda bright blue 'stripe' if you look through the hole in the anode.......if you use a magnifying glass, you can even see 'the layers' (shadow from g2 or g3 as these are beam tetrodes)
this is not visible on the glass, you can only see it in a darkened room, and if you almost put your nose against the tubes.....
I intend to look at these as good set's
then i had some very old 7027a, these had dancing blue glow which travelled around the glass, even reacting to bass!! =gass
also some old 6l6gb that had had a difficult life in an guitar amp, they were 'all' blue, starting softly when HV went up, getting brighter and brighter....they did play music however!!
i thought it wise to remove them (i did give them a tad to much B+ however....that might have influenced it a bit, but they were rotten anyway)
the JJ7027A and Svetlana(winged C) 6l6GC both give a kinda bright blue 'stripe' if you look through the hole in the anode.......if you use a magnifying glass, you can even see 'the layers' (shadow from g2 or g3 as these are beam tetrodes)
this is not visible on the glass, you can only see it in a darkened room, and if you almost put your nose against the tubes.....
I intend to look at these as good set's
then i had some very old 7027a, these had dancing blue glow which travelled around the glass, even reacting to bass!! =gass
also some old 6l6gb that had had a difficult life in an guitar amp, they were 'all' blue, starting softly when HV went up, getting brighter and brighter....they did play music however!!
i thought it wise to remove them (i did give them a tad to much B+ however....that might have influenced it a bit, but they were rotten anyway)
How much blue glow is healthy in a penthode?
I can see a faint blue glow inside the anode. Grid shadow is very obvious.
Bas
I can see a faint blue glow inside the anode. Grid shadow is very obvious.
Bas
tubelab.com said:
Wow! Now that is seriously gassy. This really does raise the question of "how much glow?" The typical glow inside an EL84 is really quite small and quite faint. I have a 6AS7G with a little blue glow near the glass and it was great fun (well, for a minute or two) pulling it around with a magnet, but I couldn't get it to show up well on a photograph. Perhaps the criterion should be that if you can't photograph it, don't worry about it.
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