Tube glow color

[unconventional]

I'm wondering if I have a bad tube. I got 7 that glow blue and amber and 1 that only glows amber on my 2:100 Power amp. One channel (A) has some intermittent crackling. What do you think?

I'm going to retube in a few weeks, both my recto preamp and the power amp 6l6's as well as the three preamp tubes in it.

Kevin

 

[fitz8005]

a bluish-purple glow near the top of the tube is normal. the crackling could be the tubes or dirty connections; get your hands on some electrical contact cleaner and give the tube sockets a quick cleaning. just spray some cleaner on the tube pins and insert them in and out of the socket a few times.

 

[unconventional]

Yes, I know the purple glow is normal, what I'm saying is that 7 of them have the purple glow / amber glow but the 1 only has amber glow, no purple.

 

[mikeymike]

Yes, I know the purple glow is normal, what I'm saying is that 7 of them have the purple glow / amber glow but the 1 only has amber glow, no purple.

I think 2 of mine are doing that. I could be wrong though... I think my amp is pretty thrashed so... don't take me saying "2 of mine are doing that" as it's normal. My 2:100 had a really stupid owner before me... I';ve been searching boogie board all night about the blue glow not showing up on some tubes.. I wonder what it means..

 

[disassembled]

Most likely it would be a burnt screen resistor due to a bum tube. I would take it to a tech and ask them to check your screen resistors.


Greg

 

[tobytheplatypus]

check your flux capacitor

 

[EirikBrandal]

on my amp there's 3 tubes glowing blue, and one that isn't. For me it looks like no tubes in that position are glowing blue, cause none of the tubes I have had in that socket have been glowing blue.

 

[mikeymike]

Most likely it would be a burnt screen resistor due to a bum tube. I would take it to a tech and ask them to check your screen resistors.


Greg

my tubes are literally like 4 days old...

 

[mercurialuk]

Hey guys i was also wondering about this, in my 2:90 i just replaced the tubes and the new ones are glowing blue and amber the old ones are just amber, does this mean they are abit old and need changing,

If anyone has the answer to this.... that would be cool!

 

[mikey383]

Taken from the "How Vacuum Tubes Work" website...


There are two reasons a tube glows....

1) Most Svetlana glass power tubes show FLUORESCENCE GLOW. This is a very deep blue color. It can appear wherever the electrons from the cathode can strike a solid object. It is caused by minor impurities, such as cobalt, in the object. The fast-moving electrons strike the impurity molecules, excite them, and produce photons of light of a characteristic color. This is usually observed on the interior of the plate, on the surface of the mica spacers, or on the inside of the glass envelope. THIS GLOW IS HARMLESS. It is normal and does not indicate a tube failure. Enjoy it. Many people feel it improves the appearance of the tube while in operation.

2) Occasionally a tube will develop a small leak. When air gets into the tube, AND when the high plate voltage is applied, the air molecules can ionize. The glow of ionized air is quite different from the fluorescence glow above--ionized air is a strong purple color, almost pink. This color usually appears INSIDE the plate of the tube (though not always). It does not cling to surfaces, like fluorescence, but appears in the spaces BETWEEN elements. A tube showing this glow should be replaced right away, since the gas can cause the plate current to run away and (possibly) damage the amplifier.

 

[mikeymike]

Taken from the "How Vacuum Tubes Work" website...


There are two reasons a tube glows....

1) Most Svetlana glass power tubes show FLUORESCENCE GLOW. This is a very deep blue color. It can appear wherever the electrons from the cathode can strike a solid object. It is caused by minor impurities, such as cobalt, in the object. The fast-moving electrons strike the impurity molecules, excite them, and produce photons of light of a characteristic color. This is usually observed on the interior of the plate, on the surface of the mica spacers, or on the inside of the glass envelope. THIS GLOW IS HARMLESS. It is normal and does not indicate a tube failure. Enjoy it. Many people feel it improves the appearance of the tube while in operation.

2) Occasionally a tube will develop a small leak. When air gets into the tube, AND when the high plate voltage is applied, the air molecules can ionize. The glow of ionized air is quite different from the fluorescence glow above--ionized air is a strong purple color, almost pink. This color usually appears INSIDE the plate of the tube (though not always). It does not cling to surfaces, like fluorescence, but appears in the spaces BETWEEN elements. A tube showing this glow should be replaced right away, since the gas can cause the plate current to run away and (possibly) damage the amplifier.

that doesn't answer mercurialuk's, unconvetional's or my question at all. We are wondering if the LACK OF ANY BLUE is a sign that the tube is NOT working since they LACK blue when in standby but when in play mode they glow blue indicating there are electrons in the tube. If a tube stays the same NON blue glow during standby and in play mode wouldn't that indicate that the tube is not working? I have two that are doing that and they are brand new almost but when i moved them to different sockets they STILL didn't glow blue. So the lack of glow follows the tube..

 

[disassembled]

Most likely it would be a burnt screen resistor due to a bum tube. I would take it to a tech and ask them to check your screen resistors.


Greg

my tubes are literally like 4 days old...

Tubes can be bad out of the box so your statement holds no weight. Also, if a tube you replaced blew out a screen resistor the problem doesn't go away just by replacing the tubes. When a screen resistor is destroyed the only way to get it to work again is to replace it. Once you replace the resistor then the tube should operate as normal.

Now, I am just speculating here so you might have a completely different problem then what I am imagining. Your best bet is to get it checked out by a pro. Without actually having the amp infront of me I can't tell you anything that would be useful.

Greg

 

[disassembled]

Taken from the "How Vacuum Tubes Work" website...


There are two reasons a tube glows....

1) Most Svetlana glass power tubes show FLUORESCENCE GLOW. This is a very deep blue color. It can appear wherever the electrons from the cathode can strike a solid object. It is caused by minor impurities, such as cobalt, in the object. The fast-moving electrons strike the impurity molecules, excite them, and produce photons of light of a characteristic color. This is usually observed on the interior of the plate, on the surface of the mica spacers, or on the inside of the glass envelope. THIS GLOW IS HARMLESS. It is normal and does not indicate a tube failure. Enjoy it. Many people feel it improves the appearance of the tube while in operation.

2) Occasionally a tube will develop a small leak. When air gets into the tube, AND when the high plate voltage is applied, the air molecules can ionize. The glow of ionized air is quite different from the fluorescence glow above--ionized air is a strong purple color, almost pink. This color usually appears INSIDE the plate of the tube (though not always). It does not cling to surfaces, like fluorescence, but appears in the spaces BETWEEN elements. A tube showing this glow should be replaced right away, since the gas can cause the plate current to run away and (possibly) damage the amplifier.

that doesn't answer mercurialuk's, unconvetional's or my question at all. We are wondering if the LACK OF ANY BLUE is a sign that the tube is NOT working since they LACK blue when in standby but when in play mode they glow blue indicating there are electrons in the tube. If a tube stays the same NON blue glow during standby and in play mode wouldn't that indicate that the tube is not working? I have two that are doing that and they are brand new almost but when i moved them to different sockets they STILL didn't glow blue. So the lack of glow follows the tube..

Mike:

You are correct if the tube stays EXACTLY the same in standby AND in operate mode then something is wrong. Some tubes don't glow that much and you have to move your head around to look for any blue inside the plates.

If you have 4 of the same tubes and 3 have a bright blue haze while 1 tube doesn't that should throw up a flag that something is wrong.

Let's not get confused, because not all tubes have a visible blue haze, like Sovtek tubes (AKA Mesa STR430's), so you have to do some investigating. A few things to check would be plate voltage, any type of blue glow inside the plate structure, and a lot of heat coming off of the tube. I know that JJ 6L6's and the Ruby 6L6's (aka STR440's) do not have very much visual representation when they are operational as a couple of currently made tube examples.

Greg

 

[mikeymike]

Most likely it would be a burnt screen resistor due to a bum tube. I would take it to a tech and ask them to check your screen resistors.


Greg

my tubes are literally like 4 days old...

Tubes can be bad out of the box so your statement holds no weight. Also, if a tube you replaced blew out a screen resistor the problem doesn't go away just by replacing the tubes. When a screen resistor is destroyed the only way to get it to work again is to replace it. Once you replace the resistor then the tube should operate as normal.

Now, I am just speculating here so you might have a completely different problem then what I am imagining. Your best bet is to get it checked out by a pro. Without actually having the amp infront of me I can't tell you anything that would be useful.

Greg

I've already replaced the screen grid resistor that was blown and i tested the others with a multi-meter. they're all reading 1kohm. Is it really possible that doug's tubes could have sent me 2 bad tubes?

 

[mikeymike]

Taken from the "How Vacuum Tubes Work" website...


There are two reasons a tube glows....

1) Most Svetlana glass power tubes show FLUORESCENCE GLOW. This is a very deep blue color. It can appear wherever the electrons from the cathode can strike a solid object. It is caused by minor impurities, such as cobalt, in the object. The fast-moving electrons strike the impurity molecules, excite them, and produce photons of light of a characteristic color. This is usually observed on the interior of the plate, on the surface of the mica spacers, or on the inside of the glass envelope. THIS GLOW IS HARMLESS. It is normal and does not indicate a tube failure. Enjoy it. Many people feel it improves the appearance of the tube while in operation.

2) Occasionally a tube will develop a small leak. When air gets into the tube, AND when the high plate voltage is applied, the air molecules can ionize. The glow of ionized air is quite different from the fluorescence glow above--ionized air is a strong purple color, almost pink. This color usually appears INSIDE the plate of the tube (though not always). It does not cling to surfaces, like fluorescence, but appears in the spaces BETWEEN elements. A tube showing this glow should be replaced right away, since the gas can cause the plate current to run away and (possibly) damage the amplifier.

that doesn't answer mercurialuk's, unconvetional's or my question at all. We are wondering if the LACK OF ANY BLUE is a sign that the tube is NOT working since they LACK blue when in standby but when in play mode they glow blue indicating there are electrons in the tube. If a tube stays the same NON blue glow during standby and in play mode wouldn't that indicate that the tube is not working? I have two that are doing that and they are brand new almost but when i moved them to different sockets they STILL didn't glow blue. So the lack of glow follows the tube..

Mike:

You are correct if the tube stays EXACTLY the same in standby AND in operate mode then something is wrong. Some tubes don't glow that much and you have to move your head around to look for any blue inside the plates.

If you have 4 of the same tubes and 3 have a bright blue haze while 1 tube doesn't that should throw up a flag that something is wrong.

Let's not get confused, because not all tubes have a visible blue haze, like Sovtek tubes (AKA Mesa STR430's), so you have to do some investigating. A few things to check would be plate voltage, any type of blue glow inside the plate structure, and a lot of heat coming off of the tube. I know that JJ 6L6's and the Ruby 6L6's (aka STR440's) do not have very much visual representation when they are operational as a couple of currently made tube examples.

Greg

(I have ruby's by the way) On the tubes that don't have a blue glow on the outside I looked through the 2 slight gaps in the plate where you can see inside right to the filament. Image:

Inside there it glows a blueish color all along the filament but its not the same color blue as that you see on the outside of the other tubes. I did some looking around to make sure that it wasn't the blue reflection from another tube by blocking them with a thick card isolating the tube in question and it wasn't glowing blue on the outside at all. No change from standby to on except that the filament inside does in fact glow almost like a neon light does. Should I hunt down the bias resistors on the power board and check them for value? I have bent all the pin grabbers in the sockets inward to grab the tube pins so thats taken care of. I'm so close to having this amp work 100% and I got it for $546 from ebay. I hope that it was worth it. Honestly when I play on it i hear nothing wrong. Both channels sound the same in loudness and bass response (signs that the wattage is up). The preamp tubes are brand new, the power tubes are brand new... and the lack of blue follows the tube not the socket... Like I said in my earlier post is it possible doug sent me 2 bad tubes?

 

[disassembled]

If you see blue on the inside then they are more than likely fine. Try swapping the tubes and see if the glow stays with the tube. He could have given you 2 mismatched sets or maybe 2 of them are made differently. It doesn't seem like a big deal to me but if you want to get anal about it you should invest in a bias meter to see if the tubes are within a few mA's of each other.


Greg

 

[mikeymike]

If you see blue on the inside then they are more than likely fine. Try swapping the tubes and see if the glow stays with the tube. He could have given you 2 mismatched sets or maybe 2 of them are made differently. It doesn't seem like a big deal to me but if you want to get anal about it you should invest in a bias meter to see if the tubes are within a few mA's of each other.


Greg

I thought about it. I looked on the power board of the 2:100 and I think I located the bias resistors and boy are they in a hard to reach spot. Installing adjustable bias is probably really hard to do on a 2:100 yeah?

 

[disassembled]

It might require a little more work than one would like to do but that's up to you. Whatever you do make sure you don't burn up those traces.

Greg

 

[mikey383]

Not all tubes will glow, and it doesn't neccesarily mean that the tube is bad if it doesn't. It just means there are impurities within the tubes that do glow. I've had a matched quad where only one tube was glowing. The other 3 still worked fine.

If you are skeptical about if those tubes are working, the best thing to do would be what dissasembled said and get them tested on a tube tester.

If you have swapped tubes around and noticed no difference in dynamics from one position to the other, then chances are there is nothing wrong with them, and they just came from a different batch.

 

[mikeymike]

Not all tubes will glow, and it doesn't neccesarily mean that the tube is bad if it doesn't. It just means there are impurities within the tubes that do glow. I've had a matched quad where only one tube was glowing. The other 3 still worked fine.

If you are skeptical about if those tubes are working, the best thing to do would be what dissasembled said and get them tested on a tube tester.

If you have swapped tubes around and noticed no difference in dynamics from one position to the other, then chances are there is nothing wrong with them, and they just came from a different batch.

Cool deal man, you're probably right. I took a look at them again in the dark and I noticed that one of the two that I thought weren't glowing was indeed glowing. So I only have one that seems to not be glowing but inside near the filament there is a neon-tube like glow coming from it so, It's probably working just fine. I notice no difference in tone or dynamic (volume fluctuations or whatnot) so I'd say they're good. Thanks for clearing that up.