what does it mean when your tube glows white?

***BillSPrestonEsq*** · 09-09-2006, 11:04 AM

Okay, I was tampering with a tube amp of unknown wattage yesterday, and hooked a preamp up to it. However, when everything was dimed it sounded great, however, when I would play hard, the glow would go from a normal ble to a brilliant white.

Red is bad, blue is good, but what does white mean? That I am driving the power tube too hard?

I was assuming driving it that hard would cause a shorter tube life, but is there a danger here?

**thesteve** · 09-09-2006, 11:49 AM

do you know what brand/type of tube they are?

a white-blue glow might be a sign of a gassy tube, though apparently mercury rectifiers will naturally glow a white-violet color.

***BillSPrestonEsq*** · 09-09-2006, 11:55 AM

Quote:

Originally Posted by thesteve

do you know what brand/type of tube they are?

a white-blue glow might be a sign of a gassy tube, though apparently mercury rectifiers will naturally glow a white-violet color.

A very old RCA 6v6. I forgot to mention it was the power tube. I doubt the latter since the rectifier is a different tube.

**thesteve** · 09-09-2006, 12:08 PM

hmmm...I actually have a 20W tube amp loaded with 4 RCA 6V6s around the house. If I get the time and circumstances that allow me to try to look for the glow later today, I will. I can't actually recall seeing those tubes have any other glow than the normal orange filament glow.

Would you be able to take a picture and post it up to give me a better idea of what I'm looking for?

***BillSPrestonEsq*** · 09-09-2006, 12:18 PM

Quote:

Originally Posted by thesteve

hmmm...I actually have a 20W tube amp loaded with 4 RCA 6V6s around the house. If I get the time and circumstances that allow me to try to look for the glow later today, I will. I can't actually recall seeing those tubes have any other glow than the normal orange filament glow.

Would you be able to take a picture and post it up to give me a better idea of what I'm looking for?

Not at the moment, but it was kind of the normal bluish glow that went to a much brighter white. Without the preamp attached they did not drive and only glowed with the fillament glow.

nate95366 · 09-11-2006, 09:38 AM

I would take it to mean that instead of there being a dominant gas inside the tube, you have more of a mixture. Vacuum tubes still have some gaseous material inside them, even though they're called "vacuum" tubes. The moving electrons inside the tube will impart energy to the gaseous atoms/molecules, causing them to glow. Generally, each type of gas by itself has a characteristic "glow color." A mixture would appear to give off more or less white light. The whole "red is bad" thing actually comes from seeing the solid parts inside the tube glowing a brilliant red (instead of a dull orange/red).

This might mean that your vacuum is failing a little faster than other tubes. Once the vacuum truly fails, though, the tube will have a very hard time of doing its job and you will notice it as a playability problem.

Nate

***BillSPrestonEsq*** · 09-11-2006, 05:18 PM

Quote:

Originally Posted by nate95366

I would take it to mean that instead of there being a dominant gas inside the tube, you have more of a mixture. Vacuum tubes still have some gaseous material inside them, even though they're called "vacuum" tubes. The moving electrons inside the tube will impart energy to the gaseous atoms/molecules, causing them to glow. Generally, each type of gas by itself has a characteristic "glow color." A mixture would appear to give off more or less white light. The whole "red is bad" thing actually comes from seeing the solid parts inside the tube glowing a brilliant red (instead of a dull orange/red).

This might mean that your vacuum is failing a little faster than other tubes. Once the vacuum truly fails, though, the tube will have a very hard time of doing its job and you will notice it as a playability problem.

Nate

Would this be somewhat normal in an ancient tube?

seriously, it could be 50 years old. Replacing it does not bother me at all. I was more concerned if I was going to frag myself with glass shards or start a fire or something.

**thesteve** · 09-11-2006, 05:26 PM

Quote:

Originally Posted by BillSPrestonEsq

Would this be somewhat normal in an ancient tube?

seriously, it could be 50 years old. Replacing it does not bother me at all. I was more concerned if I was going to frag myself with glass shards or start a fire or something.

it could be normal, as a result of a microscopic crack in the glass that's allowing a very small amount of gas in there.

I would think that the tube would fail before either exploding or catching fire though.

***BillSPrestonEsq*** · 09-11-2006, 05:38 PM

Quote:

Originally Posted by thesteve

it could be normal, as a result of a microscopic crack in the glass that's allowing a very small amount of gas in there.

I would think that the tube would fail before either exploding or catching fire though.

I would hope so... then again I have been having a string of bad luck. I am a bit gunshy at the moment.

**thesteve** · 09-11-2006, 08:33 PM

just to let you know Bill, I ran the little experiment I wanted to run.

here's what my chain looked like
Jagstang (SD JB in the bridge)-->J&H-->magnetic phono input (most sensitive input on the amp I think)-->Celestion G12M speaker.

I left the EQ flat, turned the drive down to zero on the J&H and dimed the volume (going for pure gain boost). I then dimed the volume on the amp...

This thing has three RCA 6V6 "Radiotron Electron tubes", and a fourth 6V6 from some other manufacturer.

and none of them show any fluorescence at all...they don't do blue, purple, white...anything...I was kinda bummed.

xevan · 09-13-2006, 09:29 AM

you sir have an oxygen leak it sounds like :/ not a big deal but can cause problems. I'd go down to your local music/guitar store and try to get some hands on advise.

Major Tom · 09-13-2006, 10:18 AM

I don't think I've ever seen any glow white....

I'm not 100% sure, but it seems that years ago I read that the blue glow in power tubes is an indication of age or wear, and/or maybe a less than perfect "vacuum" or gas content; that new tubes shouldn't glow blue. With as many years as I've been playing thru tube amps, I haven't really paid that much attention tho, the tubes are always in the back of the amp.

**thesteve** · 09-13-2006, 10:23 AM

Quote:

Originally Posted by Major Tom

I'm not 100% sure, but it seems that years ago I read that the blue glow in power tubes is an indication of age or wear, and/or maybe a less than perfect "vacuum" or gas content; that new tubes shouldn't glow blue. With as many years as I've been playing thru tube amps, I haven't really paid that much attention tho, the tubes are always in the back of the amp.

From what I've read, it tends to vary from manufacturer to manufacturer. Both the stock power tubes I had in my HRDlx and the replacement JJ tubes showed blue fluorescence.

***BillSPrestonEsq*** · 09-14-2006, 09:01 AM

Quote:

Originally Posted by Major Tom

I don't think I've ever seen any glow white....

I'm not 100% sure, but it seems that years ago I read that the blue glow in power tubes is an indication of age or wear, and/or maybe a less than perfect "vacuum" or gas content; that new tubes shouldn't glow blue. With as many years as I've been playing thru tube amps, I haven't really paid that much attention tho, the tubes are always in the back of the amp.

This will be in the back eventually. (Once I make a cab) Right now its a point to point wired hi-fi tube amp, soon to become a guitar amp.

Major Tom · 09-14-2006, 10:28 AM

Quote:

Originally Posted by BillSPrestonEsq

This will be in the back eventually. (Once I make a cab) Right now its a point to point wired hi-fi tube amp, soon to become a guitar amp.

Cool project ! Keep us posted on how that works out. I used to have a couple old tube amps scavenged from late 50's jukeboxes, still kicking myself for throwing them out some years back...