blue glow in vacuum tube

scat7s · 01-20-2011, 05:52 PM

peeked in the back of my amp yesterday and noticed one of my rca 6v6's had a smallish spot of blue glow to it.

is this something i should be concerned about? i know ive read about this b4, but cant remember what the verdict was...it still sounds fantastic, but i did notice a faint pop now and then, nothing obnoxious, pretty subtle really. but a faint pop nontheless.

could these things be related?

diesect20022000 · 01-20-2011, 06:10 PM

no. large amounts will indicate ionization and slow tube death but, small amounts are normal.

Alabama Thunderpussy · 01-20-2011, 06:17 PM

Not at all. Blue glow is a common effect. If anything it can indicate a hotter bias. As I've understood it, it's a phenomenon that occurs when electrons and ions strike each other at high velocity inside the vacuum tube.

The glass envelope of the tube is actually very mildly conductive at high temperatures (inside the vacuum), hence the blue glow tends to gravitate towards certain areas of the bottle, as you'll notice. Sometime's it's just a spot, other times it's more of a fractal design.

Obviously, if you decrease the negative bias voltage (bringing it closer to 0, hence LESS negative) and more current is passing, more electrons are moving within the bottle and at a faster rate, hence more blue glow.

MartyStrat54 · 01-20-2011, 06:23 PM

When tubes are made, they pull a vacuum on the tube. The better the vacuum, the better quality the tube. Once the vacuum is pulled a device inside the tube called a getter is activated. The getter splatters a barium laced stain on the tube (generally on the top). This leaves a shiny, mirror-like stain on the tube. The purpose of the getter is to further eliminate any extraneous air left in the tube. The effects of the getter last throughout the life of the tube. Even though all of these precautions are used, all the air cannot be completely removed. The small amount of gas in the tube will cause the light blue glow you see. It is harmless.

In current production tubes, there is a chance for more air (gas) to be inside the tube. Therefore the blue glow is even greater.

scat7s · 01-20-2011, 06:30 PM

great, thanks guys.

RiverRatt · 01-20-2011, 08:54 PM

Be very worried if the gas in the tube is glowing violet. That's a tube that's getting air in somewhere. Beam power tubes seem to be more prone to the blue glow. I think I have some pics of each.

Here's a dying 5Y3:

This is a pair of 5881s with the blue glow:

big dooley · 01-21-2011, 02:16 AM

Quote:

Originally Posted by Alabama Thunderpussy

Obviously, if you increase the negative bias voltage and more current is passing....

INcrease the negative voltage on pin 5 and you DEcrease the amount of electrons flowing to the anode... that's how it works
yes i like screwing ants

Rahlstin · 01-21-2011, 01:00 PM

I think the blue glow is cool. A budy of mine had a Mesa amp back in the late 80's that looked like a purple and blue plasma storm in the back of the amp. He used that thing for years and years that way with no troubles.

Alabama Thunderpussy · 01-21-2011, 05:53 PM

Quote:

Originally Posted by big dooley

INcrease the negative voltage on pin 5 and you DEcrease the amount of electrons flowing to the anode... that's how it works
yes i like screwing ants

YES!! Thank you for catching that. I meant voltage increase as in closer to positive. I should have said DEcrease.

Fixed.

Now, tell the fine folks here WHY increasing the negative voltage on pin 5 results in a decrease of electrons flowing to the anode. ;-)

MM54 · 01-21-2011, 06:20 PM

It's more negative so it repels more electrons back towards the cathode (as like charges repel), preventing them from hitting the plate, or passing the plate and whacking their tiny little negative heads off the glass

scat7s · 01-21-2011, 06:58 PM

Quote:

whacking their tiny little negative heads off the glass

funny...

MM54 · 01-21-2011, 07:00 PM

Hey, you'd be blue too if you smacked your head off a piece of glass a few billion times thicker than you while traveling at the speed of light

MajorNut1967 · 01-21-2011, 07:36 PM

well great the baboons are loose!

MartyStrat54 · 01-21-2011, 08:37 PM

How about a misplaced circus chimp?

FourT6and2 · 01-22-2011, 02:40 PM

As others have said, blue glow is just an indication that there isn't a 100% vacuum inside the tube. That's normal. If the tubes glow blue while the amp is in standby, then you have a problem.

Wilder Amplification · 01-22-2011, 05:29 PM

IMO the blue glow in a valve is one of the most badass things about them. Looks kinda eerie on some of them.

demonufo · 01-22-2011, 06:58 PM

Mercury Arc Rectifiers;

YouTube - Hewittic Mercury-arc Rectifier of Manx Electric Railway

Now THAT'S badass blue glow.

scat7s · 01-23-2011, 01:25 PM

it is very cool looking, beautiful color.

topcat 70 · 01-23-2011, 03:41 PM

Quote:

Originally Posted by demonufo

Mercury Arc Rectifiers;
YouTube - Hewittic Mercury-arc Rectifier of Manx Electric Railway
Now THAT'S badass blue glow.

Ive seen a few of those Demon,mostly in old cinemas.I wouldnt want one to break if i was near it though!

demonufo · 01-23-2011, 04:30 PM

Quote:

Originally Posted by topcat 70

Ive seen a few of those Demon,mostly in old cinemas.I wouldnt want one to break if i was near it though!

Duck and cover...

01-20-2011, 05:52 PM	#1 (permalink)
scat7s Senior Member Join Date: Nov 2010 Posts: 7,718	blue glow in vacuum tube peeked in the back of my amp yesterday and noticed one of my rca 6v6's had a smallish spot of blue glow to it. is this something i should be concerned about? i know ive read about this b4, but cant remember what the verdict was...it still sounds fantastic, but i did notice a faint pop now and then, nothing obnoxious, pretty subtle really. but a faint pop nontheless. could these things be related?

01-20-2011, 06:10 PM	#2 (permalink)
diesect20022000 Senior Member Join Date: Sep 2010 Posts: 16,631	Re: blue glow in vacuum tube no. large amounts will indicate ionization and slow tube death but, small amounts are normal.

01-20-2011, 06:17 PM	#3 (permalink)
Alabama Thunderpussy Senior Member Join Date: Oct 2010 Location: Northern CA Posts: 1,343	Re: blue glow in vacuum tube Not at all. Blue glow is a common effect. If anything it can indicate a hotter bias. As I've understood it, it's a phenomenon that occurs when electrons and ions strike each other at high velocity inside the vacuum tube. The glass envelope of the tube is actually very mildly conductive at high temperatures (inside the vacuum), hence the blue glow tends to gravitate towards certain areas of the bottle, as you'll notice. Sometime's it's just a spot, other times it's more of a fractal design. Obviously, if you decrease the negative bias voltage (bringing it closer to 0, hence LESS negative) and more current is passing, more electrons are moving within the bottle and at a faster rate, hence more blue glow. Last edited by Alabama Thunderpussy; 01-21-2011 at 05:54 PM.

01-20-2011, 06:23 PM	#4 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Now in Muskogee, by Tulsa Posts: 18,267	Re: blue glow in vacuum tube When tubes are made, they pull a vacuum on the tube. The better the vacuum, the better quality the tube. Once the vacuum is pulled a device inside the tube called a getter is activated. The getter splatters a barium laced stain on the tube (generally on the top). This leaves a shiny, mirror-like stain on the tube. The purpose of the getter is to further eliminate any extraneous air left in the tube. The effects of the getter last throughout the life of the tube. Even though all of these precautions are used, all the air cannot be completely removed. The small amount of gas in the tube will cause the light blue glow you see. It is harmless. In current production tubes, there is a chance for more air (gas) to be inside the tube. Therefore the blue glow is even greater. __________________ MARTY MARTIMUS MAXIMUS ONLINE TUBES AND OTHER STUFFHyperlink Wilder modded JCM 2204 (Sold my JMP to Joe.). Many other amps. Strats and Explorer are my main guitars.

01-20-2011, 06:30 PM	#5 (permalink)
scat7s Senior Member Join Date: Nov 2010 Posts: 7,718	Re: blue glow in vacuum tube great, thanks guys.

Today
Marshall Amps	Sponsored Links __________________ This advertising will not be shown in this way to registered members. Register your free account today and become a member on Marshall Amp Forum

01-21-2011, 01:00 PM	#8 (permalink)
Rahlstin Senior Member Join Date: Jan 2011 Location: Lethbridge, Alberta Posts: 590	Re: blue glow in vacuum tube I think the blue glow is cool. A budy of mine had a Mesa amp back in the late 80's that looked like a purple and blue plasma storm in the back of the amp. He used that thing for years and years that way with no troubles.

01-21-2011, 06:20 PM	#10 (permalink)
MM54 Senior Member Join Date: Feb 2010 Location: Penn State Behrend, Erie PA Posts: 7,770	Re: blue glow in vacuum tube It's more negative so it repels more electrons back towards the cathode (as like charges repel), preventing them from hitting the plate, or passing the plate and whacking their tiny little negative heads off the glass __________________ -Matt If you don't understand what I'm saying, assume I'm making a joke. Trust me. Lachesky Amplifiers - Home of the CA10 Orders for 2013 CA10s are now being accepted! "... And I come from a place where they drag your hopes through the mud because their own dreams are all dying"

01-21-2011, 07:00 PM	#12 (permalink)
MM54 Senior Member Join Date: Feb 2010 Location: Penn State Behrend, Erie PA Posts: 7,770	Re: blue glow in vacuum tube Hey, you'd be blue too if you smacked your head off a piece of glass a few billion times thicker than you while traveling at the speed of light __________________ -Matt If you don't understand what I'm saying, assume I'm making a joke. Trust me. Lachesky Amplifiers - Home of the CA10 Orders for 2013 CA10s are now being accepted! "... And I come from a place where they drag your hopes through the mud because their own dreams are all dying"

01-21-2011, 07:36 PM	#13 (permalink)
MajorNut1967 Senior Member Join Date: Jul 2009 Posts: 3,901	Re: blue glow in vacuum tube well great the baboons are loose!

01-21-2011, 08:37 PM	#14 (permalink)
MartyStrat54 Senior Member Join Date: Feb 2009 Location: Now in Muskogee, by Tulsa Posts: 18,267	Re: blue glow in vacuum tube How about a misplaced circus chimp? __________________ MARTY MARTIMUS MAXIMUS ONLINE TUBES AND OTHER STUFFHyperlink Wilder modded JCM 2204 (Sold my JMP to Joe.). Many other amps. Strats and Explorer are my main guitars.

01-22-2011, 02:40 PM	#15 (permalink)
FourT6and2 Member Join Date: Dec 2010 Posts: 98	Re: blue glow in vacuum tube As others have said, blue glow is just an indication that there isn't a 100% vacuum inside the tube. That's normal. If the tubes glow blue while the amp is in standby, then you have a problem.

01-22-2011, 05:29 PM	#16 (permalink)
Wilder Amplification Senior Member Join Date: Oct 2009 Location: Fresno, CA Posts: 6,165	Re: blue glow in vacuum tube IMO the blue glow in a valve is one of the most badass things about them. Looks kinda eerie on some of them. __________________ Jon Wilder Wilder Amplification - The official home of the 80s cock of the walk "Schwank" http://www.wilderamps.com http://www.facebook.com/wilderamps

01-23-2011, 01:25 PM	#18 (permalink)
scat7s Senior Member Join Date: Nov 2010 Posts: 7,718	Re: blue glow in vacuum tube it is very cool looking, beautiful color.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode