Tubes glowing

[Coytee]

Wright 2A3 amps

I know now that tubes can flouresce. The tubes in my Jolida amp will glow but it seems that the glass itself is glowing, sort of like how your shirt glows when a UV light is turned on. What I found different about this was the glow in the 2A3 tubes seemed to be INSIDE the tube, as though the gas inside was glowing.

Also, (drawing an analogy) you've seen a neon sign before where a section of the neon flickers in an on/off fashion rather than a "glow off/glow on" fashion (did that make ANY sense? ) These flick on/off, more like a lightswitch.

The glow in the 2A3's was not the glass, but was inside the tube. Furthermore, it flickered. I figured the flickering would be somewhat in sync with the beat as the power went in/out of tube. I didn't notice ANY correlation with that. I gently flicked the tube with my finger to see if perhaps that might affect it....it didn't.

I've had these tubes in for while now (Sovetek) and honestly, have not noticed this before.

When I turned the power off, the glow went out almost immediately and came back on when I turned the power on.

With all that said, I know not to worry about the GLASS of the tube glowing, but since this was inside the tube is it a precursor to anything bad?

[Colin]

I've never heard of this before and I think since it is supposed to be a vacuum inside, that such a thing is not possible-

unless like a neon tube, there is a a non-flamable gas inside that is excited by the elements (doubt it)-

so I am guessing that what you are seeing is reflection from the curved insdie of the glass....

[Coytee]

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On 8/12/2005 8:17:49 AM Colin wrote:

so I am guessing that what you are seeing is reflection from the curved insdie of the glass....

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If in fact it's a reflection (which it may be), then that infers it'd likely be the glass fluorescing?

If the glass has what ever impurities in it to cause it to glow... wouldn't it glow ALL the time rather than flicker off?

I mean, would you expect that if you turn lights out, have a UV light on and your shirt is glowing...that it (shirt) would flicker OFF even though the UV light is still on?

Life seemed so much more simple when I had no clue about tubes and their idiosyncrasies

[3dzapper]

Cool ain't it?

http://forums.klipsch.com/idealbb/files/300bweb1.jpg

Rick

[Colin]

looks like they are overheating the tubes to get more power out of them...

[Duke Spinner]

long as the Screen, or grid isn't glowing Red, don't worry ..

Gassy tube is all ...low quality vacuum on import's...???

[sunnysal]

blue glow is NOTHING to worry about, in fact is means you have VERY good vaccum:

http://www.jacmusic.com/html/articles/blueglow/blueglow.htm

enjoy!

tony

[sfogg]

"I've never heard of this before and I think since it is supposed to be a vacuum inside, that such a thing is not possible- "

Except there isn't a perfect vacuum in most tubes. I have read that the blue glow is from gases inside the tube. I had a quad of EL-34s years ago that did that and I've seen it in other tubes too.

" looks like they are overheating the tubes to get more power out of them.."

When tubes are overheating the plates tend to glow red hot. It is very obvious once you see a tube do it.

Shawn

[marting]

The Chinese 2A3s that came with my Bottlehead kits had a nice blue glow. I replaced them with Sovteks. I really like the sound of the Sovteks but sadly they don't glow like the Valve Arts. It's mainly about the sound though, so the Valve Arts are in storage.

Martin.

[JJkizak]

Sunnysal:

You have to be kidding ,right? The blue glow is caused by gasses inside

the tube. The tubes have "getters" to constantly remove the gas as the people that designed the tubes did not want any gas to interfere with electron flow, that's why they are in a vacuum. Audio wise won't make much difference but RF wise it's a disaster. In the tube days (you are trying to relive a dead issue) blue glowing tubes were tossed out and discarded like maggets on a dead racoon. The more gas in the tube the more the electrons are deflected, hence more noise, lower performance, more intermodulation distortion etc.

JJK

[sunnysal]

I wasn´t kidding, everything I have read on this on the internet says not to worry...i.e.

http://members.aol.com/larrysb/blue_glow.html

"Blue Glow In Tubes FAQ

This document is intended to address the frequently asked questions reguarding the blue glow frequently seen in power electron tubes or valves. I welcome contributions, criticisms and corrections. Please send your comments to: larrysb@aol.com

Q: "My tubes are glowing blue. Should I worry?"

A: No. Blue glow is perfectly normal. It's an artifact of operation of the tube. If the amp is otherwise working fine, relax and don't worry about it all.

Q: "Does the blue glow mean my tubes are 'gassy'?"

A: No. Gassy tubes are characterized by excessive grid currents and other poor performance characteristics. Extremely gassy tubes may glow with a pinkish cast throughout the entire tube. A faint blue glow on the glass, or inside the plate structure is completely normal. In fact tubes exhibiting this glow are frequently lower in residual gas.

Q: "My amp cuts out sometimes. When it does, I see the tubes stop glowing momentarily. Does this mean I should change my tubes?"

Q: "My tubes glow blue when the standby switch is on, and stop glowing when it is off. Is something wrong?"

A: Tubes will usually glow blue when the tube is in operation with voltage applied. When you cut the standby switch off, this interrupts the voltage applied to the output tubes, and they stop glowing. If your amp has a problem and the sound cuts out, taking the glow with it, the problem is not caused by the glow. The glow interruption is merely a symptom of whatever is causing your amp to cut out in the first place

From "Sylvania Engineering Data Service", vol. 1, pg 23 (1960?):

BLUE GLOWS

Blue Glows are not tube detriments per se. They are, however, suspects in the eyes of many receiving tube users for lack of a full understanding of their origins. There are several types of Blue Glow which can be described as follows:

FLUORESCENCE-this type of glow is usually violet in color and most noticeable around the inside surface of the glass bulb. It is most pronounced on power tubes and is the product of electron bombardment of the glass taking place within the tube. It generally has no adverse affect upon receiver performance, and in fact, tubes displaying this phenomenon are particularily good with respect to gas content.

MERCURY VAPOR HAZE-is a blue-violet glow associated with those tube types which rely upon mercury vapor for proper operation. In such cases, the blue glow should be evident indicating proper operation.

GAS-produces a blue haze, generally confined to the vicinity of the mount structure. The proper function of gas types such as thyratrons, voltage regulator and voltage reference tubes, requires the presence of this glow as an indication of proper tube operation. Some voltage regulators use neon instead of argon and as a result exhibit a pink-orange glow. It is, however, a distinct detriment in vacuum receiving types, where the presence of gas in large amounts can cause malfunction of the equipment.

Submitted by:

Doug Haugen

All About The Glow

Tubes operate on the principle of thermionic emmission. A heater filament heats the cathode until it glows a dull red. The cathode is made of materials that can emit electrons at high temperature. The tubes plate is held at a high positive voltage, which attracts the electrons emitted from the cathode. In amplifier tubes, the flow of electrons is controlled by one or more fine wire screens or grids placed in between the cathode and plate. The flow of electrons is controlled by varying the voltage applied to the grid. A small change in grid voltage results in a larger change in electron flow through the tube, amplifying the signal applied to the grid.

Many materials flouresce or "glow" when struck by electrons. Not all the electrons in a vacuum tube strike the plate. A few stray off and strike other things in the tube, such as the glass envelope. Many types of glass will give off a faint blue glow when bombarded by electrons of sufficient energy. This is the most common type of blue glow seen in power output tubes. Often you will see small patches of glow that correspond to the holes in the plate or other structures in the tube.

Another type of glow you may see in power tubes appears on the inside surface of the plate structure. The pattern of the glow will aften appear in strips that vary along with the signal applied to the tube. (i.e., the music.) This type of glow is generally normal as well. It is often caused by a thin layer of atoms that have boiled off the cathode and deposited on the surface of the plate. What you see is the slight flourescence of this material when it is hit by electrons from the cathode. The stripes correspond with the alignment of the grid wires. The varying widths of the stripes demonstrate the operation of the tube. The grid allows restricts the size of the electron beam according to the grid's voltage."

http://www.webace.com.au/~electron/tubes/blueglo.htm

"Transcribed for your convenience from "RADIOTRONICS"Technical Bulletin No. 39 - 24 February 1936

Radiotronics was published by the Amalgamated Wireless Valve Co. of Australia using technologies derived from RCA USA, Marconi, Telefunken and others.

FLUORESCENCE and BLUE GLOW

With modern valves a blue colour is frequently observed (either steady or flickering) on portions of the bulb wall; this is a phenomenum known as "fluorescence" and is somewhat akin to X-ray fluorescence and is due to electron bombardment of the glass.

The colour of this glow and its intensity depend on the nature of the glass, the voltages employed, and the design of the valve.

It has no deleterious effect, however, and actually is a sign of an extremely high vacuum.

It is particularly prominent with type 42, but may also be observed on other types, such as 6A7, 6C6, 6D6, but since in these types a black coating is used inside the bulb the fluorescence is rarley noticed.

Blue glow is a glow between electrodes caused by ionised gas. It is never observed in a really hard valve, but there are certain types in which a very slight glow may be observed which, although indicating a very small amount of gas, is not deleterious to the valve; for example this sometimes applies to type 50.

When any appreciable glow is observed inside the plate, the valve is definitely defective, due to gas, and a negative grid current will be observed if a micro-ammeter is placed in the grid return circuit. A valve reading less than 1 micro-ampere for each 10 milliamperes of anode current is quite satisfactory, and even two to three times this amount of negative grid current is usually quite permissible.

When a valve becomes very gassy, the blue glow frequently extends in the shape of streamers radiating from the ends of the anode, and the valve in this condition is completely unusable.

In high vacuum rectifiers used at voltages not exceeding 400 volts, a small amount of blue glow is not detrimental and may be rather beneficial. High voltage rectifiers, on the other hand, must have an absolute minimum of gas.

Occasionally fluorescence may be seen on the inside surface of the anode or grid; this fluorescence may be easily distinguished from blue glow by the fact that it is a thin film and does not spread through the space between the electrodes.

All types of fluorescence are completely harmless."

There are plenty of other places to find the same info...regards, tony

[D-MAN]

Gentlemen, that is what is known as "plasma" ; a heated and/or electrically charged gas. Those are fluorescing gas particles in actuality. Just like the Aurora Borealis and Australis...

In order to make a vacuum inside the tube a substance is burned which uses up all the oxigen, leaving a semi-vacuous (when it cools) exhaust gas-filled glass tube.

DM

[Randy Taylor]

Wow! "different colors in my tubes" what are you guys smoking, and where can I get some! Just kidding, my EH7591A's on my Mac 225 did the same thing when I first got them, some weird blue cloud inside the tube and after about 200 hundred hours it went away and I asked my tube dealer about it and I was told it was bad gases burning off and not to worry about, and I stopped worring about it because it made sense to me, and it didn't hurt anything and went away.

[codhead]

If you spot a significant pink glow inside the plate structure, I'd recommend immediately shutting down the amp, and replacing the tube.

I purchased a NOS pair of Tung-Sol box plate 2A3's, tested them with my TV-7D/U, and installed them in my amp. They ran without a problem for an entire weekend. I powered up my amp the following Monday night, and happened to spot a bright pink glow as I was walking by a short time later (did not affect the sound). I shut down the amp, and put the suspect tube back in the tester. The tube tested perfectly, but when I hit the gas button the plate/filament arc'd so badly it looked just like a 4th of July sparkler. The TV-7's "fuse" is a light bulb, which lit up like the sun - whole lotta current going on. Probably would have been ugly if this happened with the tube in the amp.

Every Western Electric 300B I've seen has the blue glow (around the upper mica) but none of the KR or AVVT "High Vacuum" tubes - at least the ones I've owned - have it. A brownish-color deposit also seems to form on the glass in the area of the blue glow (WE, Valve Art, TJ, Sophia).

[JJkizak]

Sunnysal:

Well, you really torpedoed my boat and I am sinking fast. A couple of things, I wasn't speaking of gas thyratrons (I worked on them in military amplidyne drives). I used to watch my Fisher finals pulse blue glowing variations every time there was a bass note and passed it off as cheapo junk but it did not seem to have an effect on things. Now I find out it was engineered for the "drug" generation that liked to watch bright pulsing lights in time with the beat. It is kind of cool though to see the tubes straining to get those huge notes out. It might help the efficiency of the tube to encircle it with a magnetic adjustable coil to focus the electron stream and keep the stray electrons from bouncing away from the main stream. Then again it might concentrate it so much you might burn a hole in the plate.

JJK

[sunnysal]

the rule is; Pink is bad and Blue is cool...LOL, tony

BTW not trying to shoot anyone down, hope it didn´t seem like that, I just didn´t want coytee worrying about something that is pretty normal, some would say "cool"

[Coytee]

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On 8/14/2005 5:29:19 PM sunnysal wrote:

the rule is; Pink is bad and Blue is cool...LOL, tony

BTW not trying to shoot anyone down, hope it didn´t seem like that, I just didn´t want coytee worrying about something that is pretty normal, some would say "cool"

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Well I'm back

I'm not terribly concerned as much as I'm very intrigued.

With my KT-90's, they have a consistant glow. The glow is clearly the glass. The glow disappears when the power is turned off.

With the 2A3, the glow is more of a cloud inside the tube. It will also blink out and blink back on with no discernable pattern relative to the music. The glow disappears when the power is off.

[mike stehr]

Yup. I bought a 5930/2A3 NOS tube. Worked fine for about 25, 30 hours.

After that it developed a little pinkish purple patch on the bottom mica spacer, and then the static noise came.

Then it moved to the plates, a pink spot or spots, it moved around. The noise continued, and then the tube would pop now and then.

One thing I noticed is when you would hit "pause" on the CDP, the static noise would stop. Hit "play" and it would return. Like once some signal voltage hit the grid, it made noise.

Eventually, the noise never went away....

I use some Sovtek 2A3's now, one does the blue glow around the top of the glass envelope, the other doesn't do anything.

Now I know that the blue glow ain't nuthin', and I have some 47 pentodes that indicate the glow in their data, but I'm with JJ. It bugs me for some reason.....

I like the light bulb effect of a thoriated tungsten filament.

[mike stehr]

"With the 2A3, the glow is more of a cloud inside the tube."

Is it just the straight blue glow, or does it have a bit of pink or white in that cloud you describe?

Who knows......

[Southern]

My avaitor is a picture of my EL34's from my 40+ year old Dynaco ST-70.

Love that blue glow.