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blue glow inside the tubes - good or bad?

OK yous guys always pick up on weird things I would do during the 60's with tube audio my Dad owned. I would watch in amazement the blue glow, either on the glass or the inside of the plates flickering with the music, when turned up.
I built a copy of a Dukane 100 watt PA amp using 4 ea 6CD6's and an 0D3 VR tube regulating the screens, and it would blink with the music also.

Fred
 
Fast_Eddie said:
I'm pretty sure that particular glow means you need to give me your speakers...
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:D:D:D:nono::nono::nono:
I actually tried the the tube amp on several different speakers. Same problem. I thnk it woulod be easier to give you my tube amp. :yes::nono:
 
GordonW said:
Actually, it's more likely Bremsstrahlung radiation... :scratch2: :D

Regards,
Gordon.
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From Wikipedia:
Bremsstrahlung (pronounced [ˈbʁɛmsˌʃtʁaːlʊŋ] (help·info), from German bremsen "to brake" and Strahlung "radiation", i.e. "braking radiation" or "deceleration radiation"), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. The term is also used to refer to the process of producing the radiation. Bremsstrahlung has a continuous spectrum. The phenomenon was discovered by Nikola Tesla[citation needed] during high frequency research he conducted between 1888 and 1897.

Just an FYI - tried to understand this, and I get the most basic understanding of it. I think I will still call it the "purty blue glow" or PBG instead.:D

Gordon, Thanks for the insight and help on all of this stuff - it is appreciated!
 
GordonW said:
Actually, it's more likely Bremsstrahlung radiation... :scratch2: :D

Regards,
Gordon.
Click to expand...


Mebbe? I just pulled out the first scary-sounding thing that popped into my head when I hear blue glow...the nuclear reactor cores submerged in water.

I haven't a clue if it's even remotely related. :dunno:
 
Jcricket said:
From Wikipedia:
Bremsstrahlung (pronounced [ˈbʁɛmsˌʃtʁaːlʊŋ] (help·info), from German bremsen "to brake" and Strahlung "radiation", i.e. "braking radiation" or "deceleration radiation"), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. The term is also used to refer to the process of producing the radiation. Bremsstrahlung has a continuous spectrum. The phenomenon was discovered by Nikola Tesla[citation needed] during high frequency research he conducted between 1888 and 1897.

Just an FYI - tried to understand this, and I get the most basic understanding of it. I think I will still call it the "purty blue glow" or PBG instead.:D

Gordon, Thanks for the insight and help on all of this stuff - it is appreciated!
Click to expand...

Cerenkov radiation is even cooler. The speed of light is different in different media (and in a vacuum). A very fast particle may be at sublight speed in one medium, but, if it crosses into a medium with a different refractive index, it would be going "faster than light". Einstein says it can't do that, so it's gotta lose some energy. Thus the blue glow. This may be seen in old-school water-cooled nuclear reactors (like the one I have...).
 
Reviving this old thread as i also recently encountered blue tube glow.
Here is the simplified story: bought tube my first tube amp, a HK A300, and first thing i did a complete recap. Then bought new tubes, and yesterday i cleaned the tube sockets from the power tubes. After the operation i plugged it in to see if it is all ok, as i had some weird stuff happen once in a while, and was surprised by a blue glow from the 6p6s tubes. Until now the tubes were dimm, so i turned the amp of, as a precaution.

Now i wanted to hear some expert oppinions if this is one of the good blue glows, or the bad kind. Here is a bad foto i took last night.

20220706_234550.jpg

Thank you in advance and regards
Robert
 
That blue glow looks a little excessive but as long as it sounds good and the plates themselves are not red plating, you are fine but I gotta ask if it was a typo when you said the tubes are 6P6's?

They should be 7408's which are a 6V6GT variant.
 
cademan said:
That blue glow looks a little excessive but as long as it sounds good and the plates themselves are not red plating, you are fine but I gotta ask if it was a typo when you said the tubes are 6P6's?

They should be 7408's which are a 6V6GT variant.
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Thank you for your input. It is a big excessive as i took the photo at night, so it looks more intense than it is.

The 6P6S is a russian version of the 6v6gta/7408 - as i unnderstan it sits right inn between regarding the specs. Here is a link with some more info:
https://www.radiomuseum.org/tubes/tube_6p6s.html

Is it not weird that this phenomenon started after cleanning the tube sockets? Might the amp have not worked 100% until then?
 
You should be fine as long as they are not red plating. I remember my original 7408's looking like those also.
 
A blue glow along the glass inner surface is fine. If you see blue glow inside the plate area among the tube's electrodes, then that can be troublesome.
 
What problem(s) might exist when the blue glow is inside the plate rather than on the glass surface? Isn't this also normal with some tubes and high plate voltage?
 
It is hard for me to visualise where the glow is located, as the tubes are coated black on the outside, only the top is clear. But still it appears as the plates have a faint blue glow that is only visible at night.
 
@robiles : that blue in your tubes, combined with what looks like overheating plates looks to me like something's off voltage-wise in those tubes. The blue in your tubes seems excessive in my rather limited experience. Compare to other pics in this old thread. I'll bet they're overheating along with the nuke-action inside. I'd be checking voltages on plates, grids & bias supply.
 
The blue on my Westinghouse 7591 tubes usa made blue light goes with the beat of the music sorta cool to watch at night
 
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