In the early 1970's I built a stereo amplifier from plans published in Stereophile magazine. It used, I think, EL34's as the output tubes. Each plate had, on opposite sides of the tube, two oval cutouts, one above the other. The glass envelope had two places on each side that glowed purple; they were level with those cutouts and in the same shape. I guessed that the glow was from electrons passing through the cutouts and hitting the glass. I built it to drive a pair of KLH-9 speakers that I had splurged on. Man, do I miss that setup; these days it's YouTube through Bluetooth to some computer speakers.

Back to the point: I've never found out what I was being irradiated with while listening to that rig. Can anybody tell me that?

thanks

 

Nothing but purple light.

 

You get far more harmful radiation from our Sun than an electronic amplifier tube. That and the soup of electronic RF "noise" from the environment that we live in.

 

Electrons man. Just ordinary run-o-the-mill electrons.

 

Like this?

 

The glow is caused by residual gas in the tube, typically argon or nitrogen.
It is just light with no harmful radiation emitted.

 

Like this?

Only if the tube is an operating nuclear reactor.

 

Like this?

View attachment 364762

That's more of a blue color from the FTL (in water) particles light shockwave moving in water.

Nothing like tube glow. Poor example to use, unless it was a joke.

 

Cherenkov radiation - You are right. It was meant to be a joke.
I worked at a nuclear reactor and witnessed the blue glow daily.
(There is a personal story when I set off the radiation monitor.)

 

Not only EL34, but 6L6, KT88, 7591, even a lowly 6BQ5 would exhibit a blue glow that was modulated with the music.
And with the filament’s warm orange glow in the background, it was pure eye candy.

EDIT, bonus points: if the device used regulator tubes like the 0A2 that glow purple.

 

EDIT, bonus points: if the device used regulator tubes like the 0A2 that glow purple.

Sorry, full-wave silicon bridges.

 

The glow is caused by residual gas in the tube, typically argon or nitrogen.
It is just light with no harmful radiation emitted.

But I saw the glow coming from the glass, not from the gas inside.

 

https://www.thetubestore.com/blue-glow

FLUORESCENCE (Photo 1)- 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 particularly 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. (Note from thetubestore: Mercury Vapor tubes are rare and almost never found in common guitar or hifi amplifiers)
GAS (Photo 2)- 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.”

 

This has gotten me interested in having a go at resurrecting this thing. Any tips on finding new B+ filter capacitors. The ones in there now are 500 MFD 310 VOLTS; each channel has two of them in series.

The power supplies are mostly military surplus that I collected over a number of years. Separate chassis that I don't remember every trying to lift.

 

View attachment 364790

Right; that's exactly what I remember, except that my ovals run horizontally and are stacked vertically. Might it be that the cutouts in the plate are there to produce this glow so that one can tell at a glance that the tubes are ok?

 

Like this?

View attachment 364762

Is it the Cherenkov effect from a Nuclear Plant ?

 

Is it the Cherenkov effect from a Nuclear Plant ?

Yes it is; MrChips was joking.

nsaspook's post above tells all, with pictures even.