BLue hue

[Brap]

Probably nothing to worry about, but after about an hour or so, I 'm getting a slight blue hue from my 2A3 tubes on one channel alone of a 2 channel amp. I thinking it's slight manufacturing debris in the tubes?

thanks

 

[Colt45]

On the glass, or in the elements?

 

[Brap]

It's on the glass portion, near the "shoulder" if that 's the correct terminology

 

[Sch3mat1c]

Perfectly fine. I even have a 6SN7 that does it.

Tim

 

[PeteM]

Sounds perfectly normal Enjoy

 

[fdegrove]

Hi,

Maybe someone should explain, once again, where the blue hue comes from and how it will affect the useful life of a tube?

Don't ask, it won't be me doing the 'splaining again.

Cheers,

 

[Sch3mat1c]

It's on the glass portion, near the "shoulder" if that 's the correct terminology

Maybe someone should explain, once again, where the blue hue comes from and how it will affect the useful life of a tube?

Yeah yeah, blue glow on glass is perfectly fine, blue/purple/white glow from inside the structure might not be. I have some Russian 6L6s (erm.. 6pi3C-E or whatever) where the plate coating fluoresces light blue where the electron beam strikes it. I can barely see (due to visual obstructions and low current) the same in Hept'AU7's 12AU7s too. The real thing that you should worry about is a discharge between the cathode and plate, not a generic glow from inside.

Tim

 

[Duo]

Yeah, this is pretty simple. There are often just impurities in the glass or elsewhere in the tube that are easy to ionize and also emit light when this occurs. If the color shows right on the glass and not just floating inside the tube, then I see no problem.

I, like others here, have had tubes with a light glow on the glass or plates. They usually give me plenty of fine operation just like a tube that doesn't glow unusually.

 

[Majestic]

I've got one set of Philips/Siemens EL34's that do this.

I've never observed any sonic difference or penalty from having a blow glow from a set of tubes, but I've got to say thay look damn fine when listening to music in a darkened room!