so I fell for the snake oil

[cbass]

Burned em in for several hours all within 1mA of each other
I noticed when I hit the low e there's a bit of a purple kinda beam I can see reflecting off the mica spacer . I need to go back over when its dark and check again.
I doesn't seem like arcing it builds and dissapears with the loudness of the note.

[cbass]

I'm gonna drop the bias splitter resistors from 220k to 100k . good idea?

[martin manning]

The purple glow is not necessarily a symptom of something going wrong; some tubes will do it at idle. I wouldn't wory about the bias feed resistors either unless you see red plating after setting what should be a reasonable idle bias, or you get blocking distortion when you hit big chords. Those would be symptoms of bias excursion due to too much impedance to ground (the bias supply voltage) in the grid circuit.

[matt h]

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[martin manning]

I don't know if it is more common in beam tetrodes, but that is where I have seen it personally. The source is supposed to be stray electrons hitting the glass, so it would depend on the internal construction of the electrodes and the support structure.

[matt h]

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[Structo]

I've read various theories why some tubes glow with that blue/purple color.

Contaminates in material or gasses, low vacuum, getter problems, etc.

What most agree on is that it doesn't necessarily mean the tubes are defective or failing.

I think I had some TAD tubes do that as well as a Tung Sol RI 12ax7.

http://www.thetubestore.com/Resources/M ... /Blue-Glow

[cbass]

Just reporting that after maybe 20 or 30 hours of rockin tubes are still tightly matched and sound great .

[Structo]

Cool!

[cbass]

Yup and if you turn the lights out and plauy real loud that purple glow really gets goin

[matt h]

(deleted)

[Zippy]

Yup and if you turn the lights out and plauy real loud that purple glow really gets goin

That should be sufficient reason to play loud with the lights out.

[cbass]

To bad the neighbors can't see. Im Sure they can hear it.

[JazzGuitarGimp]

I love the purple glow. Of course, I love just about anything purple... 😄

[TUBEDUDE]

What's the difference between pink and purple? ..... The grip!