Tubes...Slight blue glow good or bad?

[charvel750]

Guys, I just had a tube head biased by a local tech. I noticed when you first power it on all the EL-34's glow orange, when you engage the standby, there is a small amount of blue glow from them. Is this normal? Tech says it's small amounts of air that got into the tube, not completely vacuum or something. The amp seems to play all right, and the tone is great, but that tiny blue glow, good or bad?

[thetroy]

Is the blue glow saying "Use the force, Luke"?

[Rupe]

Absolutely normal

[nsubulysses]

I usually get a blue glow in my tubes when I palm mute stuff.

It's been happening for like a year and it still sounds fine.

Why does that happen?

[chrisolson]

When I play my Mesa F100 in the 60 watt mode, the middle two tubes get the "blue haze", and when I kick it on to 100 watts, all four glow. It's kinda cool-looking... The amp sounds god-like, so I'm thinking the blue glow is not a problem (this coming from a Line 6 guy - be careful!!).

Gotta say, thanks to my SpiderValve, I've been pushed back into the tube world... There is something to be said for those little light bulbs.

[DonP]

Why does that happen?

Because that's how tubes work.

Tubes control electricity, turning it on an off (hence the UK term "valves"). The electicity comes from the heated (red) "cathode", and hits the "plate". What you are seeing (the blue glow) is the electricity "flying" through a vacuum just like lightning from the cathode to the plate. The "grid" is the spicket that turns the flow on and off. in simplistic terms, your guitar is hooked up to the grid, controlling the flow.

While the cathode is is meant to be hot (from the heater element), plates should not be red. If they are, the amp is biased too hot and will fry the tubes.

[Spivonious]

Normally a blue glow means some air got in there and is being excited by the electrons. This is how neon lights work (of course they're not all neon, since different gases emit different colors when "excited").

Completely normal of course, and nothing to get worried about. If the tubes start shooting lightning out at the glass of the tube (arcing), then it's time to get them replaced.

[Rsmacker]

Nicely put, Don. You too Spiv, but please tell me, what the fuck is a "spicket"???????

[Jayster]

a spigot is a ball valve ,that can throttle (restrict and allow)flow ,a spicket ?

[DonP]

Nicely put, Don. You too Spiv, but please tell me, what the fuck is a "spicket"???????

Damn brits, my bad

http://www.wsu.edu/~brians/errors/spicket.html

[charvel750]

Thanks, guys, I appreciate the answers, glad to know it's ok...