Tube question--what does a round black mark on the side...

[racerevlon]

of the tube mean? I had a quad of 6550's in a VH4 for a few months and I just pulled them and replaced them with a set of EL34s. The 6550s each have a round black/scorch mark on the side of the tube on the inside, all in the same specific place where there's a small circle on the inside of the glass. Anyone have any idea what this means? Were they over/under BIAS'ed? Is this just a normal sign of use?

I'll try and get pics in daylight tomorrow.

Cheers,

 

[glpg80]

its barium. glass envelopes are pulled to a vaccum and the barium is used to clean the air during the sealing process. the mica/mercury colour is the effect of a near vacuum atmosphere inside of the tube, if the tube were to lose vaccum this metal would turn snow white.

the black mark could possibly be due to the soot of the flame as the glass envelope was in its sealing process.

as long as there is vaccum, electrons can move more freely, and the tube will function as designed. otherwise it does not matter.

 

[racerevlon]

Thank you!!!

 

[gibson08]

its barium. glass envelopes are pulled to a vaccum and the barium is used to clean the air during the sealing process. the mica/mercury colour is the effect of a near vacuum atmosphere inside of the tube, if the tube were to lose vaccum this metal would turn snow white.

the black mark could possibly be due to the soot of the flame as the glass envelope was in its sealing process.

as long as there is vaccum, electrons can move more freely, and the tube will function as designed. otherwise it does not matter.

Well, That clears it up. I have seen this on some tubes as well, but never had a problem so figured it was ok.

 

[Mailman1971]

its barium. glass envelopes are pulled to a vaccum and the barium is used to clean the air during the sealing process. the mica/mercury colour is the effect of a near vacuum atmosphere inside of the tube, if the tube were to lose vaccum this metal would turn snow white.

the black mark could possibly be due to the soot of the flame as the glass envelope was in its sealing process.

as long as there is vaccum, electrons can move more freely, and the tube will function as designed. otherwise it does not matter.

Well, That clears it up. I have seen this on some tubes as well, but never had a problem so figured it was ok.

I was going to say thats the Magic Fairy Pixie Dust.....but didnt want to look foolish.

 

[Jimmie]

I was going to say thats the Magic Fairy Pixie Dust.....but didnt want to look foolish.

with that kinda dust, it doesn't matter how foolish you look, at the same time you just don't give a shit.

heh

 

[Mailman1971]

I was going to say thats the Magic Fairy Pixie Dust.....but didnt want to look foolish.

with that kinda dust, it doesn't matter how foolish you look, at the same time you just don't give a shit.

heh

Yup.....and Fairies Wear boots....Ya gotta believe me.....I saw it with my own two eyes.....