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I did do a search and found black flashing to be okay, in fact normal in some tubes like Mullards but in those cases, they came that way.I installed a new set of EH6922's in my preamp about 6 months ago all with shiny silver flashing. One of 6922's has turned to black (not dark grey). I know what white means, but what makes it turn black? and because it wasn't originally black, does it indicate anything is wrong with the tube?
Edits: 09/21/15Follow Ups:
for the record:
I didn't even know it had turned black. The CJ ART preamp has a tube cage over the tubes and I couldn't see any of the tops of the tubes but I had been noticing that the left channel was sounding better than the right. It was when I went to put in a new set of tubes in that I noticed the one "black" top in the weaker channel. Just one of those coincidences.
btw, not only did the new set of tubes balance everything out, it made everything better. I was reminded why I love the ART so much.
Great link JKT, thanks. Now if I can just find 9 more "black tops" so I'll have the 10 I need for the ART. :-)
I found this posted on the DIY Audio site:
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
That article is NOT correct about rainbow-colored flashing. Several years back, I bought a small lot of NOS 211 tubes. A number of them had flashing that was only about 1/10 to 1/4 the area of normal. The flashing in those tubes was very thin, somewhat see-through, and was rainbow colored starting at the edges and extending into the flashing to various degrees. Every tube with that degraded flashing produced a nasty internal arc when 1KV anode voltage was applied. They were useless in my amplifiers, and I lost a lot of money on the deal. I'm not sure the rainbow symptom affects smaller tubes the same way, but I'll never buy tubes again that look like that.
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Buy Chinese. Bury freedom.
In the last paragraph he writes:
"Let us make a blanket statement, to adequately cover the subject of tube viability: the only way to accurately determine the health of a tube is to test it electrically. Period. Anyone who discards a tube, because its getter flashing is slightly discolored, is wrong."
NOS Sylvania and Philips tubes are notorious for having "rainbow" edged getter flash. It's completely normal. And the vast majority of them test just fine.
So I think saying the article is incorrect - is not exactly correct. But proper testing is an additional way to screen out tubes with issues in many cases. Observation of the getter flash alone is not the final word on a tube's condition.
Are we still discussing power triodes like the 211? If so, I stand by what I've said. The article is wrong. To quote:
"(chalky white all over)... is the only case of a getter flash visually indicating a problem in the tube."
Absolutely untrue, and I have seen the physical, real-world evidence. You know, I only posted this experience thinking it might save someone else some grief. I lost hundreds of dollars on those tubes and felt damn stupid when it was all over. I don't want to argue about it fifteen years later.
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Buy Chinese. Bury freedom.
I was just saying that in some cases on some tubes (not necessarily a 211) some rainbowing is pretty much normal.
That's right on, excellent link! The black getter is not a problem, in the real world they may actually be a bit more efficient than the shiny silver.
Where does the average tube user find a good tube tester to use? They don't have them at the hardware store anymore.
Steve
The Electronics magazine referenced in the link is the magazine I read. I have a large number of the issues from 1938-60. It's excellent!! A great amount of information about the pre-war, war, and post-war years production....you see how electronics changed as you move through the issues). The ads are great too, from all of the parts manufacturers mentioned on this site (less the Chinese, etc.)...some are worth framing.
If someone knows where this magazine can be found online, that would be great.
"I can't compete with the dead". (Buck W. 2010)
I thank you for getting me off the JJ 6922's long ago. Are your newest EH's still one of the better recommendations? I know you like the Genalex's, I might consider them on that next purchase I'm working on. (Had a slight delay after I emailed you).
Yes, I still recommend the EHs - the quality is still tops and they are very rugged!!
Awesome! Thanks for that! I saved the document referenced in the website you linked. I breezed through it, but it offers some interesting information about getters :D
Very cool!
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May your tubes be warm, long-lasting, and always lively. Holy be thy heater.
Well, my knowledge of chemistry and chemical engineering limits my answer, but I have a theory on that...
1)Metals are shiny as a fact of the electrons being densely packed yet "loose".
2)When metals are hit with photons, the electrons reflect those photons back, giving us that "luster".
3)Typically, the heavier the element, the easier it is to rob them of electrons and sever chemical bonds (hence why the first 20 or so elements are the most reactive).
4)Pure barium (#54) in a balanced ground state has two free electrons to give out.
Suppose the anode's voltage was high enough to rob those electrons from the atom, it would change the frequencies of light which barium absorbs and reflects, thus changing its perceived color and luster. In this case here, the barium may have lost its electrons and thus its shininess.
Has this affected the performance of the getter? I don't believe so... If need be, there are plenty of electrons to be had within the valve (especially during its operation) to supply the chemical reaction. All in all, I wouldn't worry a bit...
I threw in a little demo video of what electrons look like (weird, I know!). In the experiment, what seems like a metal in the middle of vial is actually a solution where the electrons are solvent and free. So, the solution in the tube looks like a metal when it is in fact a salt reacting with peroxide (if I remember haha). Hope that helps!
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May your tubes be warm, long-lasting, and always lively. Holy be thy heater.
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