| Author | Message | ||
     Swede |
My tubes has, apart from the normal glow a kind of cool blue glow in them. I have for russian tubes of some kind in my 410HD-130 from 76, dunno the brand. But is that glow supposed to be there or does it indicate some problem? I'm new at this and try to learn by checking this excellent forum but couldnt find anything about this. | ||
| Langley |
Blue glow is OK. | ||
| Zacheria |
Swede, I wish to disagree with Langley. A blue glow can be a sign of mis-biasing so check you bias and try to enjoy the rest of your day. | ||
| Langley |
The following is quoted from www.svetlana.com/docs/tubeworks.html "Glass tubes have visible glow inside them. Most audio types use oxide-coated cathodes, which glow a cheery warm orange color. And thoriated-filament tubes, such as the SV811 and SV572 triodes, show both a white-hot glow from their filaments and (in some amplifiers) a slight orange glow from their plates. All of these are normal effects. Some newcomers to the tube-audio world have also noticed that some of their tubes emit a BLUISH COLORED GLOW. There are TWO causes for this glow in audio power tubes; one of them is normal and harmless, the other occurs only in a bad audio tube. 1) Most Svetlana glass power tubes show FLUORESCENCE GLOW. This is a VERY DEEP BLUE color. It can appear wherever the electrons from the cathode can strike a solid object. It is caused by minor impurities, such as cobalt, in the object. The fast-moving electrons strike the impurity molecules, excite them, and produce photons of light of a characteristic color. This is usually observed on the interior of the plate, on the surface of the mica spacers, or on the inside of the glass envelope. THIS GLOW IS HARMLESS. It is normal and does not indicate a tube failure. Enjoy it. Many people feel it improves the appearance of the tube while in operation. 2) Occasionally a tube will develop a small leak. When air gets into the tube, AND when the high plate voltage is applied, the air molecules can ionize. The glow of ionized air is quite different from the fluorescence glow above--ionized air is a STRONG PURPLE COLOR, almost pink. This color usually appears INSIDE the plate of the tube (though not always). It does not cling to surfaces, like fluorescence, but appears in the spaces BETWEEN elements. A tube showing this glow should be replaced right away, since the gas can cause the plate current to run away and (possibly) damage the amplifier. PLEASE NOTE: some older hi-fi and guitar amplifiers, and a very few modern amplifiers, use special tubes that DEPEND on ionized gas for their normal operation. " | ||
| Zacheria |
I'm going to go ahead and disagree with you. Thank you and goodbye. | ||
| Langley |
Splonge! | ||
| Steve Kennedy |
Those with little first-hand experience who dismiss or ignore the learned opinions of those more experienced are doomed to wander through life without a clue. Steve (Message edited by admin on February 25, 2004) | ||
| michael kaus |
Totally clueless. And we are TRYING to help him. Mike. |