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    Building, troubleshooting and testing of these amplifiers should only be
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    the safety precautions around high voltages.

Blue Tubes the glow

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dice45 said:
Brett,
those 845 amps on your pix, aren't they Chris Brady's 845 Verus amps? They have mercury rectifiers.
Hi Bernhard,
Yes, they're Chris' Verus amps. Sorry I thought I credited them on the first post with the pic this morning. I can see no real benefit in the use of 866's myself, except for the cool aesthetics, unless you plan on building a GM100 amp and need the 10kV PIV.

I think Dave Slagles amps' have them too, but I couldn't find a link, and I was in a hurry this morning.

Remember to have asked my buddy vinylsavor recently whether he has experinece with mercury recitfiers. He reported to have abandoned it on his 211-driven 211 SET amp.. Too much HF hash. He reported, apart from the gorgeous look he experienced no real benefit and even the cool look was spoiled when he decided he had to shield them to protect his phono.
211 driven by a 211, eh? Very Sakuma-san.(bows deeply)

Cheers
 
Colt45: No the 83 in the hickok won't glow unless you pass some really high current through it. I have a high end stark tester and it uses an 83. Usually 83's are used in those testers for testing special super high voltage diodes that are very rare now. I checked mine even with a diode check in progress and it didn't glow at all, further testing will tell if there is current of any sort flowing through the tube but I'm not sure for now.
 
Yes, the 83 does have a constant voltage drop, because the mercury also acts a bit like gas in a regulator tube. But it won't glow very brightly until current flows through it though it is said to emit lots of ultraviolet light. I don't doubt it glows under normal conditions and the reason mine didn't is either it's too old or I had too little current flowing through it. The paper does tell the truth though, the tube will possibly hae a gentle blue glow under the riht circumstances
 

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Two quick points:
1) A tube will glow blue if a stray stream of electrons hits the glass envelope; some compositions of glass will fluoresce quite nicely under these conditions. 6L6 tubes, in particular, are quite prone to this. Differentiate between whether the glow is coming from inside the tube or from the glass. Yes, some tubes glow blue naturally, just as a byproduct of how they work. We've had several threads on this at the rate of about one every six months. There was one nice one (pictures included) with mercury rectifier tubes, but I can't remember the name of the thread at the moment. Last fall, maybe? And, yes, I believe Cary Audio had/has some product like that.
2) I believe the small tube in the first picture is lit from beneath with a blue LED firing up through the hole in the center of the tube socket. Any color of LED will do for this...green, yellow, blue...but most folks use red or yellow if they're going in for supplemental lighting. Carver just uses little incandescent lights behind each tube in one of their preamps. It's just there for looks.

Grey
 
OK folks,

I do not recall if anyone identified that one tube circuit on PCB that had that "blue glow" on the bottom... but that is a blue LED under the tube. I have a friend that did the same thing. It is pretty, but not real.

OTOH, I have five vintage blue glass 27's. They are blue tinted glass. I will post a pic in the near future, for those who are interested. I am planning on making a small stereo amp with the 27's as pre's and 45's as outputs.

As for those... what look like very high voltage tube amps... that do actually glow blue... I think it is due to the high voltage as well as whatever ionized whatever there is inside.

Mercury rectifiers do glow a nice blue also, but why would one want to introduce the noise?

Gabe
 
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