I have a old tube radio. It uses EL84 for output, and the output tube socket is not very godd and sometimes it lose contect with one or more tube pins. When it happens I just move the tube's top a little bit ant it has contect again! A few minutes ago it became loose again and I moved the tube. But I noticed that blue glow is coming from tube, but radio works normal, there is no distortin or something like that. Tried three tubes butthe glow was in all three. The top of the tubes is black, not wite. Is these tubes dead or blue glow in EL84 is normal?
In Kaunas almost all tubes cost 20Lt (~6Euros). In Vilnius, which is 100km from Kaunas, The 6P14P (EL84) tube costs 7Lt (2Euros).
It's easy to find EL84, ECC88, 6P41S, 6N2P and other small tubes, but I have never found 6AS7, 6SN7, 6SL7, 6S33S, 220V/220V transformers and output transformers (Except "Visaton TR.10" 16k primary, taps at 8k,4k,2k and 1k; 10W; 25Lt (7EUR))
It's easy to find EL84, ECC88, 6P41S, 6N2P and other small tubes, but I have never found 6AS7, 6SN7, 6SL7, 6S33S, 220V/220V transformers and output transformers (Except "Visaton TR.10" 16k primary, taps at 8k,4k,2k and 1k; 10W; 25Lt (7EUR))
If you go have a look at some of the old electronics repair shops, you will find that there are plenty of pretty much any tube in the baltics, if you fail to get what you want in Lithuania, pick up some next time you are in Latvia. I know for a fact that there are no shortage of any tube in Latvia, as I brought something like 200 tubes back to Denmark last time I was in Latvia, I thought I'd better get some before it becomes a problem to get them, or they get expensive. In my case I paid a bottle of Scotch and a plate of chocolate for those, and there vere plenty more this summer. A simple walk through the socalled technical market, you know the one where they have little stands selling used stuff, will surely bring you what you need, as they do not care for tubes anymore, actually I would guess they would be rather happy to anything at all for them.
The only ithem of the leftovers from the russian military I have found shortcommings for lately in Latvia is titanium, perhaps the biggest paper in oil caps as well, but that's it.
If you need a hint on where to go in Riga or Ventspils to find such things, drop me a line, as I have plenty of connections in Ventspils, and I know the market for such ithems pretty well in Riga.
Magura
The only ithem of the leftovers from the russian military I have found shortcommings for lately in Latvia is titanium, perhaps the biggest paper in oil caps as well, but that's it.
If you need a hint on where to go in Riga or Ventspils to find such things, drop me a line, as I have plenty of connections in Ventspils, and I know the market for such ithems pretty well in Riga.
Magura
@ Pentium100
This horse has been beaten to death!
The blue glow is harmless. It can be considered that your tube(s) are alive and well. It's that dreaded PURPLE glow that's bad. One way to ease you fears: If the bias is stable and where it should be, ie doesn't wander and the plates (anodes) don't glow cherry red, your tubes are in good shape. Every new EL34 - 84 I've used has that BLUE glow inside and on the inner suface of the glass envelope. If the glow starts wandering around that MAY be a sign of a bad tube! Just from my experience!
Wayne
This horse has been beaten to death!
The blue glow is harmless. It can be considered that your tube(s) are alive and well. It's that dreaded PURPLE glow that's bad. One way to ease you fears: If the bias is stable and where it should be, ie doesn't wander and the plates (anodes) don't glow cherry red, your tubes are in good shape. Every new EL34 - 84 I've used has that BLUE glow inside and on the inner suface of the glass envelope. If the glow starts wandering around that MAY be a sign of a bad tube! Just from my experience!
Wayne
Hi,
Wayne,
You make it sound as if every good output tube SHOULD have this blue glow when new and healthy.
This is certainly not the case and as you indicate yourself; the blue glow usually goes away after a period of use which only indicates that the getter is burning away some gassy remains.
That in turn means that there was some leftover gas in the tube (bad of ailing vacuum pump seals) or that the emissive coating contained some contamination or a combination of the above.
If the blue glow starts to develop within a used tube then that's a good indicator of a "going to fail anytime soon" powertube.
Cheers,
Wayne,
You make it sound as if every good output tube SHOULD have this blue glow when new and healthy.
This is certainly not the case and as you indicate yourself; the blue glow usually goes away after a period of use which only indicates that the getter is burning away some gassy remains.
That in turn means that there was some leftover gas in the tube (bad of ailing vacuum pump seals) or that the emissive coating contained some contamination or a combination of the above.
If the blue glow starts to develop within a used tube then that's a good indicator of a "going to fail anytime soon" powertube.
Cheers,
fdegrove said:
<Begin shameless post ripoff>
Frank,
You make it sound as if every good output tube SHOULDN'T have this blue glow when new and healthy.
This is certainly not the case and as you indicate yourself; the blue glow usually comes back after a period of use which only indicates that the getter is burning away some gassy remains.
</Shameless>
Y'know Frankie... there's an interesting quality to electrons that you might want to be aware of.... namely, they travel farther when there ISN'T gas in the way. Blue glow (on the glass) is a sign of good vacuum as much as anything.
Tim
@ Frank
I find that when the blue glow on the inner surface of the glass bulb starts to fade in a new tube (EL34), I usually have to re-bias the tube. Blue glow on the inner surface of the bulb is caused by electrons striking the glass. In a new EL34 it's almost always a sharply defined hourglass or an 8 shape. And when there is no BLUE glow at all (inside or where-ever), the tube is DEAD or near dead (or biased off)! We're not talking about a gassy tube. In a gassy tube the color is almost always PINK-PURPLE and is not sharply defined. It's more like a floating blob! Of course the blue glow will become less intense as the tube ages. I'd say it's the chemistry of the glass changing at that point and the spacing of the grids or maybe a less intense electron stream. But I don't recall any new EL34 that didn't exhibit this phenomenon. Now if the blue glow is moving around, that suggest something is going on (usually bad) that's altering the flow of electrons within the tube.
I don't think a blue glow indicates a gassy tube. In a good tube such as an EL34 there is a blue glow inside near the grids, it's always sharply defined and held in place. I believe that's caused by the electron stream knocking electrons off the grid wires, the same as the inner surface of the glass bulb. All tubes have some gas in them, argon I believe or some other noble gas.
I hope I'm not
. I'm not a Mr. Know-it-all, at least I try not be!
Wayne
I find that when the blue glow on the inner surface of the glass bulb starts to fade in a new tube (EL34), I usually have to re-bias the tube. Blue glow on the inner surface of the bulb is caused by electrons striking the glass. In a new EL34 it's almost always a sharply defined hourglass or an 8 shape. And when there is no BLUE glow at all (inside or where-ever), the tube is DEAD or near dead (or biased off)! We're not talking about a gassy tube. In a gassy tube the color is almost always PINK-PURPLE and is not sharply defined. It's more like a floating blob!
Of course the blue glow will become less intense as the tube ages. I'd say it's the chemistry of the glass changing at that point and the spacing of the grids or maybe a less intense electron stream. But I don't recall any new EL34 that didn't exhibit this phenomenon. Now if the blue glow is moving around, that suggest something is going on (usually bad) that's altering the flow of electrons within the tube.I don't think a blue glow indicates a gassy tube. In a good tube such as an EL34 there is a blue glow inside near the grids, it's always sharply defined and held in place. I believe that's caused by the electron stream knocking electrons off the grid wires, the same as the inner surface of the glass bulb. All tubes have some gas in them, argon I believe or some other noble gas.
I hope I'm not
. I'm not a Mr. Know-it-all, at least I try not be! Wayne
Metal never (or almost never?) fluoresces, so unless your grid is hella leaky (coated with cathode material, bombarded by ions, etc.), you're seeing the plate coating. As I said, the gray plate coating can fluoresce with more than say 200eV striking it. Electrons are slower outside the tube so any that do escape and bend back towards the plate likely don't have enough energy to show up. (Although, I've done some weird trickery to a 6L6GC at night before and made the glow move from the glass to a darker glow clinging to the plate!) Of course, the ones going straight still have enough energy to make the glass fluoresce.
I've spotted the blue plate glow inside 6L6s, 6V6s, even the 12AU7's in Hept'AU7!
Tim
I've spotted the blue plate glow inside 6L6s, 6V6s, even the 12AU7's in Hept'AU7!
Tim
On a slightly different subject, but relating to tube death. I have built a full wave bridge out of UY85's and everyting works fine. However one of the valves has a bright orange flare at the base of the valve upon switch on. This lasts barely a second and then fades. The tube seems to heat up slightly slower than the others.
otherwise it seems to work OK.
Is this a sign of near death ?
Shoog
otherwise it seems to work OK.
Is this a sign of near death ?
Shoog
I've seen blue glow many times in tubes of TV's in a number of tubes, 12AU7, 6FQ7, 6GH8, vertical-horizontal output tubes and the like. Intense GREEN glow in HV shunt regulator tubes (beam triodes) such as 6BK4 - 6EN4 etc. WARNING: DO NOT try this at home! 25,000 to 32,000 volts is nothing to play around with! We do not discuss TV circuits here on this forum! Very dangerous!
The blue glow I was speaking of near the grids seems to be held in place near the screen grid in bands or some other shape I can't quite detect because of limited visibility. Ionized gas held in place by the space charge? ie from electrons knocked from the gray plate coating, or just from the leftover gases after the pumping process? I don't think getters will remove inert gasses.(?) The figure 8 on the glass is always opposite (across from) the slots in the plate used for grid alignment. And it's COOL to look at with the lights off. It changes intensity with the music!
Can't say for sure. Does this happen when @ idle or while music is playing at a good volume? If it happens while playing music this may be normal. I'd say as long as you don't hear any popping or crackle and the tube biases up properly you have nothing to worry about. Crank it up and enjoy the show! I've often seen blue glow near the mica on beam tetrodes many times, ie 6V6, 6L6, 5881, 7591, horizontal outputs and so on.
I think I've added enough confusion to this thread for today!
Wayne
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