Blue glow in tube. Is the tube dead or not?

[Pentium100]

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?

[845]

Read about blue glow here

[Pentium100]

The glow is inside the anode. Then it means that my tubes will die soon And the new tube costs ~6 Euros.

[Magura]

hey....don't forget where you live. It is easy to find such tubes in Lithuania for a lot less than 6 eur a piece. I would rather guess a sixpack per dusin or so.

Magura

[Pentium100]

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))

[Magura]

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

[Sch3mat1c]

If you look too hard you'll see a blue glow on the inner (gray) coating on the plate surface. Harmless fluorescence, as is the glow present on glass, if any. Look for a distinctly purple glow such that would indicate a trace of something like argon.

Tim

[Pentium100]

The glow is on the anode but on the inner side.

[cogsncogs]

@ 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

[Pentium100]

Thanks, you saved me from buying lots of EL84s