Took out 6P41S of my SE amp and connected EL84 (of course connecting to higher impedance primary of the OT) just to look at that blue glow more closer. So, the glow is at about all inner anode surface (not in space between anode and cathode), but grid wires make shadows. If the volume is set to high value the brightjness of glow varies with music. Is this type of glow bad for tube or not?
I recently noticed the blue glow on ECC88. I built an headphone amp (http://headwize.com/projects/showfile.php?file=cmoy5_prj.htm the optimized amplifier), which uses three of them for stereo. I found that tube, used as V2 gas the same blue glow on the inner side of anode. When I turn on the amp ant tubes begin to heat up, there is a blue glow all inside the anode (on the fullsurface and on the plates that are above and below the anode, if tube is hed vertically. It decreases in about 3 seconds to just a line on the inner anode surface that is nearest the cathode. Is it normal?
Actually I would think current doesn't matter, but voltage does. Since quantum things (we've got subatomic particles here remember) will only work above a certain threshold. Which leaves current level (number of electrons) proportional to intensity. But it may also be that current, if too low, is too dark to be seen.
Oh, and only applies to plates that are electrofluorescent (if that's a word). Gray plates seem to do it.
Meh, if I look inside the 12AU7's in Hept'AU7, I can see a shade of blue on the plates. They're running around 8-9mA each. (For a total of 100mA, since I seem to be missing a tube (yum, redundancy
). Hum, the name has changed to Hex'AU7.)
Tim
Oh, and only applies to plates that are electrofluorescent (if that's a word). Gray plates seem to do it.
Meh, if I look inside the 12AU7's in Hept'AU7, I can see a shade of blue on the plates. They're running around 8-9mA each. (For a total of 100mA, since I seem to be missing a tube (yum, redundancy
). Hum, the name has changed to Hex'AU7.)Tim
C'mon guys, that beautiful blue-glow is perfectly normal! Sch3mat1c is correct, the blue-glow will change/vary in intensity when you are playing music at a fairly high level. The more electrons and at a greater voltage=energy you have stricking the plate, the greater the intensity of the glow or should I say you have more glow! And less when the tube is conducting less. If the tube is at or near cut-off the glow will disappear or become so dim you can't see it. And as I stated in an earlier post, when the tube is nearing the end of it's life, i.e. the loss or lessening of cathode emission, the fewer electrons you have striking the inner surface of the plate or the glass envelope, therefore less "blue-glow" But this is not true in every case! Nearing the end of it's life that is.
And the appearence, shape and the location of the glow has to do with the spacing and alignment of the grid wires or beam forming plates. Just as long as you don't have the dreaded "purple-glow" and it's not a blob of any color that's floating around, the tube is just fine!
Wayne
And the appearence, shape and the location of the glow has to do with the spacing and alignment of the grid wires or beam forming plates.
Just as long as you don't have the dreaded "purple-glow" and it's not a blob of any color that's floating around, the tube is just fine! Wayne
Guys
Here's a pic of what you DON'T want to see coming from you amp that was posted by karma:
www.diyaudio.com/forums/showthread.php?s=&threadid=36139
I'd say that tube has gone to meet it's maker. 
Wayne
Here's a pic of what you DON'T want to see coming from you amp that was posted by karma:
www.diyaudio.com/forums/showthread.php?s=&threadid=36139
I'd say that tube has gone to meet it's maker.
Wayne
Unless that's a slit in the plate, it looks like it's glowing
Oh well, ratings shmatings
My Revision 3, the proper blue glow
Well... a little overexposed. And blurry. Not bad for a dark shot though...
Oh well, ratings shmatings
My Revision 3, the proper blue glow
An externally hosted image should be here but it was not working when we last tested it.
Well... a little overexposed. And blurry. Not bad for a dark shot though...
Ok guys, I did a couple of shots of an E34L in a normal operating condition taken in the dark. I manipulated the pics in photoshop to highlight the blue glow and to cut down on image size. I could've increased the bias current to make the blueglow more prominent but...
The first pic shows the blue glow inside the tube. You can see it through the slots.
Wayne
The first pic shows the blue glow inside the tube. You can see it through the slots.
Wayne
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And in the second pic you can see an 8 shape on the inner surface of the glass. It's kind of hard to see...
This is absolutely normal guys! When the tube was new this glow was more prominent! So don't fret! I can't stress this enough: If it's a pretty blue it's normal; So crack a beer and sit back and ENJOY the SHOW! If it's purple or pink and floats around that's bad and you will get a lot of noise that's not musical (to most of us!) coming from your spkrs!
Wayne
This is absolutely normal guys! When the tube was new this glow was more prominent! So don't fret! I can't stress this enough: If it's a pretty blue it's normal; So crack a beer and sit back and ENJOY the SHOW! If it's purple or pink and floats around that's bad and you will get a lot of noise that's not musical (to most of us!) coming from your spkrs!
Wayne
Attachments
Waveborne: that's a good one of a bad one; Try another 88; a serious damaged screen:
On warm up most of the blue was on one side; with a small concentrated area lower left.
The other pic is ++ current half tube rating, the electron beam is one sided.
(If you donna turn up the juice you won't see all the defects).
Symptoms; high thd.
Motto. Use screen resistors !
richy
On warm up most of the blue was on one side; with a small concentrated area lower left.
The other pic is ++ current half tube rating, the electron beam is one sided.
(If you donna turn up the juice you won't see all the defects).
Symptoms; high thd.
Motto. Use screen resistors !richy
Attachments
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