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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 4:58 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 530
Location: Monte Vista, CO. USA
I think I just spotted something else.

On the side of the tube where the much smaller, non-parallel white line is, it looks like it could be in line with the small vent opening in the plate. I'm guessing that the angle of that vent opening matches the angle of the smaller white line.

Even if I'm right, I'm not sure what that would tell us.

Can you see inside the plate structure well enough to see if the screen grid looks normal?


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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 5:39 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5396
Location: Sunbury, Ohio 43074
Just paint the whole tube white........ :-D

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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 5:42 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 530
Location: Monte Vista, CO. USA
That would remove ALL of the distortion, rendering the tube worthless to audiophiles. :)

Is anyone willing to break the tube and test my cocaine theory?


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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 5:51 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5396
Location: Sunbury, Ohio 43074
Silly of me......I meant paint the whole tube black, with a “whiteness inside for extra quality” label added

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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 6:00 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 530
Location: Monte Vista, CO. USA
Wow, you've got the right idea, but at the wrong time in history. If you did that now, the tube would be labeled racist and shunned.


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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: May Mon 27, 2019 7:43 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5396
Location: Sunbury, Ohio 43074
LOL Ok, point taken. I should have read my post before posting it, although it clearly refers to paint, not living beings.

Perhaps we should paint it green then? You could still use the 'whiteness' label.

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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: Jun Sat 01, 2019 5:23 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 530
Location: Monte Vista, CO. USA
Norman was kind enough to send me this tube for analysis. After careful inspection, I can see why he created this thread. It is a very unusual mystery.

The pictures are misleading, because it is difficult to separate what is inside the glass from reflections. Here is what I have noticed:

The white substance is on everything, not just the inside of the glass. Particles of it are stuck to the plate, the insulators, and even the under side of the getter flashing. So it was obviously deposited after the getter was flashed.

Since the substance is basically immobile, I believe that rules out cathode material. My experience with cathode material is that it remains loose in the tube, or at least can be knocked loose. Whatever this substance is, it sticks tight to whatever it touches. Also, a cathode activity test shows the cathode to be quite healthy with lots of life left. After increasing the heater voltage to 40% over normal, there is no indication of any grid emission at all, so I think a thermal runaway event is unlikely.

I agree with Norman that there are no signs of overheating on the plate, insulators, or glass. The getter flashing shows normal minor erosion around its edges, and there is some telltale emission-related darkening of the glass right above the tiny plate vent, so the tube definitely has some (I assume normal) hours of use.

I can see the very top of the screen grid and it appears perfectly normal, as does the top of the beam former.

But one thing I am now certain of is the concentration of the substance on the glass is related to the distance to the plate. There is only one seam in the plate, which sticks up approximately 1 mm above the rest of the plate surface, and is unquestionably where the plate structure is the closest to the glass. The widest, heaviest deposit line lies directly above it. The second heaviest deposit line lies on the opposite side where the plate is not quite as close to the glass. The internal structure is not 100% parallel with the envelope, which makes the deposit appear to not be parallel with the plate, but it is consistent with the distance to the plate surface.

The rest of the tube's internals, including the plate itself and the inside of the glass (even above the top insulator), are dusted with what seems to be a fairly uniform amount of this magic white substance.

So the only thing we know for certain is we have a perfectly good tube with many hours on it, with the mysterious white substance's density being related to distance to the plate. Close inspection of the density pattern near where the plate meets the mica indicates that heat was ultimately the driving force. That speculation is reinforced by the fact that there are quite large gaps between the plate and the mica insulators on the sides of the plate that are furthest from the glass which show no effects at all. This means the material could not have been spewed from the inside of the plate structure during some kind of horrific but temporary abnormal event.

My take on the lime getter theory is that if this were related, then we should have seen this more by now. But after the many thousands of tubes I've had pass through my hands, like you I have never seen anything like this.

My best guess is that this tube had something in it that should not have been there, but it didn't affect the tube electrically. So the tube was sold, used normally, and over time the heat vaporized whatever it was, resulting in the pattern we see today.


Last edited by PhilF on Jun Sat 01, 2019 5:48 pm, edited 1 time in total.

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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: Jun Sat 01, 2019 5:42 pm 
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Joined: Nov Sun 04, 2007 6:01 am
Posts: 3360
Location: Redding, CA
Phil:

Thanks for your assessment. Must be cocaine!

Norman

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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: Jun Sat 01, 2019 5:47 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 530
Location: Monte Vista, CO. USA
Hmmm. Not sure if you mean the substance in the tube is cocaine, or the analysis was done on cocaine! :)

P.S. If the substance is cocaine then you probably won't be getting your tube back in one piece, lol!


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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: Jun Sat 01, 2019 8:19 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
Posts: 5396
Location: Sunbury, Ohio 43074
It is an alien life force trapped in the glass enclosed vacuum. The poor travelers were just in the wrong place at the wrong time.

They are happy though......but if you break the glass and let them out, they will eat us. The end

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https://www.bbtvtestequipment.com


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 Post subject: Re: What is this white deposit inside a 12L6 tube?
PostPosted: Jun Fri 07, 2019 6:11 am 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 11812
Location: Powell River BC Canada
Shine your ultra violet LED flashlight at the mark through the glass
and see if it it fluoresces.

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