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Ever seen a tube wear pattern like THIS??

 
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Thu May 26, 2016 10:53 pm    Post subject: Ever seen a tube wear pattern like THIS?? Reply with quote


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Try to figure out how THIS happened!!!



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Tim in Phoenix




Joined: 21 Oct 2006
Posts: 4378
Location: Phoenix


PostLink    Posted: Thu May 26, 2016 11:19 pm    Post subject: Reply with quote

Hmmm

That's a lot of bottom pin, a cylindrical screen at a big down angle perhaps.
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Thu May 26, 2016 11:23 pm    Post subject: Reply with quote

Notice that the dark/light wear pattern is REVERSED? Worn phosphor is normally DARKER than unworn phosphor.
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AnalogRocks
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Joined: 08 Mar 2006
Posts: 26690
Location: Toronto, Ontario, Canada

TV/Projector: Sony 1252Q, AMPRO 4000G


PostLink    Posted: Fri May 27, 2016 6:58 am    Post subject: Reply with quote

Looks like they used the outside to do a border. Instruments or HUD perhaps? Maybe Bogie's?
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Fri May 27, 2016 3:02 pm    Post subject: Reply with quote

I'll tell you later, after a few other people have decided to take a stab at it.
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ecrabb
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Joined: 13 Mar 2006
Posts: 15909
Location: Utah

TV/Projector: JVC RS40, Epson 5010


PostLink    Posted: Fri May 27, 2016 6:25 pm    Post subject: Reply with quote

The geometry is easy... Projector level with the top or bottom of a curved screen, like a wrap-around sim display or planetarium. Looks like it may have even been soft-edge-blended on the sides.

But, I don't understand why the wear pattern is reversed... That makes no sense. I like Analog's idea... Like this tube was making the "outside" image on a screen and blanked in the middle, while another projector was displaying a high-res image in the center. So, the bend might not be fitting on a concave display at all, but maybe matching the contour of a window/viewport, or HUD like Jeremy said.

Too many unknowns here to know for sure what this came out of unless you saw it yourself.

SC
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Fri May 27, 2016 6:34 pm    Post subject: Reply with quote

Incidentally, no, this is not a camera trick or photoshop or anything like that. This tube looks just like the picture
as seen in real life.

I'll reveal the answer tomorrow.
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Tim in Phoenix




Joined: 21 Oct 2006
Posts: 4378
Location: Phoenix


PostLink    Posted: Fri May 27, 2016 6:54 pm    Post subject: Reply with quote

Guys

There is a phenomena called "bright burn", haven't seen it since the Novabeam days.
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ecrabb
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Joined: 13 Mar 2006
Posts: 15909
Location: Utah

TV/Projector: JVC RS40, Epson 5010


PostLink    Posted: Fri May 27, 2016 7:33 pm    Post subject: Reply with quote

cmjohnson wrote:
Incidentally, no, this is not a camera trick or photoshop or anything like that. This tube looks just like the picture as seen in real life.


I've done so much photography and Photoshop work over the years, I can typically recognize those kinds of tricks pretty quickly. Plus, I wouldn't see your motivation for doing so, so I didn't suggest that as even a possibility.

SC
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ecrabb
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Joined: 13 Mar 2006
Posts: 15909
Location: Utah

TV/Projector: JVC RS40, Epson 5010


PostLink    Posted: Fri May 27, 2016 7:34 pm    Post subject: Reply with quote

Tim in Phoenix wrote:
There is a phenomena called "bright burn", haven't seen it since the Novabeam days.

Never heard of that, Tim. Knowing (in general) the process by which tubes are normally burnt, I'm having a hard time understanding something where the opposite happens. I'd love to hear more.

SC
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cmjohnson




Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s


PostLink    Posted: Fri May 27, 2016 7:43 pm    Post subject: Reply with quote

I'm just going to tell you now. No sense in making you wait and bite your nails.

This tube is one I got recently and it didn't look like that when I got it.

It had the wrong pin base on it and I went to change out out, carefully so as not to break
the glass button and let all the vacuum leak out.

Well, that didn't go quite according to plan. Crack....hisssssss.....

And the interaction of the air with the aluminization and phosphor layer, coming into the tube slowly,
caused the wear pattern to become emphasized and reversed. For reasons that a chemist might better understand
than I can, the worn area basically did not change, while the UNWORN area exhibited a clearly visible darkening.

I've seen tubes that had been cracked with larger cracks, allowing air in faster, which show a bullseye pattern on the
phosphor face, too.

And I've seen tubes that had just flat out been snapped at the neck and the inrush of air just blew the whole phosphor layer clean off, too.
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Tim in Phoenix




Joined: 21 Oct 2006
Posts: 4378
Location: Phoenix


PostLink    Posted: Fri May 27, 2016 9:26 pm    Post subject: Reply with quote

Hey Steve

I never understood bright burn either, it was a small crosshair pattern in the center of a Novabeam green tube. I only saw that once.
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