Disappearing BTN

Van

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WOW!
 

tdtastic

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Sep 16, 2014
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I honestly can't remember -- it happened when our LD was doing a dimmer check with her crew. I was on the other side of stage dealing with something else. It got the attention of ERRRBODY in the venue though....
 

JohnD

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Impressive indeed. I wonder if @DELO72 has ever seen that happen?
 
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JD

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Jan 1, 2005
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North Wales PA
Doesn't look like any filament sag. My guess is it took on air and then when turned on the air expanded and it popped like a balloon.
 

Van

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Les

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I pulled a naked GLA from an ellipsoidal a few weeks ago. But mine differed in that there's still glass inside the instrument's housing. You might want to sweep your floor just in case.

I've seen reflectors like this on older 65Q instruments. Seemed like they would wilt like a flower even under normal* operating conditions.

*I can't rule out the possibility of a 1000w lamp being run in a fixture only rated to 750w being the root cause.
 
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DELO72

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Aug 8, 2007
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New Hampshire
Word from the factory engineer is this, (I'm paraphrasing) "Wow- that fixture sucks! there is nothing reflective!" Which I had to agree with- optically these old fresnels DO suck at capturing and directing light. BUT- that said, he pointed out that he's never seen this behavior before in an end-of life. The lamp definitely burst, but what is odd is that the coil is still completely intact, and so the quartz must have expanded quickly and violently.

Possible causes are the halogen cycle wasn't working, and Tungsten deposits on the quartz caused localized bulging and rupture. Fingerprints or other contamination on the quartz "" "" "". Or- He isn't convinced that the quartz could get hot enough to melt AND bend the reflector, so wonders if perhaps the reflector was bent to begin with, and that is what caused the lamp to overheat and expand (by proximity). The filament looks like it has less than 30% of lifetime on it. You've managed to completely impress and show something new to a lamp engineer who has worked in the same factory for over 35 years. WELL DONE! :)
 

gafftapegreenia

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That era of 65Q reflector was prone to burning up. Every one I’ve seen has been scorched.
 

ship

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Mar 29, 2003
Location
Illinois
I totally agree with Mark's observations in never having seen an intact filament, blackened, melted and bent reflector.... No glass, and sand (filler inside the base) from the ceramic glue holding it in breaking away and letting the sand out.

-Was the silica sand inside, the fixture hung up side down and than the sand draining down after the catastrophic event?
-Can you take a photo of the side label of brand/printing? Not familiar with a fluted ceramic support for the lamp. ( I don't buy/use them much these days.)
-I have seen something similar to this before!

Way back when... like 15 or more years ago we were using a lot of 6-cell 1Kw cyc lights as normal for a summer music festival. Reflectors had similar damage and lamps were blowing out. Not simialr lamp and not studied if intact, but possibly similar reflector damage.

After some study, we surmized (department head denied it).. that some tech person cleaned the reflectors with Goof Off before the show! Was a sustainable theory in what happened and possibly similar.

If the case... that would be a stand down moment in cleaning all lamps/reflectors ASAP!