# dome of Cree XR-E broke off



## rayman (Jan 15, 2009)

I really have no idea how this could happen but the dome of a Cree XR-E on the Terralux dropin broke off. How could this happen?







Under the dome there is some kind of jelly. Anybody know what this is.

Is it possible to use the Cree emitter anymore?

rayman


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## Cydonia (Jan 15, 2009)

Maybe high heat build up weakens the bond and allows the dome to come off when stressed? That is a MiniMag drop in right... twisting the bezel/head down to turn off the light might have contacted the led dome and broken it off. I find that this nearly happenes on the TerraLux drop in I have. Plastic reflector comes too close to the led for comfort.


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## gillestugan (Jan 15, 2009)

the jelly is optical silicone used to bond the lens to the chip and encapsulate it.
You will not be able to repair it to what is was, sorry.


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## rayman (Jan 15, 2009)

@Cydonia
Yes, I think you're right. I used a Cree optic and by turning off the MiniMag with the head the optic crushed down the dome and broke it off .

@gillestugan
I know . But I'll just use it without the dome as it is only a backup backup backup light .

rayman


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## LukeA (Jan 15, 2009)

rayman said:


> @Cydonia
> Yes, I think you're right. I used a Cree optic and by turning off the MiniMag with the head the optic crushed down the dome and broke it off .



You can prevent it happening again by cutting the rim off of the optic holder (making the holder of smaller diameter than the optic) and snapping that onto the LED. It doesn't interfere with the optic's function, it protects the LED, and it ensures correct optic placement.


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## trout (Jan 15, 2009)

I was going to ask the same question only for a MCE The dome got broken off due to hamfistedness.

It still works . can I put it back on with silicon or something 

I know it will be substandard output 
but what have I got to lose .


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## TONY M (Jan 15, 2009)

Oh no, I hate hearing about cree domes getting knocked off. NEVER touch the dome, the only good to come out of this is that it will never happen to you again now that you know not to touch it. :thumbsup:

I'm afraid that the cree's days are over, and you can not fix it properly... :mecry:

Have a nice day.


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## Bullzeyebill (Jan 15, 2009)

TONY M said:


> Oh no, I hate hearing about cree domes getting knocked off. NEVER touch the dome, the only good to come out of this is that it will never happen to you again now that you know not to touch it. :thumbsup:
> 
> I'm afraid that the cree's days are over, and you can not fix it properly... :mecry:
> 
> Have a nice day.



Yeah, happened to me too, playing around with an optic, and my Cree P4. Knocked off the dome. It can not be replaced correctly, and running it without it presents a really crappy beam.

Bill


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## trout (Jan 15, 2009)

TONY M said:


> Oh no, I hate hearing about cree domes getting knocked off. NEVER touch the dome, the only good to come out of this is that it will never happen to you again now that you know not to touch it. :thumbsup:
> 
> I'm afraid that the cree's days are over, and you can not fix it properly... :mecry:
> 
> Have a nice day.


 

ok so I cannot fix it properly
but what is the result if I put it back on with clear silicon


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## Bullzeyebill (Jan 15, 2009)

trout said:


> ok so I cannot fix it properly
> but what is the result if I put it back on with clear silicon



Try it, no harm can come of it, and report back.

Bill


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## trout (Jan 16, 2009)

Bullzeyebill said:


> Try it, no harm can come of it, and report back.
> 
> Bill


 
Ok I have done it and restuck the dome with clear silicon 
it is on and works . dont know for how long it will stay on and work though.


this is a mce from the same bin dome untouched and the one on the right is the fixed one the same optic was used for each shot and the camera setting fixed also

tha tapes are 1 mtre long and 2 metres away


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## Bullzeyebill (Jan 16, 2009)

Looks ok. What are your thoughts looking at it in person?

Bill


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## wildstar87 (Jan 19, 2009)

I had some luck with Superglue. I scraped off a bit on the rim of the metal part, then put some Superglue on the rim, then put the dome down onto it, you have to keep it pressed down for a bit, but it seemed to work, there are still some artifacts in the silicone, but other than that it has worked ok.


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## 1 what (Jan 19, 2009)

Hi Rayman.
Welcome to the Cree XRE Dedomers Brotherhood.
I did a similar thing to a (non teralux) Cree about a year ago. 
It gave me a tighter spot using a DX reflector and the Cree is still working.
Probably not a good thing to do on a regular basis since I've been told you can easily damage connecting wires in the Cree.


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## DonShock (Jan 19, 2009)

I had good luck reattaching one with clear 2-ton epoxy. After mixing it up, I spread a thin layer out on a paper plate and then used some tweezers to dip the bottom of the dome in the epoxy before setting it in place.


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## Illum (Jan 19, 2009)

some brands of superglue may dry up as opaque so I'd recommend using some off source and see if they don't. 
Not sure about the heat, but I'm willing to give a dab from the cold glue gun to see if it domes


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## Superdave (Jan 19, 2009)

stick it back on and put a few dabs of superglue around the dome. It'll be fine.


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## Fallingwater (Jan 19, 2009)

How does the beam behave without the dome? I'm thinking it should be floodier as the dome acts as a lens. Am I right?


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## starburst (Jan 19, 2009)

DonShock said:


> I had good luck reattaching one with clear 2-ton epoxy. After mixing it up, I spread a thin layer out on a paper plate and then used some tweezers to dip the bottom of the dome in the epoxy before setting it in place.


 
Same here, but mine was a rebel its not exactly the same tint as the 
other three ( flood light with 4 rebels ) but I have to look over in the 
edge of the light to tell which one it was. At least its not royal blue
now like without the dome.

Starburst,


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## DonShock (Jan 19, 2009)

Fallingwater said:


> How does the beam behave without the dome? I'm thinking it should be floodier as the dome acts as a lens. Am I right?


Mine was installed in a quad-cree light running at 1A. After the dome popped off, that LED was very dim while the others remained at full brightness. As soon as the dome was glued back on, you couldn't see any difference in brightness between the untouched LEDs and the repaired one.


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## Fallingwater (Jan 19, 2009)

Huh... weird. How do you explain this?


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## Bullzeyebill (Jan 19, 2009)

Fallingwater said:


> Huh... weird. How do you explain this?



If you mean how is the output dimmer without the dome?  It is because the emitted light from the domeless Cree is scattered, not focused, and not a lot of it makes it outside. There will be a tiny, tiny hotspot, and much spill that just gets lost. I have also knocked off a dome and the resulting beam is just disgusting and lightmeter with bounce shows a significant loss of output, probably about 30% loss compared to Cree with dome.

Bill


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## DonShock (Jan 20, 2009)

It wasn't the beam that was dimmer, it was the LED die itself. I was looking directly at the bare LEDs. I have no explanation for why it happened. Since they were series wired, all had the same current. Initially, I just glued the dome back on to protect the wires on the die from damage until I could get around to swapping out the LEDs. The fact that normal output was restorred was a bonus. The LED without the dome was very dim, about what you see when the LED only has 50ma or so running through it. It was not just an apparent drop in output due to being unfocused, it was a dramatic drop in actual output.


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## Bullzeyebill (Jan 20, 2009)

DonShock said:


> It wasn't the beam that was dimmer, it was the LED die itself. I was looking directly at the bare LEDs. I have no explanation for why it happened. Since they were series wired, all had the same current. Initially, I just glued the dome back on to protect the wires on the die from damage until I could get around to swapping out the LEDs. The fact that normal output was restorred was a bonus. The LED without the dome was very dim, about what you see when the LED only has 50ma or so running through it. It was not just an apparent drop in output due to being unfocused, it was a dramatic drop in actual output.



Output on mine, while reduced, was still fairly high, though center beam was very narrow.

Bill


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## bwilli (Mar 6, 2009)

Ugh! I broke off THREE domes off my Cree Q4 PCB. I'm off to the pet store to buy some clear silicone to try to glue the domes back on.

I'll post later with results...


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## bwilli (Mar 6, 2009)

The silicone glue for fish tank repair isn't so clear... It's kinda cloudy.


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## znomit (Mar 7, 2009)

bwilli said:


> The silicone glue for fish tank repair isn't so clear... It's kinda cloudy.



Its clear when squished thin between two flat objects.


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## bwilli (Mar 7, 2009)

:sweat:You give me hope! I glued 'em this morning. We'll see how it goes.

Thanks.


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## manoloco (Mar 7, 2009)

would a micro drop of norland 61 help here?


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## csshih (Mar 7, 2009)

it only cures with UV light, so you'll have to stick it in the sun or use UV light.


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## bwilli (Mar 7, 2009)

Well, the domes I glued look a *touch* more cloudy than the factory glued domes, but not bad. I'll wait 'till it totally cures before firing them up. I'll see if I can get some pics with factory domes and glued domes.


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## bwilli (Mar 8, 2009)

Here's what I get:





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They look good. I can't tell a difference between the LED's I reglued and the factory glues LED.

<whew>


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## manoloco (Mar 11, 2009)

yup that was the idea, though if a dome comes off in one of my stars/lights, i would probably prefer to replace the emitter/star.


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## AlexGT (Mar 12, 2009)

I was wondering if replacing the glass with a small aspheric lens would yield better brightness.

Something small like this

http://www.surplusshed.com/pages/item/l3982.html


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## bwilli (Mar 13, 2009)

Ooh... That'd be neat to try. I didn't replace the emitter 'cuz it's soldered to a 3 up board and I didn't want to hassle with trying to get it off.


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## bshanahan14rulz (Aug 13, 2009)

One of my cree p4s I had lying around lost it's dome. I removed the metal ring and almost all of the gel and there has been no noticeable tint shift. Using a 3" lens from a BMW "E55" projector I got a spot the size of a quarter on the ceiling 6 to 7 feet up.

Also, using the stock Cree lens but about twice as high as stock created a hotspot about 1ft wide on the ceiling, but it was pretty dim.

Sorry for reanimating an old thread, but it was kinda relevant.


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## J_C (Oct 10, 2009)

I found this topic because I've just torn the side of the dome loose on an XR-E while trying to clean some residue off, it had been contaminated sitting out for awhile.

Visually you can see a tiny tear on the side but the dome didn't come all the way off so I left it as-is, put it in a light and can't see any artifacts at all (probably due to OP reflector in the light).

Now that this topic has aged a bit, has anyone observed or does anyone feel there is a long term lifespan or reliability/sudden-failure-risk change from having a missing or damaged dome? 

A few thoughts I wondered were if it keeps the bond wire temps lower and spreads the die heat a bit better, though on my specimen none of the silicone appears to have leaked out.


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## manoloco (Oct 11, 2009)

csshih: Yup, point was that you can put the drop, and let it harden in the sun (the fact that its very fluid would effectively cover the die and create a nice bond, light transmission is great with Norland 61 plus it hardens pretty good, i think it would end up really nice but the beam characteristics would change (as the drop would flatten instead of creating a dome)


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