have you ever had the tiny bead covering the diode on your led come off?

i just have on my ~2 week old romisen rc-n3 q5. i noticed a piece of, what looked to be, lent on it so i unscrewed the head and touched it with a paper towel dabbed in alcohol. without much pressure applied at all it popped right off of there. it looks like all that was holding it on there was some sort of clear hot glue-looking material. is this because it is a relatively cheap light or are all diodes manufactured this way?

All Cree XR-E's use what's called a "gummy dome". The "hot glue" like substance is silicon. It's best to just not touch the dome, many of us have learned that the hard way.


Also don't try to "polish up" your reflector, trust me...

Congratulations :thumbsup: you've managed to remove the lens from the LED. Don't wory, many of us have also done it from time to time.
All LED's are made this way and some seem to come apart easier than others.
Don't touch the LED just screw the top back on your torch and it will probably still work. The size of the central hot spot might have changed diameter. If it no longer works you've now got a perfect project for an easy mod.....just find a suitable new LED and off you go.

I never touch the domes on the new power LEDs. Not a problem with the old 5mm plastic ones, and it was kinda safe to do with the luxeons as they had a solid hard epoxy type resin dome, but the new ones are either soft silicon or very soft silicon with a thin lens over it. It's really easy for a cloth or something to pull the dome off. Just try to never get the dome too dirty, and if you want to dust it off use an air bulb for camera lenses. I prefer the giotto air rocket, easily a match for the power of canned air and it never goes empty or sprays freezing liquid.

What am I missing here? To the best of my knowledge the Crees use hard resin and the SSCs use the slightly milky soft silicone.

fnj said:

What am I missing here? To the best of my knowledge the Crees use hard resin and the SSCs use the slightly milky soft silicone.

Click to expand...

what came off is a hard, bulbous "lens". under it is where the silicone was. i presume that's how it was attached to the diode.

anyone know if there are any drop-ins for the rc-n3 or would i have to build my own? oo:

jrmy0641 said:

what came off is a hard, bulbous "lens". under it is where the silicone was. i presume that's how it was attached to the diode.

anyone know if there are any drop-ins for the rc-n3 or would i have to build my own? oo:

Click to expand...

If by 'build it', you mean 'solder in a new emitter' then yes, you will have to do that.

Marduke said:

Also don't try to "polish up" your reflector, trust me...

Click to expand...

heh i learnt the hard way on my dereelight SMO 3SD droppin...I tried to clean the dust off but all it did was leave more dust and added scratches.

LukeA said:

If by 'build it', you mean 'solder in a new emitter' then yes, you will have to do that.

Click to expand...

beyond my capabilties :/ i guess i'll buy another throw around light off of dx

fnj said:

What am I missing here? To the best of my knowledge the Crees use hard resin and the SSCs use the slightly milky soft silicone.

Click to expand...

The cree's use a floating lens, there's a hard "lens" over a soft silicone filling, sort of like a jelly donut :thumbsup:

It happened to my RC-N3 also...

I got another light as when I was trying to remove the board from the pill the pliars that I used damaged the pill's threads meaning that it no longer fitted back in the light. (I was an idiot so just make sure it doesn't happen to you).

You could buy a Q5 on a 16mm board and resolder it to the pill as this would make it a little brighter.

Dust is best removed using a can of compressed air. Never touch reflectors or LED emitters with anything other than tools specialized for it.

xevious said:

Dust is best removed using a can of compressed air. Never touch reflectors or LED emitters with anything other than tools specialized for it.

Click to expand...

+1 Don't touch the dome and don't get finger prints on it!

If the compressed air is too powerful I'd imagine it could misplace the dome as the only time I decapitated a dome it came off extremely easily, I just don't want to try it again to see if they all come off that easily.:laughing:
It may depend largely from emitter to emitter but it is a pain when it happens and you can't be too careful.

I once decapped a everLED and glued it back on with epoxy resin and it has held up for about 5 years now, they really should not come off just from being dropped like mine was.

TONY M said:

+1 Don't touch the dome and don't get finger prints on it!

If the compressed air is too powerful I'd imagine it could misplace the dome as the only time I decapitated a dome it came off extremely easily, I just don't want to try it again to see if they all come off that easily.:laughing:
It may depend largely from emitter to emitter but it is a pain when it happens and you can't be too careful.

Click to expand...

Rebel domes come off VERY easily, though the only cree dome I've ever removed was very tricky to get off.

Jarl said:

Rebel domes come off VERY easily, though the only cree dome I've ever removed was very tricky to get off.

Click to expand...

I suppose some cree domes are well stuck down and others are not then. The only dome (P4) I removed just "moved" off so easily. I think even compressed air could have blown it off in that case.

Photon Joe said:

I once decapped a everLED and glued it back on with epoxy resin and it has held up for about 5 years now, they really should not come off just from being dropped like mine was.

Click to expand...

I stuck mine back on but the beam quality was really terrible as the silicone was no longer smooth and transparent.

1 what said:

Don't touch the LED just screw the top back on your torch and it will probably still work.

Click to expand...

It will? I seem to remember reading the die doesn't dissipate enough heat without the gummy dome on it and bakes itself to death very quickly indeed.

jrmy0641 said:

beyond my capabilties

Click to expand...

It's really very easy, all you need is a soldering iron and a replacement Cree LED.

ehh.. i'm just glad that it was my least expensive light. i'll probably just replace it with an ultrafire c3

I have never touched any of my LED's but I never thought the little dome would come off. Glad I read this thread, though I'm sorry you may have ruined your light. I will never touch the LED's on my lights.

Bill