That’s much better tint than I expected. I expected royal blue, but that really doesn’t have too much purple in it. I’m impressed that that much phosphor can be removed and still have a useful tint.
I wonder how much the phosphor contributes to output. We need someone that knows more about this stuff to chime in.
I don’t know for sure, but I think that, maybe, one thing I did different was what, as I said, I was really concerned about leaving the emitter soaking for a really, really long time, based on some comments about the phosphor being “like paste”. I was really worried that if I just left it like that, all the phosphor would “drift off” (my mental picture).
That was why, when I got to the point of trying to get the larger clump of stuff off of the emitter, I didn’t just leave it in there, but pulled it out before I went off to my appointment, and also why I hesitate soaking it again now, to get that last tiny piece of stuff of off that one segment.
Again, I don’t know. I know others, including comfy, have said that they left XM-Ls in gasoline for weeks, but maybe the chemical composition of either the phosphor or the dome are different for the MT-G2s than for the older emitters like the XM-L?
All I know is what I did, which seemed to work “ok”, and hope what I documented helps others…
Yeah, I would call it a success. Many people prefer the tint you achieved. Especially, for throwers. I applaud your efforts and reporting. Good stuff. I hope you get that baby to 100% more throw.
Thanks.
I don’t know about that last thing though. I just was outside, comparing it to my STL-V6 with dedomed XM-L, and, even with the spill effect masking the throw, it was pretty clear that the STL-V6 spanked the DST :).
My last hope is adding the parallel 0.5 ohm resistor, but I kind of seriously doubt that’ll make up the difference. Would definitely be nice, but I’m kind of doubtful.
Based on djozz’s test results on severly overdriving the MT-G2 (It survived 16A), I think you can probably get rid of the resistor all together. Do it at your own risk, but I would try it if I had that setup. I think it will not go over 5A, maybe 6A and only for a short time as the cells drain.
Will do, but, not purposely being a “doubting Thomas”, but I think “lumens <> lux”.
Perhaps if you get a bigger reflector?
I just was thinking (it happens :)!): If the MT-G2 tint gets cooler when it’s dedomed, does that mean that lumens would increase, rather than decrease with a dedomed MT-G2?
If lumens increased, then why would the dome be on in the first place? :o
Slewflash. Im just guessing here but I’d say the dome is for 1) mechanical protection, 2) to produce a particular beam pattern.
The dome increases output on every LED. SST90, XPG (2), XML (2), XPE (2), XRE (2). After dedoming a drop in lumens is always observed, and I think Cree is aiming for maximum lumens/watt.
It would be highly irregular for the output to increase after dedoming, but at this point it seems kind of plausible since the tint shifted towards the cooler side of the spectrum instead of warmer like every other LED.
I think it’s unlikely the dome adds lumens to the output. I’m quite confident it’s a factor of where the light from the emitter goes. With a dome, it’s concentrated in approximately 100 deg range, without the dome, the light spreads 180 deg or more. I’m sure lumens drops only becaue the reflector can not catch all the light from the LED anymore.
I’ll bet with a mod where the LED is inside of the reflector (such as a maglite mod), as opposed to ‘at the base of the reflector’ there would be less of a lumens drop when the LED is de-domed.
Not sure I follow you on that one. If you increase the lumens and change nothing else, the throw will also increase.
Regarding the dome, it serves two purposes. The first, and most important to lighting engineers is beam pattern. The dome is actually a small lens. it focuses the light into a particular shape so someone making a light fixture optic/reflector can capture as much of the light possible and send it where they want it.
The second is emitter protection, also important.
scaru once explained lumen drop as a side-effect of additional reflector loss. Since photons exit the dedomed emitter surface at any angle up to 180 degrees, and not focused toward the front 100 or so degrees, more of them hit the reflector and go straight out to become part of the hotspot.
The problem is, photons that hit the reflector have a greater chance of being absorbed. Reflectors can eat around 15% of all light that hits them. This is bad for total output, but good for throw.
Yes, I ended up with a royal blue MTG2. This LED is built different. Look close and you can see the yellow phosphor is covering the entire round area under the dome, and not just on top of the dies. I think the phosphor is in the bottom layer of silicone and not attached to the die like on the others that survive de-doming with the phosphor intact.
Hi guys, as promised some pictures.
First of the dome itself, removed, from the top. For lack of a better description, the dome was basically just twisted/slid/pulled off the LED by the reflector itself moving the reflector aperture to the side;
Dome from the bottom;
The LED itself, still inside the reflector (and the freaking stubborn head that I just can't seem to twist off);
Incredibly, it still works, and still puts out way more light than an XML2 T6.
Looks like a grilled cheese sandwich
Yup. To my eyes, the last two photos are closer in terms of color, to how it appears to me.
LOL grilled cheese 
Dedoming doesnt seem like a good idea at this point….
The color is shifting to cooler tint because the phosphor is being removed. This emitter isnt special in terms of light production, still a blue die with phosphor on top. It does appear that the phosphor is in the dome itself, at least stuck to the dome. If you look at the MTG-2 you can see a rippled surface texture on the coating versus the SUPER smooth coating on other emitters from cree. It also blankets the entire visible surface under the dome, not just the dies.
Something I overlooked earlier, but the phosphor covers the entire top surface of the square substrate (not just the circle under the dome). Forgot about that as most of mine end up with the silicone scraped off the corners, it's really fragile and easily damaged so most times I just clean it off before even starting. :)
I wonder if all that phosphor surrounding the emitting portion can be relocated over the emitter portion. Also, the phosphor remaining on the dome.