Wow! That is fantastic. You got quite a beastie there. Thank you for the beam shot.
EDIT: I was just admiring that beam shot again and noticed there is a good amount of blue in the beam. Maybe it is due to the concentration of the light by the aspheric. I don't know as I don't have much knowledge of aspherics. It could, however, be due to inadequate heat sinking. I've had blue in a couple of my MT-G2 builds. In both cases, improving the heat sinking got rid of it. Getting the emitter on copper and then linking the copper well to the flashlight is what fixed up my blue beams.
I think the blue hue comes from the optics, though in real life its not as visible as especially in the white wall shot I think premium glass lenses would be more in the range of $100+ than a few tens of dollars. Also, have to remember that the dome itself is big and dedoming would probably help too. I’ll try dedoming sometime, although it seems not to be easy. I have some ideas to try out anyhow.
About the heatsinking, which is important. Please correct me if I’m wrong, but I think the early thermal path is Ok, since the led is on copper and the copper MCPCB is actually soldered on brass pill. What would help is to have a better thermal dissipation from this “led pill neck” to aspheric head thermal radiator. This would increase the runtime on high as well as led could be driven with higher amps. Currently, its better to have a max runtime of 1 min on high. Inserting thermal grease on neck threads is probably a remarkable improvement, however, have not done that because I want to have the option to quickly change a dedomed XM-L2 or XP-G2 neck/pill without mess to have those hundreds of Cds of throw 8).
I think the blue hue comes from the optics, though in real life its not as visible as especially in the white wall shot I think premium glass lenses would be more in the range of $100+ than a few tens of dollars. Also, have to remember that the dome itself is big and dedoming would probably help too. I’ll try dedoming sometime, although it seems not to be easy. I have some ideas to try out anyhow.
About the heatsinking, which is important. Please correct me if I’m wrong, but I think the early thermal path is Ok, since the led is on copper and the copper MCPCB is actually soldered on brass pill. What would help is to have a better thermal dissipation from this “led pill neck” to aspheric head thermal radiator. This would increase the runtime on high as well as led could be driven with higher amps. Currently, its better to have a max runtime of 1 min on high. Inserting thermal grease on neck threads is probably a remarkable improvement, however, have not done that because I want to have the option to quickly change a dedomed XM-L2 or XP-G2 neck/pill without mess to have those hundreds of Cds of throw
Sounds good. Brass pills are not the best, but it's good that you reflowed the base to the pill. I hear you on the thermal grease. I really don't like using the stuff. What works way better anyway is to wrap the threads in copper tape. You will feel the difference right away. Just clean the threads real good with alcohol to get the grease out of them. I find copper taped threads work real smooth without lubrication. Try it. It's standard procedure for me.
EDIT: I forgot that you mentioned dedoming. I highly recommend it for reflector lights. It is easy using the procedure in Post 42 of the following thread:
I say easy, but you still want to be careful. It's really a mostly dedome that I currently do. I done 3 so far, all successful. It would significantly improve your throw, but I don't know if the focused beam would become ugly with the scraps of silicone that I currently don't remove. The scraps can probably be removed, but I would recommend a steady hand since the area over the diodes is 3 dimensional.
EDIT2: I disassembled light that has been subjected to high currents this weekend. The adhesive from the copper tape was hard to clean up. It also looked like the copper and aluminum were undergoing a galvanic reaction. Because of this, I am now going to use plain aluminum foil for most thread wraps. It will be a little less effective than copper transporting the heat across the threads, but seems the lesser of two evils.
The MT-G2 doesn’t take kindly to de-doming in my experience, and that is also what others say. It’s very easy to mess up the beautiful tint it has, with no gains OR simply destroy it in the attempt. The phosphor is completely covering the die base, with 72 independent tiny dies lying underneath it. Very often the phosphor comes off those tiny dies and gives a blue or purple tint to the light, meaning too much UV is escaping.
Try de-doming it only if you’re prepared to replace that $18 emitter.
The MT-G2 doesn’t take kindly to de-doming in my experience, and that is also what others say. It’s very easy to mess up the beautiful tint it has, with no gains OR simply destroy it in the attempt. The phosphor is completely covering the die base, with 72 independent tiny dies lying underneath it. Very often the phosphor comes off those tiny dies and gives a blue or purple tint to the light, meaning too much UV is escaping.
Try de-doming it only if you’re prepared to replace that $18 emitter.
I guess I'm pretty lucky with my shaky hands and bad eye sight to have a 100% success rate on these emitters. Tint and cri even improved on all of mine. I'm for sure too hard headed to listen to what others say can't be done to take it on faith. But I do agree, dedoming any emitter involves risk. Since there are no exposed bond wires, you won't kill the emitter. But you can accidentally remove some of the phosphor. That is why I leave a thin layer over the crystals. I just need a good steady hand day and some form of magnification to tackle that too.
I predict that one year from now, dedomed MT-G2 lights well be pretty common on BLF. I for sure will continue dedoming mine.
Maybe you gather up the phosphor around the crystals, grind it up, and then glue on top of the crystals. If that doesn't work, you could build a remote phosphor light application.
I also think that mt-g2 dedomes will be more common, successful and easy in the future. There is just some learning curve needed. What I was thinking to try is, firstly cut most of the dome top away with a razor and then make multiple cuts to the rest of the dome (probably in between the phosphor lines in order to avoid damage to the phosphor) and then leave it to gasoline (or some other solvent) for some time, try to take off the rest of the dome and mostly see what happens
Cutting may be a good idea. Using a pick, I try lift off as big a good chunk of the dome as possible. From there, I may get one or two good size pieces and then I'ml basically picking at it from there. It kind of crumbles apart. The area outside the crystals comes off clean. I pick as close to the crystals as I dare and stop there. I would suggest doing the same, using the emitter, and then deciding if you want to do a more aggressive dedome.
I'm guessing DBCstm's emitter may have got too hot, because it looks like there was a lot of melting going on there. Hopefully, he can give a couple more details on what he thinks may have gone wrong. I feel that my guide that I linked above has adequate warning, but he was right to also warn you.
I think gasoline will dissolve your phosphor. Ohaya did a dedome using gasoline and lost most of the phosphor. I don't know about you, but to me the phosphor is a big part of what makes the MT-G2 so great. I think aspherics tend to cool down the beam. So a dedome without losing phosphor could end up being real sweet with this emitter. Ohaya may be able to add details on that.
I usually use gasoline to de-dome, but didn’t on the MT-G2. Instead, I used the Vinh method pretty much like Markow is describing. I cut the dome off with a new XActo blade, very close to the die. It was actually pretty good at that point, but when I went further, well you see what happened.
What is this talk of crystals? There are no crystals. I have the die with zero phosphor, if there’s crystals it’s a microscopic thing that I can’t see with a 10x loupe. I, uh, well, kinda took it down to the trace underneath everything to see what makes it tick. Didn’t see anything that made me think crystal. Probably missing something though, usually do.
So if I hook this back up to power, what will it do? It has nothing on it what-so-ever. Just the trace looking swirling lines that connected all the dots. Hey, when you mess up, go all the way right?
Looking forward to hearing about this, very curious how these things work.
Inspired by you Markow, I decided to play a little bit with a 59mm apsheric lens and a DST with the reflector portion of the head removed. The lens has a pretty short focal length. Before this thread, I wouldn't have considered the MT-G2 and aspherics a good match. I didn't get results like you have here, but I don't have your lens either. I measured lux and it was quite disappointing. I intend to keep trying though. I have a 100mm on the way from FT that I will try next. I could see a light with a big hot spot and no spill being potentially handy.
What I wanted report was that when I fully focused the beam, I could see flaws in my dedoming. The image wasn't hideous, but it wasn't a nice perfect image of the emitter either. I could see variations in the tint across the die and one small spot that was blue. It can't see the spot in a picture I have of the emitter. I will have to try to take a real close macro sometime.
I notice that both DBCstm's emitter and mine have a "black" spot in the same place outside of the field of crystals. I wonder what that is. It looks like there is something under there. It doesn't show in the projected image from the aspheric, but neither does the phosphor area outside of the crystal field.
The beam looked fine, though, when it was just slightly out of focus.
I don't know if this means that complete dedome would look better or worse. I think it's the silicone scraps that I left attached that are causing the variations in tint. It's hard to tell because the die itself has it own variations from the crystals and the gaps between the crystals. The question is, would any phosphor come off trying to get all of the silicone off.
EDIT: I just realized the above is not the emitter in the DST. I'll try to take a picture of that one. I do remember accidentally hitting one of the emitter's crystal field with the pick when dedoming. I also remember that it removed some phosphor at the point of impact. The DST emitter must be that one.
I think premium glass lenses would be more in the range of $100+ than a few tens of dollars. Also, have to remember that the dome itself is big and dedoming would probably help too. I’ll try dedoming sometime, although it seems not to be easy. I have some ideas to try out anyhow.
I think premium glass lenses would be more in the range of $100+ than a few tens of dollars. Also, have to remember that the dome itself is big and dedoming would probably help too. I’ll try dedoming sometime, although it seems not to be easy. I have some ideas to try out anyhow.
