MT-G2 dedome & polish method

Flashlight Modding and DIY Parts
1

I have been working on this for a couple weeks now- destroyed 2 MT's in the process (one was pretty far gone to begin with tho) and I've finally got it to a point I think it's worth sharing, what I mean by that is I feel confident if you use the same grit's as I used here you atleast won't destroy your LED in the process.

I started out trying this with 1500 and 2k grit SiC paper... Don't do that!

[after the failures] I started out with a dome on MT, I use a brand new razor blade to slice the dome off (I also remove the outter edge of silicone/phosphor). Not only do you need to get a clean slice, you can not deposits and dirt / oil / pet hairs on the surface of the remaining silicone. If using a brand new blade make sure you wipe any oil off.

(Sorry for the poor focus)

You want the remaining surface to be as smooth as possible. It is about .25mm or so thick after being trimmed up (if needed) with the razor blade.

The next thing I did (well the only other thin I did) was to lap it, I originally didn't think this would work. Actually at first it didn't, that's how I destroyed the first two. I figured SiC paper wasn't working so I went to my knife hobby and got out my custom ceramic 2-side stone. This stone started it as an 8x2" Spyderco ceramic "fine" stone, I hand lapped it (using Diamond lapping plates) on both sides, one side I took to 3k grit (the final grit of my stone, it took a much finer plate) and the back side I took to 10k. I used soapy water as lube and went to town.

I also used the 365mn UV light to keep a close eye on the phosphor

After lots and lots of very careful lapping on the 3k grit side, all with ZERO preasure I flipped it over and did it all again at 10k and the final outcome-

I've never been good at taking pic's of shiny stuff but these two do show a reflection of the T5 strip above, IRL it's as bit more clear than that, the surface of the silicone is perfectly smooth and has a very slick, glassy sheen.

Note DO NOT touch the finished surface (really don't touch the surface at any point) a single speck of dirt will melt into the remaining silicone the moment you turn it on and ruin the whole damn thing.

Installed in my K40M

Low, surprised me to see PWM!

Mode 2 with backlight

Driver is resistor modded, currently has 2 R082's (stock) and one R050.

Dome on- 4037 120kcd

Polished "window" style dedome 3573 148,200Cd

I think, based off experience and how much of the white isolator is visible in the front on view of the reflector, that removing the isolator and seating the LED just slightly further in the reflector will get it just right, I initially hoped for 200k, when I bump the current [again] I'll also tune the reflector, probably won't get to 200 but 175-180 is my new goal for that light. I'll probably try this dedome method on a few either light's I have in query to really see how it does, I feel safer about it than a regular dedome already tho.

edit: did the math, 12% Lumen loss with a 25% increase in lux.

2

Nice work. Did the tint and beam pattern change at all?

3

Interesting stuff.

So the idea is to end up with a very “shallow” dedome without having to bring the blade so close to the phosphor?

4

Nice! Thanks. :party:

5

Pretty clever working under UV light I’d say!

6

How does the beam look? It almost looks like the dome has a frosted layer on top?
My method is with heat and a knife and it comes out pretty good!

Here:

7

cool thank you for your experiment

8

Wow, that is some impressive problem solving and skill in action there. Congrats. I wonder if keeping that little bit of dome keeps the lumen output at a domed level.

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OK guy’s got the OP reformatted and edited so you can actually read it!

I also checked the number’s, the increase in lux was lower that what I would expect to see from a dedome job on an XM or XP, only 25, but overall lumens also fell less than expected, only 12.5!

The tint also fell some, to the lowest end of “neutral” (I like that tho). The spot is about 1/2 the size and with a donut hole up close (under about 6-8”) as you can expect. Condition’s are horrible for beam shot’s but I will get some soon as weather permits. I only have other Q0 bin MT-G2’s with dome’s, I dont have any with a regular dedome to compare.

All in all I’m pleased with the method, I will be happy with the light if I can get it up to that 175k mark, if [another] resistor mod cant get me there I will be somewhat dissapointed but we shall see…

10

Thanks CK.

11

Nice write up, this looks like a very safe dedome method.
Reminds me of the early XML methods with polishing wheels and such, never really worked that well for me. Really critical is keeping the dome spotless as you say.

Did you make the initial slice along the top of the silicone lip that runs around the dome, or did you use some other spacer to ensure the right height?

12

Excellent development! Have you considered putting on a thin coat of LED Seal to help with the durability of the emitter?

13

What durability issues do you anticipate with a partial dedome?