Mod: (w Beamshots!) UltraFire T90 (TF X6 Clone), Cree MT-G2 Emitter Swap

My MT-G2 emitters came in today which I ordered specifically for the UltraFire T90 that came with an SST-90. After seeing Match's test results showing the monster output of the MT-G2, I ordered a couple thinking they may improve the throw of the T90.

My plan from the beginning was to try to drive the 6.0V MT-G2 with the stock driver which was driving the 3.6V SST-90. The difference in Vf is significant, to say the least. I tested this on a pair of XM-L emitters in series first (cheaper if they blow instead of the MT-G2). IT worked just fine, and drives 5A into a 6V load no problem.

Getting the LED in was simple, just like any other emitter swap. I got it centered in the reflector, loaded up the cells, snapped it on and... hmm, that's not much brighter...

I was a bit underwhelmed. When looking at the test chart from Match, driving this beast at 5A should yield close to 2800 emitter lumens; to be conservative, estimate 2400 OTF. I measured about 1900. The SST-90 build was close 1500 lumens OTF. I was expecting a much larger jump in output.

Note: I currently do not trust my lumen readings for absolute use, so the only thing I have is relative comparative numbers.

Moving on to throw, again some more disappointment. The SST-90 driven around 9.5A was giving a respectable 71kcd. The MT-G2 brought this down to around 50kcd. Even though lumens went up, the throw dropped a lot.

The spot looks to be a similar size, maybe a little larger (obviously cannot do a side-by-side), with a simply awesome tint (very nice neutral white) and very good spill. The emitter surface area looks to be a lot larger, so I suspect that surface brightness of the MT-G2 is lower than the SST-90.

I put the second emitter on my bare emitter heatsink and at 5A I get 2810 lumens, Match got around 2825 lumens... maybe my lumen measurements are not that far off.

I held the reflector up in front and the numbers dropped close to the 1900 OTF number above. It looks like a lot of light is not getting into the reflector.

All of this is preliminary (assembled for 60 minutes so far), and will be updated as the mod progresses. I posted this now just to see if anyone has ideas about what might be going on and what I can try to figure this out.


Update1: No changes to the light, but I did get a new light meter. The OTF lumens is now 2230. This is closer to what I was expecting. I was thinking there was a lot of loss in the reflector/lens. Now it appears to have been a bad meter (it measures lower on the 50k setting than on the 20k setting). The beam is very nice, nice large hotspot with a smooth spill. It will light up a large area for a long ways; it's about 51kcd for throw, so it's a drop in throw. I'm still contemplating my next move; maybe dedome the SST-90 and put it back in, or mess around with the MT-G2 some more... More to come.

Update 2: Beamshots!!!

I decided to get out and do some beamshots to compare this to my other high output lights; BTU shocker and modified Yinhex YH-X9 (5xT6 @ 12.6A)

All shots: 4s, f/5.6 ISO200, WB Daylight, mouse-out UF-T90, mouse-over named competitor

First set, 35m to trees in center shot. Oops, no control; it would have been black.

UF-T90 vs BTU Shocker:

The T90 has a nice tint with a very defined hotspot. The BTU hotspot is smaller and brighter. The T90 spill is wider but the BTU spill is brighter. Overall, I like them both for their different qualities.

UF-T90 vs YH-X9:

This is the first time I've had either light outside for any serious comparison. I am impressed with the wall of light from the YH-X9. It dominates in the flood department, hands down.

All three, UF-T90, YH-X9, BTU Shocker:

The tint difference is really obvious here.

OK next set; brick wall at 25m. Same camera settings.


UF-T90 vs BTU Shocker:

UF-T90 can't keep up, but it does have a tint advantage. It does not light up the air like the BTU. When I was testing for distance, I found the BTU could reach further, but the beam tended to get in the way more too.

UF-T90 vs. YH-X9:

Here you can really see the well defined, and quite large, hotspot. Again, the YH-X9 takes the flood prize.

All three, UF-T90, YH-X9, BTU Shocker:

I turned it off when the dried flowers started smoking. This is just about 7300 lumens total. ;)

For my exposure settings, I tried to expose so the spill looks like what I see for real. This results in blown out hotspots, especially on that last shot.

Trying to expose for the hotspot prevents the spill being visible. I did take 2 second shots as well, but I found the spill is too dim to represent what was real.

Hello relic, is it because you’re driving a 6V load with a 3.6V driver? Maybe a dumb question? :bigsmile:

Unlikely. That light uses a constant current switching buck driver. As long as input voltage is higher than the required output voltage (which it is in this light) then most buck drivers won’t care if the Vf changes.

I suspect he’s right on the money with his assumptions that the light simply isn’t getting into the reflector properly.


has the relative position of the base of the LED and the base of the reflector changed at all? Does the MT-G2 fill the hole at the bottom the same amount as the SST-90? Are the emitter angles the same? Are you able to vary the reflector height above the LED and measure the output? Might be worth trying to shim it out a bit and see if that makes a difference. Almost a 1/3 of the output lost is pretty high, what a bugger. Are there any other large reflectors that would fit? I remember Troutie tested a bunch with an MT-G2, although I think the one he like was 80mm in diameter!

thanks for the info

i suspect we’ll eventually figure out how to get the most out of the mt-g2

it has been tough at work for a bit but I hope to get back to my project soon

The position is very similar, which I think is not deep enough in the reflector. This MT-G2 seems to throw a lot of light sideways. It also has a thinner base so the reflector needs to go deeper into the head. The head design isn’t ideal for fine adjustments.
The dome size is similar, but the emitter surface area is larger. This is where part of the throw goes away I think.
I think the emitter angle is slightly wider, didn’t check the specs yet.
The output is droping a lot, I will do a bare emitter test on the SST-90 tonight to see if it suffered similar losses.

Do you mean that the driver is not able to regulate output very well? Or just that reflector is absorbing a lot of light?

hmm, from my minimal experience with changing XR-E lights to XP-E/ Nichia (plus an incorrect optic holder on an XM-L), you would expect more of a spot/ throw from having the reflector sit too high, at the expense total light output. When I machined the heads on my modded Romisens so that I could screw the reflector down further, I actually got more of a flood past a certain point. Correct focus seemed to be about 1/2 way between fully screwed in and the previous height. That depends on reflector of course, but it might help.

If the emitter surface is larger, most likely you’ll need a larger diameter reflector to get the same amount of throw. Not much help I’m afraid :frowning: Still, might be worth checking to see if there are MT-G2 specific reflectors in the diameter you can use - changes to the reflector profile might help mitigate some of the focusing issues.

the thing is, the emitting area isn’t as big as the dome makes it seems

mtg2, mtg2 badly dedomed, sst-90 (which has since been dedomed, well :stuck_out_tongue: )

If I were a betting man I’d put money that if dedomed you’d see a huge change in lux. I’m thinking that the cause for your issue is the dome on the MTG-2. You have two of them. Dedome one and see how it works in your torch.

that sounds suspiciously like an experiment :slight_smile:

Actually I have 5, and two have been destroyed by de-doming :Sp
the 2nd attempt was close to success, and it is highly likely I would succeed if I try a third. I haven’t decided yet, but curiosity usually gets the better of me.

I did a reflector position ceiling bounce test, and reflector position wasn’t a significant factor in overall output (unless much too far away). I didn’t test lux relative to position.

It will be interesting to see if relic gets reduced output when he tests the sst-90 bare and with reflector.

My power supply only goes up to about 6.5A, so I tested it at the max available.
Bare SST-90 at 6.5A: 1582 lm
SST-90 with T90 reflector/Lens: 1106 lm
OTF output is 70% of the bare emitter.

Bare MT-G2 at 5.0A: 2810
MT-G2 with T90 reflector/lens: 1900’ish
That puts OTF at 68% of bare emitter.
The losses are basically matching. Not looking good for this reflector/lens…

As a control, I took an XM-L at 3.0A and measured bare and then with a HD2010 reflector/lens:
Bare XM-L U2 at 3.0A: 1036 lm
XM-L U2 with HD2010 reflector/lens: 728lm
Again, OTF is about 70% of bare emitter.
I suspect some of this discrepancy is due to my integrating box not integrating perfectly. Another 8-10% is in the uncoated lenses. The numbers may be close to real. I may need a small ‘box’ factor to adjust for focused sources.
Mule/bare emitter sources appear to be somewhat accurate.
I hope to get more time for this on the weekend; the next day or two will be rather busy for me.

Posting up some info on the Luminus SBT-70:

German Video:

to be honest, the general rule of thumb is OTF lumens = 70-80% of theoretical lumens (bare LED, cooled well), so while 70% is at the lower range, I don’t think it’s completely out of line. I’m also fairly certain that reflector efficiency for a given effective emitter area increases with diameter (I think TIRs stay fairly constant). I don’t really know how big either of the reflectors you used are (not very familiar with torches), but it could be that you’re on the lower end of that efficiency curve.

You’re still getting almost 60% more OTF lumens with the MT-G2 though, which is not to be sniffed at!

I added a small update in the first comment
With my new light meter I measure a more expected OTF output of 2230 lumens. Throw measurement is about the same, since the faulty meter seems to be a problem on the 50k scale only (I measure throw at 3.65m usually).
More to come… contemplating my next move. :wink:

Well you have certainly given this mod a good shakedown. I think it was in one of troutie’s posts that he found that the MTG2 simply doesnt have the surface brightness to be a monster thrower in spite of the plethora of purpose built reflectors he had to play with. Placing 3 XML’s together via direct bond (so the emitters were about touching) produced some rather spectacular results in a large reflector. If you give up on that monster cree, maybe try 3 of the smaller ones all jammed up together. They seem to enjoy each others close company!:smiley:

I’m starting to like the floody nature of it. Plus, the NW tint gives it a real throw advantage; the air doesn’t seem to light up as much.
I may dedome one and see what happens… dunno for sure.

It sounds like youve struck a great useful combination. Range, flood and great tint… all in one. Id guess the SST90 that came stock would probably be low bin. I wonder if a nice new SBT-70 or SBT-90 would be a worthwhile investment? They arent exactly budget emitters though. If it were mine, Id live with the big fat cree for a while and see how that goes.