# Surefire U2 Cree MC-E



## Icarus (Dec 20, 2009)

*Surefire U2 MC-E*
· Surefire U2
· Machined reflector
· Cree MC-E M-flux WD-tint (wired 2p2s)
· Custom made heatsink
· Stock driver



 



Deepest part of the back of the reflector is deepened by 0.25mm.
Getting the head open without damage was a real challenge. :sweat:

It's best to run the light off 2x CR123 cells (I suppose two 3V R123's should be fine too). 
However it didn't run in regulation on a single li-ion (3.7V) at the highest level.

Enjoy the pictures and thanks for looking. :wave:


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## TDK-R (Dec 20, 2009)

*Re: Surefire U2 with Cree MC-E*

Great mod as always Freddy :thumbsup:!!!


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## mudman cj (Dec 20, 2009)

*Re: Surefire U2 with Cree MC-E*

Beautifully done! And hey, is that an SW-01 fatty on there?


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## Icarus (Dec 20, 2009)

*Re: Surefire U2 with Cree MC-E*



TDK-R said:


> Great mod as always Freddy :thumbsup:!!!


:thanks: Stefan! :wave:


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## Icarus (Dec 20, 2009)

*Re: Surefire U2 with Cree MC-E*



mudman cj said:


> Beautifully done! And hey, is that an SW-01 fatty on there?


It's an RPM clicky. Looks great on the U2 isn't it? 
I'm told he'll do a new run soon...


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## ICUDoc (Dec 20, 2009)

*Re: Surefire U2 with Cree MC-E*

I agree the RPM clicky looks cool on the U2!
I did this mod with a warm white MC-E. The beam has a noticeable central cruciate darkening. I can't remember what I did to the reflector. I guess what I want is beamshots, baby, beamshots......
Addit: is that machine reflector original, or a new one cut to fit?? 
Addit II: Oh I see it is original but has been made LESS deep (not deeper) by your machining: looks beautifully done as usual.


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## Icarus (Dec 21, 2009)

*Re: Surefire U2 with Cree MC-E*



ICUDoc said:


> I agree the RPM clicky looks cool on the U2!
> I did this mod with a warm white MC-E. The beam has a noticeable central cruciate darkening. I can't remember what I did to the reflector. I guess what I want is beamshots, baby, beamshots......
> Addit: is that machine reflector original, or a new one cut to fit??
> Addit II: Oh I see it is original but has been made LESS deep (not deeper) by your machining: looks beautifully done as usual.


The light already left my house, so no beamshots, sorry... :shrug:


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## criollo (Dec 21, 2009)

*Re: Surefire U2 with Cree MC-E*

Outstanding work Freddy ~ very impressive !! :twothumbs:twothumbs:twothumbs


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## Icarus (Dec 22, 2009)

*Re: Surefire U2 with Cree MC-E*

Thanks all for the kind words.


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## Erasmus (Dec 23, 2009)

*Re: Surefire U2 with Cree MC-E*

Congratulations Freddy! This is a dream light. Of all the lights I ever had, the SF U2 was the one I liked most. With an MC-E this must be the ultimate flashlight for me


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## Justin Case (Jan 10, 2010)

Icarus said:


> Getting the head open without damage was a real challenge.



Any photos or suggestions on what it takes to open the head? Thanks.


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## darkzero (Jan 10, 2010)

Justin Case said:


> Any photos or suggestions on what it takes to open the head? Thanks.


 
It's not too difficult once you've done it. Like any SF heat is what you need to unscrew the top portion. You don't really need to access the driver if all you're doing is an emitter swap but it may be risky melting if you expose the selector ring to the heat source by accident if you don't remove it.

There are a couple different ways on removing the selector ring. Search for Kroma Disassembly. The method I use is turning the selector ring past the point where it stops so it "unlocks" & then the selector ring can be pulled off.


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## Justin Case (Jan 10, 2010)

Thanks a lot!

On the U2A, do you know if it uses the plastic stop piece or the machined-in aluminum block? Opinion on using the yclo method of soda can shims vs your method?


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## maxspeeds (Jan 10, 2010)

Hey Justin :wave:. The U2A is exactly the same as the U2. There is a machined Al block. The plastic stop piece is in all Kromas which makes them more fragile when taking apart.


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## Justin Case (Jan 10, 2010)

Great, so that's at least one less part to break. :thumbsup:

Any difference in removing the selector ring by turning it cl vs ccl past the stop point to unlock the ring? How much force to apply?

I probably won't swap drivers, unless the driver is really underpowered. Any numbers on the drive current for a U2A? I've seen numbers tossed about that seem to range from about 600mA to 800mA.

Thanks in advance.


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## maxspeeds (Jan 12, 2010)

As far as removing the selector ring, don't use the force method. I followed this: https://www.candlepowerforums.com/posts/2427471&postcount=6. It's fairly easy.

Not sure on the drive level for the U2A as I don't own one anymore. It was fairly bright. Knowing Surefire, I'm sure it's atleast 800mA on level 6 (probably higher)


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## Icarus (Jan 12, 2010)

With Vin=6V, output current measured 780mA on high.


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## Long John (Jan 13, 2010)

Great work Freddy, like Cassian said, outstanding and impressive:thumbsup:...:twothumbs 

All the best

_________
Thomas:wave:


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## Justin Case (Jan 14, 2010)

No joy on either the yclo shim method or the alternate force-the-selector-ring method. 

I seem to have a very recent vintage U2A. It has a Seoul P4 with no plastic sleeve in the bore. And the bore is barely large enough to fit an AW17670 cell (the silver label drags). The selector ring seems very tightly fitted (and stiff to rotate), with barely any gap available to insert an Xacto knife blade or soda can shims.

I tried to muscle the selector ring to jump the aluminum stop by going past the minimum setting, but that didn't work either. Used some bike tubing for grip on the head and the ring.

Any words of wisdom, such as use a bigger hammer?

Do you think I can use some focused heat, such as from a butane lighter or a torch to release the threadlocker, and dispense with removing the selector ring? Or is the risk too high of excess heat melting/cooking the ring? I was thinking of wrapping the exposed surface of the ring with metal foil, hoping that the minimal contact with the rest of the light would mean minimal heat transfer to the ring.

In any case, the light itself in stock form seems quite nice. The beam is a very nice white, and very smooth, though possibly a bit narrow. I measured about 8000 lux at 1 meter for the hot spot. Tail current draw on max was about 0.7A. On my bench supply, it looked like the driver pulled about 3.7W-3.8W when running in regulation. The minimum input voltage to reach regulation looked to be around 4.5V, which unfortunately means that 1x17670 (or 1x18650 if I bore the tube) isn't going be ideal. Since I can't open the head (yet), I couldn't measure Vf or If. A ceiling bounce comparison to a Seoul P4 U2-bin driven by an SOB1000 was very favorable. The U2-bin was only slightly brighter using my Mark I eyeball measurement.

Any ideas as to the max Vin that the driver can take? I would assume that 6.4V for at least brief periods is ok, since that would be the OCV for fresh 2x123As. But can it take 8.4V for brief periods, and 7.4V-8.0V for longer periods without frying?

TIA.

Edit: I got the selector ring off. The head is still uncracked. Probably needs more heat.


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## Justin Case (Jan 15, 2010)

darkzero said:


> It's not too difficult once you've done it. Like any SF heat is what you need to unscrew the top portion. You don't really need to access the driver if all you're doing is an emitter swap but it may be risky melting if you expose the selector ring to the heat source by accident if you don't remove it.
> 
> There are a couple different ways on removing the selector ring. Search for Kroma Disassembly. The method I use is turning the selector ring past the point where it stops so it "unlocks" & then the selector ring can be pulled off.



I assume you've taken a peek at the U2 and/or U2A driver? If so, can you provide a photo of them, esp the U2A? Identifying the buck IC would go a long way in estimating what the max input voltage might be. I'm sure many are hoping that the driver can withstand 2x16340.

Also, when you use the twist past the stop method, doesn't the metal stop gouge the underside of the plastic selector ring a bit when it rides over the sharp edge of the stop?


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