# Surefire KROMA mod/review/how-to...(many pics) COMPLETED 4/21



## cryhavok (Apr 12, 2009)

I've been itching for a Surefire Kroma forever so I finally picked one up...and that same day, I opened the head and had it completely disassembled :devil:

A little about the Kroma: I opted for the civilian version, meaning 2 led colors in addition to the white main beam. The light houses 16 3mm LEDs with a distribution of 8 blue and 8 red. The red and blue LEDs are very bright and produce a huge amount of light for only 3mm LEDs. Keep in mind, 3mm LEDs actually use the same die size as the more common 5mm LEDs...they just have less optical plastic and are more floody.

The red LEDs easily light up an entire room on high and are excellent for preserving night vision on low. I decided to keep these LEDs stock as they are a useful color.

The blue LEDs are also extremely bright. Apparently they are useful for tracking blood but I don't have any real use for the color. I decided to switch them to UV leds...tracking body fluids is more my thing  ...more on this below.

The white led is a luxeon 3 behind an optic similar to the KL1 (note:not KX1). The beam is very interesting with many weird lines and not much of a hotspot. It does not have a similar beam to the old KL1...this light has a lot more spill at the cost of much less throw. I'm actually crazy about throw, so I knew I wanted to do something to improve the beam (besides updating the LuxIII to a modern high power LED).

Now for some pictures:
Note: I alread removed the central optic and Luxeon LED in the following pics.

Opening the head:
I followed these instructions and they worked great. I used 4 coke can shims equally spaced and the ring came right off with minimal effort and no damage. 

Pics of the head open:
Here is what the head looks like right when you open it










Here is a picture comparing the KL1 (left) and Kroma (right)




Another:





The optic is just free floating, so it should come out easily. You may need to bend some of the 3mm LEDs outward as they kind of hold the optic in place.

Next, remove the plastic ring that "aligns" the 3mm LEDs





Next, use a small flat-head screwdriver and pry the light engine out of the head. There are 4 slots around the head...just keep going around as it wiggles out. Notice the slot in this picture





There are 2 circuit boards that attach by 2 sets of pins. As you wiggle out the top piece, you are separating the 2 boards. Here is the bottom of the light engine unit:





And here is the inside of the head:





Have you ever seen such a complicated circuit layout for a flashlight  

Here are some side shots of the light engine:









And after removing the 2 screws shown above, you can move the heatsink a bit (but you cannot remove it from the circuit board as the blue LEDs won't fit backwards through the holes:





Now a thing to note is that the entire black piece is 1 single chunk of anodized aluminum.  I don't even want to know how many steps it takes to machine just one heatsink. It really is an ingenious design. The heat from the main led actually has a large surface area to dissipate. Additionally, the heat will spread to the flashlight head through the outer rings of the heatsink (you can see the gray goop in the shot above of inside the head...that is actually heatsink compound)


Stage 1 of the mod involved swapping the 3mm blue for UV LEDs. Now I am very particular in the LEDs I use...I don't want to throw in any cheap 3mm


----------



## cryhavok (Apr 12, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

What the heck happened to the rest of my post 

This is only 1/2 of it...it was there last night :thinking:


----------



## cryhavok (Apr 12, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

I'll try to remember what I had typed last night...

Stage 1 of the mod involved swapping the 3mm blue for UV LEDs. Now I am very particular in the LEDs I use...I don't want to throw in any cheap 3mm UV LEDs in. All of the 3mm UV one I found were over 390nm in wavelength...much too violet. Although they may appear "bright," they are actually emitting a ton of violet light that washes out what little fluorescence you get. Also, 3mm LEDs don't' throw very well.

I had some 360nm Foxgroup 5mm UV leds. They are very high quality and have very tight tolerances, but I find they are a bit too deep in the UV spectrum to make the majority of things fluoresce and appear a bit too "dim." From my research, ~375nm seems to be the best trade-off.

I was finally able to find some UV leds that were suitable...they are the Nichia 375nm 10 degree beam. Unfortunately, they only come in 5mm metal can type. I went ahead and ordered some (at roughly $10 a piece :huh: ) and hoped I could make them fit.

Here is a shot comparing the Nichia to the current 3mm blue in the Kroma









As you can see, they are quite a bit larger.

I went ahead and desoldered the first blue LED from the Kroma and put in the Nichia. It was easier than I expected...desoldering braid is a must!!
Soon after, I had all 8 in the head, reassembled the head, held my breath, and turned the light on. It works!!

Both the high and low levels work as expected. The UV light emitted is extremely high quality...just a faint "white" light that makes things fluoresce very brightly. I wanted the light to be able to throw the UV light and I achieved this with these LEDs.






















Stage 1 is completed and I must say I am very pleased with the result. I will align all the LEDs once I'm ready for final assembly (anyone that owns a Kroma knows that some of the LEDs are a bit cockeyed...)

Stage 2 won't be completed for a few weeks as I wait for some new optics. It is interesting that the heatsink is both square and circular...as if they wanted to keep their options open when a new LED would arrive.





The square heatsink probably was meant for the Luxeon K2 TFFC, but given that I can't change the drive current to the main LED, I won't be using that LED as it isn't as efficient as the Cree or Seoul offerings. I will likely be using a Cree R2 in my final build


----------



## griff (Apr 12, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

I love the "How to" fix, make it ,take it apart threads
I wish we had a group of members that would share more
of the "dark secrets" 
Disassembly is a big part of the battle and is something that interests me.
3rd Shift was a master at sharing this type of info!
Noy to take anything from the Guys who make $$ doing mods . I just want to be able to tinker and having" Helpful Hints" makes the process more fun!


----------



## brighterisbetter (Apr 12, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Thanks for sharing the progress thus far. I agree with griff that the pics are very helpful. Very anxious to see how the finished light turns out.


----------



## GunSmoke16610 (Apr 12, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Excellent post! Keep the details coming. lovecpf


----------



## schiesz (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*


----------



## tebore (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

It's true Cree is more efficient than the TFFC based LEDs at the moment but I'd give them a shot if you want a cleaner throwing beam. No Cree rings with a shallow refector the lens of the LED also makes the die look smaller than an XRE(works better for throw unless you're going aspheric). 

I've been looking at specs and testing lately and I'm starting to think that the latest batch of TFFC K2s might be as or more efficient than U2 bin SSC P4s and you don't get the color shift as you move from the centre of the beam. As well as better thermals and high current handling. 

Just something to think about since the heatsink is pre-cut.


----------



## cryhavok (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

I agree that the spirit of CPF should be sharing knowledge. 

Regarding the main LED, I'm still on the fence as to what to use. I have never been a fan of Seoul P4's, so I don't think I will use one of those.

I am mainly looking to use a Cree XR-E and small aspheric lens. I recently put a K2TFFC in a KL3 and the light definitely is brighter as compared to the Seoul P4 that I originally put in. 

I don't know if a K2 + optic/reflector will be able to outthrow the XR-E with small aspheric lens. I have a few different options currently, so we'll see what works out as I start to get the samples.


----------



## Icarus (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

:wow: excellent thread! :twothumbs and... I love the close-up pictures!  ... :wave:


----------



## bullettproof (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Yes very good thread it will be cool if you can get the Aspheric to work with the R2. What is Surefire driving the factory main LED at??? I take it that it would be very difficult to put a new driver in.


----------



## cryhavok (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Icarus,
Thanks...I always enjoy viewing your build threads :thumbsup:

bullettproof,
I'm not sure of the drive current to the luxIII...Anyone know? It would be impossible to change the driver and keep the 6 levels activated by the selector ring. Now if someone had some insight on which resistor could be changed to alter the drive current of the main LED...that would be awesome. I know CPF member CM did used to change the resistors on SF circuit boards to up the drive current. I'm sure it's possible, I just don't know where to begin.

I hope it is at least 700mA. I suppose I should measure it now while the head is open...


----------



## Superdave (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Surefire seems to run Luxeon leds pretty hard. I found the Vf to be around 5V on my U2. The U2's driver turned a Q5 angry blue when i was testing it.. It handled the MC-E just fine though. 


I bet a MC-E wired 2S2P would perform very well in there with a reflector. :thumbsup:


----------



## Bullzeyebill (Apr 13, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*



cryhavok said:


> Icarus,
> Thanks...I always enjoy viewing your build threads :thumbsup:
> 
> bullettproof,
> ...



It probably is at least 700mA to LED as that is what it would take to make a Lux III have some decent output, and that would only be about 70 lumens or so. Maybe they used one of the high flux Lux 1's

Bill


----------



## cryhavok (Apr 14, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Superdave,

I'm assuming you were using an older LuxV head when you tried the Cree XR-E? That head put out ~700mA at 6V, so yes that surely would cook a XR-E. Given that this light is meant to drive a LuxIII, a MC-E won't work well as it would have to be wired all in parallel. You are only going to get ~3.6V and 500-700mA from the driver. This is why the newer U2A's are unsuitable for MC-E mods...the circuit boards just don't put out as much power as before (at the benefit of gaining runtime).

Bill,

The light is only rated at 50 lumens from Surefire. I'm going to assume they were using U-bin LuxIII's (this was the top of the line back in the day. As an aside...I remember paying $30 for one of these a few years ago...and thinking I got a good deal  ) 

Looking at the binning sheats of LuxIII, this translates to 87.4 - 113.6 lumens at 700mA. Of course, Surefire is always conservative on their lumens ratings, but by how much? 


The best thing would be to figure out how to up the drive current of the stock driver. I know it is as simple as stacking another resistor on top of a sense resistor...just which one? Hmm...


----------



## toby_pra (Apr 15, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

Cant wait to see the results! :twothumbs


----------



## bullettproof (Apr 15, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*



cryhavok said:


> Superdave,
> 
> I'm assuming you were using an older LuxV head when you tried the Cree XR-E? That head put out ~700mA at 6V, so yes that surely would cook a XR-E. Given that this light is meant to drive a LuxIII, a MC-E won't work well as it would have to be wired all in parallel. You are only going to get ~3.6V and 500-700mA from the driver. This is why the newer U2A's are unsuitable for MC-E mods...the circuit boards just don't put out as much power as before (at the benefit of gaining runtime).
> 
> ...


 

Well I guess you can try each resistor and find out LOL since its out then post the info for us.The Kroma is such a cool looking light. I wish Surefire would step it up in the Lumen output department for as much as they cost you think they would.That light would be super awesome pushing an R2 @ 1.2A with that little Aspheric.It would deffinately have a wow factor.Even if the driver is only at 500ma with the R2 it would be 154 Emitter Lumens and at 700ma 199 Emitter Lumens. I would find out first what the driver is putting out and go from there.Either way its gonna be a huge difference from say 80 lumens its putting out with the factory Led.


----------



## tebore (Apr 15, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

The original LED was probably a T bin as it was much easier to get a T bin in volume than a U-bin. If you factor some losses it would give you the 60 lm rating with a T bin driven at spec.


----------



## cryhavok (Apr 21, 2009)

*Re: Surefire KROMA mod/review/how-to...Stage 1 (many pics)*

So I was finally able to complete the mod today when I received the optics from DX.

I went ahead and measured the current to the LED as well. I got 700mA from 1x17670 @ 4.06v. With 2 new CR123s, I measured 1A. This is great news!! :thumbsup:

I ended up using a Cree Q2 WH. I didn't have any R2's left and these Q2's have an exceptional tint. I will likely swap the LED once the next brightness bin comes out. I had to trim the corners and the ends of the LED a bit for it to fit.

The optic from DX was the biggest surprise. I wasn't expecting anything as good as what I received. It produces a clear, sharp image of the die and throws quite well given how tiny the optic is (~21mm diameter I think). It only needs to sit a few millimeters above the Cree dome, so it actually has ample room to spare. I used an O-ring as a placeholder for the optic and glued the optic down to that o-ring once it was where I wanted it. 

Now for some pics. I don't have much time now, but I will post up the beamshots later.






This shows the red led beam vs the UV. 









As you can see, the spill of the red leds is being limited by the head. They emit a huge wide beam. Contrast that to the narrow 10 degree UV leds. The light remains relatively tight, giving the UV some throw. Both of these shots are the low setting. 

Here's 1 beamshot of a P1D Q5 vs. new Kroma. Exposure turned to -2





lux meter shows 8,500 @1 meter for the 17670 and 10,000 [email protected] meter for the 2cr123s. This baby has some throw! Contrast that to the stock LuxIII and optic, which was below 2,000 [email protected] meter if I remember correctly.

All in all, I think this is one of my most satisfying builds. It came out way better than I had anticipated, mainly because the drive current of the LED is high enough and the optic works great.


----------



## bullettproof (Apr 22, 2009)

Looks good Im impressed with your build. So how long all in all did it take to do this mod?


----------



## cryhavok (Apr 23, 2009)

If you had the parts, you could complete the build in 1 day.

I just received a new optic that I'm going to try out instead of the lens. It should give a more traditional type beam without sacrificing too much throw. We'll see if it fits...


----------



## toby_pra (Apr 24, 2009)

Exellent Beam!!!


----------



## cryhavok (Apr 25, 2009)

New day, new optic :nana:

The light now sports the same optic as the malkoff M60's. Produces a great round beam that is pretty tight and throws well. I lost a bit of throw while gaining a much better looking beam.


----------



## RyanA (Apr 25, 2009)

So what are you doing with the old optic?


----------



## tebore (Apr 25, 2009)

cryhavok said:


> New day, new optic :nana:
> 
> The light now sports the same optic as the malkoff M60's. Produces a great round beam that is pretty tight and throws well. I lost a bit of throw while gaining a much better looking beam.



So when are the new beam shots coming?


----------



## cryhavok (Apr 27, 2009)

Finally got around to taking some new pictures.

First some notes: 
I'm really liking this new optic. The beam is very similar to a SF w/ Cree & TIR. It produces a well defined, tight spot with sufficient spill. I had a difficult time finding a way to mount the optic, but as it stands it is OK. I have some Cree R2 WH and more optics on the way to rebuild this head.

I've noticed a slight flickering on high of the main LED when using 1x17670. I'd say it flicks ~10% in output for full blast for the rechargeable battery. Note that I measured ~700mA to the LED when using a fully charged 17670 and 1A when using 2xCR123's. The circuit is definitely buck type.

No flickering at all when using 2xcr123s...rock solid regulation. For around the house, I'm going to use the 17670 as the flickering isn't noticeable until you are shining at a white wall and looking for it. If I need to take the light out on a trip, though, I'll use the 2xcr123's as it was intended for full output and no problems.

I am pondering ordering some more Kromas to do this mod. It really updates it into an excellent performer. Plus, it is just darn cool with the selector ring. Is there any interst in a Kroma modding service? I have not tried any of these new high CRI crees, but they might make for a nice LED swap.

12" from white wall on low






Fenix P1D Q5 on left vs. Kroma on right





Same as above with -2 EV





Showing new optic with red LEDs on low


----------



## Bullzeyebill (Apr 28, 2009)

Would be interesting if you would post the current at tailcap of the different levels using a 17670 and two CR123's. It might be regulating at the lower levels where vf is lower, with the 17670, and might give similiar reading for two CR123's at those levels. 

Bill


----------



## cryhavok (Apr 28, 2009)

Here are the current readings from the tailcap. Note that I actually had to use the tailcap in the circuit as the lower levels are controlled by some sort of resistor in the tailcap

17670 4.13v
Red low: 30 mA
Red high 150 mA
UV low: 30 mA
UV high: 80 mA
white low: 30 mA
white high: 700 mA

2xCR123 - 6.06v
Red low: 30mA
Red high: 190mA
UV low: 30 mA
UV high: 180 mA
white low: 30mA
white high: 850mA

I'm not quite sure what to make of these numbers :thinking:


----------



## bullettproof (Apr 28, 2009)

I think you should go back in and find which resistor needs to be changed out.If you could get the light with an R2 in it with a nice optic and push it to 1.2-1.4A I think it would be an excellent light that would really perform and be sought after especially by the M&P crowd.


----------



## Bullzeyebill (Apr 29, 2009)

Well, the light runs in regulation in low with both 17670 and 2CR123's. It does not run in regulation on high with the 17670, not enough voltage.

Bill


----------



## gollum (Apr 29, 2009)

great mod you've (bravely) done 
I'd be freaking out dismantling the heck out of it like that
but I'm not a modder 

close to a perfect allrounder (for me anyway)


----------



## cryhavok (May 2, 2009)

bullettproof,
With this type of circuit, I don't think there is a resistor that I can change that will up the current. As Bill said, it is a buck circuit and 1 rechargeable battery doesn't provide enough voltage.


----------



## tebore (May 2, 2009)

cryhavok said:


> bullettproof,
> With this type of circuit, I don't think there is a resistor that I can change that will up the current. As Bill said, it is a buck circuit and 1 rechargeable battery doesn't provide enough voltage.



Just throwing this out there. 
Maybe look at changing the circuit to allow for 2xRCR123 and reducing the amount of buck. The circuit looks really hard to trace however.


----------



## Afraid-of-the-dark (Nov 14, 2009)

That's a pretty sweet mod. I wouldn't mind having the main LED on my Kroma upgraded to a brighter LED.

Is there anyone out there that offers this treatment as a service?


----------



## ceriksson (Oct 15, 2010)

Ok I have to resurrect this thread back from the dead as I find it fascinating.

I'm not necessarily new to the site more of a lurker. I post over on the marketplace section.

I just ordered a Kroma for work. I am active duty Navy working on the bridge of a warship and I wanted a good quality multi-color light for night work where a low and high red output is necessary.

at home I am also a hunter so the blue light also sounds good, however I love the idea of switching out for UV for tracking.

I am really considering carrying our your part one mods to switch over to the UV as I'd find it more useful than the blue.

I'll see how it goes when it arrives and whether or not it is a task I can do myself or whether or not I need to track down a SME to help me out nearby.

I can solder and desolder. I've done that, but I don't have much experience working with the other parts of the unit. From what I can see for the part one, the task is more or less the removal and replacement of the blue>UV LEDs. I'll likely also go with your lead on the same LEDs unless there is something better available since you first did your mod.

Also while i'm in there, any one know of any spots on the Kroma that would work to include a trit vial? I have a bunch lying around and I figured I'd see if I could include some before closing things back up.


----------



## tobrien (Apr 12, 2013)

phenomenal work!

what DX item # was the optic? is it absolutely necessary to replace the optic if I, say, install an XP-G2 in the main LED spot?


----------



## T_zero (Apr 17, 2016)

hello.

and if I wanted to do this mod today, which led I should use?

thanks


----------



## T_zero (May 6, 2016)

T_zero said:


> hello.
> 
> and if I wanted to do this mod today, which led I should use?
> 
> thanks




any help?


----------



## m4a1usr (May 6, 2016)

T_zero said:


> hello.
> 
> and if I wanted to do this mod today, which led I should use?
> 
> thanks



I haven't modded mine yet but I have the head opened and ready. Just haven't settled on whether to dump the TIR optic and go with a standard reflector. Decisions, decisions! Well back to your question. Which LED to use? I don't know all of the variations of the Kroma myself so I can only speak from mine in hand but mine has the Lux III led, just like the OP has, and that LED has a max Vf of 3.99 volts. So your options could be (but not limited to) any of the following choices. You could use an XPG, an XPL and of course the venerable XML. You could benefit from using an LED with a larger die. But it might also create some issues. If you have already gotten involved with swapping emitters your probably well versed in some of the issues that could require some customization. Good luck with your mod and post some pic's if possible. It would be nice to see this thread updated with a modern LED.


----------

