looks like it desoldered itself due to too much current 
i would try to resolder that ripped off thingie (Transistor?)
it cracked and opened in half not just desoldered and i smelled burning , look at the 1st pic
well as i cant fix this driver and i know i cant find a 17mm driver that can take 2 cells in series so i will trim the bill and flat it then i will try to use a 26mm driver something like this TR-0124B 8.4V but i want a driver with a smaller height so can any one please suggest me a driver with 26mm diameter with a short height and can be modded to 5 or 6A ?
I am using this 17mm LD-40 (or LD-4B as how IOS calls it) in my 1405. This driver delivers about 2.2~2.3A to the LED in stock form. I have replaced the the R100 resistor with two stacked R120 resistors and measured 2.45A at tail - which should be translated into >4.0A to the LED.
It works, but I must say the driver is really pushed to its limit already. The mode changing has became problematic after the resistor-mod, and the light cannot be left on high for more than 4 minutes, otherwise the light will becomes dimmer and dimmer over the time and finally shut off by itself. I thought either the driver or LED was burnt but after a few minutes the light works as normal again. I think the driver cannot handle the heat produced at boosted current like this.
I hope you will finally figure out a way to use a larger buck driver in there, because this is also exactly what I wish to have with my 1405.
I have a similar problem, the modified 1405 I just bought from someone on this forum started smoking as soon as I turned it on and burned up the driver. It was almost a really bad situation as it burned the battery holder and almost burned the battery before I could get them out. I am now gonna rebuild it with a new driver and looking at the LD-4B linked above because it can be used with 2 batteries. I dont really want to cut/ or use a dummy cell as I need the run time of two batteries for my work. However, looking at the LD-4B driver you linked, I noticed it says,” *Suitable for 1-2-3 18650, 16340 or 18350”. Does that mean no 26650? And also since the input voltage is for,” *Input voltage: 3-16V ” could I add an extension and add another battery?
Is your modified 1405 using the stock driver?
Your 1405 situation sounds like a short-circuit to me - a short-circuit which involves two batteries in series, definitely not fun at all. My advice to you is make sure your batteries are still healthy before you use them again, check if they still can be charged without overheating, and see if the batteries still can hold the charge for more then 24 hours without significant drop of resting voltage.
I stacked one R100 resistor on the stock driver and it has killed two of my emitters in a split second due to excessive output voltage - something is not right after the resistor was added. Now I label the stock driver as scrapped part so that I won’t forget and reuse it again. Everyone should be reminded that the stock driver of 1405 is not good for high current application. ohaya and wight have done some test and analysis this thread and it is found not suitable for current boosting. I know some members may have good result with the stock driver anyway but I think there is still certain risk associated with it. And I don’t think LD-4B is good for current boosting either.
To put it simple, we don’t have a reliable and high-current capable 17mm buck driver yet.
26650 has the same voltage as the 18650 (neglect the different chemistry), so yeah you can use two 26650’s with the LD-4B driver without any issue, given that your LD-4B is functioning properly of course. By adding another extension does that mean you will use three batteries? So the input voltage will be 12.6V? If that is the case I believe this is still falling within the specification of the LD-4B thus acceptable, but I have not tried and confirmed this yet so just take my words as a grain of salt.
Messing with lithium batteries especially in series could be a dangerous thing, please be careful with everything you do.
I think it is the stock driver, its the flashlight from here: [SOLD] UniqueFire UF-1405 >400kcd
Ran it less then a minute when it started smoking. Batteries used were 2 almost brand new 18650 EBL 2600 Mah.
Here’s more pictures, maybe someone can tell me what happened from these:
I tested the batteries, one is fine at 4.19 volts, the other one that was in the front is showing 0.0 volts.
Beware of that front battery at .00Volts CK for a Short from battery case battery Tube.
I haven’t got a clue of how that happened but I assure you that the light was tested before and after the mods.
After a minute it did get hot and I’m guessing that the solder could have reflowed and bridged.
lawenforcementguy, are the batteries protected or unprotected? If the one showing 0.0V is protected battery then maybe it is just the protection circuit failed, or need to be reset; But if it is unprotected battery then I’m afraid 0.0V means the battery is gone.
Chazzy, wow you have boosted it to 3.6A! that’s too high for this driver and I guess this is exactly what causes this to happen? My stock driver already failed at 2.20A measured at tail (only one extra R100 was addded).
Yeah they were unprotected, but for sure the next ones will be protected! Taught me a lesson for sure. Chazzy, no worries I knew it was a gamble anytime to buy modified stuff I sure ain’t blaming you. I am looking forward to doing the new driver myself and learning more.
Since you want to keep it running with two batteries I think LD-4B is the only choice at the moment. If you don’t stack resistor on the LD-4B the output current is about 2.2-2.4A to the LED (particularly from IOS). If you use dedomed XP-G2 you will still see fairly good throw running it at 2.4A, probably around 250kcd and you have the good High-Med-Lo modes.
And again stacking resistors on the LD-4B is not advisable. We just got to be a bit conservative with this driver for better reliability especially you will use it on your duty.
I have tried to fix the Driver
as long as i do big numbers of laptop pulls and i was keeping those battery circuit boards for something like that
i have tried 3 components that have the same shape of the fried one on my driver
the 1st one worked but i was getting only one mod and it was very low
the second one gave me the whole five mods but the high mod was only 600ma
With the third one i have decided to replace the working component on the left to replace the damaged one on the right, and used the new one from the battery circuit on the left just in case and then hooolaaaa the driver back in line and working as nothing happened to it H)
ofc i was just lucky iam not an electronics expert or anything it is just luck 8)
Any way I have Fixed the driver 
You're a true component magician!, who knows how many types components come in that package?.... and you found one that does the job!
Great modding!
Well I got the LD-4B driver for mine and put it in the De-domed one.
This pic doesnt do it justice, its noticeably brighter in the circle then the stock one.
LD-4b on right dedomed, stock 1405 on left.
Cant wait to test the throw out tonight at work when im doing the perimeter security. Thanks for the heads on up on this driver.
Nice. What LED are you using now?
hi, could you suggest me a new driver to mod my unit? i would push higher amps and lumens from the original xm-l2 led.
but… i only find driver that does require 1lithium battery. i need one that can push over 4amps and accept 2s battery configuration
AFAIK there is no any good 17mm buck driver that can handle high current (>4A) at the moment.
I use the LD-4B in my 1405 with an added R120, I did not measure the output current but I got 2.4A at tail. Its light output is good but I personally won’t recommend anyone to go high current with this LD-4B because high current is really pushing its limit. After the resistor-mod the driver mode changing behaves strangely and and the light cannot be operated for more than 3 minutes on high mode otherwise the driver will be overheated. In short it is not really a good setup but I can’t find anything else better right now.
The focal length looks very short from the pictures, I thought longer focal lengths are better for throw. Anyone knows what is the focal length of the lens?
I’ve never measured the focal length of it, but focal length has nothing to do with throw. The lens diameter is what matters.