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Thread: Broken Nitecore MH25 tear-down, analysis, repair attempt

  1. #1
    Flashaholic* Overclocker's Avatar
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    Default Broken Nitecore MH25 tear-down, analysis, repair attempt



    so here's an out-of-warranty Nitecore MH25 that just suddenly stopped working so i figured why not take a crack at it generous threadlockers were used throughout. even the driver board was GLUED to the aluminum body required some advanced techniques to disassemble



    first thing i noticed was the PINK teflon wire that goes to LED+ wasn't connected to its solder pad on the PCB. this was probably what caused the flashlight to stop working...



    but as i poked around one leg of the inductor also came loose. this only means one thing: COLD SOLDER JOINTS

    very disappointed with the low-quality soldering. will look for more bad soldering and will attemp to fix tomorrow. will update soon...

  2. #2
    Flashaholic* Derek Dean's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    It's a shame that they build these really neat flashlights with the potential to last a lifetime, and then mess up the soldering. It seems that the electronics which give us such a flexible user interface are also the weak link in modern lights.

    Thanks for a look inside.

  3. #3
    Flashaholic* Overclocker's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Quote Originally Posted by Derek Dean View Post
    It's a shame that they build these really neat flashlights with the potential to last a lifetime, and then mess up the soldering. It seems that the electronics which give us such a flexible user interface are also the weak link in modern lights.

    Thanks for a look inside.

    the surface mount components seem to be ok since they're done by wave. but the inductor and leads are done by hand, probably by someone on her 1st day on the job. this is not the first time i've seen bad solder joints on a Nitecore

    yep the driver is the weakest link. just look at this 3-piece driver, it's ridiculously complex. and they're even advertising this as a weapon-mountable hunting flashlight

    enlarged view:


  4. #4

    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Great job getting that flashlight apart! Looks like you've found the problems. A little solder and you should be good to go!

  5. #5
    Flashaholic*
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    You can thank RoHS act signed into law by the European Union forcing companies to do away with lead based soldiers.

    Tin based soldiers require more head, aren't as ductile as lead and unless conformal coated start to grown small whiskers which short out electronic devices.

    I've also taken apart items that contained numerous cold soldier joints, so it's not just Nitecore that has the problem.

    As for the soldiering to the pad, piss poor design. This joint should have been a thru board joint to keep the pad from lifting as well as maximizing the joint area.

    Good job on the dissection!

  6. #6
    Flashaholic* Tmack's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Since our discussion on this particular light, I have switched my gun light to a convoy m1. I know it still has the driver components directly in front of the cell, but this light i personally built. All my solder joints are extremely well reinforced with a non conductive epoxy, and I installed about a 1/2" rubber washer that seats around the driver spring to help cushion the driver from the cells impact. I have since then fired over 75rds without problems. Even though my mh25 was holding up after a couple hundred rounds, I didn't want to take a chance and have it fail while using it, so I built my own.

    Thanks very much.

    Great job with the pictures btw.
    Tk75vnkt*TK61vn-Tcr10vn*Tcr2vn-C20cvn*V11Rvn*V25cvn*D40avn-D25cvn*S200cvn*MX25L3vn-Mm15vn-X60vn*K40mvn-Hc90vn-Sd6vn

  7. #7
    Flashaholic* Overclocker's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Quote Originally Posted by Tmack View Post
    Since our discussion on this particular light, I have switched my gun light to a convoy m1. I know it still has the driver components directly in front of the cell, but this light i personally built. All my solder joints are extremely well reinforced with a non conductive epoxy, and I installed about a 1/2" rubber washer that seats around the driver spring to help cushion the driver from the cells impact. I have since then fired over 75rds without problems. Even though my mh25 was holding up after a couple hundred rounds, I didn't want to take a chance and have it fail while using it, so I built my own.

    Thanks very much.

    Great job with the pictures btw.

    nice! good call. between this dangling inductor atop a wobbly 3-PCB driver and a linear driver i'd very much rather have a simple linear driver for a mission critical application.

    here's the other side of the thru-hole for the inductor. no wonder it came loose, they cut the stub too short. indeed a very poorly made driver


  8. #8
    Flashaholic* Tmack's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Wow. Pretty sorry looking :/
    I picked mine up at REI so I wasn't expecting gold. Not to say REI doesn't have anything good, but I'd rather buy my lights online.

    Oh and I think you'd appreciate my setup. I actually took the rubber washer from a laser light. So it originally protected a sensitive DPSS laser module. It should be nice and overkill for my setup.
    Tk75vnkt*TK61vn-Tcr10vn*Tcr2vn-C20cvn*V11Rvn*V25cvn*D40avn-D25cvn*S200cvn*MX25L3vn-Mm15vn-X60vn*K40mvn-Hc90vn-Sd6vn

  9. #9
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Quote Originally Posted by Tmack View Post
    Wow. Pretty sorry looking :/
    I picked mine up at REI so I wasn't expecting gold. Not to say REI doesn't have anything good, but I'd rather buy my lights online.

    Oh and I think you'd appreciate my setup. I actually took the rubber washer from a laser light. So it originally protected a sensitive DPSS laser module. It should be nice and overkill for my setup.

    we'd love to see it

    anyway.. it's alive!



    i soldered in the inductor on both sides of the PCB



    and replaced the pink wire with a 22ga of the proper length. the original pink was waaaay too short


  10. #10
    Flashaholic* Tmack's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Awesome! Good work my friend. Always a good feeling to resurrect the dead.
    Tk75vnkt*TK61vn-Tcr10vn*Tcr2vn-C20cvn*V11Rvn*V25cvn*D40avn-D25cvn*S200cvn*MX25L3vn-Mm15vn-X60vn*K40mvn-Hc90vn-Sd6vn

  11. #11

    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Wonderful job putting that light back together! You'll get a lot of use from that light. I mostly use 63/37 solder myself. I also find that using extra flux helps most solder flow better.... Lead free solder melts at higher temperatures and it is tricky getting good wetting. I use it for plumbing only....

  12. #12
    Flashaholic* subwoofer's Avatar
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    Default Re: Broken Nitecore MH25 tear-down, analysis, repair attempt

    Nice thread, thanks for sharing.

    I've also learnt a new term. I was always taught that the bad solder joint you have shown was called a 'dry joint', but now see there are two types of bad solder joint. The 'dry' joint where not enough solder is used, and the 'cold' joint where despite there being enough solder, the temperature was not high enough to flow the solder correctly.

    Can you provide details of the 'advanced' techniques you used for the disassembly?
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