Broken Nitecore MH25 tear-down, analysis, repair attempt

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Overclocker
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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 Wink generous threadlockers were used throughout. even the driver board was GLUED to the aluminum body Sad required some advanced techniques to disassemble Wink

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 Sad

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

ohaya
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Hi,

What happened to it?

Also, actually, though it’s not 100%, it looks like that inductor lead was not soldered at all? Also to the left and up, there’s another inductor lead that is just in the through hole, but doesn’t look like it’s soldered either?

EDIT: Or maybe those two leads are just there to mount the inductor to the PCB, i.e., just mechanical. It’s kind of hard to tell for sure, but it looks like they’re a different color (silver) than then actual windings on the inductor (copper colored)?

Overclocker
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hi! well it just stopped working. never been dropped. not even a single scratch.

the inductor legs are actually soldered on the other side of the PCB but was done very poorly. will try to take a pic later. btw these are electrical connections to the inductor. the ends have been stripped of the lacquer coating

on the bright side those R050 resistors seem like they’re sense resistors. perhaps a resistor mod is in order to boost the power Wink

likevvii
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Wow 3 layers of pcb!! How come so many??? Is there a really special feature to this driver?

I love heatsinks!

WarHawk-AVG
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Apparently it is USB chargeable and has the ability to act as a USB portable power unit…so one of those boards is more than likely the control circuitry for all that.

Quote:
Features of Nitecore MH25 860 lumen USB Rechargeable flashlight: • premium CREE XM-L U2 LED • dual power options – use the included USB rechargeable lithium-ion battery OR 2 CR123 batteries • Specs using the included 18650 lithium-ion battery: Turbo* – 860 Lumens, 1.75 hour runtime, 236 meter beam range (774 feet) High – 320 Lumens, 3.25 hour runtime Medium – 130 Lumens, 8.5 hour runtime Low – 40 Lumens, 28 hour runtime • Clickable tail switch for momentary on or constant on in turbo + 1 user-selected mode (twist head to activate) slightly loosen flashlight head and lightly press switch to access all modes mode sequence – High > Medium > Low > SOS > Strobe press and click to select the desired mode • Intelligent memory function stores your last used brightness level in user-selected mode • Powered by a rechargeable lithium-ion battery (included) OR 2 ea. CR123 batteries • USB charge cord allows you to charge the included 2300 mAh battery inside the flashlight (AC wall adapter not included) charging indicator light: red indicator blinks twice every second – battery is charging red indicator light is steady – charging is complete red indicator blinks rapidly – battery is not charging (indicating a problem) *Note: the MH25 must be in the “ON” position to successfully charge the battery • smooth reflector optimized for long-range beam – over 774 feet • Reverse polarity protection prevents damage due to incorrectly inserted batteries • Stainless steel retaining ring protects the core components from damage • Ultra-clear mineral glass lens with anti-reflective coating • Constructed from aerospace grade aluminum with hard-anodized finish for extreme durability • Waterproof to IPX-8 (two meters submersible – not dive rated) • drop tested to 1.5 meters • Measures 6.3” long x 1.6” head diameter x 1.1” body diameter • Weighs 6.75 oz with included lithium-ion battery • Made in China • Limited 1 year warranty (damage caused by battery leakage or misuse is not covered) • Includes Nitecore MH25 flashlight, Nitecore NL183 rechargeable battery, USB charge cord, tactical ring nylon belt holster (open bottom), wrist lanyard, removable metal pocket clip, spare switch cover, and 2 spare O-rings
likevvii
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ohh, thanks for the explanation.

I love heatsinks!

Gurthang
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Perhaps now would be a good time to update the LED w/ a XM-L2 on a sink-pad. Here’s hoping that the repairs are as simple as one or two solder joints.

WarHawk-AVG
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Yeah, it looks like its upgrade time

  • XM-L2 on sinkpad/noctigon and bonded well to shelf on the head below the reflector (make sure you insulate the solder joints)
  • Solder in some 22ga wire
  • Solder in that inductor good on both sides
  • either add another R050 on top of one or both of those (they look like the current limiting resistors, you could bridge them but not sure if that will be too much for the electronics of the driver)

I would almost bet the wire was the culprit, if that inductor was soldered on the other side it might not have needed it on the top, but a little blob there probably couldn’t hurt

snakebite
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what beautiful workmanship Wink
hopefully the converter didnt self destruct with no load.

Overclocker
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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

Overclocker
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WarHawk-AVG wrote:
Yeah, it looks like its upgrade time
  • XM-L2 on sinkpad/noctigon and bonded well to shelf on the head below the reflector (make sure you insulate the solder joints)
  • Solder in some 22ga wire
  • Solder in that inductor good on both sides
  • either add another R050 on top of one or both of those (they look like the current limiting resistors, you could bridge them but not sure if that will be too much for the electronics of the driver)

I would almost bet the wire was the culprit, if that inductor was soldered on the other side it might not have needed it on the top, but a little blob there probably couldn’t hurt

you’re right! it was the pink wire. waaay too short.

well this light has a crappy UI so i probably won’t waste a good XML2 on this one

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

DanAlS
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Hey all, I have had the same issue it seems, although I cannot figure how to take apart the final piece from the casing to expose the conductors and wiring inside… Can anyone help me out please?

edupenna
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Hi, I have a MH25 Nitecore and it was working very good during several months. Tomorrow it started only to work in low light. All the functions work (strobe, sos, etc), but all with a low level light. So a openned it. Is hard to take the reflector part off, it’s glued to the body o the MH25. To open it, unweld all the wires, take off the screw, and with a small screwdriver, in the openning of the USB charger, where you see a small piece of the blue PCB, hit a little hard. Then you will see the board coming out of the body. After all, my problem was the led, a cold weld in the two contacts of the led chip.

awsomeavi
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Hi @overclocker – Could you please advise what advanced techniques did you used to dismantle the driver board which was glued to the aluminium body.

I need to open my flashlight.

Your support will be really appreciated.

Thanks.