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  1. #1
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    XM-L U2 emitter just died, help me figure it out.

    Hi, so last january I bought a Hi-Max light with the XM-L U2 emitter and I've been happy with it, until this May when all in a sudden on my way back home the light died on me. I took it all apart and checked the voltage right at the emitter's connection and it was something along this :

    high mode : 1.5v
    low mode : 0.5v
    high strobe mode : 0.5v-0.98v

    The emitter was heating up pretty quickly, but wasn't emitting a single lumen. I assumed the emitter wasn't receiving enough volts so I took a 2-pack AA batteries (3v) and with the light on high mode, plugged into the usual 9.6v battery pack, I added the 3v right on the emitter's connectors and just like boosting your car's battery, the whole thing started again. Since then I used it a few couple times without issues, but I was noticing that the light output wasn't linear, but having slight variations of the power, like if the emitter was having trouble keeping a constant luminous output. But it was working, so I didn't payed attention to it much.

    Now on my way to a friend's house last night, after 10 minutes of riding the light went off and you know the rest.

    Anyway, now I have the light apart on my countertop, I measured the voltage and drive current going to the emitter for each modes and even with boosting the emitter like I've done once had no result. Here's the data so far :

    High mode : 8.28v @ 1.95A
    Low mode : 3.38v @ 0.57A
    High strobe mode : 3.89v to 4.50v @ 0.89A to 1.05A

    So now I suspect it's not the board, but the emitter itself that has issues. I'm pretty sure the data above isn't what it should be normally, but I don't have any other emitter to test it out now.

    Does anyone who have some knowledge with these LED's can tell me what's going on and if I have to replace only the emitter or the whole PCB too.

    Thanks !

    This is the light, comes with 1 year manufacturer warranty, but it's probably gonna cost more money to ship it back to them than else.

    HI MAX 1300LM Cree XML T6 U2 LED Headlamp Rechargeable Headlight SET | eBay
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  2. #2
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    LEDs can fail in a shorted condition. I've had that happen on a dual XPG light. In that case, they were series wired and though one went dark the other continued working. Replaced the LED and has been fine ever since. Should be pretty easy to replace the LED.

  3. #3
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    XM-L U2 emitter just died, help me figure it out.

    Quote Originally Posted by Vancbiker View Post
    LEDs can fail in a shorted condition. I've had that happen on a dual XPG light. In that case, they were series wired and though one went dark the other continued working. Replaced the LED and has been fine ever since. Should be pretty easy to replace the LED.
    Yeah, it's a piece of cake to swap in a new emitter. But I just want to be sure the new emitter won't get toasted because the PCB isn't working right either.
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  4. #4
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    I don't think that you can say either way (LED or driver) what's going on for sure, but it's far easier and cheaper to replace the LED than the driver, so try that first XM-L LEDs can be found for as little as $4.50 if you search around, so it won't be an expensive experiment.

  5. #5
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    If you're reading current through the LED and the die is not emitting than it's the LED for sure. Like Matt said, it's only $4.50. You could also try to revese the voltage through the led wit 2AAs in series. Desolder the wires comming from the driver first, than hook the batteries in reverse just for a moment.

  6. #6
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    XM-L U2 emitter just died, help me figure it out.

    Quote Originally Posted by Toaster79 View Post
    If you're reading current through the LED and the die is not emitting than it's the LED for sure. Like Matt said, it's only $4.50. You could also try to revese the voltage through the led wit 2AAs in series. Desolder the wires comming from the driver first, than hook the batteries in reverse just for a moment.
    So you're saying to simply hook up the emitter to a 3v power source, on a close circuit ? I'll try it when I get to remove the emitter to see if it sparks again.

    What I also want to know is if the readings I'm getting from the driver are correct or if the driver has issues too.

    Thanks
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

  7. #7
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    Yes, bat+ on LED-, bat- on LED +.
    Went through your readings again. You measured 8.28V and 1.95A on emitter? At 1.95A there should be about 3.1V on emitter so there is something wrong with the driver. The LED will never light up again if it was exposed to +8V, but you can try it anyway.

  8. #8
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    XM-L U2 emitter just died, help me figure it out.

    This is correct, 8.28v at 1.95A. I guess this is what busted the emitter too.

    I'm contacting the seller to see what can be done on the warranty side.
    Quote Originally Posted by NicoleB28 View Post
    topless. that's what all mtb girls do. we go ride, get topless, have pillow fights in the woods, scissor, then ride home!

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