inexperienced replacing mj808e led- Mtbr.com
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  1. #1
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    inexperienced replacing mj808e led

    I have the mj 808e light: MagicShine MJ-808E HA-III CREE XM-LT60 3-Mode 1000-Lumen LED Bike Light Set (4x18650) - Worldwide Free Shipping - DX.

    after about 6mo the light went out at the top of a climb (fortunately the last one on the ride). The rear battery indicator light still works, so I figure there's a good chance the led is bad and the controller is fine.

    so I want to try soldering a replacement led on.

    is this a good emitter to work with? seems to be fairly cheaper than anywhere else (usually $10, but free shipping elsewhere) if I buy 2 or more. $6.2 | Cree XML T6 1000 Lumen LED Emitter with Aluminum Base Worldwide Free Shipping!!!

    I know I need a fine tipped soldering iron and flux would be helpful. I believe will also need thermal grease for everything back together so the housing of the light can easily aborb heat from the metal that houses the emitter and controller (heat sink?).

    Am I missing anything? The light has just been sitting around since it broke, so I figure I have nothing to lose. Thanks for your corrections and suggestions.

  2. #2
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    IMO the odds are low that the emitter has failed. More likely a driver problem. I would look there. I have repaired 2 earlier version MS lights that the inductor had broken one of it's connections due to vibration from not being properly secured to the PCB.

  3. #3
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    for a quick test of the emitter, pull the reflector off, and the little plastic ring exposing the solder contacts for the emitter.

    wire 3 AA's in series either Nimh or alkaline to give you a 3.6-4.5V source (no more than 5 volts), and connect some leads to them. Touch the appropriate leads to the emitter's solder connection momentarily and see if it lights up. Don't leave the leads in contact with the emitter for long.

    If you can't figure out how to get the batteries wired up - look around for a spare wall-wart AC power supply for something like a cellphone charger that you don't need anymore. check what the output is - again you're looking for 5volts or less, and a Mah rating in this case in the 200-1000 range just to be safe. Cut the end off and strip the wires. (with the power supply unplugged of course).

  4. #4
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    Quote Originally Posted by adrenalnjunky View Post
    check what the output is - again you're looking for 5volts or less, and a Mah rating in this case in the 200-1000 range just to be safe. Cut the end off and strip the wires. (with the power supply unplugged of course).
    If you go this route, also check that the output is DC. Some of those wall units are AC output.

  5. #5
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    Awesome, thanks for the responses. I'll check the emitter first and inspect the driver.

    adrenalnjunky, I presume that you mean for me to do this while the emitter is still soldered to the driver, i.e., the <5 volts won't do anything bad to the driver if it is in fact the emitter that is bad. As soon as I see a flicker of light (or not) I know if the emitter is good or not.

  6. #6
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    Quote Originally Posted by adrenalnjunky View Post
    for a quick test of the emitter, pull the reflector off, and the little plastic ring exposing the solder contacts for the emitter.

    wire 3 AA's in series either Nimh or alkaline to give you a 3.6-4.5V source (no more than 5 volts), and connect some leads to them. Touch the appropriate leads to the emitter's solder connection momentarily and see if it lights up. Don't leave the leads in contact with the emitter for long.

    If you can't figure out how to get the batteries wired up - look around for a spare wall-wart AC power supply for something like a cellphone charger that you don't need anymore. check what the output is - again you're looking for 5volts or less, and a Mah rating in this case in the 200-1000 range just to be safe. Cut the end off and strip the wires. (with the power supply unplugged of course).
    Make sure you look really really closely at those tiny little solder contacts just before you connect it to the battery BLAMOOOOOOO nice big blast of XM-L straight in the eyes.

    In other words be careful not to be looking straight into the LED's when you connect them. First time I test wired my first LED project I looked straight into them when I made that first connection with the switch in the on position. Kinda sucks.

  7. #7
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    Quote Originally Posted by shirk View Post
    Make sure you look really really closely at those tiny little solder contacts just before you connect it to the battery BLAMOOOOOOO nice big blast of XM-L straight in the eyes.

    In other words be careful not to be looking straight into the LED's when you connect them. First time I test wired my first LED project I looked straight into them when I made that first connection with the switch in the on position. Kinda sucks.
    For clarification - Shirk doesn't mean the LEd will exploge, he means you're basically going to be looking straight into a light source kinda like looking at a welder does.

    And yes,you can do this with the emitter still connected.

    Let us know how it turns out. The bad news is that the Magicshine driver board is kinda proprietary and replacements aren't available on the market. Actually I'm a bit impressed with their function and ability, although the quality of the components they use are a bit on the lower end. Integrated clicky switch, led voltage monitors, ~2.8A output etc. If it were available from someone like DX, there's probably be a lot of builds here using them.

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