HELP! Soldering to LED PCB

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John5box
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HELP! Soldering to LED PCB

I have just tried building my first light with:
XHP70.2 on a 16mm PCB with 17mm direct drive driver in the UF1405 from MTN electronics with 2×26650
Maybe I’ve gone too high as a first go!
I had the torch put together and it looked to me like everything was soldered correctly BUT when I turned it on the LED came on but then the PCB began to smoke and the wires from the driver desoldered from the board! What am I doing wrong? Is the LED just too hot for a 16mm PCB or is it an issue with my heat sinking?

Completely in the dark, if only I had a good flashlight. New modder looking for illumination!

chops728
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Might have a Direct Short on the + side —- too little heat sinking will cook the LED—Both wires desoldered

John5box
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Thanks for this! So is that an issue with the PCB or just bad soldering on my part?

Completely in the dark, if only I had a good flashlight. New modder looking for illumination!

chops728
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A direct short means it was grounding to the reflector or the host —- hard to say what it is without seeing pics —- take it apart and examine it—I had to burn up a few things before I learned to check for shorts with a DMM before powering up

e1000
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what driver exactly? If you didn’t choose the zener mod, it’ll go poof

Skylight
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Did you use thermal paste and have you pressed the 16mm star down firmly? If the wires desolder, it sounds like the thermal paste is not good enough.

Always looking for: used or damaged flashlights for repair and MODDING

John5box
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Thank you guys, it’s the 6v Zener mod, thermal paste looks pretty good, I’ll check for a short and see if that’s the issue

Thanks again!

Completely in the dark, if only I had a good flashlight. New modder looking for illumination!

mikelights
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Hey I did a very similar mod to my 1405 but with a xhp 70 not 70.2, I made a video on it This is a link to the thread. Just thought you’d be interested since i think it comes out very well with the aspheric lens ! Share pics when your done I’d love to see some

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Lightbringer
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Did the LED come on bright or just glow dimly but with good/expected color? Or did it go blue and dim?

Blue and dim means it’s being pushed way over peak output, and is generating more heat than light.

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Lightbringer
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Oh yeah, you might wanna lap the pcb nice and flat, and especially the shelf it sits on. Sometimes the lathing process leaves a tiny nipple in the center that unless ground flat will stick up like a very shallow thumbtack and keep the pcb from sitting flat on the shelf.

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clientequator
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did you check if your flash light reflector is touching soldered wire on led board? This mean a direct short and will melt wires.

John5box
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Thank you all for the advice! I’m just waiting for another driver to arrive! In the meantime I’ve changed the thermal paste to a well recommended one that isn’t electrically conductive and managed to get a stable light from the LED with 6v which is impressively bright, so I can’t wait for the driver to arrive

Completely in the dark, if only I had a good flashlight. New modder looking for illumination!

chops728
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Get you a cheap DMM and check for shorts before you power it up —— I built a light yesterday and if I wouldn’t have checked —the driver would have been toast — I had a direct short on the + side