Have you ever seen the death of an appropriately driven (<1.5x max current) and appropriately heatsinked LED?

LED Flashlights – General Info
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Didn’t care to start a new thread so posted in the first appropriate thread Search showed me :slight_smile:

An XML died on me yesterday. It was in a Convoy C8 and driven by a 2400mA driver. Technically, the LED isn’t DEAD, it lights up but at 0.00001 lumens. lol. (bright enough to distinguish on from off and no more.) It’s strange because there are no black spot on the die. Can anyone guess what went bad? Thanks.

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Global warming, of course. :party:

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  • Double-check the bondwires under the dome to the LED. You’ll need a magnifying glass for this… the aspheric lens from a zoomie flashlight works well. It could be that one or more of the tiny bondwires wires broke.
  • Another possibility is a bad solder joint. I had something like that happen very recently on a modded light. The problem turned out to be a bad solder joint under the LED when I reflowed it onto the star. You might try reflowing it to see if this fixes the problem.
  • The problem could also be in the driver and not the LED. To check this, the first thing I’d do is disconnect the star and then test the LED using a single cell in direct drive from a battery carrier, with wires attached. If the LED lights up with no driver when outside the light then I know the problem isn’t in the LED or star.
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Huh, what key words did you use to find this thread, I’m curious.

Did you check if there was enough thermal paste below the PCB?

What you’re describing seems like what happens if you put too much current through an LED, 6A+ and it becomes very dim. If you you increase the voltage, it does get a little bright, but not by much. Can you see if the three bond wires are intact?

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The driver works. The LED has been in the Convoy for a year now with a Qlite and only used occasionally to play. I looked at the bond wires with a 45x glass but didn’t see anything strange. Will look again. WRT solder joint, to test, i connected a LiFePO4 cell to the little bits of exposed solder just outside the chip and got the same result.

I thought that if a wire has burnt out, at least part of the die would stop working?

Death of an appropriately driven LED that’s properly heatsinked drew me here.

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If the led was bought preloaded it’s possible that the solder joint under the die is iffy with a partial cold joint that failed. If you haven’t reflowed an led this might be a good opportunity to try your first by removing/reinstalling the led. A broken bond wire might show as a very tiny flaw in the dome or a very tiny dark spot. If there was solder on the +/- pads but not on the center thermal pad the die would still overheat.