I had a bit of a scary experience after modding a S2 with a 2mm WF. I soldered the LED to an XP board and it was fine. I put the light together with one of convoys “ramping” linear drivers. The light was working great and I had been playing around with it for a bit.
I then was adjusting the brightness of one of the modes which with this driver involves ramping the brightness slowly up through the max current which is 7-8A, so the light naturally gets a bit hot during this process. At the end of the ramp it starts again at the low modes. It was here that I realized the light was still getting hot, like very burny hot, as if there was a short, but it was still producing light. I quickly turned it off and unscrewed the tail cap.
I immediately did a very short current test with a clamp meter and it was over 20A, and still producing light. I looked for the usual suspects: reflector shorting the pos LED wire, pos wire cut by spinning MCPCB, with this driver the positive solder point is close to the edge of the driver so I thought that was a potential source.
It turns out the short was at the LED footprint between positive and ground. I measured it the next day at room temperature and it was 20 Ohms. Apparently at high temperature the short greatly decreased in resistance enough to pass a lot of current, but not enough to totally short the LED and shut the light off.
Has anyone experienced this before?