what happened? McCapsule short

I was attempting to replace the LED from a TW0J to a UW0J on my prized longbow Micra, and I ran into a bit of a problem. I used solder wick to remove the solder on the pads for the led and the attached wire. I removed the TW0J without any problem and placed the UW0J in. I then fired up the light, and no light. I quickly turned the light off and switched the Leads (assuming that it was just a miscalculation on my part. I fired up the light again, and again no light. I then assumed that my R123 was dead so I went a grabbed a primary and once again no light, but this time the battery got very hot. I disassembled the light. There is no apparent physical damage to the McCapsule that I can see, and all of the exterior connections look good. Is it possible that the board melted when I was desoldering the leads? Maybe some solder inside the capsule flowed? The inside is incased in thermal epoxy, but this was my first mod, so I guess that there could be air bubbles in the epoxy. My iron was on 700 F and it was able to get the solder off very quickly (I build robots as a side hobby and therefore am very good at desoldering ).

What converter is in it? Did you find out if the wires where reversed on the first try. Some convertors don't have protection for "no load". I killed a Wiz2 board once when my LED cathode lead touched the bare heatsink while the light was powered-up. Do you have a power supply to test the emitter?
700F is alot of heat for this small stuff, I keep my soldering station set at 330-350 and even at that I killed one emitter by being too slow.

Yeah the heat was up a bit high, I actually didn't look at the temp till after it was a problem. It was a Nextgen 500 in the McCapsule.

mccavazos said:

Yeah the heat was up a bit high, I actually didn't look at the temp till after it was a problem. It was a Nextgen 500 in the McCapsule.

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Nexgen's do not have open load protection, so if the pos. and neg. where reversed the Nexgen would see that as an open load and kill it instantly when voltage was applied. Also, if the heat killed the the emitter during soldering you would get the same result but now with both the LED and the converter dead.

Lumiled's states that 626F for 1.5 seconds is max soldering temp and time. I know I can't do it that fast.

testing for problems
first, recommend, that you unsolder the LED, then apply 3 volts to the correct +ve and -ve leads to confirm that the LED is not dead
if LED lights up, then its move on to next problem, the board
as morelite said, the nexgen does not have open load protection,
i fried my first downboy when i accidentally turned on the switch without the LED's connected
i think the board is fried, if the LED lights up by itself in direct drive with 3 volts applied across it
but the good news is the board is fairly easy to remove and replace, (unless bonded in, in which case heat and dremel away)

when replacing the LED, the trick is to pretin , pretin the + and - wires, and pretin the LED leads. if you are using a mcgizmo centering thingy, pre tin that too, when all parts are pretined, it takes a fraction of a second to solder things (literally you touch the solder iron and it will have a bond)
also, when working inside the confines of the longbow head or PR head, a small screwdriver that has a notch to position wires, and bend them and hold them in place is a usefull tool


hope you can fix it and get it running again

I looked into the cost of replacing the board inside the emitter, and its going to be too expensive. So the micra with the stock capsule and some extras in on sale in BST. The LED is fine, I was really only touching it for about a second, MAYBE two. There is no physical damage and it lights up np. I was entirely unaware of the open circuit problem, but that's definitely a good thing to know. Thanks for all of the help here, and I learned something!

I second the other's suggestions about the no load state killing the converter, but I have skated on this thin ice for a LONG time... I vaguely recall connecting an LED backwards polarity wise once and the battery and wires heating... of course its a diode resisting the backflow of current to its limits. I always use a DVM's diode check feature (or resistance check - sends a tiny current) to see if theres an ever so faint illumination of the LED. If so, the polarity is correct. Its a nice way to check polarity before risking damaging the converter. THEN I solder the connections and have a one hundred percent record of connecting LEDs with correct polarity. However, my soldering is pitiful, I take way too long, and have broiled half a dozen LEDs usually disfuguring their dome lenses with excessive heat. But proud to say I havent killed a converter with open/no load yet!