Help-Custom build isn't working! (3XP-Ls & Buck Driver in Convoy L2)

I'm relatively new to building flashlights. This is my 5th light...and it's not working! I'm pretty sure it's a compatibility problem, but I want to understand why. Any help is appreciated.

Here's what I'm using (all purchased from Mountain Electronics):

• Host: Convoy L2
  • with 2x18650 unibody tube
• Driver: LD-4B 2.4A 17mm Buck Driver (3v-16v)
  • I used this driver thinking it would give be the most output with no frills...That was my understanding of buck drivers, but maybe I'm missing something.
  • The L2 calls for a 20mm Driver, so i used a Brass Adapter Ring because I didn't have 20mm on hand. I soldered the ring in place.
• LED: 3x Cree XP-L High-Intensity U6 3C LEDs on Noctigon 3xp MCPCB (pre-bridged)
  • I removed the pre-soldered wires and soldered the leads from the driver into the same spots where the wires were connected on the MCPCB.

I was sure this would work no problem, which tells me that I'm probably missing something essential to continuing in this hobby...Thanks for your help!

Well your assumption about it all working combined is sound. There doesn't appear to be any compatibility issues. Lots of places to start trouble shooting. I would begin using the process of elimination. I'd begin with the driver and the MCPCB first. The triple should be as easy as it can get. Connect a 3v source directly to the input. This can be a CR123 with a wire soldered to each end. If you don't have one already, make one. They are invaluable when needed.

I'd check the output of the driver next. Using a single 18650 do the same thing as with the MCPCB but connect a DMM to the driver output. You don't need an LED connected but one could be. It should be showing something like 3 to 3.7v output. Soldering on an adapter ring has been known to kill drivers. I know I certainly have done it myself. All depends on how much heat you put into the driver when soldering.

If both of those are working your going to move on to the host components. It could be simple connectivity and that goes back to the process of elimination again. Put it all together again and using the paper clip method bypass the tailcap. I.E. install the cells and using the paper clip make contact between the host body and the end of the last battery. If it's working then you know its the tailcap. If it's not working then the issue could be the pill to the body connection. Check that with your DMM. If your getting good continuity between the pill and the host body move on to the talicap and see what you get there.

If all of the tests above show things are fine you might have a wire to the LED's inside the pill having been cut on a sharp edge. It's been known to happen and not to be over looked during assembly. Let us know how things are going. BTW welcome to CPF!

Well after doing a bit more thinking about your build it occurred to me to check inventory of drivers just because there was something familiar about you mentioning the LD-4B driver. So I checked mine and its one of the few 6 volt buck/boost drivers available. It's Vf is 5.7 to 7 volts. Your using XPL LED's, probably wired in parallel, so the LD-4B is putting out too much voltage. And if you have them wired in series its not enough voltage. Either way it is a driver not suited to your task. An AX2002 would have been a better suited choice if you needed 1-3 cell input with a 3 to 3.4 Vf. But you wont find any with a CC of 2.4 amps. Most are 1.5 amps or lower, however there's an old thread floating around here on CPF about swapping the sense resistor and you can vary the output current somewhat.

Re: Help-Custom build isn't working! (3XP-Ls & Buck Driver in Convoy L2)

Good diagnostic tips there. I'll add them to my 'trick bag'

Re: Help-Custom build isn't working! (3XP-Ls & Buck Driver in Convoy L2)

Hi,
How was it? Did you figure out how to get it to work?