The first thing we have to do is to remove the plastic lens from the flashlight. We do this for two reasons: First of all, you will probably have to remove it in order to get to the LEDs. The second is that plastic tends to diffuse and attenuate infrared energy. I pierced the lens with a sharp object and popped it out, as you can see in the following image:
Lens removed
As you can see, the LED assembly is now loose in the case. If we remove the assembly and turn it over, we can see how the LEDs are connected to the battery pack. The positive or anode end of the LED is connected to the center terminal of the pack while the negative or cathode end of the LED is connected to the case.
Rear view of PCB
