Hi all, looking for some advice. i have an older Fenix LD01 that all of a sudden stopped working on me. won't turn on when tightened down. i took the tail spring out and added copper braid to see if that helped. still didn't work. removed the bezel and put leads to the pads. LED lights up fine. i put leads to the underside of the driver and nothing. when i shake the light hard, it turns on and off. Driver issue?
Edit: Light has been fixed! see post #9
It would certainly seem so. Ain’t got that particular light, so can’t say for sure.
Maybe try to buff all contacts points, including the end of the battery tube, retaining-ring (if any), center pad, etc.
If it’s got a RR, loosen it or remove it even better, buff it (and both sets of threads as much as possible), snug it down hard.
A Q-Tip dipped in alcohol after buffing will both remove grit and also clean things as a solvent.
Beyond that, btfoom.
Thanks, i’ll try cleaning the contacts. that’s all i can really do i guess as removing the driver looks impossible. looks to be glued in place with no holes for a tool to thread out. No access from the top either as it’s just two hole for the wires. What a pain. its been a good light.
Wellp, here’s the thing… “It’s been a good light” sounds like you’re gonna toss it. Don’t.
If the LED works, then it’s likely that replacing the driver could/would fix the light. So if it’s a 17mm driver (or whatever size), you could even drill out the old driver and replace it with a new driver in the right size. Lotta drivers have vias around the outside that’re filled with solder that you could press-fit the driver into the hole. And if not, people’ve soldered thin wire strands ’til it is press-fit.
So get even a cheap 1-mode or 3-mode or whatever driver, and you can get it working pretty easily.
No one says it has to be a direct-drive driver that could fry the LED in seconds. Start modestly, tweak later. For a long time, my EDC was a 1-mode 1.4A ’502, simple on/off when I needed it, reliableAF, nothing to break. Did like 98% of what I wanted it for.
Just goggled it now, and it’s a teeny little thing, an AAA light.
Wellp, Convoy, Sofirn, etc., might have drivers for their AAA lights. Probably also press-fit.
Anyhoo, I’ll defer to others who may’ve done similar.
The center positive contact on the head in your picture looks dimpled, has it been crushed by overtightening the battery? If so a dab of solder to raise the contact up might help.
its looks fairly flat close up. Also when i tried the center and outer ring with leads it didn’t light up. i think something is loose and it makes contact when i shake the light.
Mine’s still kickinm (2013), but I recently replaced her. 
Decided to open up the head again to see if I could fix it. I didn’t want to give up on it. every time I shook the light it turned and off randomly and I could hear something loose. I don’t know what it’s called but it is the biggest component on the battery driver side. it had coils around it. this piece was loose and lifting off the board. I wedged a thin piece of heat shrink between the top of it and the upper driver board too keep it from moving. I applied power to the contacts where the battery would be and it worked! Probably not a good idea but I injected some regular hot glue in there to make it stay as I don’t own any potting compound. Everything is back together and works as it should.
Solder instead of hot glue would have been better. 
That part is the inductor. Typically the heaviest part on a driver board for a single cell. They are notorious for breaking free after a number of drops. That’s exactly why potting increases reliability.
Excellent job on the repair!