I was playing with my 980L this evening and brought it to work. My friend goes to test it out, and suddenly, it flashes but won't stay on. We try repeatedly and with different batteries. Same problem. We get a flash or a 1-second on and then it goes dark. I fiddled with it by unscrewing the tailcap and discovered that if I have it barely screwed in or hold it away from it at an angle, it works, but if I screw it down like I always have--same problem. I can't use the light this way, though.
Any ideas about what could have gone wrong and what I can do about it? I've had it for 4 months now.
the retaining ring might be loose. try tightening with snap ring pliers. if that doesnt work loosen the ring and remove the switch and check solder joints.
Like Jamesearl said, make sure everything is snug. The switch might be bad, or going bad. When you say it stops working when you screw it down suggests the possibility of the battery shorting against something. Make sure the positive nubbin (whateveryacallit) touches only the center spring of the driver and the bottom touches only the tail cap spring.
Appears to be okay now. I took it off and I guess my friend who powered it up twisted the cap on wrong. It made a sound and did that until I took it off and screwed it back on more carefully. If I put it on wrong, it still can flicker, but not when done properly. I'm finding a lot of budgeties have tailcap connection issues.
Sometimes had the same problem, twisting the cell almost always made the fix, tho a shake could change modes. Just put a 3*1mm magnet at the positive end of the battery -> fixed.
Have you tried a different 18650 cell? I have had bad protection circuits do some strange things when the PCBA is pressed against from the spring force.
Test the light without the tailcap by using a paper clip to touch -B to the body tube. Press gently against the battery and see if you can induce the same intermittency. If it cant be replicated then the problem is with the tail cap or switch.
