WF-800 Not working

[Ahab20]

Hi all,

I have a WF-800 (this). It worked marvelously for a little while, but suddenly developed a vexing problem. Most often, it will start at full brightness but very quickly fade, until it becomes apparent that the fading is in fact flickering. The frequency of the flickering continues to decrease, with no bottom limit (very short duty cycle, no matter the frequency). It appears to have a 'memory' of sorts, because if the light is turned off then on again, it resumes flickering at the same frequency where it left off, but if the light is turned off for several minutes before re-lighting, it begins the cycle fresh. On top of that, on occasion it will simply flash on then go out with no fanfare.

I've taken the flashlight completely apart, down to the circuit board and nothing looked wrong. I don't have much in the way of testing equipment, other than an old analog multimeter.

I'll say this, I am a newly minted EE, so I know my way around a circuit, but have zero experience with flashlight circuits specifically. I assume the problem is in the driver, probably related to a reactive element (cap, inductor) or a component overheating.

Any help is appreciated. If it's fixable, I'd love to do that. If not, what sort of driver would you recommend (assuming that's the issue)? I'm using 2x 18650 batteries and it's running a Cree Q2 emitter, though if I change the driver I'd be more than willing to swap in a brighter emitter.

Thanks!

P.S. I'm new here, so if this is in the wrong section, many apologies.

 

[Fichtenelch]

I don't completely understand how you mean flickering. I had an issue with my mte p7 light with sb 8x7135 driver in it, which starts to ramp down and then back up again. last week i took it apart, resoldered the ground connection from driver to host, sprayed contact-spray on the threads and put some vaseline over. after that it works perfectly, no more issues since.

 

[qwertyydude]

I've had a similar problem to that. First thing to check is continuity. You'd be surprised how consistent some continuity problems can be. Take the pill out and connect a positive lead to the center and another to ground. If it still does the flickering then you've got a driver problem. It's really easy to replace, not real worth it to replace components on a $3 circuitboard. Just unsolder it and pop out the board and replace with another the same size and voltage/current range. As a precaution you need a very hot iron to install and remove these as the pill tends to absorb heat quickly and applying heat for too long may destroy your new board.

If you're replacing the led make sure to get the correct size star and also clean up the silicone heatsink "compound" and apply a better one. I use arctic silver heatsink compound and then epoxy the edges to hold the led in place, unless you've got screws then you don't need the epoxy. This provides maximum heat transfer capability.

 

[^Gurthang]

Ahab,

Another item to check on your light is the tail switch. If it becomes loose it can cause exactly the type of flickering you see.

You need some fine tipped needle-nosed pliers or tweezers or even better snap-ring pliers. Try [gently] to tighten the switch retainer ring, this will solidly connect the switch to the body and eliminate the intermittent contact issue. If this solves the problem you'll probably want to remove the retainer ring and switch, clean and lube all the parts then reassemble. Poor contact problems are pretty common w/ DX and KD lights...