xml2 u2 in ultrafire c8

Hi there, newbie here so go easy :slight_smile:

I have a c8 which was using a xml u2 led on a 16mm board but it stopped working . So i purchased two xml2 u2 hc and replaced however for some reason it is still dim it shines but no where near its full potential, i know its not the led or driver as i have tried two xml2s and two different drivers (both 2.8a) i think the problem is how far the reflector sits down over the led but im using the same centering ring and the xml2 looks identical dimension wise as the xml u2 :frowning:

Any suggestions?


Welcome to the forum , H1ST .

Try it without the reflector.
Also, what kind of cells are you using? Did you try different ones?

The led works fine itself and is full brightness i just dont see why its not as bright once the reflector is on.

It looks like the xml2 is seated normally but its almost as if the led doesnt sit high enough inside the reflector although the old xml u2 was exactly the same and worked fine then.

not sure if im explaining it very well.

using sony 18650vc3

because reflector is touching contacts on the emitter making short circuit…

Ohh no no i should have mentioned its definitely not shorting, the centering ring raises it well above the wires and ive also tried with an insulating ring over the wires with still no avail.


Is there a difference in brightness if you bridge the battery to the tube rather than powering through the switch?

Just tried it and thats not it either.

I put the other xml2 in an ultrafire wf 501b with smo reflector also being driven at 2.8a and it throws just as far as the c8 with more flood. Doesnt make sensw to me!

+1 on blaming the reflector.

Can you try turning the switch ON and then assembling the light? You said it seems full brightness w/o the reflector, so at some point during the re-assembly process you should see the output drop off… The root cause should be apparent at that point.

IIRC, the C8 has a loose reflector… Could you assemble the light w/o reflector or bezel then slip the reflector in place & mash it down with fingers to reproduce the fault?

Interesting problem you’ve got there!

PS: How much difference in brightness are we talking about here?

You could try unscrewing the pill a bit so the reflector pushes down around the led more. This should bring it up into the reflector more.

Yeah i tried that and nothing changes as i place the reflector ontop whilst the led is already on. :confused:

Im sure its the height that the reflector is sitting above the led but it doesnt make sense because its the same height as when it was using an xml u2.

also the centering ring seems like it obscures the sides of the led as if it makes the led shine at much less than 180 degrees but again the xmlu2 was exactly the same in the same centering ring and was twice as bright before

do xml2 u2 and xml u2 shine at the same degree angle? Or is this nothing to do with it?

Thanks for the help its much appreciated sorry about this!!

Does anyone have a c8 with a xml2 u2 they can showme how theres is set up inside?

Ok its definitely the centering ring raising the reflector too high above the led but i dont understand why it didnt before with the xml u2 :s

its as if the led star should be 20mm rather than 16 so that the solder connections are futher apart and the reflector can sit flush against the star but the pill is for a 16

i dont really know to solve it because without the centering ring the relfector still sits on the solder connections which still make it too high up and a bad focal point

I have a few C8 reflectors and none use a centering ring with an XML (2), just the insulating film. The square substrate centers the reflector directly. I’ve only seen the centering rings used to adapt smaller emitters.

Stupid question but if it does need a centering ring, is it upside down?

WAG: Large solder blobs on the + and - solder pads raising the reflector? Can you post a photo?

Yeah the reflector does center itself on the small led square but it cant because of the solder tabs being where the reflctor should sit. theyre not big blobs at all it is less than 0.5mm its only the wire touching which raises it higher but just makes it seems so odd that the xml u2 never had this problem even though it was identical to the xml2 u2 star and it definitely came with a center ring installed.

Which part are you suggesting might be upside down?

All this faff over ÂŁ10 worth of torch! Expecially when its probably something so simple

The centering ring.

You can try to catch the very outside edge of the solder pad with the wire and flatten as much as possible. Even the 20mm Noctigons have that problem.

Ah no its the right way up.

Its not getting caught the wires have no choice but to be under the reflector.

the reflector at its smallest end is 16mm the same as the 16mm star so without the centerring to raise it higher they would always touch, an inuslating ring will stop the short but the wires will always be under the rear of the reflector

I use these http://www.fasttech.com/products/1194800

in my 16mm c8 pills. It covers the entire star and solder tabs and the opening can be used to center the emitter. Sometimes I have to unscrew pill to get reflector to push down but it works with xml. I use clear nail polish to isolate + and - with dedome so the reflector rests on the star.

Edit: my reflectors aren’t completely flat on the bottom. Maybe sand or grind away some of the outside edges.

Is it a plastic reflector? They’re thicker because they’re not as strong as aluminum.