Q5'd D-mini quite a fizzle - problem?

[Daekar]

So I finally got a replacement light-engine for my D-mini, but when I put in the Q5 I got from Cutter a while back and stuck in an RCR123a the output was completely underwhelming... as in, high is less bright than my LP M1 on low. I have a low setting too, it's just VERY low. I know my batteries are in right, and the LED is working so I'm pretty sure I got the leads soldered correctly... is there something I'm missing? I didn't expose the Q5 to excessive heat, if anything this was my fastest solder-job ever. Is it possible to cause this kind of issue by filing down the edges of the star? If so I'm going to kick myself... I mean, I did about the same thing I did with the star for my MRV, so I wouldn't think so, but... I'm shot for ideas. I can take pictures if that would help. Any suggestions?

 

[Gunner12]

Maybe another broken light engine?

Have you checked for shorts and cleaned all the contact points?

Maybe a bad LED?

That's all I can think of.

 

[Daekar]

I did clean the contact points, I'm not sure how to check for shorts...

Either a bad light-engine or emitter sounds like the most likely cases to me, but I have no way to test this. I'm thinking all I need is a multimeter to check and see what the voltage/current flowing is... if the current isn't correct or the voltage isn't correct then I can presume it's the engine... and if it IS correct at both contacts on the LED then I can presume it's the emitter... right?

 

[Gunner12]

I think what you said is correct. If voltage/amperage is not right, exchange the module, if it is correct, change the LED.

 

[StefanFS]

I did clean the contact points, I'm not sure how to check for shorts...

Either a bad light-engine or emitter sounds like the most likely cases to me, but I have no way to test this. I'm thinking all I need is a multimeter to check and see what the voltage/current flowing is... if the current isn't correct or the voltage isn't correct then I can presume it's the engine... and if it IS correct at both contacts on the LED then I can presume it's the emitter... right?

Hej,
measure forward voltage over the led, touch the probes to + & - on the star where you soldered the contacts when the light is on high. On my Multimeter the lowest setting is up to 20 Volt, be careful so you don't touch the pill walls with the probes.

Check battery draw. Just off with the tailcap and close the circuit with the probes, one on the battery and the other on the end of the batterytube. Be sure that you set your multimeter on 10 A and switch the + probe to the socket marked 10 A.

On a D-Mini with an Cree Q5 with "normal" forward voltage you should get max ~3.6-3.7 Volt in forvard voltage on RCR123. Battery draw on my D-mini with stock driver is just about 900 mA.

Stefan

 

[Daekar]

Thanks a lot Stefan! Now I've just got to go out and buy a multimeter... I've been meaning to and this seems like a good excuse to me.

 

[3rd_shift]

Some Cree XRE's do seem to have a higher forward voltage than other leds for some reason.
That has been my experience with them.
That might have something to do with it.

 

[discoverEDC]

I had the same issue with my LF2. I installed the q5 and lost half of my output. I'll be looking for a low Vf q5 or Rx in the future for my LF2.

 

[vetkaw63]

If you filed down the edges of the star, it is possible to expose the circuit on top. This could possibly lead to a minor short. I file mine at an angle inward towards the top of the star. This leaves room between the circuit and heatsink.
I doubt the forward voltage is high enough on a Q5 to lead to lower light output.
Mike