Incredibly Dim CREE issues

[sevin7]

I have 3 mag lights modified with the KD cree q5 drop in. All 3 of them at some point in time have ran in to this issue, as well as a couple of my DX cree lights. This issue is this:

Randomly, out of nowhere, when i try to turn the light on, it appears to do nothing. I then look at the LED and notice that it is indeed on. It is VERY VERY DIM , like 1 lumen dim. It actually looks very cool, because you can perfectly see the cree die glowing, without it harming your eyes what so ever. I will then turn the light off, then back on, and it does the same thing. Then randomly it starts to work properly again after a random period of a few minutes, all the way up to a few hours. I've checked the batteries, they are not the problem. It just makes no since how it works perfectly for days, then randomly when i power cycle it, it quits working properly, then a random amount of time later it works perfectly again.

This problem has never happened when the light was already on, it only happens when i turn it off, then back on again. Sometimes shaking the light seems like it might help fix the issue, other times I left it completely still and it later started working fine.

I've checked to ensure all the connections are secure.

What the hell casues this?

 

[mds82]

i had some issues where the LED's werent secured to the MCPCB securely. try pushing down on the led's to see if it makes a better connection

 

[sevin7]

What exactly does MCPCB stand for?
And did you experience the same thing that I just described due to this problem?

 

[DArklite]

I've checked to ensure all the connections are secure.

What the hell casues this?

Ruling out all batteries having the same voltage, if you've already cleaned all contact points (end of tubes, threads, head, tailcap) with alcohol and have tightened the tailcap inner ring (tweezers or needle-nose pliers work fine) and it's still an issue, then it's either poor heatsinking which has damaged the emitter, the tailcap switch itself may be defective, or if it's a no-name drop-in, then I doubt that there is any type of quality control for the unit - the classic "you get what you pay for".

 

[sevin7]

Ruling out all batteries having the same voltage, if you've already cleaned all contact points (end of tubes, threads, head, tailcap) with alcohol and have tightened the tailcap inner ring (tweezers or needle-nose pliers work fine) and it's still an issue, then it's either poor heatsinking which has damaged the emitter, the tailcap switch itself may be defective, or if it's a no-name drop-in, then I doubt that there is any type of quality control for the unit - the classic "you get what you pay for".

• I have ruled out batteries
• Contact points are clean
• The switch is a mag light side switch, and the tail cap ring is tight in the two DX lights that have done it

Once it comes back on, the emitter works perfectly, so how could it be damaged?
One more thing, while messing around with a cree Q5 emitter on a star with a 3.7v 18650 and two wires, it happened! I connected the + and - of the battery to an emitter not installed in a light, and it lit up with a dim glow, I ensured all the contacts were secure. I then proceeded to remove the wires, and reconnect them again, and this time it lit up perfectly. I'm messing with it right now. I've removed the wires and reconnected them about 30 times now, and I can't get it to reproduce the dim glow effect again. I'm guessing the actualy emitter is the cause?? The one I'm messing with now is DX sku 2394 . I have not run it for more than about 10 seconds at a time, as I don't want to allow it to overheat since it is not heatsinked at the moment.

 

[DArklite]

Either the emitter (or PCB) has an internal issue, or the way its soldered onto the PCB is making less than ideal contact.

 

[mds82]

MCPCB is a Metal Core PCB - just what the LED's are mounted to.

 

[Erasmus]

This is definitely not a Cree issue, as the title implies. It's an connection problem or a problem with the driver.