Please help me understand what's going on with my L2

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BrianK
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Please help me understand what's going on with my L2

3 weeks ago my L2 stopped working. This would be the 2nd occurrence when after charging the cells that it has stopped working. I tried a few things thinking maybe it was dirt in the works. I couldn’t get it to work this time. Time passed and today I had some time to fiddle around with it a bit and my meter told that I was getting juice through the switch and had it across the top cell and light body. I unscrewed the brass ring and board and couldn’t see anything obvious. Then I took a Q-tip, wet with alcohol, and wiped everything that might have been a conducting contact surface. Still no joy after reassembling it. Then I unscrewed the bezel and looked around in there under the reflector and LED. I put it together and the light worked for a few seconds. I unscrewed the bezel again and put it back together, now the light is working. I’m thinking that there is a contact surface somewhere that I missed. I’d really like to understand what’s going on with it so that I can fix it and be able to trust it. What did I miss? Or am I totally barking up the wrong tree?

TIA

eebowler
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doesn’t sound like a dirty contact to me, more like the head is shorting contacts on the LED , or there’s a broken wire that gets knocked into or out of position when screwing the head. Remove bezel, put on light, weather it works or not, take a plastic pen and poke the wires going to the LED and see if it comes on or off.

My gratitude to those who are willing and able to help others (in whatever way you can)! Being human is more than just existing for yourself. Smile

bilakos10
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As eebowler said, it looks like that the reflector might be shorting out the driver.
To avoid such issue, you can either flatten the soldering on your positive and minus contacts of your emitter or you can try to apply some kapton tape on top of those connections.

Try to tighten the head's bezel a bit. If the flashlight won't turn on after that, then a reflector short is your problem.

BrianK
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Thanks gents!

I’m seeing spots in front of my eyes. Smile

OK, I took it apart again and removed the 2 screws holding the LED down onto the flange. I moved the LED around pretty good. It stayed lit the entire time. Did that twice, the second time I got a bit more “violent” with it. It still stayed lit.

Bilakos10, I think you gents are correct about the shorting out based on how much I was moving the wires. So if I’m following this when it shorts out the protection of the cells is kicking in shutting the light down, correct? Or is something else going on on the driver board? Maybe protection on it?

I probably ought to buy some teflon tape. Does anyone know of a source? Hopefully there is some available that has one self adhesive surface.

FWIW, right now the light is still working and I rotated the spacer so that it’s right next to both solder joints.

bilakos10
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BrianK wrote:
I’m seeing spots in front of my eyes. Smile

OK, I took it apart again and removed the 2 screws holding the LED down onto the flange. I moved the LED around pretty good. It stayed lit the entire time. Did that twice, the second time I got a bit more “violent” with it. It still stayed lit.

There was no point moving around the LED.
The short should be caused by the reflector touching on the + and – contacts of the LED.

Put everything back together and crank the head’s bezel tight.
See if it turns on this time.

BrianK
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Yup, still working with the bezel screwed down tight.

I moved the loose LED around (screws holding it down removed) to move the wires. I was looking for an intermittent break in them.

cera@1967
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It seems that you'll have to reflow your led.., one of the contacts ,plus or minus is not soldered properly ! Sometimes is a problem with the quality of  the solder or inadequate temperature (too low ) , in the fabrication process...Happened to me few times , with new leds...

Adrian

Lexel
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cera@1967 wrote:

It seems that you’ll have to reflow your led.., one of the contacts ,plus or minus is not soldered properly ! Sometimes is a problem with the quality of  the solder or inadequate temperature (too low ) , in the fabrication process…Happened to me few times , with new leds…

I did reflows lately on prioduction light, some just for emitter swap
seen some manufactors with very low amount of solder, one had the center pad not connected to the LED board, getting blue after half a secons and the emitter did not look well

using solder paste there is a risk one pad does not get contact if no pressure is applied from above

BrianK
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Lexel, I would see it if the LED was in trouble, yes? I’ve used the L2 for quite some time now, certainly more than a year.

IF I have to reflow it would it just be a matter of heating it up and pressing down on it as it cooled? Or would it need to be removed, cleaned up, fluxed and soldered?

Dutcheee
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Put some Kapton tape on your mcpcb solder points as eebowler and bilakos10 pointed out. For now you can even use ducktape or cellotape for short bursts to test. Kapton tape is heat resistant.

If still no luck maybe a reflow of the LED can help, but a short via the reflector seems most obvious to me. Never hurts to tape it off.

And yes, the protection circuit should cut off power, since you have a direct short via the reflector in that case. Be happy to have used protected cells if this is the issue!

BrianK
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Dutcheee wrote:
Put some Kapton tape on your mcpcb solder points as eebowler and bilakos10 pointed out. For now you can even use ducktape or cellotape for short bursts to test. Kapton tape is heat resistant.

If still no luck maybe a reflow of the LED can help, but a short via the reflector seems most obvious to me. Never hurts to tape it off.

And yes, the protection circuit should cut off power, since you have a direct short via the reflector in that case. Be happy to have used protected cells if this is the issue!

That definitely went through my mind as I was thinking about a short.

Thanks for the Kapton tape. I dropped the hammer on a roll.

Dutcheee
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Thumbs Up

I don’t own an L2 yet, so for the record I can’t judge the internals for the likeliness of a reflector short.
It does seem like a very nice light to mod into an XHP70.2, but I will await by BLF GT first and see if it is not too large to put in my car next to my seat.

BrianK
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Dutchee, I don’t know if they’re even made anymore. I looked for a new one when my L2 pooped itself and I saw that they were discontinued. But maybe there is old stock somewhere. What a shame if they’re no longer made; it was a nice light with good throw.

In looking at the solder blobs on the joints a short is possible. They do stand a little proud.

Dutcheee
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I assume you ment the convoy L2?

Seems to be for sale on gearbest, bilakos10 has a coupon today.

https://www.gearbest.com/led-flashlights/pp_310975.html?lkid=12652976

eebowler
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brain, sometimes the solder blob connecting the driver, output wires to the LED, are a little pointy, and probably in your case a bit raised above the plastic spacer round the LED (hence being shorted by the reflector). What I’ve done in the past is to take a flat head screwdriver, place it on the blob and gently tap with something like another screwdriver (not hammer!) to flatten the blob. IF you dare to try this, it’s at the risk of the screwdriver slipping and KILLING YOUR LED, so think twice before trying. Evil

My gratitude to those who are willing and able to help others (in whatever way you can)! Being human is more than just existing for yourself. Smile

BrianK
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Dutcheee wrote:
I assume you ment the convoy L2?

Seems to be for sale on gearbest, bilakos10 has a coupon today.

https://www.gearbest.com/led-flashlights/pp_310975.html?lkid=12652976

Hmmm, I thought I did a search for the L2. Maybe I typed in something different. Who knows what I do late at night? Maybe it came up at a distributors and I didn’t catch the difference.

EEbowler I was thinking of abrading the visible high spot, but I don’t know if the extremely fine grindings would muck up the driver board below. I could put a vacuum suction on it to catch them. I still intend to put the insulating tape on it when it arrives.