I was installing a new MT-G2 pre-mounted on a 20mm Noctigon into a new Convoy M1 tonight. I installed a contact board for direct drive checking the board first to make sure there were no shorts.
Soldered the leads from the board to the Noctigon and visually inspected, nice clean solder on those big pads. Assembled the head and performed one last short check and found a dead short from the + spring to the pill.
I figured it had to be the reflector but after removing the reflector the short is still there. Removed the contact board from the pill and un-soldered the + wire from the Noctigon, wire and pad look fine, no solder running out to the pill.
Check the + pad and find 0.8 ohms to the pill, I don’t get it. The mask looks fine, no sign of burning or damage.
I haven’t removed the Notigon from the pill yet, it will have to wait until tomorrow.
I was thinking the same thing on excessive solder. I just sent an email to Intl’ Outdoor, I don’t want to try reflow until I see what their response is.
Good thing I always check my work before powering up, I wonder how two fully charged IMRs would have responded to a direct short.
Possibilities, in order of decreasing probability:
- There’s a solder bridge under the LED, connecting the LED+ and thermal pad together.
- The PCB is defective - either a short between the LED+ trace, through the insulating layer into the base, or a extra trace of copper somewhere where there shouldn’t be.
The LED is defective, and for some reason the thermal pad and LED+ are internally connected.
Only way to know for sure is to yank the LED and inspect underneath, then ohm out the board/LED.
Burnt wires would be my guess. I had a meltdown on one of my mods, I can’t remember which one but it melted the wires in an instant. It was a jumbled up stinky mess.
The light was never fully assembled or powered up. All components are new.
Comfychair,
I never checked the LED. I always check my reflows by powering direct with 3AAs. I didn’t have a 6V source handy and since this was new and factory mounted I didn’t even think to check it.
to - is open circuit with my Fluke 73 regardless or polarity. - to ground is open circuit, + to ground 0.8 ohms.
I have a Fluke Megohmmeter but somehow I think it unwise to check with that.
That’s a good idea, I do it with one 18650 all the time to test a XML. Of course I could also use a DMM but what fun is that when you can temporarily blind yourself instead.
I would bet you could get away with two 18650’s as well I do this from time to time to test lights before I put the batteries in. I just hold two 18650’s with two wires and then touch them to the positive and negative spots on the driver. (it helps to have big hands) Just a quick tap lets me know if it’s lighting up or not. More taps to check modes. I’m sure this is not the recomended way of doing things but it works for me and I haven’t killed anything yet this way. (I have burnt myself a few times though)
“I was just guessing what would have happened if you turned it on. Wires would have burnt would be my guess. It happens fast too.”
I’m a little slow tonight…
For testing my usual LEDs, mostly XM-Ls or XP-Gs I picked up a couple of 3AA serial battery holders. Soldered alligator clips on an install 3 alkys and use for quick checks of drivers and LEDs.
I use a bench power supply picked up at a cheapo cell phone shop, they use these to repair cell phones, it’s a variable 0-15v 2amp, it also is a voltmeter.
$30.
After Hank gave me the ok that I wouldn’t loose the replacement option I removed and reinstalled the LED. No obvious problem seen but neither the LED or Notigon were shorted when checked separately. Back together and working like a charm now.
On a side note, MT-G2 + Convoy M1 + 2 AW IMR 18350 + Direct Drive = :bigsmile: A little over 6A at the tailcap but the batteries sure don’t last long. Puts my 5.3A triple XP-G2 to shame. I literally giggle every time I turn it on!
That’s the problem with this hobby, every time I meet with success my first thought is I WANT MORE!
