Swapping emitters in a Niwalker ET Mini V2 (never seen a 3737 before!)

Some time ago I ordered a Niwalker ET Mini V2 from FastTech, after reading ZeroAir's excellent review on it and being drawn to its feature-packed design. It just came in the mail the other day!

Unfortunately...as soon as I tried it out, I was struck by just how green the triple 6000K emitters were. Time for an emitter swap!

My spare 5000K LH351D emitters seemed like a good fit. I was a bit apprehensive about how the Osram PUSRA1.PM emitters had a slightly uncommon footprint of 3737, but I think it turned out quite well!

For anyone thinking of similarly modding their ET Mini, I wrote down a few tips that could come in handy:

First off - a comparison of the LEDs. While the PUSRA1.PM (2W) does have a larger footprint of 3737 versus the LH351D's 3535, it actually has a smaller dome. However, the anode and cathode layout are so similar that they should be easily interchangeable. (On the PUSRA1.PM the middle pad is also a cathode, but that luckily has no impact here).

The larger dome of the LH351D also fits just fine in the ET Mini V2's optic. There's less play so you need to be more precise with alignment, but that shouldn't be too hard on this MCPCB.

The bezel has 5 notches in it, which may cause you to gravitate towards snap-ring pliers. Don't use them! Avoid slips and scratches by unscrewing the bezel with a jar opener or a grippy mousepad instead.
With the bezel and lens gone, the optic is next. I use a Nerf dart for this to minimize the risk of scratching the optic or breaking a leg.
After pulling out the optic, you can remove the glow gasket and the LED board is accessible! No pictures from the reflow, but the process is fairly standard. Just a few notes:
  • On either side of each LED pad is a loop you can use to align your LEDs; if one side is more covered than the other, then you know the LED is off-center
  • Polarity of the LEDs is labelled - the cathode goes on the outer ring, and the anode the inner
  • The solder seemed to have a higher melting point than solder I've encountered modding other lights, or the Chipquik solder paste I use
  • No need to fret over excess solder beside your LEDs, since there's no centering gasket around them (which is great because I'm not very neat)

Lastly, when screwing the bezel back in, watch for cross-threading since the threads are so fine. If you encounter resistance, take another look to see if the bezel is crooked before forcing the bezel down.

Also note that the glow gasket doesn't quite fit around this optic, so you may feel something pushing back when you reassemble everything. As long as the emitters and MCPCB holes are lined up with the optic, this is normal.

Nice work! After having the mod functional for 5+ months, how do you like the result?

I tried several rubberized devices to unscrew the bezel on my ET mini V2… not budging at all. Maybe they used Loctite or equivalent adhesive on some of them. I gave up.

Did you reflow the emitters in place or did you extract the MCPCB? Also, did you check and see if the optic matches Carclo?

One major annoyance with this model flashlight… I’ve found the parasitic drain is very high. You have to do a physical lockout to avoid it.

Hey that’s a great mod and post! Nice job. I like that photo of the bare emitters resting in the optic.

Also, the nerf dart is a great idea and I need to find one of those to put in the tool lineup, thanks!

Honestly, even though the form factor is novel and I do like the beam it casts…I haven’t chosen it very often for day-to-day use.
I’m not sure if I ended up with a lemon, but the electronic whine from the light is incredible - I can hear it from across a room when on its highest mode, so when it’s at arm’s-length it is quite unpleasant.

That’s too bad about the bezel - I’ve sometimes found that pressing bezels face-down into a strap-wrench (against a solid surface) sometimes helps.
Or even 3D-printing a bespoke bezel-removal tool, though that’s not nearly as accessible of an option.

I did remove the board to reflow them - unfortunately I was so engrossed in aligning the emitters that I have forgotten to take pictures during that step.
There are no screws or adhesives holding the board in place, so desoldering the leads should be the only thing you need.
As for the optic - I didn’t check it myself, but other reviews/listing have indicated it comes with a Carclo optic, so swapping to others should be fine.