Two years ago I made an Anduril buck driver for the Zebralight SC64 : Zebralight SC64 Anduril Edition, since then I did several Zebralight mods that I haven’t shown yet, here’s one I did recently :
Yes that’s indeed a Nichia B35A, since they have a weird footprint without a central neutral pad, I can’t use the usual Zebralight driver construction with a copper insert in the driver board, Instead I got made a very high performance, tiny MCPCB :
Specs are : 2oz copper, 40μm, 7.2W/m.K dielectric.
Common MCPCBs usually have a 0.1~0.15mm 1-2W/m.K dielectric, so the thermal resistance of my MCPCB is about 9~27x lower (better) than a common MCPCB, allowing to keep it cooler and drive it at higher current.
6V 3A boost driver, this time I used 3 sense resistors like Loneoceans does (”UDR”) instead of just two because the usual method I use for eliminating the startup flash didn’t work well with the chosen boost IC, here the large value of the moon range sense resistor prevents any startup current spike on its own.
I didn’t do any efficiency measurements this time, but it should have about ~97 % peak efficiency and about 93~95% at full output, the current draw in moonlight is better than the usual MP343x based drivers (about half, so double the moon runtime).
On the backside there is the boost circuit, and we see the copper lug, the MCPCB is soldered to it which then transfers the heat to the body, and the copper lug is soldered to the PCB so that everything is joined together :
The switch assembly is also different, one thing that I wanted to improve is the switch illumination, on my first SC64 mod, only the top was illuminated, so only half of the boot was lit, now both sides are lit. There are just a bit of shadows from the switch elevated corners, but I should be able to improve that by spacing out the LEDs more.
Installed inside the light, you might notice two wires coming out of the hole, one is the batt+ wire of course, the other one is the UPDI wire for flashing the MCU. This was one of the major problem of my first mod, in order to update the firmware I had to remove the press fit glass window and reflector to access the flashing pads. Now they are on the other side down the tube :
Another improvement is potting, providing better shock resistance and more importantly better thermal dissipation between the driver and body (pretty much necessary for good thermal regulation) :
The tail cap spring (and PCB) is also changed for a better one (5mΩ vs 25mΩ) :
Fully assembled :
The beam shape is quite similar to the SC64c LE (LH351D, left), and more floody than the SC65c (719A, right) :
It’s a 4500K B35A (R9080), it’s pretty much neutral in low/med, and start to shift a bit towards rosy in high and is about -0.0050 at full output, that’s a pretty typical amount of tint shift for the B35A at this current on a high performance MCPCB.
There is no color shift across the beam except a slight eggyolk in the middle, less visible than the SC64 XHP35 HI eggyolk so it’s quite faint and only visible when hunting it on a white wall. Might be possible to completely eliminate it with height adjustment but not sure it’s worth it.
It’s very nice because I think that the 719A and dedomed 519A are a bit too throwy for a small EDC light, I like something between SC64c LE and SC64 HI better, and of course tint is great as always with B35A, as is color rendition.
With the higher drive power and higher efficacy of B35A (vs LH351D, 519A and 719A) it has higher brightness than any stock SC6x, especially SC65 which is a bit anemic, I don’t really have a good setup to measure output but with a crude box+ceiling bounce it has more than twice the output of SC65 while the spot intensity is on par (tiny bit higher)
Thanks for reading 
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