Convoy C8 + ryansoh3 pill + kaidomain MT-G2 = fun times

Flashlight Modding and DIY Parts
1

I’m a pretty big fan of the Convoy C8 - build quality on the thing is great, the price is right, and it’s just an all around great flashlight. So when ryansoh3 offered copper pills, I bought a couple with the intention of building something nuts. So I bought this MTG2 to get started:

http://www.kaidomain.com/product/Details.S022342

“But it’s a 20mm PCB, and the C8 takes a 16mm PCB!”… Oh, I’ll make it fit.

I started by grabbing the hot air pencil and removing the MTG2 from the PCB. With that done, I gave the MCPCB a going over and discovered the center pad is the copper base! It’s the same thing as a Sinkpad/Noctigon - couldn’t be happier with that. I proceeded to take tin snips, a dremel and a file to the MCPCB and surprisingly, managed to not short either of the +/- leads to the base in the process of cutting it down small enough to fit.

Then onto Ryan’s pill. I can’t say enough good things about the pill - it’s well made, and it’s heavy as heck. I didn’t have to do a whole lot - just machine out a bit of copper to make room for the “ears” on the cut down MCPCB, which I did on a desktop milling machine at work. I’m no machinist, the pill wasn’t well secured, tool speed was too low, tools were blunt, so the result is a bit ugly - but hey, it’ll do.

Now for the install. I started by tinning the back of the MCPCB with a bit of solder and ohmed it out again (still not shorted!). Then I sat the C8 pill on a ceramic tile, turned my hot air pencil up to maximum heat, put a cut piece of solder in the center of the pill, and started heating up the pill. On the maximum heat setting, the hot air torch can normally blow small 0603/etc parts off PCBs like a leaf blower in the fall. Alas, Ryan’s pill took about 3 minutes before the solder began to melt. I tinned the inside of the pill, dropped in the MCPCB, aligned it and took away the heat.

OH FRIG! THE LED!

I ran back to my desk, got the LED, came back, sat down maybe a minute later - and the thermal mass of the pill was enough that the solder between pill/MCPCB was still molten. I fluxed the MCPCB, put the LED in place with a pair of tweezers, and surface tension snapped the LED right into place. I didn’t have to apply any heat. I set the hot air pencil to lots of air/no heat, and cooled the pill down for a couple minutes with it so I wouldn’t cook the LED. It had to sit there for several minutes before I could pick it up.

End result:

And thankfully, LED+/LED- are still isolated from the base. I’d call this a success.

Up next: modifying the reflector.

2

I just love it when a plan comes together .

3

I like it! Awesome job! MT-G2 is still one of my favorites in the smaller lights... just something about the beam/light quality that makes it pleasant to use.

Are you going direct drive with this beast?

4

In the short term, I’m gonna use a 2.8A Nanjg 105C with a zener diode mod. Already have a pair of Efest IMR’s to run the light with.

Long term, LTC3783-based “holy buck” driver, when I get that design finished.

5

I’m using this reflector, which is identical to the one used in the empty Convoy C8 shell sold by FT:

http://www.fasttech.com/products/1617/10001275/1220101-aluminum-alloy-orange-peel-reflector-for-cree-xm-l

Anyway, using a stepped drill bit held by hand, and taking my time, I bored out the hole in the bottom of the driver. I also used the same bit to lightly chamfer the inside of the reflector, to avoid any sharp edges. Managed to do it without making a single mark on the reflector!

It fits the MTG2 perfectly now:

Right now the reflector rests on the four corners of the LED, which is actually a fair amount of surface area so I don’t really mind leaving it that way. Next up, modding the 105C driver.

Unfortunately I misplaced my zener. More to follow when I track that down.

6

That is one very nice pil led combination mod you have created. I’m looking forward to seeing this one finished. The led linked is the cheapest by along way that I have seen the MTG-2 for and copper star as a bonus.

7

I had the reflector screwed tight onto the corners of a mtg2, and it squeezed the thin layer of silicone that is there to crumbles and because under the silicone are electrical connections to plus and minus, the reflector shorted the led. Because it was a direct drive mod, it killed the switch. Best is to cut the silicone around the dome away and put a thin spacer there, I used a thin piece of cartboard with a round hole for the dome, works fine.

8

I’ve been to KD and saw that MT-G2. I just assumed that it was unmounted, but after reading your post, it sounds like the emitter came mounted to the base. So, did it come pre-mounted or emitter and base separately?

9

You measured electrical continuity between the center pad & the backside?

10

yeah I’d be interested in this too, looks like a copper pcb without a direct thermal path to me.

11

Thanks for the advice. I’ll come up with a suitable spacer, which will probably end up being a few dabs of epoxy around the edges of the LED.

Came pre-mounted - I separated the two of them so I could hack up the MCPCB.

Yeah, I measured continuity after pulling the LED. And cleaning the pads afterwards with solder wick/alcohol, the LED /- pads cleaned easy but the center one was a bitch to get hot enough - and it’s a smooth copper surface which is lower than the two/- pads. It’s built like a sinkpad, except they didn’t bother punching the base to raise the LED center terminal.

12

Wow! nice job, gmarsh :slight_smile:
You must have really steady hands…

13

Looking good so far.
I’d like to see it finished, are you using an extension tube and 18650s on the C8 ?
or are the Efest IMRs 16340s ?

14

I'm digging this. I just got a Convoy C8 in the mail today from Mountain Electronics. I might do the same thing.

15

Efest IMR’s right now. I’ll pick up a C8 extension tube sometime, to make the battery life a bit more sensible - hopefully “standard” C8 extension tubes work on the Convoy.

Anyway the light’s built, currently running a 2.8A Nanjg driver with a 4.3V zener mod.

Problems so far:

- Not really a problem, but it’s virtually impossible to solder the driver to the pill and achieve a good ground, because the pill pulls away all your soldering heat. I couldn’t do it on my Hakko station at home, I’m gonna heat up the pill with hot air at work and use a big Metcal tip to get a more positive connection. In hindsight I should have tinned the driver end of the pill before putting the LED in.

- This ain’t a 5000K LED as Kaidomain claims, it’s either 3000K or 3500K. I’ll snap some shots of it next to my 5000K XM-L2 “daily” C8 tonight for comparison.

- If I tighten down the tailcap all the way, the light turns off - I’m not sure what’s going on, gonna assume something’s getting pushed too far in the tailcap. Gonna take everything apart and find out.

  • I dabbed epoxy onto the four corners of the LED to support the reflector, and sure enough, the corners of the LED are silicone and everything fell apart. I’m gonna remove the silicone from the corners and epoxy everything again.

Those issues aside, the light’s working pretty well and it’s comically bright. After 5 minutes of runtime at 2.8A, the C8 is warm to handle, but not unacceptably. I can’t foresee any major thermal problems with 4-5A in the LED.