COURUI DO1 'Big Head' (Black/GRAY NOW AVAILABLE) $29.99 @ Gearbest ( use coupon: gbcourui) A long-throw modder's light!

Quick question guys, if I piggyback two R100's on top the existing R200 what should that compute to for current?


Assuming fully charged batteries & resistance mods, I’m guessing around ~3.5 Amps. Could be a little more.

Well my Courui mod didn't go so well (: . I had a short at the reflector due to a sharp peak of solder (which I couldn't see) poking through the kapton tape. I smelled a little bit of a burning smell but I didn't see any bad components. I found and fixed the solder peak then tried it again. It worked, but output looked really weak. I do have the "moonlight" mode when off, then outputs look like Low then High instead of High then Low. Highest output looks around +/- 200 lumens or so. Tried different batteries (first started with a single weak cell) but still weak output. I ran out of time to work on it and put it away all disgusted.

So do you think my driver is ok since it's still giving me modes? Could my triple stack of resistors be an issue? (I don't see how it would be any worse than a direct short across the stock one.) Would this be typical behavior of an LED after a short? (Still works but output way low.) This was a dedomed XM-L2 on copper.

And by the way, I had an awful time trying to get the reflector centered! The butterfly insulators don't "snap" to the reflector opening to hold it centered.


FmC that seems awful low. I read some other mod posts and came to a conclusion that adding one R100 should have been sufficient. My objective was to have nearly direct-drive performance by way of ultra low sense resistence.

And you responded moments before I posted my new issue.


It’s soooo easy to short out the driver with this reflector :frowning:

I’d say that you have burnt out one of the Fet’s.

I guess it depends on what type of battery you are using. Honestly, I’m just guessing on the figure here. With high drain cells you may well see over 4 amps. …well, you may have, before it was damaged…

Time to get a BLFDD driver in there!

- edit - I looked back through my own thread, as I was sure I had taken some current readings. With the resistor completely bridged, I saw just over 4.5A using a fully charged 25R.

Hmm, ok. So you think the LED is still fine most likely? I plan (when I get time again) to try and connect an 18650 direct to the emitter wires and see if it has the output level I expect. I kind of already did that during my first investigation but the light was face down and I was only interested to find out if it lit up.


I have (3) 4.35v cells for this light, but haven't uses them yet as I wanted to make sure it was working properly first.


My guess is that the LED is OK.

I’ve done several Courui’s, & managed to short the reflector in one of them as well…. same symptoms. A few others here have done the same as well.

It seems like those little Fets are not very robust.

Those little FETs aren't easy to buy and replace, are they? I'm guessing not.


I would also say it’s a fet gone “wild”. In my experience leds are really hard to kill if you are not planning to kill them.
Try other driver with that led and you will see.

Easy to replace, particularly if you have a hot air setup.

I don’t know if anyone has been able to identify them? They just have “3400” written on them.

AiT Semiconductor Inc. AM3400 mosfet

Ebay source

Cool! Thanks! Now would there be a reason to stack those FETs?


I don’t think it would be of any benefit to stack them.


I’m just getting underway on my Courui mod. I’ve installed an omten lockout switch and braided the springs, now I’m just waiting on emitter, driver and mcpcb.

I’d be happy to swap my stock driver for your damaged one since I’ll just be using it for a contact board.

Shoot me a pm if you’re interested.


Looks like my FETs are marked "A0DG". I ordered some of the ones linked above (just in case as itinifni has graciously offered his to me). I couldn't find much searching Google for "A0DG".


So Itinifni and I swapped driver boards. I immediately stacked 2 R100's on top of the stock R200. I've got 22ga silicone wiring to a dedomed XM-L2 U3 1A on copper. Tail cap copper modded as well as springs. Tough to get a current measurement as I have to do it "SRK style" (so tail cap doesn't even come into play). On 2 fully charged LG 4.35v cells (too tough to hold 3 cells together) I'm only getting 3.05A on high. I was expecting much higher. No bonus moonlight mode though.

Does this driver just not want to push high amps through? I was hoping for more like 6 amps. Inside the beam just looks meh. Gotta wait til dark to try it outside.


When I bridged the resistor completely, I only measured a little above 4.5a, using a 25r.
That was with an XP-G2, that I bought quite a while ago.

I notice you are using an XM-L2 U3. If it’s like any of the recent one’s people are getting, that’s most likely why you are getting such a low reading.

Do you have an old XM-L to try for comparison’s sake?

I do have an old XM-L but would hate to do the swap. Do these XM-L2 U3's have really high vF? Like 4.2v at 4A or something?

Tried the beam out my backdoor now that it's dark. It's pretty impressive, more so than I expected. Can't get to a better test location right now due to all the snow.

I wonder if I should try bridging the sense resistor?