[Mod] ThruNite TN-31, How to increase the current to the led

Flashlight Modding and DIY Parts
10

I think the TN31 can safely handle more amps, it has a thick copper round star being held by 2 screws to the aluminum host with some kind of thermal grease or adhesive, Here is a pic, credit goes to TurboBB

when I get my hands on a good XM-L2 I will replace the thermal grease with some Arctic Silver Thermal compound.

So far the mod has been working great and the light does not heat up much, here is the german thread about the mod curtesy of google translate, those Germans sure know how to party! :beer: 8)

11

The skinny test leads and the resistance of the meter’s internal shunt will reduce the measured current somewhat but the difference may be negligible for this application.

12

Comparison beamshot

Left Modded TN-31 at around 4.6a to the led, right Modded ZY-T13 at around 3.2a to the led both are U2 Bin XM-L’s as you can see the TN-31 owns the poor modded ZY-T13 which in turn was brighter than the EagleTac XM-L I used to own.

13

Just did mine too. I didn't have any 0.12 so had to go with 4x 1R0 on top of the existing 2x R082.

image courtesy of taschenlampen-forum

There isn't much room so they had to be staggered to sit on top, not enough height clearance to place them piggybacked.

Calculating it back I now have 0.035 Ohm as opposed to the original 0.041 Ohm This has taken the battery carrier reading from 1.38A to 1.60A

Calculating this back again has taken it up from approx 3.6-3.7A to approx 4.2A at the emitter.

So looks like I've gained about half an amp, not a massive difference but there's a definite intensity improvement in the hotspot.

PS. The pic shows the TN30 driver but the TN31 driver is the same on this side.

14

The resistance on mine was lowered from 0.042 to 0.030 ohm, It was not a hard mod to do, and the results are noticeable, I plan to play a little with the reflector height over the led, I have a gut feeling that sanding down the thickness of the led centering ring will yield a smaller, more concentrated hotspot, I have some spare led centering rings to file down and try, will report results.

PS. will change the title of the thread to reflect results

15

Modded mine. Thanks for modding suggestion. Mine with 250mOhm already making TN31 a 19W flashlight. Yours are driven harder.

16

Alex - did you piggyback your 0.12R resistor on one of those 2 shown in the pic? Or just cut it in with wire, laying it along side somewhere. Spasmod is saying there's not enough height space.

17

I piggy backed it on top log the existing one, I later bought a R082 SMD resistor from Digikey and soldered it instead of the R120, for a little more current to the led.

The digikey part number for the 1206 0.082 ohm SMD resistor I used is P.082AVCT-ND which is 0.75mm tall and does fit with no issues.

18

Hi Tom, I should have made it clearer.

Since I used 4x SMD's (due to not having the right ones I had to improvise) it would have meant stacking them three high.

There's enough room to stack a single on top of the existing SMD just not enough to stack them 3 high. :)

19

The R120 seems to be getting up there already. Do you recall what amps the R082 produced?

Also, do you know if that stock copper star is a direct thermal path type? Didn't pull mine yet, but I'd use a SinkPAD if it's not.

20

I very lightly filed the center pad with a dremmel just enough to expose the copper, Stock PCB appears to not have a direct to copper path.

Here is a google translate of the German Light Forum where they talk extensively about the mod along with current measurements at the LED

Here is the detailed mods I did to mine

How to open the head up

HTH
AlexGT

21

I measure mine, voltage was 0.1494v. German forum mentioned 0.144v if I remember right.
So your 0.1494/(0.082/3) = 5.47A. I wonder what is the output lumens now.

22

Don’t know but its freaking blinding! Just how I like it! 8)

My best guess would be at least 1,500 lm.

23

AlexGT - thanks!!! Very much thanks for all the useful postings and info and addressing all my PIA questions!!

I had them at work order the 1206 0.082R resistors from DigiKey today (P/N you provided), and still need to decide on what emitter to go with. Thinking of super-thrower of de-domed XP-G2/SinkPAD -- if it's too low, I'll simply mount it on a 18 or 22 gauge copper disc - did this before on other mods, like the T08's. Plan is to use AS5 so center easier, but that assumes I got a good alignment piece for it -- I'll see. I'm 100% on gas method for de-doming, so will stick with that. I'll post measured results when it's all done, not sure when though..

24

Hi guys,
Just wondering with the tn31 sense resistor mod, I’ve got some 0805 resistors on the way (0.1R,0.2R,0.12R,0.15R,0.18R) which is best for the tn31 mod? 0.12R? If so will i be in to stack 2 0.12’s on top of original sense resistors, what sort of current will I be looking at, (don’t have a DMM) also with the second bit circled in the picture what’s it for…
!!

25

Why not just bridge the two resistors shown in post #12? It's how the TN32 is done and how Vinh mods the TN31. IIRC it makes just over 6.5A.

26

Sorry I’m a noob with circuits, still learning! Bridging is taking the resistor out and leaving a solder trace right?

27

Yes, or just leaving them in and soldering a wire over them.

28

Ok thanks! Great help! :slight_smile:

29

I recently did this along with some other things with my TN31. Made a hell of a difference!

I chose to pull the resistors off completely and replace with a solder blob rather than soldering over the top. This was because you don’t want it to be too high because the battery carrier contact plate which screws on top of the driver doesn’t have a very big recess in it.

My current measurement at the battery carrier holds stable at about 3.45A. Not sure what that translates to at the emitter?