Here is how to mod the ThruNite TN-31 flashlight...

That should put you at about 6.77 amps to the emitter. I don’t know if that jives with your tail current reading. Someone that knows more can chime in on that. I would think your emitter will be fine if you thermal path is clear. Watch for tint shifting towards blue. If it starts doing that, I would take out a resistor.

What is the beam like? Must be beastly bright.

I already dedomed the LED, though its still the stock XM-L U2, so the tint has turned neutral white. If it starts turning cooler then I’d get the extra R120 and replace it with an R500.

I also sanded/polished the bottom of the stock copper MPCB with P1000 sandpaper after dedoming the LED and also the top of the pill and added a thin film of Fujik thermal grease (not glue) to ensure good heat transfer.

My tail cap reading is 2.67 Amps at 11.58 volts. Not sure whether it jives with your computed current to LED either.

So the constant you’re using to get the current to the LED using the total resistance is about 0.1435? How did you derive it?

Thanx ImA4Wheelr for the help by the way. :bigsmile:

Read in a German thread that the driver tries to regulate .1435 volts across the resistor bank. Changing the resistors causes current to increase or decrease to get .1435 volts across it. As you deduced, .1435 / .0212 = 6.77.

Another info ‘saved’. :slight_smile:

Thant’s what I love with BLF. Tons of knowledge can be learned here.

Thank you ImA4Wheelr! :bigsmile:

You’re very welcome. I hope someone chimes in on your tail cap reading. I just don’t mess with tail cap readings unless it’s direct drive or amc7135’s. It makes sense that it’s higher than the computed emitter current, but I don’t know if the magnitude of the difference is right. It does sound reasonable to my amateur common sense. I need to find some 1206 sized resistors to get my light to about the same current as you modded to. I’m using some 805’s, but I think the solder bridge is increasing the resistance.

I forgot to tell you that I was thinking xml2 when I said your emitter should be fine. I don’t know what the xml is good for current wise. I guess if you do fry it, it will be a good excuse to upgrade to xml2. :bigsmile:

Please report back after you get a chance to use that modded light of yours outside at night. It sounds like it should be pretty sweet.

Yes my K40 now throws a lot farther that when it was stock. However this is only my assessment when shining the light towards the sky (sky method) as I don’t have a lux meter yet. It also has a more intense hot spot but its beam (the pencil-like streak of light seen from the flashlight to the sky) seem less brighter than before. Maybe because its warmer that’s why it appears to be so. I ordered a lux meter because of this and I can’t wait for it to arrive.

What also ‘confuses’ me is when I compare my modded K40 to my modded T08. My K40 has a longer beam (sky method) and a slightly smaller hot spot than my T08 but the beam of my T08 seem brighter than my K40. Maybe its because of the tints but I’m not quite sure - the more that I wan’t my lux meter to arrive early.

My T08 is also dedomed but I’m using its original 25 mm aluminum MPCB. I have a 20 mm Noctigon XM-L2 T6 3C but I did not use it yet because I can’t sit the T08’s reflector if I use 20 mm and I’m not sure if I would like the tint of a dedomed XM-L T6 3C. I also used a V10+ 4 Amp driver (won from RaceR86) for the T08 and the modding was done mostly with Relic38’s help.

I think the resistors (also courtesy of RaceR86) I’m using are all 805s. They’re similar to the ones sold at FastTech. Before installing them for resistor mod, I connect them side by side (parallel) to each other first since its a lot harder to solder them one by one into the driver.

I have several XM-L2 T6 1Bs ordered from Simon Mao (Convoy-Flashlight in BLF) and I’ll be installing them to the K40 and the T08 when they arrive. I just hope they really are XM-L2s and their tints are what is stated.

I'm taking my own TN31 that was originally a XML U2 and upgrading it for testing. Think I got lower #'s in this one because of the LED -- I was fooled by KD's claimed XM-L2 U2 1A, so replacing it with a IOS XM-L2 U2 1A (real one) -- had to take it off the Noctigon, a shame, but only true 1A I got right now. Also changing the wires to 20 gauge (maybe 18 gauge?). Doing the pre-cut method on gas de-doming -- forgot who came up with this, but they said 30 mins total by doing that.

Also since I got a new 2013 TN31 next to a 2012, interesting to note the anodizing and height of the carrier end caps look different. I think they tried to improve it: maybe less anodizing and newer one is slight higher in height, that should result in better contact.

With 2 R082's I got 2.4A measured (7.2) at the carrier, 5.2A at the LED, so I may actually try 1 more R082... HHmm....

Looking good Tom!!

I wasn’t able to achieve the calculated theoretical emitter current either with resister mod. Also 5+ amp. I have to go back into my light sometime. I think there must be something wrong or maybe I fried a resisters when installing them.

May I ask at what distance you measured lux? I get higher numbers at 24 feet (381kcd) than at 10 feet (347kcd). Has anyone figured out the best minimum distance to measure at.

EDIT: I just saw your post #57 at:

Thanks for that post. Very good info.

EDIT2: The two measurements above had been take a separate times. Something else must have been different, because I have been remeasuring and getting fairly consistent results at the two distances.

Ok - vinh removes the resistors, direct wires the connections instead for both the TN31's and K40's. That explains a lot to get 6.5A. Interesting that the lights don't poof by smoking components, but he's done a ton of these lights, maybe only recently with this resistor mod though... Hhhmmm, should I try it??

For measuring throw, rdrfronty has a done a great deal with that, many distances, many lights. I'm pretty sure he stated 15 meters as ideal, anymore than that doesn't seem to make a difference. For under 15 meters, basically the closer you are, the lower the #s because of focus, but I'm sure depends on the beam pattern too.

Direct wire makes sense. I was getting so frustrated trying to get higher current that I ended up added one R030 and two or three R100 resisters on top of the stock resistors. I should have been getting close to 13 amps at the emitter (wasn’t going for that, just wanted to get up to 7ish), but was measuring 5.x amps. Don’t recall the exact current I got. I didn’t like the way I was connecting to the meter either. It was not a good day to be moding a light like that. I can say with confidence I was not getting over 6 amps.

I assume he is using wire that provides almost no resistance. I saw some discussion in the German thread about that. I think the poster said the wire got pretty hot, but he may have been using wire designed to provide measured resistance. I need to find that thread. I remember it was a bit vague though. The Google translation makes it even more hard to follow.

Thanks for the input on the lux testing Tom. I’ll post here next time I go in to the light.

Generally 10m is the point that most serious throwing lights I tested started getting their peak numbers at. 5m works for 90% of the throwing lights too. But a few still readily slightly low at that distance. I generally just go with a longer distance to be safe, usually at 15-25M. If you don’t have help like I do with my brother or have a good max save on your meter, just try to get the longest distance over 5m that you can still read the numbers. Now of course I’m talking throwers, meaning a light over 50K. Not sure if my Preon 0 would even register on my meter at 5m :slight_smile:
My rule of thumb is - When in doubt, increase your distance. You never have to worry about going too long a distance. It’s surprising just how far you can get true readings on a lights throw.

So dividing the constant 0.1435 by the total resistance to get the current to the LED is just a theory but not quite accurate in reality? :~

If TomE’s adding of 2 R082s gets 5.2 Amps to the LED when using the theory above it should get 6.685 Amps (i.e. the actual is 77.786088% of the theoretical value) then adding a third R082 in parallel should have a theoretical current to the LED of 8.435 Amps or an actual current of 6.56 Amps to the LED. :slight_smile:

Ok, here it is... Direct wired over stock resistors, de-domed an IOS XM-L2 U2 1A (real thing), running KP 3400's (not fresh). Ready?

throw: 456 kcd (measured at 4.3 meters, suspect it's really 480-500)

lumens: 1,734 at start, 1,680 at 30 secs

So, think I reproduced vinh's #'s - yes, he's not crazy, and yes the #'s I believe are real.

All modes work fine, it appears. This is a 2012 XML U2 model. The tint looks great, actually maybe too white - I was getting used to the yellow tint. Ok, got another to do asap. I can easily measure carrier amps, will post soon.

Simply awesome Tom!!!

Ouch, 3.5 minutes, it's pretty warm, touchable, but uncomfortably warm to hold.

Is that the norm?

I think that’s what vinh said. Its gets hot easily. :~

I guess I’ll be joining the bandwagon then and do direct wire. :slight_smile:

I don’t want to derail the thread, but I have a thought about that kapton tape underneath the copper.
May it be there to prevent the galvanic corrosion of the aluminum in presence of the copper? I know from electrical equipment that these two materials musn’t be connected together, because of the galvanic incompatibility which may cause the aluminum to be corroded by the contact with the copper. An intermediate piece compatible with both materials must be put amid them.
I think these effects are faster in connections under voltage, but can also be present without electricity,just with the presence of an electrolyte, which could be moisture ( and I am trying to recall all this data, if everything is wrong feel free to correct me)

OR maybe they just forgot to remove the protection tape… This seems more plausible coming from the Far East

2nd TN31 measured 461 kcd throw at 4.3 meters, slightly better, effectively the same. I measured amps at the carrier on #1 and it was 3.48A -- ouch, 10.46A effective -- holy crap!