Sounds like that's what vinh is doing to get 6.5A at the LED, and supposedly 480 kcd or so. I'm gonna try it - just no time yet...
Thanks for your input. I think I saw you mention the idea of MG-T2 modding your TN31. Stock, the driver will not drive the MG-T2. I tried last Saturday. Driver only puts out 4+ volts unloaded. Based on my playing with the MG-T2 in other reflectors and light, I think it will be pretty floody in the TN31. I hope someone proves me wrong though because it would be a pretty cool general purpose light that way.
Wow, thanx for these new info. 
I was apprehensive at first that I might fry my K40 so I only added an R120 and got 1.99 Amps at the tail cap @ 11.48 volts (original was 1.35 Amps @ 12.4 volts). 
Last night I added an R500 resistor and the tail cap reading increased to 2.06 Amps @ 11.69 volts. With this new info, I’ll be removing that R500 tonight and add 2 more R120s. The result should be slightly better than 2 R082s. J)
i just got my tn31 modded by vinh on cpf. He put a dedomed xml2 at 6.5 amps. the throw of this thing is unreral. it out throws my xseacher with dedomed xpe2 at 3 amps by a suprising amount and that light gets about 380k so this light must be between 450 and 500k . vinh said his friend measured it at 480k
I would say they are closer to 500K. Mine will hang right with my POB HID. Saablaster tested his POB to be around 540K.
Vinh does super work.
Wow!
So he should have used 2 R082 resistors in parallel instead of one to boost that thing to 6.5 Amps. I’m gonna try this on my K40 too. J)
I got some beamshots of vinhs modded 6.5 A tn31 vs a dedomed t40cs and a xseacher with dedomed epe2 @ 3 A
Vinh modded tn31………………………………………………………………………………….dedomed t40cs also done by vinh
xseacher with vinh dedomed xpe2 3A pill
Distance to trees is 150 feet
Just finished removing the extra R500 from my K40 and added 2 more R120s or a total of 3 R120s. This should be equal to a single R040. Two R082s in parallel would be equal to a single R041.
When I took the tail cap reading, it was 2.67 Amps at 11.58 volts. This is about 30.9 watts. Is this safe for the K40? :~
What percent of the total current will go to the LED? I’m apprehensive because my computations says its more than 10 Amps. Also the head of the K40 warms up easily when turned to high. Is this normal? Should I take the third R120 off? :~
Your math seems good assuming you also don’t have the stock resistors still in place. 3 R120’s should give you about 3.59amps at the emitter. Are you chips stacked high enough that the driver cover might be touching and shorting? Maybe some excess solder is shorting.
Nice photos alex1234 and fern chan. Thank you for sharing. Welcome to the forum to both of you.
The stock resistors, R100 and the R082, are still intact so all 5 resistors in parallel should be about equal to a single R021 (if it even exists).
I have removed the excess solder before putting back the driver cover and the three R120s were placed side by side over the stock resistors so shorting is not an issue. Its not hot actually, it just gets warmer faster.
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’.
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.