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

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

Here is a tutorial on how I modded the thruNite TN-31, I did the mods over several days, and the results are well worth it! :bigsmile:

Sorry but the SD card where I had the pics became corrupted! :_(

To open up the light and to access the emitter you need to put the TN-31 head in a plastic ziplock bag for 2 minutes in boiling water then use strap wrenches to open it up.

Be careful not to loose the tiny steel ball and gold spring that are under the metal brightness selector ring, remove them and put them inside a ziplock bag for safe keeping along with all the screws, LED centering plastic ring and O rings.

1 Using a very hot soldering iron unsolder the wires to the LED, the manufacturer seems to have used a high melting point solder or the copper absorbs the heat pretty fast, so use a thick soldering tip with at least 40w iron or you will not be able to unsolder the wires.

2 Remove the plate that covers the circuit board by removing the 3 screws that hold it in place, put screws in plastic bag and notice how the black plastic insulator goes installed on the plate, remove and polish the aluminum plate to a mirror shine using Flitz and a dremel with a polishing wheel.

3 Replace awg 26 stock silicon wires with awg 20 PTFE or Silicon wires, be careful not to bend much the negative wire once soldered or you will tear off the pad! I sugest you pre solder the wires before installing.

4 Install an extra R082 smd resistor, you can buy them from Digikey, it will increase the current to something between 4.6 and 5A

5 Remove PCB By Removing the 2 screws that secure it to the heat sink, put screws in plastic bag.

6 Clean the PCB from thermal grease with de natured alcohol and Q-Tips

7 Remove what appears to be a kapton tape layer from under the copper PCB and lap to a mirror finish using 2500 grit sandpaper and flitz polish. I got no clue what were they thinking for leaving tape in there!

8 Replaced the stock XM-L U2 with a XM-L2 U2 1C emitter from illumination supply, I direct bonded it to the copper of the stock PCB by filing off the central pad’s dielectric layer with a dremel, do not put too much presure and over do it, stop once you see the copper.

I used a heavy tortilla iron skillet in low heat to replace and reflow the emitters, be careful not to over cook the emitter.

9 Polish the heat sink to a mirror shine using Flitz to maximize heat transfer between the copper PCB and heatsink.

10 Polish using Flitz the 2 contact pads of the heatsink where it makes electrical connection with the circuit board, there is a lot of gunk there! once you finish cleaning and polishing clean it with alcohol, then deoxit then use progold as a final coating.

11 Use the soldering iron to put more solder around the base of the spring of the circuit board

EDIT 8/12/13 I soldered a copper braid inside the head spring (+) contact (Kind of like the old Mag Mods) to reduce the resistance of the spring, also added copper braid to both springs in the tail cap switch, apparently there is a slight increase in brightness by doing this mod, keep them small and be careful to not short out the springs.

12 Clean the gold ring pad on both sides of the circuit board using alcohol, then deoxit and finish with a coating of progold.

13 Re install the circuit board but before you put the polished plate back, clean the underside of the plate where it touches the circuit board with alcohol, deoxit and put a layer of progold. Do not over tighten the screws.

14 I used Arctic Silver 5 as my thermal compound, I completely covered the back of the polished copper PCB using a spatula used to spread thermmal compounds on computer processors, make the layer as thin as possible.

15 Before you install the PCB notice what side is the positive and negative so your wires match.

16 Re install the PCB retaining screws and do final adjustments to center the led in the heatsink. Tighten up the screws real good but be careful not to strip them.

17 Re solder the thicker wires to the LED and re install the centering ring making sure it sits flat at the base of the PCB. Use lots of heat and flux, be careful not to touch the dome with the iron! If You can use something to cover the emitter while you solder, it will be much better.

18 I used super lube thick grease on the selector ring, makes the switching of modes smooth as butter! Fill the hole on the underside of the selector ring with grease then insert the gold spring and steel ball, then grease all the detents and flat surfaces of selector ring and align the triangle marking with the stand by marking on the heatsink and re install, test for proper function and then re install o-ring.

19 You could put some thermal grease on the tread of the to help transfer heat to the massive head.

20 If you did everything you should have a VERY bright light.

Next stop, modding the battery carrier and switch…

PS. let me know if I missed anything!

Edited by: AlexGT on 08/12/2013 - 13:18
AlexGT
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This is how to beef up the battery carrier

1 Remove the 3 screws on each side of the battery carrier, put screws in bag, remove the 2 aluminum plates, notice how the black plastic center post isolator go, then remove and store in the plastic bag.

2 Use Flitz polish to polish the aluminum plates to a mirror shine

3 Use alcohol then de oxit then progold on each of the gold contacts where the screws go in.

4 Loosen the center positive contact, it is a screw you just use pliers to twist it open, Polish with 2500 sandpaper then clean with alcohol, then deoxit then progold. pay attention to cleaning and progolding the underside of the screw where it contacts the PCB

5 Use a hot iron and soldering to beef up the contact between all the springs and the PCB base.

6 Put progold in all the screw holes before reinstalling the center screw

7 Firmly tighten the center screw using pliers on both sides of the battery carrier, careful not to strip them.

8 Clean the underside of the polished aluminum plates where they contact the PCB then use alcohol, then deoxit, then progold.

9 Make sure all the gold contacts in the Battery Carrier where they contact the aluminum plates are clean and progolded

10 Re install the black plastic positive contact isolators then the plates and tighten the 3 screws on each side firmly, careful not to strip them.

You are done with the battery carrier!

This is how to beef up the switch PCB plate

To access the contact PCB plate you will need to boil it inside a ziplock bag in hot water and use strap wrenches to open it.

1 Remove the PCB switch assembly.

2 Clean all the gunk from the tread using alcohol and Q-Tips, pay special attention to the shinny shoulder at the end of the treads

3 Polish the shoulder using Flitz to a mirror shine, then use alcohol, then deoxit then progold

4 Clean both sides of the PCB with alcohol to remove the gunk and grease from factory

4 Beef up the 2 spring contact with the PCB using a hot iron and solder.

5 Beef up as needed the contacts between the switch and the PCB, and the electrical connections of the switch

6 Clean with alcohol, then deoxit then progold the gold ring around the PCB and all parts that have electrical contact.

7 Re install the switch PCB and lube the Tailcap O-ring, tighten the tailcap

You are done!

Slim Pickens
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Wow, why would they leave kapton tape in there? Foolishness!
Nice step- by-step description. I’m looking forward to hearing your impressions on the light post-mod. Maybe beamshot or two for good measure? 8)

Tom E
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Alex - this is a sick mod! Since this is designed for throw pretty much, would be great to measure it. If you don't have a light meter, bunch of BLF'ers in Tx that do. Q's:

- What is Flitz? Probably been mentioned, but not familiar with it or where to get it

- you dremel'ed out the PCB dielectric layer, but not clear what you did with the hole? Maybe I'm confused...

AlexGT
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Yea it was kind of dumb to leave a plastic tape between the copper and the heatsink, it is much better now

I do not have a light meter and most of my lights are not stock I will post a comparison beamshot against a 35W HID I think the modded TN-31 can hold its own against that monster.

I did not drill a hole with the dremel, I just scraped the dielectric layer off until I got to the copper

This is flitz

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Pictures against the 35W HID on the right

rdrfronty
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Very good step by step instructions. I think that anybody who feels confident enough to fellow your procedure will and up with a awesome light. These TN31’s can be really beastly when modded. Heck, they are very impressive bone stock.

Spasmod
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AlexGT wrote:
7 Remove the stock kapton tape layer from under the copper PCB

This is very concerning.. I have tried to get some clarification from David at Thrunite but it’s like trying to get blood out of a stone.

I’m worried about using my TN31 now !, especially on longer runs.

Thanks for the info Alex

Tom E
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Spasmod wrote:
AlexGT wrote:
7 Remove the stock kapton tape layer from under the copper PCB
This is very concerning.. I have tried to get some clarification from David at Thrunite but it's like trying to get blood out of a stone. I'm worried about using my TN31 now !, especially on longer runs. Thanks for the info Alex

I'm suspecting they want electrical isolation, which is what you lose when you have a direct copper thermal path, like in a SinkPAD. Interesting, I've asked this before about the SinkPAD's but guess no one seems to know. Original MCPCB's has the substrate layers to electrical isolate the middle pad of the LED, but with  a SinkPAD type of MCPCB, you lose that isolation.

dthrckt
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as I’m sure you realize, the middle pad is neutral, and doesn’t need electrical isolation…

so that use of tape is really strange

Tom E
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Then why the substrate layers in standard stars? Thought it was mentioned they were there to electrically isolate the middle pad for the battery negative running through the body. Maybe something left over from older design LED's?

Update: this CREE App Note explains the issues: CREE - XLamp_PCB_Thermal.pdf. They say:

 "The pad is electrically isolated from the anode and cathode of the LED and can be soldered or attached directly to grounded elements on the board or heat sink system."

Not sure though if the housing could be considered grounded.

Slim Pickens
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but I wouldn’t be surprised if it’s simply cheaper to produce MCPCBs with a dielectric layer under the thermal pad than without. I imagine that in common designs, the dielectric that isolates positive and negative traces is the same as that which ends up beneath the thermal pad. Thus, eliminating/removing the dielectric in the thermal path would necessitate an extra step. Just a guess, and I could very well be wrong.

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Slim - could very well be, but makes you wonder why ThruNite engineers designed it with that kapton tape there... Electrical isolation is the typical use of it, but maybe they were just playing it safe and being overly cautious, thinking it wouldn't impact the heat transfer much. You would think they would do thermal testing, but who knows what really goes on in the design/prototype phases with these manufacturers.

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I finally got the info from David at Thrunite. He tells me that there shouldn’t have been Kapton tape on the back of the sinkpad.

He says that it should be directly coupled with thermal glue.

Kinda weird though, where did the tape come from then ? unless the sinkpads come with a Kapton tape backing and they didn’t remove it this time.

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Ok, I was offbase here... Wow, this sounds like a ThruFire brand Smile. Maybe this is some of the quality problems people have been experiencing with ThruNites lately.

AlexGT
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What I suspect is that it was some sort of surface protection for the copper PCB and it was supposed to be peeled off prior to instalation, it is like the very thin kind of tape the factory puts on the back of new watches and the user has to peel it off before use.

When I first removed the led PCB the copper back looked the same color as the copper wire used in transformers, that is what gave it away, then when cleaning it to remove the white thermal grease, it started to peel off.

I was able to source an extra stock TN-31 copper PCB from another member who moded his light, when it arrives will check the back for the presence of the tape and post pics if its there.

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Tom E wrote:

Ok, I was offbase here… Wow, this sounds like a ThruFire brand Smile. Maybe this is some of the quality problems people have been experiencing with ThruNites lately.


That’s my guess too Silly
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My TN31’s MCPCB did not have tape under it when I modded mine. Just thermal paste.

I tend to agree with AlexGT’s observation about what it is and I’m putting it down to poor QC on Thrunite’s part.

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I’m glad I haven’t bought one yet – I’d have to pull it apart just to check lol

too much of a Laser + spill for me anyway, so if I did it would be to mod it anyway…

which is feasible with these great instructions Smile

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wow thanks for the how-to! just wondering which SMD resistor that one is. unfortunately i don’t have a pic of the tn31 so i just stole turbobb’s k40 pic, i hope he doesn’t mind. is this the one? i hope tn31 has a similar pcb

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Overclocker wrote:
wow thanks for the how-to! just wondering which SMD resistor that one is. unfortunately i don't have a pic of the tn31 so i just stole turbobb's k40 pic, i hope he doesn't mind. is this the one? i hope tn31 has a similar pcb

Yes that's them.

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Yes that is exactly the one, you just solder another smd resistor over it and the current will increase, BTW while you are soldering an extra resistor you can also upgrade the base of that spring with more solder.

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AlexGT wrote:
Yes that is exactly the one, you just solder another smd resistor over it and the current will increase, BTW while you are soldering an extra resistor you can also upgrade the base of that spring with more solder.

awesome! can’t wait to do the mod! so it boosts all levels, right?

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oh btw don’t use Flitz on any thermal interface. it gets into the pores of the metal and inhibits thermal transfer. instead use thermal grease to polish the surfaces. doing this impregnates the metal with conductive particles

i learned that the hard way when i was working on a watercooled 172-Watt thermoelectric cooler

AlexGT
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The resistor mod does not alter the other levels as far as I can tell, only the highest level is what gets boosted.

The digikey part number for the 1206 0.082 ohm SMD resistor I used is P.082AVCT-ND,

Thanks for the tip OC, I did clean both parts with alcohol before using AS5, and I know the results are better than what came from the manufacturer, I can tell right away the led module heating up fast when in use, so the thermal transfer must be working as planned.

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great! moonlight mode is retained!

that’s the problem with metal polish, once it gets into the pores it’s very hard to get out even with alcohol

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Have you tried recovering the SD card? How did the photos become corrupt?

Try recuva to recover them.

BLF ≠ B-grade Flashlight Forum

 

AlexGT
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When inserting on card reader it does not recognize it or even confirm something was plugged in, phone does not read it either.

The link you posted goes to a webpage not found

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Yikes, that sucks. Sorry, fixed the link.

Have you tried your camera’s card reader? Does it recognize it at all?

BLF ≠ B-grade Flashlight Forum

 

AlexGT
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Thanks for the link will give it a try tomorrow

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Alex,this is a great tutorial thanks for sharing.I will eventually do this mod when I have time.Can a 20mm sinkpad be used instead of the factory board?I assume it's smaller than the factory board but would it be a disadvantage to do so?

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