Mod TK70

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33696933
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Mod TK70

Anyone mod their Fenix TK 70? I feel like changing the leds to XML2 for more output and getting a look inside.
Driver Battery contact

Updated : Pictures

Driver top board

Driver bottom board

LEDs on MCPCB

Plastic reflector

After MCPCB was removed Note there was no thermal interface material

MCPCB 18 AWG silicone wires

Back of MCPCB

Edited by: 33696933 on 07/10/2013 - 23:01
33696933
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FMcamaroZ28
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From what I’ve heard, its a real bear to open it up. Loctite city.

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I opened mine up really easy, just put it in the vice and a rubber strap wrench . Wasn’t that hard in my opinion. It has a Triangle MCPCB like the TK75 and also uses a plastic reflector. It didnt even have thermal grease under the mcpcb. I will get pics later

jamio
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Good work, looking forward for the pics! 

Could you also add picture of the rubber strap wrench you used? I don't have this tool yet and sometimes it could be handy.

oRAirwolf
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Awesome. Some pics would definitely be appreciated. I am a little disappointed to find out the reflector is made of plastic. I wasnt expecting that. Either way, I look forward to seeing your results.

33696933
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OP is updated with pictures

33696933
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Easily opened the TK70 with 2 strap wrenches and a vice. Reflowed Cree XM-L2 T6 3C leds from Illumination Supply. The copper MCPCB has no dielectric layer under the neutral pad. I measured current between the led and driver This is with XML2 T6 3C led
Power supply set at 6.13 V
First numbers is the current between driver and led second is the input current to the driver
Turbo : ~2.81A | ~5.6A
High: ~.956A | ~1.5A
Medium: ~0.288A | ~0.4A
Low: ~.018A |

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Very nice, thanks for sharing!

BLF ≠ B-grade Flashlight Forum

 

Tom E
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The plastic reflectors can be high quality, and in the Fenix lights, they probably are, all depends on the quality of the coating. Reduces weight significantly - Shocker sure would benefit from one... Not familiar with the TK70, but big part of the TK75's benefit is it's light weight.

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Nice mod. Was there any thread locking compound on the threads? I dont see any in your pics, unless youve already cleaned it off.

To your eyes, does it appear brighter after the emitter swap?

Its strange that they didnt use any thermal paste.

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FlashPilot wrote:
Nice mod. Was there any thread locking compound on the threads? I dont see any in your pics, unless youve already cleaned it off.

To your eyes, does it appear brighter after the emitter swap?

Its strange that they didnt use any thermal paste.

It appears to be brighter than the older XMLs , its just a bit dimmer than my BTU shocker with the same leds. It had threadlocker but was still not that difficult to disassemble it. Yeah I was surprised it didn’t have any TIM .

DENGOH
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Interesting to see inside of TK70. Fenix has been using plastic reflector for many years. To me, that is their strength, not weakness. Surface coating quality is the most important aspect of reflector.

cool i'll see you when you get there

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33696933 wrote:
FlashPilot wrote:
Nice mod. Was there any thread locking compound on the threads? I dont see any in your pics, unless youve already cleaned it off.

To your eyes, does it appear brighter after the emitter swap?

Its strange that they didnt use any thermal paste.

It appears to be brighter than the older XMLs , its just a bit dimmer than my BTU shocker with the same leds. It had threadlocker but was still not that difficult to disassemble it. Yeah I was surprised it didn’t have any TIM .

Thanks for the fast reply. Its encouraging to hear that you broke it open, even with threadlocker in place. Nothing like breathing new life into an expensive older light. You’ve got one of the great ones there!

Can you tell us more about which strap wrenches you have? I assume you have 2 and twisted them in opposite directions while using the vice to hold the work in place. I just broke my rubber straps and need to replace them with something professional grade. Darn those glued flashlights! Big Smile

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FlashPilot wrote:
33696933 wrote:
FlashPilot wrote:
Nice mod. Was there any thread locking compound on the threads? I dont see any in your pics, unless youve already cleaned it off.

To your eyes, does it appear brighter after the emitter swap?

Its strange that they didnt use any thermal paste.

It appears to be brighter than the older XMLs , its just a bit dimmer than my BTU shocker with the same leds. It had threadlocker but was still not that difficult to disassemble it. Yeah I was surprised it didn’t have any TIM .

Thanks for the fast reply. Its encouraging to hear that you broke it open, even with threadlocker in place. Nothing like breathing new life into an expensive older light. You’ve got one of the great ones there!

Can you tell us more about which strap wrenches you have? I assume you have 2 and twisted them in opposite directions while using the vice to hold the work in place. I just broke my rubber straps and need to replace them with something professional grade. Darn those glued flashlights! Big Smile


Well I couldn’t find my old Craftsman one but I went to Home Depot and saw a New tag on their strap wrenches so I used 2 of those. I actually wrapped one part with a strap wrench and put that in the vice to not damage the finish and get a grip. Then used the other to get the bezel off as that part was tricky. Figure if I break the wrench I can just get it replaced at Home depot .
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Great idea using the vice to secure one strap wrench.

Reading your post again, seems the reflector couldnt be removed from the bezel. When you turned the bezel, the reflector didnt get hung up on the emitters? I assume the reflector can turn freely inside the bezel? Just making sure…

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Oops forgot to edit that out. I actually somewhat loosened the bezel that let the reflector spin freely. Eventually I got the bezel off that that part. The reflector is held on by those three notches on the head so it doesn’t spin on the emitters

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Ah, it all makes sense now. I’ve got someone that wants a tk-70 modded with XM-L2 3C. Given the stories of massive threadlocker overdoes fenix is famous for, I never would have attempted this mod without your post. Ive got a set of mega-strap wrenches on the way. Thanks a bunch for explaining. Given the huge amount of questions pertaining to cracking the tk70, I hope others find yours post.

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Cool pics, I opened my TK-70 a few weeks ago and tore it to all hell.Used everything in my repertoire to try to open it including strap wrenches.Thank god it was a non functioning one I bought for a host.It seems to be a brass led board rather than copper in mine,and it fits into the light by way of cutouts in the light body.Good to see someone was able to mod it successfully,nice work 33696933.

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DARCANGEL, well thats not good news. Since these are hand assembled, there has been reported a variance in the difficulty in tearing them apart. Maybe yours had clean/degreased threads before the thread locker was applied. Was the host damaged while trying to twist it apart?

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FlashPilot wrote:
DARCANGEL, well thats not good news. Since these are hand assembled, there has been reported a variance in the difficulty in tearing them apart. Maybe yours had clean/degreased threads before the thread locker was applied. Was the host damaged while trying to twist it apart?
I did damage the indented part below the bezel when a wrench slipped.There was also an ungodly amount of threadlocker on it which explains the difficulty getting it apart.That was just removing the bezel ring,not the"cup"that the reflector sits in.The head is actually 3 pieces and I wasn't able to unscrew the cup piece from the neck of the light.Good luck to anyone taking Fenix lights apart,it seems some have more threadlock than others.
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Hmmm… I might pass on this one. I guess I could give it a good twist with a strap wrench and see how it goes. Good thread lockers are usually unaffected by heat unless they are heated above 600 F. Cheaper ones, meh…

If everyone would just ban glued flashlight all together, there would be no more of them! >)

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I should probably be banned for saying this, but, it seems that the increase in output going to XM-L2’s is not worth the risk of destroying a $200 flashlight. I love my TK70 too much to harm it. The BTU Shocker, on the other hand, is a great light to mod.

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I did this same mod to my TK-70. It was I pita getting it apart. I used the strap wrenches also along with a few good sweeps with a small propane torch. I was nervous about the plastic reflector, but no harm done. Since the mod of the xml2 emitters, I have noticed it does not like 4 cells. It could be a tail cap ground issue, but it does seem brighter with the mod even on 3 10000mah tenergy cells.

I plan on doing a tail cap mod with a copper braid. I will drill and tap the tail cap from the inside to fasten the copper briad. Then solder as usual to the end on the spring. I already did the driver spring copper briad mod.

Ken

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Looks like the only mod I would do to TK70 is to make her accepting 18650s.

cool i'll see you when you get there

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Thank you for the great pictures. Gives a good idea of the internals. The color of the copper mcpcb looks off. Is there kapton tape adhered to it?

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Is there a resistor mod for the driver? I wouldn’t mind maxing out the current to the emitters. 3A? Or 3.2A?

J)

Ken

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Hyprmtr wrote:
Is there a resistor mod for the driver? I wouldn’t mind maxing out the current to the emitters. 3A? Or 3.2A? J)

Ken


I don’t know
FlashPilot
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Im just awakening an old thread for other TK70 owners.

I swapped out the stock nasty green tinted XM-L’s to some XM-L2 1A I had kicking around and was duly impressed. While the lux only increased by about 20%, the best part is in the nice white beam I gained. The old stock green tinted emitters were just awful, which made the light completely unusable for me. So there it sat in my closet for several years… until now.

Notes:

  • There were no thread locking adhesives used on my example. Big Smile
  • There was no thermal paste under the triangular LED MCPCB.
  • The LED MCPCB was a copper direct thermal design with no dialectric layer obstructing the thermal pad.
  • It still took some brute force with large strap wrenches to crack the bezel threads lose.
  • I removed the D cell extender tube and now power it from a pair of TF32650 unprotected cells (8.4V total). It picked up about 15 minutes run time, lost a good amount of weight (versus 4 x NIMH cells) and shortened the flashlight considerably. To take up the difference in total cell length, I used a maglite D cell spring (old gen with a cross bar on the big end) and soldered a 2mm x 20mm round polished copper disk to the small end. A copper wire bypass keeps resistance low. The modded mag spring is dropped in after the cells. The stock tailcap & spring compress perfectly against the mag spring 20mm copper disk. This is important because it is critical to maintain the stock resistance for the boost driver to function properly.
  • Before the mod when testing in the field, the stock TK70 kept up with my stock XM-L2 BTU Shocker. Now it beats it with less current. Probably because the TK70 has a higher quality/more efficient reflector.
  • FAR more friendly grip with the D cell sized tube than the fat BTU shocker tube, and also a lot less weight to carry.
  • Only 2 cells to recharge now, instead of 4.

After the small mods, its a much nicer & updated package to handle. The boost driver still kicks down from max to the next lower setting when the cells have been depleted (with the usual sound of the inductor screaming for about 10 seconds as it switches). If you haven’t heard a TK70 switch down when the cells have become depleted, its quite entertaining because the sound pitch decreases as the driver switches into the next lower mode. Upon depletion, I quickly removed and tested the cells and each measured 3.2V resting (and rising). Since its a boost driver, its hard to guess just how deeply the cells are being discharged while under load (as voltage drops, amp load is increased with the boost driver to maintain CC at the emitters). This is very demanding on cells, although the TF32650’s have proven to perform well under sustained heavy loads. I might have to rig some heavy wires from my DMM and have a look… but maybe I wont. LOL

All in all, Im very pleased with how well this turned out.