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Fenix TK75 - How to remove bezel?

Light superglue

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I have purchased a used TK75 from ebay and wanted to open the head and discard the LEDs. But it does not unscrew. Has anyone used this thing as laser host before? Any clue how to open he head?

I was interested in this host because of big diameter - almost 75mm heatsink with many modules (and optics) inside might fit in.
It is also interesting that the 4-Li-batteries holder inside connects them as 2 pairs of 2, so the voltage input into driver would be 8V.
 



Encap

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The TK75 has a sealed head and warning in the instructions " Please don't disassemble the sealed headasdoing so can cause damage to the flashlight" so it is probably has epoxy glued threads. You can try heat to weaken the glue, not sure if that will work in this case.
 

Light superglue

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Thank you, Encap!

With heat gun we managed to have it open.
Strange that the glass circle diameter is 80mm. I thought it should be 75 as stands in the torch name.
 

Encap

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Lucky you got it apart without ruining the head. Good job.
 

Light superglue

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This week I received 2 extensions for this body (seller did not recommend to use more than 3 battery packs at once - what makes 24V input into driver) and checked the voltage/curent in this torch when light was on.
Soldered into the circuit am/voltmeter only reads 10V-2.8A at full luminosity.

Facit: the internal diver output is not great for setups with 4-8 combined high power LDs. Maybe 10V will be OK for 2 PBSed NUBM07 but 2.8A - what a crappy overdrive!!!

I want to look for an alternative boost driver to convert these 24V into 50V at 5A or simlar...

01.jpg02.jpg
 

ImA4Wheelr

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I may be remembering incorrectly, but I thought the Tk75 battery carriers were designed to so that they were electrically parallel. So 4 carriers would be 2S8P or 8.4v at full charge.

EDIT: IIRC, the stock TK75 driver is a boost driver and the LED's are wired 3S. You might be able to recoup some of your costs selling the driver and MCPCB. Best wishes on your build. Sounds like it will be pretty awesome.
 
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Alaskan

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I bought one of those TK75 flashlights a few years ago and disassembled it just fine. The battery packs are series parallel, 2 x 2 per pack and each pack added to the flashlight with additional thread on tubes are simply in parallel with others, no matter how many you add, 8.4 volts full charge. If you want to have something machined to add to the front end of this flashlight (after removing the LED's) it is ideal for use as a (edit: high power) laser pointer host. I also particularly liked the glass window with the uber nice visible spectrum AR coating on it, if you don't want the window, I'll buy it from you.
 
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Light superglue

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Oh, wait, you are right - all these carriers are parallel - the voltage is 8V all the time. Strange tipe of torch, not like others where more batteries mean more voltage... I have to check how much current it can pass - hopefully my 100A ammeter with shunt should be enough? Do you know what the max current setting of these 18650 protected batteries could be?

Maybe this host can be of use for a such thing:

Alaskan, you are right, the glass window has blue reflections - it can be some kind of AR coating. Was it written anywhere in specs what kind of coating it is ?
I would like to replace this glass by a focusing lens with same 80mm diameter and AR coating but do not know where to find one. I have one 80mm biconcave from ebay - it can focus but apparently does not have any coating.
 

Alaskan

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That glass window is awesome it's almost a shame not to use it, can you use a 85 mm diameter PCX lens with about 3.5 inches focal length, or is that too big? I need to mail one out to Paul, could mail one out to you too. This lens is very high quality with AR coating. I'm not sure the exact focal length, somewhere about that plus or minus .25-.5 inch, I believe. trinh has one he's building a 520 nm host with, RedCowboy has a couple of them too.

Regarding the battery packs, can you solder in some extra wire to increase the diameter of the conductor between the paralleled or series wiring? I did that with a similar battery pack, but didn't try it with the packs from the TK75, don't have that host at hand right now to look at it, but on the other battery pack I modified I had to take it completely apart as well as the PCB boards to solder thicker copper conductors on them too. I used braided copper solder wick and tacked the braid to the traces and conductors in the pack with a hot soldering iron..

Regarding the batteries, I am not sure, some are rated for 5 amps, some 10, I believe some 20 or more. Ratings or claimed current can be quite different from reality, you might go over to candle power forums and see what test results they may have for your battery, or other 18650 batteries, I found some really good info there a couple of years ago regarding this kind of thing.
 
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Light superglue

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Hi Alaskan,

Thank you. It looks interesting.
84mm lens would pass into Fenix bezel for sure, 85mm might be too close. If the lens thickness is not too big, I could try. Anyway 85mm would for sure pass into the big 28 XM-L T6 LED chinese torch I recently bought from ali but I did not yet explored what kind of driver is inside.

Where did you get these lenses - a GB? What is the thickness at edge?
 

Alaskan

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The edges are ground, only .5 mm off around the edge and you would have it, or maybe better to take it out of the bezel? Edge is close to 3 mm. I bought them on ebay for five dollars each, I have a few here in Qatar, but most are in storage in Alaska.



You might as well take it, if at all interested, free.
 
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Light superglue

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Thank you, this is very kind of you!

Is it easy to ground lenses without destroying them? I think that a very precise equipment would be needed for this and not at all the same which is used in CNC shops working with metals.

You were lucky to get lenses with AR coating so cheap, I look at ebay and no one selling big lenses mentions anything about AR coatings, so all lenses for sale at the moment must be uncoated...

If you are ready to give it for free, can I at least pay you the shipping?
 

Alaskan

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PM me your address, let me check.
 

Light superglue

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And where is PM option now, I only see "Start conversation" clicking over your name in this LPF version.
 

Alaskan

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That's the PM, click on start conversation.
 







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