Fenix TK61 teardown and mod thread

Good luck with the new driver…
Soon you will be lighting up a whole mountain from 1 km away!! :smiley:
So this light has to be one of the best stock single emitter throwers around?
Cheers
Anton

Yes, one of the best. Probably the best if you are considering throw vs runtime.

TN32 is a very nice option too. Maybe better stock depending on what you are looking for. Its got more power/output. I would highly recommend you to check out that light too.

Thanks RaceR86! Although those are awesome lights, I don’t think I will ever buy one, as my budget max is around $50 per light!(At the moment… :smiley: )
I do however like to keep track of what lights are best/close to best, and then see what budget options are available to compete(well, almost compete)with those lights. I am very happy with my srk,zyt08 and even Yezl Y3!
Cheers
Anton

Thanks for the excellent write up on this light. I wasn’t sure if I was going to resistor mod mine or not, but I think I will now. I already de-domed it and added some thermal paste to the pill before putting it back in.

I also don’t mind the reflector. I’m digging that the light is as lite as it is. The extra weight up front would probably make it top heavy and I like my lights better balanced. 6amps would be nice put I’m still not convinced that the heatsinking is all that great on this light. I wasn’t even sure I cared to push it a whole lot harder than it already is. But reading this I think I’ll just do and and see how I like it that way. I can always swap it back if I change my mind.

Thanks again, excellent job on the post.

Hey man, my friend is in process of modding mine. We will only make a current bump, from 3A to 4/4.2A, with 1x R100 (max for “safe” operation with stock transistor - recommended by Vinh) resistor i think it was. It should get nice bump to around 1000>1350lm i think?

Is dedoming a very hard thing to do? if yes, would it better idea to first order few XM-L2 U2 1A or 1B in order to have replacment if the current led is burnet/damaged during the process, or if it get green tint which i cant stand? thanks in advance.

De-doming is very simple now that they figured out the gasoline method. All you do is soak the emitter in gasoline for a few hours and the dome falls off. After than you have to be very very careful of the emitter though. There are tiny bond wires on it that WILL break if you bump them. They are absolutely fine as long at you don’t rub something like the reflector up against them. A lot of people use rubbing alcohol to get rid of the smell of the gas. I just very gently run mine under warm water until the smell is gone. This seems cool enough that mine came out neutral rather than green. But as always batches vary so yours could be different.

I just resistor modded mine just now. Very simple to do. I used a r025 that I pulled off an old driver and it’s rocking out pretty good now.

Thanks for sharing, i just got my R200, i think i will go for the Vinhn recommendations, even its just ~ 1/1.2A bump, i guess i will get around 250/300lm + from it, over that and even at 4.2A you are risking of burning the transistor, and i’m to lazy to search/ordering an new transistor…

BTW my resistors are 1/2 watts, will that do the job? is 1 or 2W resistors better?

About dedoming, not sure yet, btw do you wash the led it self with water? and even in gasoline? its work after? :~

Sorry i’m fairly new to this stuff, thanks.

I’m not really sure on the watts of the resistors maybe somebody else can chime in on that. But I have de-domed hundreds of emitters with Gas and they work just fine and stay working too. I have some that are over a year old and still running strong.

Just soak for a good long time in the gasoline and the dome will fall off. The warmer it is out the faster it will fall off. If after a few hours it hasn’t you can always pick it up and tap the star sideways on something so it falls off, but it’s better to just let it kinda float off by itself. It will come off cleanly. You can even leave them overnight if you want. It won’t darm the emitter at all. After I have pulled them out I rinse mine very gently in warm water. Many others use the rubbing alcohol. They just give it a soak in it then let it dry of course. This is by far the easiest way to double your throw. The biggest thing to be careful of is not bumping the top of the emitter after you have the dome off. If you do it’s likely to kill it. Probably the trickiest part is putting the reflector back on without bumping the emitter. It pays to take your time. I don’t even want to think about the ones I have killed by bumping them because I wasn’t paying close attention.

Sensing resistor, okay 1/2 watt, ;)

Excellent pictures! I always enjoy watching pictures like these. And showing the internal parts of the expensive flashlight is highly appreciated. Thanks

Thanks alot for the help!

Now i need to know some things,

1. how do you take of the bezel on top? can it be broken if you apply too much pressure with hand? on which side clockwise do you push?

2. Does the contact board take of easily? any tips? do you take it off with screwdriver by applying pressure on both left and right side slowly, step by step, or one is enough?

3. Does the contact board looks the same - its glued in the same way like on the TK75? (my friend will be modding my 75 as well) what if its glued to strong? :frowning:

4. Dedoming, gasoline vs Nitro-Thinner?

Thank you so much.

1. Mine wasn't glued, but was tight from the factory. I used some rubber strap wrenches, but you could probably do it by hand if you were determined enough!

2. I very slowly worked it loose from each side with first a very fine screwdriver then with a larger one.

3. The contact board is just glued in, although I've never seen a TK75.

4. Never used nitro thinner, just gasoline and the heat method. I can imagine that there are some solvents that would also hurt the phosphor, but I'm not sure which ones would.

Thanks alot, so by hand its possible to “unscrew” the top bezel (the stainless steel part -just to make sure we talk for the same part) on which side do you rotate it clockwise to unscrew?

Yes, the stainless part. It is threaded normally (RH) so screw the stainless part counter-clockwise.

Thanks so much!

Fresh gasoline, in a warm environment, seems to work best for the de-doming. I just drop it in overnight (making sure it’s sitting dome up) and in the morning if it hasn’t floated off it pops off easily. I use a toothpick to pop it off if necessary, from the negative side. Then use the toothpick to clean any remnants off, making sure to leave the bond wires strictly alone. I rinse with de-natured alcohol to cut the gasoline smell. It evaporates cleanly and is dry within minutes.

I typically use an XM-L2 U2 1A, but even those sometimes have a bit of a green hue to the tint when de-domed. A trade-off, it would seem, to the doubling of throw. If anyone knows of a specific emitter that de-domes to a neutral white or a technique that allows the same, I’m all ears…

Dale, lately I've been moving towards the hot dedome method. This is purely anecdotal, but I seem to be getting slightly less green shift with this method. More risk, but perhaps more reward. I have killed a few emitters doing this, but Lisa couldn't put up with the smell anymore! Our apartment makes things difficult sometimes, and even though I try and do almost everything outside, some smell always makes it in.

I'll post full details tomorrow if all works out, but I've got mine cranked up to 5.8A to the emitter now. There is no way the stock driver MOSFET(s) could handle this kind of current, I have a few burned fingers to prove it! (low tech thermometer! ) If it survives a few 10 minute runs on high, I'll post details here. I also have a stock light to compare it against and get some readings from (lumens, lux.) I put the stock emitter back on the stock MCPCB, so the two lights will be equal in that regard.

Both the hot de-dome and the 5.8A. Will be watching closely…

Hot de-dome at time of re-flow? I heard that a med firm press on the dome right after re-flowing the emitter makes it pop right off. Haven’t tried it.

Some of my best dedomes have been accidental!

Here's how I do it (very similar to Vinh's method on Youtube.)

1. Heat emitter until solder flows.

2. With a sharp knife, quickly cut the corners and end of the base of the dome opposite the bond wires.

3. Reheat until solder flows again.

4. As soon as solder solidifies, take your knife, slide it under the dome, and quickly pop it up and away from you (towards the bond wires.) If you do this while the dome is still hot enough and with enough precision, you will have a nice dedome. If you don't, you will have potentially lost phosphor, broken bond wires, or a dome left partially in tact. I have killed a few emitters doing this, but have been mostly successful. XP-G2s are much more difficult to do this way since they are so small!

There is a bit more risk involved with this method than with the gasoline method, but some may feel the tradeoffs are worth it.