Sure. 
Having mosfet fever, so I bought 3 mosfet. Checking the resistance between D and S, they are all non measurable, that means they can be considered completely open. I will use the Infineon mosfet to repair another Haikelite TA driver and put it into my old MT03 12000lm.
And the two Haikelite SIR800 are each about 42Mohm and 55Mohm. This is good indicator it is not open enough.
Two SIR800, BSC009NE2LS5ATMA1, SIRA22DP-T1-RE3, NTMFS4H01NT1G
OMG Infineon mosfet is crazy. Now my old MT03 is the brightest. Much better than Vishay SIRA60.
Was too excited and forgot to mention this.
Both Haikelite TA driver having glowing during off with SIR800 mosfet. They are out of box defect, without extended use.
Both are successfully repaired by swapping with Vishay SIRA60 and Infineon BSC009.
Yep, that is what I expected. The FET is generally the weak link with this sort of issue.
Good to know you got them fixed!
I’m very glad that the culprit is confirmed.
I already have a replacement FET (BSC009NE2LS5IATMA1) thanks to Arrow’s free shipping but I need more soldering practice before I attempt the repair.
This is good to be aware of. I'm close to pulling the trigger on a MT03 TA. I guess I'll plan on ordering a new mosfet as well
I don’t think there’s much soldering involved. You need a hot air gun for mosfets.
Ya, FET definitely is the culprit in my two drivers.
I am glad it got sorted out and now I have over 32k lumens with two MT03 left and right. They got hot from cold really really fast. I plan to play with momentary mode side by side.
Thanks to you all who care, for all the help provided to me.
Yeah, I’ve got hot air. I just need to reflow quite a few more things before I take on my most expensive light.
That’s the craziest FET. I think you will notice at least 30% boost on brightness.
I didn’t practice, I was afraid of damaging FET with hot air, but it turned out working fine. Hot air temperature was 400c, I tried to complete it within 15s.
For modders, it is great light and really easy to open and repair or upgrade.
My FET is different from yours.
BSC009NE2LS5-I-ATMA1 vs. BSC009NE2LS5ATMA1.
I got the product number from Lexel but now I see that yours has lower RdsOn, higher current rating and lower price. Oh well. Anyway, it surely is a good FET. 
The key with hot air is distance. You can set an arbitrary temperature, on the high side, and control the heat by moving it closer or farther. Start off maybe 8 to 10 inches to heat up the FET and everything around it. After a minute or so have your tweezers ready and move your nozzle closer to the FET. Hopefully the solder will go liquid in about 10 seconds. Then lift it out of the way.
I usually remove the old solder with an iron and solder braid. Then I add flux and fresh leaded solder to the pads. Then add more flux and set the FET on top.
Then same thing, heat from a distance for a minute or so, then move in close looking for the FET to drop into position. Then I push it down with tweezers and remove the heat. Once cool, I clean any flux residue and it’s just like factory.
I’ve only done a few, but they came out perfect. If anyone has any more tips, I’m interested.
Thanks JasonWW. Will keep your hits at mind until I’m ready to do the repair.
You can also practice on junky circuit boards to get a feel for it.
Interested!
Your saying your interested in buying one and want the coupon code?
After all that has been said? Lol
I guess Freeme is still doing coupons for this light, I’m not sure. This thread was started in 2017. Just keep in mind there is a small chance you’ll need to replace the big FET on the driver.
I see. An extra “I”, yours is faster FET I guess.
Can you take picture on the FET when you got it, would like to see what’s the printing on the chip?
Now they can sleep in total darkness inside my camera bag that I have betrayed. 
