My Trustfire F20 just stopped working for no apparent reason yesterday. It is the same light as an AKOray K-106 which many of you are familiar with. I tried taking it apart but the pill is soldered into the headpiece, and there does not appear to be any way to remove the tail switch.
Is there a trick I am missing?
BTW, I've never used 14500 batteries with it, just eneloops or alkaline AA's.
My F20's driver died about 15 mins after i bought it while using it with a 14500. I pulled the driver out and rewired it to direct drive. It's perfect now! One mode and bright. 
Did you have to de-solder the pill to remove it?
Yes. It's fairly simple if you're handy with a soldering iron.
I removed the chips and resistors on the driver and cut some notches on the side of the driver to run the wires through and onto small blobs of solder. One to the center of driver and one to edge of the driver. It wasnt pretty but it was my first light mod and it worked out great.
Give it a shot.
I have the Akoray 109. If yours really is just like this one you can remove the tail switch easily. I torn it up before I realize this however :) The tail cap end unscrews. It isn't obvious. I'm not talking about where you put the battery in either. Look at the side of the body at the tail cap end. There is a groove and then looking toward the head there is another groove. This is where the tail cap unscrews.
Hey trooplewis,
I bought a Akoray K-106 about 2 weeks ago, 4 days on alkaline, 6 minutes on a 14500, poof!
Anyways, I used a small pair of vice grips, (curved jaws), and a piece of about .006" aluminum, (24oz beverage can). I gently but firmly gripped the outer most rim, with the aluminum used as protection, adding more pressure via the tension screw, until the end plug turned. Note how the pocket clip looks as you take it out, it's not so easy to get back into place.
As far as removing the pill, that's no problem. A small soldering iron might get you into trouble though. Heated too slowly, the entire pill gets hot, maybe hurting the (I know it's burnt), circuit board. I have an old 100w-140w soldering iron and on high it takes about 3 seconds to melt the solder. I used a small jeweler's screw driver to pry the edge of the circuit board up.
Make sure that you clear away the old solder to make room for the new board.
BTW, I have found a 3-mode 15mm 4.2v circuit board at shiningbeam for around $6 + shipping. I haven't found a buck/boost driver that small to allow use of AA alkaline's and lithium-ions too.
Keep us up to date on this repair!
later,
I usually use this driver on my AA lights. It allows use of AA and 14500s and the output can be regulated by a small pot on the driver, also has one group of modes with L-M-H.
It is soldout at the moment on DX and KD, dont know if it is availlable elsewhere.
http://www.dealextreme.com/p/3w-19-mode-universal-regulated-circuit-board-for-flashlights-7882