Are you sure the tk40 uses an electronic switch? That sounds like it may not be.
Mine does.
Ok, then I'm out of ideas. :(
Yes sir ! the battery carrier has a contact at the back which contacts to spring on tail cap . the clickie in tail cap is electronic click . Light press needed only . Definatly not a reverse or forward clikie . im thinking of modified the carrier and adding a forward clicky switch. thatl require taking out the negative points from the front of battery carrier .
Scaruuuu dont give up now ! 8)
i will get a 1000 lumens from this thing urrrgghhh !!!
Just PM DrJones. He makes and sells Electronics Drivers so he can definitely hook you up. Simple 7135 drivers are about all I can handle. :( Good Luck. :) Oh yeah here the description of his programs are from this thread.
I sell drivers like the NANJG105C 2.8A with custom firmware. I have written three firmware programs for these:
- luxdrv, for usual flashlights with a clicky. Key features: Ramping; programmable (i.e. modes are configurable by the user, by a number of taps), the number of modes can be changed, too; battery indicator. Special UI that allows to have many modes without the need to cycle through all of them.
- lumodrv, for flashlights with an electronic switch, like UltraFire T50, SkyRay King, UltraFire H3. Unfortunately all those light are not quite modding friendly. Key features: Ramping; hidden extended modes; double-click to high; momentary mode; battery indicator.
- lumo35drv, for flashlights with a clicky (for power) and an additional electronic switch (for modes), suited for the TK35 and it's clones for example (requires modding to parallel battery setup). Key features: Ramping; hidden extended modes.
- I also can do some custom firmware; recently I sold some drivers with varying frequency strobe only.
The driver hardware always is a linear driver using AMC7135 current regulators:
- Input voltage: 3V-5V (more like >3.3V to stay in regulation), well suited for driving an XM-L with a single Li-ion cell or multiple cells in parallel. Driving multiple XM-Ls is possible with a master driver and some slave drivers. Driving 2 XM-Ls in series with 2 Li-ion cells in series should work in a special setup (i.e. if you know how to do it. Don't connect >6V directly to the driver!)
Links: luxdrv -- TheKlone35 & lumo35drv and a review -- lumodrv
has your tk40 led gone dark brownish in colour ? I felt mine was around 300 lumens on turbo ! Thats why i screwed up the driver by doing crazy stuff to it
Thanks scaru !
Il get a bunch of drivers and try diffrent methods and see how it goes !
scary whats a normal driver you know of that drives a xml really hard . 2 wire normal driver . il remove the electronic switch , put a clikie . Reroute the negative to body .il solder the driver to body . I think …umm . Sheeesh .phew phew
Mine is fine so far (crossing fingers)
I saw a thread on the “other side” where someone else had the same issue, but I don’t think it’s a pervasive problem.
yah google did lead me to “the other side” and i saw his photos. anyways il put an xml in there. kind of an upgrade to tk41 
status
will let you know how it goes with photos and beamshots etc next couple of weeks .ordered driver and a xml t6 just now from china The land of the free … Ooops i meant cree
How about a driver such as a B3flex from taskled? I know that it uses a momentary switch for changing modes etc.
Ive never seen a tk40, but from the photos it looks like the wire that is screwed to the housing is the permanent gnd. The centre contact on the reverse is pos and the outer ring around this is the momentary gnd contact used for the modes.
Of course i could be wrong…….but if im correct the taskled driver will work!
Woody
thanks woody ,this looks like a high end driver ! Costs $35 !
i ordered these 2 drivers from lightmall . They should be here in 2 weeks!
http://www.lightmalls.com/super-output-ssc-p7-led-driver-board-low-high-middle-5-5v-15v-2
lets see if they work
Since Dr. Jone’s drivers are AMC based it will not work in the TK40 unless you wire the battery holder for parallel instead of series. Perhaps you can find a way to use a regular driver by finding a way to isolate the negative ring on the driver and replace the side switch with a momentary off switch. Then you can wire from the negative ring to the switch and back to the driver. Then you can keep the side switch mode changes without a special driver. Sorry I didn’t answer your PM sooner but I was waiting to see what you found in the driver. I didn’t see this post until now. 
johnny , when you didnt reply i thought you were in the operating room getting your knee repaired !!
heres my plan !
bought these items. scream at me if im doing somthing dumb
Be warned that is not a 17mm driver, it's 19mm.
meaning??? :cry:
driver details
Details
15V Super Output SSC P7/Cree XM-L LED Driver Circuit Board (Low/High/Middle,5.5V~15V)
Fit fot the Cree XM-L,SSC P7 emitter
- Current regulated at 3.0A
- Input voltage 5.5V-15V, (no more than 12V would be the best option for protection of LED board according to accurate test)
- Buck Voltage Current Regulated circuit
- Gives 1+ hour current regulated (3.0A) output with four Eneloop AA
- Gives 3+ hours current regulated (3.0A) output with two protected 18650 batteries
—Gives 90~95 efficient output
- Measures 19mm in diameter, and 8mm in height
- Multi-Mode: Low(5)/High(100)/Middle(35%)
- Designed for SSC P7,Cree XM-L LED for maximum output 300lumen-1200lumens
- 1xLED+, 1xLED-
- Prewired, ready to use
and the tk40 battery pack has 8 AA battries
i scrapped off all the circuits from the driver board … drilled hole untill the positive got exposed ….
1-now will place the new driver on top on old driver…
2- solder the positive …
3-send positive and negative wire to the led….
4-solder a wire from new driver negative input to body …
5- attached a new forward clicky switch …
Note : the Old drive is only needed as compartment cover and provide the positive contact from the battery pack . all circuits are removed . Its a just a flat board now
Very interesting thread. I have a tk40 that I haven't used in about a year and a half at least. It's actually one of my best dust collectors. 
I'll have to dig it out and see if it still works. 
lolzz… its a great light isnt it! mine was used to search for a friend who died while on a fishing trip back in my homeland fiji ioslands)! so im attached to it emotionally. and will give my best to make it at least 900 lumen (more bight then its elder brother tk41 
)