I managed to take my j18 apart and can confirm that the led’s are wired in series.
Thank you mate. 
This is good to know.
Update, with nothing to loose, I decided to play with the driver a bit.
The J18 driver I got looks almost the same as the ak-47 driver found here
and looking at the post by richie, he mentioned that one of the resistor was loose.
Well, I am not sure if mine is the same, but I do not have a resistor on that far spot…… does not even look like anything was there to start with (this light did work properly in the beginning tho).
Anyhow, I got my 20 ohm trim pot I had left over from modding my small sun zy-t13… soldered it into the spot, and just played with it. Turning the trim pot I can make the flash light brighter… up to a point…… once you pass this point the flashlight will give you a very bright flash then shut off…
Using 3 cells, I just tuned it until I got the max brightness without getting the bright flash followed by nothing……
To be honest, I do not think this is a proper fix. The light is still not as bright as it should be (I am showing just a hair over 2 amps draw at the tail with 3 cells… not sure what this works out to be) and the driver gets HOT. I mean that round coil on the driver gets up to ouchie temps in about 2 seconds when I was holding it.
What I can see is that, I think I do in fact have a driver problem… or a really bad battery problem… haha…
Jon.
One more update.
The light is brighter with 2 cells…
two 26650 TF flames I am drawing just shy of 6 amps at the tail… dropping fast… haha…. down to 4.5 amps in under 3 seconds.
About 2.1 amps with 3 cells is grossing 23.31 watts which is very low. At 4.5 amps using 2 cells, you’re looking at grossing 33.3 watts, which is the same as a stock AK-47 with only 2 sense resistors on the driver.
Ok, one more update. The light seems to be pulling less and less amps. On 2 cells I am now only able to pull 2.3 - 2.4 amps and on 3 cells, about 2 amps. Seeing how all the led’s seem to be working, wiring seems to be “in tact”… and batteries are able to (at least for a short while) pull 6A without the protection kicking in… I’m thinking it has to be the driver…
so… one last try…. I orderd one more driver from IO this time (the last one, which looked the same was the customer programed one from KD… which looks identical to the IO one).
fingers crossed. I will let you guys know when I get the new driver delivered and installed
thanks.
Yeah, 17 watts - 22 watts is no way correct. It should be at least up into the mid to upper 30 watts range. Keep the updates coming.
Hey, I got mine today. Can’t figure out, how to remove the reflector? Are there not a custom drop-in module? Should the driver be screwed out to gain access to the screws holding the reflector?
Btw the light force doesn’t impress with the originall driver at all. My modded TR-DF003 with three xm-l has the same brightness or even brighter… This has tighter spot though.
Uh oh… just figured out myself. damn. This is not going to fit my purposes to be disassembled and used in a custom made diving lighthead… I thought it would’ve been something like this:
Pretty amazing test results with the Intl outdoor shop driver!
From the driver to the leds: 3.04 A / 22 V = 66.6 W
Tailcap: 6.04 A / 12.12 V = 73.2 W
So this driver seems to be also really efficient: 90.9 %
I’m back on the drawing board. Gonna build a whole new lighthead suitable for diving with a battery canister…
Agree - I measured 5,500 lumens with the IOS driver using 3 KK batteries - swapped my mod'ed one for a stock, now ordered another IOS driver - will do the same.
+1… thanks Tom
Didn’t quite get the last sentence, did you take out the IOS driver and put back the original or what? Did you mean you’re also building a dive light by that “will do the same”?
Ooops, sorry. No, I swapped my mod'ed J18 with another BLF member for his stock J18, so now I'm back to the stock J18, which means I'm upgrading to the IOS driver again 
.
I just can’t get the driver out… the copper loop on the inside sits so that it won’t fall out no matter how I try to manipulate it… is there a trick?
I’ll put this here also
Didn’t understand that wound copper wire thing, mine had nothing else keeping the driver than the power wires. The reflector is not glued, it’s attached with two screws which you can loose from the inside after moving the driver away. The leds are glued to the frame. Silly way since you can’t take out a “drop in”…
Few days ago I figured out that the frame is separateable to two pieces, if one would like to do some additional plotting…
jaws - didn't have that problem with mine - driver came right out. Got the pic in the other J18 thread to show it dangling. Not sure what you can do...
A pic would help a bit? Maybe jammed threads if you mean the copper ring that keeps the spring against the driver?
Is there a way to mod in a variable control switch in the tr j18 and if so, where to get one that fits that monster?
Managed to get it out - now to determine the fault. It took a lot of force to remove. The copper coil on the board had bent out a little so I needed to pry with a lot of force on an angle to remove it. Pushed the copper coil back down now it slides in and out easily. Still works too, albiet the same at only up to about 50% power…