That is extremely helpful Kramer, thank-you very much. I didn't know that the head/heatsink was 2 pieces, though I had my suspicions.
Since I didn't hear anything rattling inside the button, de-tempering of the spring makes perfect sense. Guess I will add a new spring with copper braid (I think I have some old RG-58 floating around - the shield would probably work well for that). I might see if I can retain the button spring cover as well. I will try to post pics and measurements once I get everything all fixed. Once I get repairs done, I may get one of the tr-j10's and see if I can properly drive the led - they look like they could be good throwers.
Anyway, I am really impressed with the output from this light, as well as the seemingly good thermal transfer to the air. I would love to see real measurements of the output using a true integrating sphere. The folks in Asia always pad all their numbers to make their products look better in advertisements.
It also seems, from looking at the performance curves from Cree, that the individual leds in this light are driven nearer the most efficient part of the curves than typical single-led lights. My only real complaint (other than the poorly-chosen spring design) is the fact that this light is very top-heavy - makes it cumbersome to hold and maneuver.
So everyone knows, I am an old-school flashlight modder, back from the days when xenon and halogen were the cutting-edge technology. Since Cree, SSC, Luninus, etc., have gotten the efficiency so high on leds, I can see no purpose for those old tungsten relics, except as museum pieces.
With Kramer5150's help, I figured out how to get everything apart in the head of the TR-J12. Same problem - spring was de-tempered and squashed. I will also use his fix - adding a piece of braided copper to assist current flow. I suspect, however, that the contact between the spring and the button is creating a high impedance failure point (maybe even arcing?), which may be contributing more to heating than anything. Also suspect is the cheap plating on the spring. I will try to dig up some conductive grease or epoxy so that the spring and cap make better contact.
So if anyone else purchases this light, prior to use, some braided wire should be installed at both ends and perhaps this failure may not happen?? Thanks.
Sure np... if you are familiar with incan mods, the wire braid is the same thing. Current is current, wattage is wattage, be it LED or incan.
It should be noted that time duration is also a factor. If you only use it for short burst only, then you may not really need to add the wire braid. Mine only melted after leaving it on for 10-15 minutes to intentionally get it cooking, to let some moisture vent out of the head.
The 7.5a manufacturer rating is current output to be split between all 5 LEDs. That equates to around 24 watts with XM-L vf. Yours, pulling 6.8 amps at the tail, is at around 55 watts and if the driver is letting all that to the LEDs will be at a current output of around 18 amps! Well over the rated 7.5.
I am starting to wonder if we have different driver board components. I am wondering if the SMT components in our lights are all identical... or if the supplier populated the boards with close-compatible parts, and scratches out the part numbers. Threads like the one below make me wonder about the manufacturing process quality of the PCB-fab houses.
Not sure about everyone else but my J12 has scratched out part numbers. Why on earth would the supplier go through the extra work to do that, other than to hide the identity of the part or BIN used?... and why would they want to hide that in the first place? It would certainly help explain why some of you are pulling upwards of 50-55W from two cells, benkie in particular pulls a typical 27W from 3 cells.
Most flash lights have scratched of part numbers, i think we have diffrent drivers and yours was a bad example as it has had moisture, discoloration and spring issues.
Did I? Sorry if you were joking about it being under the rated specs or something else? Maybe I did miss it.
Just these other posts seem to back up what you said in the latest one too.. I just wanted to point out that the 7.5a regulation does not refer to what you should measure at the tailcap. It is the output current and so correlates to around 3 amp tailcap current on two cells.
The Tr-1200 is digitally regulated at 2 amps and will pull this on 2 x 18650,s at the tail cap. The tr-3t6 is digitally regulated at 3 amps and will pull this on 2 x 18650,s at the tail cap, i have other multi cell trustfire lights that work in the same way.
So then one could think if the tr-j12 is regulated at 7.5 amps and if it was like the other genuine tr lights it would be 6 or 7 amps on 2 x 18650's but not go over the max 7.5 amp regulation, mine behaves in the same way as the above regulated lights and will not go over 7.5 amp as the volts drop, till it hits low voltage and drops out of regulation and dims and the current draw drops right off.
Cause some sellers claim max out put of 7.5 amps, some claim current of 7.5 amp, others claim 7.5 amp max with no reference, the same seller claim 3 amp for the TR-3T6 and other sellers claim 2 amp max for the TR-1200, so i would not take any of what they say to seriously.
I would not take it as written in the Bible because some Chinese shop says 7.5 amp Maxim out put, even more so when others say 7.5 amps max as its not clear, i have read on here and else where more people are getting readings like me, some are on this forum and have not posted some are on other sites. Either way mines still working well.
The TR-J12 has to be digitally regulated or the amps would just keep climbing up as the voltage drops and the light will burn up like the early skyrays.
I found my fluke today and my cheap multi meter i ordered on line turned up this arvo so i will re test and compare to my results from my first post over the weekend so i will have 3 digital multi meters to compare to.
Yeah now that I got mine dialed in its running great. Spring issues have been resolved although I still might buy some higher current springs at a later date per Eriks suggestion, and the moisture is definitely gone now too.
You mentioned earlier your meter probe wires are getting hot. Thats something I have never encountered. I am not sure if or how that can throw off your tailcap measurements, but measurement inaccuracy I think still might be something to keep in mind.
I'm kind of curious, at 55W / 8.4V, wheres the extra power going if you are able to run your light for ~20 minutes straight? Lets assume driver efficiency around 80%, which is typical for most FET driven non-7135 circuits. With 5 emitters your light should be doing 8.8W per XML. Estimating Vf at 3.4V, your light should be pushing each LED with 2.6A. That equates to 800Lumens per LED (and a TON of heat). Your J12 should be in the 4000 lumen ballpark, it should also be SMOKING-scorching hot within a minute or two. I mean my J12 pulls around 28W, factoring in an 80% efficient driver that equates to a very modest ~1.35A into each LED. Even at that low current it gets very warm (borderline hot) after a few minutes.
If your light is not doing 800 Lumens per LED (full charged cells), then a lot of those 55W are being lost somewhere in the the driver, switch or contact springs. Something in that light should be getting really hot. I would think its borderline thermally unstable at the end of a 20 minute run with panasonic NCR cells. Panasonics are KILLER cells, so I think we can rule out V-sag under load.
puzzling... something is not adding up in my mind.
I have checked current on both of my TR-J12 between driver and led. One has alot of brass around the driver and the other has mostly plastic and smaller brass middle.
Using Sanyo 2600 fully charged and partially depleted gave similar results .
If total current to the leds is about 1.5 amps, then manufacturers' spec of 7.5 amps are totally BS (imagine that). That also means the voltage to the led array is on the order of 18 volts, but regulated at 1.5 amps.
It's really interesting that they would mis-represent the specs in that way. Whether they are wired in series or parallel, the effect would be the same as far as electrical and optical power output are concerned.
I got 15.35 vacross the led array, using 2 18650 Pansonic NCR's at 4.06v each. BTW, the top of the chips on the driver are also ground off. Also, I smell the distinct odor of burning epoxy in the driver portion of the host - maybe because the faulty spring is heating up the driver board.
The DDM probe wires did get hot when they when kinked at the probe end and running along the inside of my hand against the probe but keeping the wires straight they are ok.
The unprotected panisonics will give around 28 mins run time from 4.17v to 2.5v @ 6.2 amps, since these trustfire multi cell lights like around 6v min it gives me around 20 mins run on 2 x unprotected NCR18650A's around the house, on 2 unprotected NCR18650A's i try and use it in short bust on high and medium for around 5 mins tops.
The light does get really warm i would every say very hot, it will also hurt your skin after a few seconds, but with it being winter here now, the cold weather is here its not hot and dry so with active cooling (walking around) it seam to handle the short burst. The batteries also get hot.
If i really want some run time out of it say for camping and fishing i use it on 3 x protected 26650's current draw is lower, heat is lower and run time is increased. But i have not taking it night fishing for about two weeks. I feel much bettery running it on protected cells.
The driver Seams to be current regulated on mine and its seams to be a SST 50 or most likely SST 90 driver.
