Just received my TN31 (XM-L) and immediately opened it up for a resistor (solder blob) mod and 20awg leads. Well, something must have gone sour because I’ve only got the two lowest modes and strobe. I first did the test with some half drained Sanyo 2600 laptop pulls to maybe save anything that may not have liked max current. I’ve since de soldered the blob from the resistors and the problem still exists.
Any ideas?
UPDATE: 12/7/14
Just wanted to update this thread here in case anybody runs into the same issue down the road…
I managed to figure out for certain what caused the driver’s erratic behavior. As optntdr13 suggested, it was in fact a cold solder joint. I know this for sure now as I experienced the same issue tonight while modding my K40M. Weak iron + large wire + crazy copper DTP heat sinking and you get a bad joint if yain’t careful. One bad joint on the +LED pad and you’d think you crapped another driver.
@ scott Yes I did briefly test it prior to the mod. (You need to know the before to appreciate the after.) It was working properly. All that I did was remove the 26awg leads and replace with 20awg versions and the solder blob over the sense resistors. Oh, and I removed the kapton tape from the bottom of the star.
@dan I will try and get some pictures but I really don’t know what could have happened. I’m not a pro but I’m not a rookie either. I was very careful and tried not to over heat anything. I simply used a ~5mm piece of solder wick to bridge the resistors and replaced the wires.
I read! on “the other forum” about people having similar issues but I’ve checked the connections a few times over already
I wish I had some advice to offer but the pics of your work might help. I know the frustration of a botched mod. On a light like the tn31 it really sucks. :(
Thanks for all the help and kind words. It seems I got it working. Who ever said two wrongs don’t make a right?
So I don’t know exactly what did it, but I think it’s fixed. (knock on wood)
Here’s the things I just did since I posted last…
*Remove both r082 resistors
Resolder blob the sense pads (without the resistors this time)
Put old 26 awg leads back on (for safer workability… don’t want to lift a pad now)
Solder wicked some solder off of the LED+ pad at the capacitor (there seemed to be more than necessary)
Threw in some fresh charged batteries
*Replaced the XM-L with a gen 2 emitter (the old one was “foggy” under the dome near the bond wires. thought I may have lost 2 of the 3 or something)
???
I’m doing further testing to figure out why this happened. I’ll report back shortly.
I’m okay not knowing for now because I know in the process of figuring it out I’ll probably break something for good. I’m exhausted right now and judging by how many times I’ve misplaced my tweezers (and the whole driver for a moment) I don’t think it’s a good idea to continue.
But I do have a question or two…
How tight are the heads and tailcaps typically? The first time I went to spin off the battery tube, the head loosened first. On the contrary, I can’t open the tailcap for the life of me (no strap wrenches either).
Next, is there a way to regain mode spacing after the resistor mod? I know the TN32 runs hot but still has the mode spacing. JohnnyMac I believe it was you who had some good pictures of the TN32 driver. I believe the inducter and sense resistors were different, along with an added transistor? in parallel maybe?
Cold Solder joint, no doubt in my mind anyway. For some reason, flashlights are uber-sensitive to CSJ’s, no idea why. No idea on regaining modes though I suspect you could redo the mod and not bypass but rather stack resistors and regain them quite easily. Mine is bridged, dedomed, rewired, arctic silvered and that’s what I wanted. Ultra-throw was my goal, ymmv.
