You mean you measured from the B+ spring/pad to ground, and it did not show a short?
When I check continuity between B+ and B- it shows a short. I also checked between B+ and the outside ground ring on the driver, still mounted, and that also shows continuity.
Yep. When I fly, I take my battery carrier out and put it in backwards.
You sure all 3 LED's are working ok? I've been fooled before, thinking driver problems. It would be good to know 100% before driver swapping (I sure know that...).
I forget, is the TK75 4 cells in series, and 3 LED's in series?
shimey-both the positive, and negative, terminals are raised, and on the same end of the battery carrier. I don't see how turning around the carrier and screwing on a solid aluminum tailcap wouldn't short out the carrier. Tom, I don’t know if the LED’s are ok. I haven’t tried powering them from an external source yet. I believe the carrier is 2S-2P as it shows 8.37v with un-tripped cells, then after inserting the carrier and removing it shows 4.18v. Think Comfy is on to something here with the dead short between B+ and ground. Now how to fix this?
I also believe probably there is some short, and that explain why safety is triggered in batteries. one of the things I will not do in this point is to put unprotected batteries.
u have to find where the short is. Am not familiar how tk75 is build internally but first thing i have to check is battery compartment, if he can be pulled out do the short again happen between + and - ?
if yes problem is there, if no than continue to check the path the + goes till the driver and to the led. somewhere in this path must be a short circuit which tigers safety mechanism on batteries.
from what you say i think to things can happen when you put on bag. one is like you say the flash turn on but it heated up very much being modified and lacking fresh air to cold so led can go dead but i thing is very improbable that ALL three leds go dead in the same time, so probability driver have gone dead heating to much and probably is shorting something. or some wire unsolder-ed from heat and also make short somewhere.
or if u drooped it hard somewhere something in battery section have moved and is shorting from plus to ground, but this is probably less likely to happen.
two batteries at 3.94v seems to have worked some sec at high before something go puff and short inside…
If the short were on the output side (reflector touching MCPCB pads, or wire got hot and unsoldered itself, etc.), it wouldn't trip the protection until the light was switched on. It's not doing that, it trips as soon as the carrier is inserted & tail screwed on. It has to be something on the input side of the driver and not the output.
I've never been into one of these lights, anybody have good clear pictures of the driver?
Comfy, I don’t own a good camera, and the pictures I took with my phone are not good enough to post. Anyone else have pics?
Cells are 2s2p. 3 leds in series.
Thanks for the great pictures, Racer. Update- I desoldered the battery contact board and checked for a short there, and everything is fine on it. So, the short is certainly in the driver itself.
Check for shorts in the caps, the yellow blocks on the second photo and one on the first photo.
Thanks Ryan, how would I do that? Isn’t there always continuity across a capacitor?
Yup, you’d check for continuity with your DMM.
Capacitors will be shorted at the very instant you put your leads across it, but the resistance will rise to infinity as it charges and doesn’t pass electrons through.
Yes! Tailcap IS anodized, but I (forgot to mention) I cut a thin plastic disc that press fits in the tailcap for that very reason.
Ok Ryan, The cap, in the second picture, to the left of the “big square thing” is showing continuity, all of the time. The other caps are acting like you predicted they would.
Great, we have a lead. The cap is directly across the battery inputs, and the shorted cap may be tripping the battery protection or something else along the two paths might be the culprit. If you can desolder the cap on the left, that will verify that it’s the issue.
Edit: Upon closer inspection, does it show any signs of overheating or damage?
The cap does not show any signs of damage. I de-soldered it and now it acts like it should, and does not have continuity across it. The solder pads on either side are however still showing continuity.
I see, then it seems like something else is shorted out when it’s not supposed to be. How many Ohms is the short reading, 0.x?
Getting the same meter reading across the pads as when I touch my leads together
Hmm yeah it’s start to trace back I think. Unfortunately I don’t have a TK75 so I don’t think I can be of any more help, sorry!