Arc III bright then dim....

My modded Arc with Lux III no longer stays bright constantly. It starts out high on switch on and then drops to a low setting as though I have it on the lower setting on gadget_lovers two stage switch.

I have tried different batteries and switches and the head with the lUX III behaves the same in all scenarios.

Does anyone know what is happening here please??

Dave G

It could be a complex electrical problem, but start with the simple stuff first. I would check if the retaining ring is tight first off, could be as simple as a loose connection there. But I'm a bit more compulsive so I'd also remove it and check for corrosion/crud between the retaining ring, the copper wave washer, and the circuit board. Note, if you have a fraen optic in this head, you well probably have to re=center the board after doing this, which can be a PITA. If that doesn't do it, its probably a problem on the board.

Good luck

Mine does this too (running it at 800+mA w/swapped sense resistor) after a while of constant-on, but I believe it is due to the switch (Kroll or Ram, I have and tested both), because mine does not do it with a twisty.

gatesy3 said:

My modded Arc with Lux III no longer stays bright constantly. It starts out high on switch on and then drops to a low setting as though I have it on the lower setting on gadget_lovers two stage switch.

Did this happen right after you replaced the led? if so you might have a bad solder contact with either the positive or negative terminals of the lux3. Did you bump the current up by adding/changing sense resistors? or just stayed at the stock 333mA? Worst case scenario is the LT1618 chip that's gone bad what's the bin on that lux3?

I assume yours is the rev2? mine does the same thing. whenever i clicked on for the first couple of times, always start with low and subsequent clicking will give me low, high alternatively. But after about 30 clicking, it now behaves normally. Wonder what is wrong in it though. Tried adding solder at the + contact, resolder the diodes, caps, and inductor and none correct the problem. Tried removing and installing the resistor and the led, but none works too. it drove me crazy. But somehow, it works now /ubbthreads/images/graemlins/icon3.gif

I hope my arc ls rev 2 does not start having problems.
how long did it take for your lights to have problems
after you modded them ?
I put a twoh(low vf) and a reflector and a glass lens in it.
I left the current sense resistor stock.
it draws 390 ma from the battery with a fresh cell.

very bright white and it has a great hotspot and nice side spill.

it stays really cool untill the battery starts to go dead.
never really gets hot.

it seems like I get between 2.5 to 3 hours in regulation
moon mods seems pretty bright.
I guess I should waste another battery and see how long it runs untill it goes out of regulation