1. Can someone guess why this happened:
a) battery inserted wrong, - instead of + first or
b) reflector was screwed too tightly and shorted + and - contacts on the emitter
those two black components were the same and had written on them “3400”, what is that?
I would hazard a guess that the emitter was shorted but I could be wrong. I've never had this happen before (a or b). As for what that part is, it looks like a generic version of an AMC7135 chip. I wonder if you could replace them with 7135's. I'm sure someone of the electrical genius persuasion will chime in shortly.
Big maybe, but it would be extremely difficult if it were possible. At this point, I would just replace the driver.
Chip is:
http://www.ait-ic.com/uploads/2010-07/20/\_1279589055_y0juls.pdf
Not a problem to replace (if you have them) but big question is are mcu and eeprom chip alive as well…
Just replace the driver, it’s toast! Not worth the effort to repair IMHO. There are lots of replacement options for around $4.
Unfortunately I don’t have replacement part, who has AM3400 mosfet lying around the house anyway!!!
I took it off just to see will it be hassle to do it, no problems there, I could easily solder new one if I had it…
Ordered nanjg 105C from DX, let’s hope that it will be here in 2012 
P.S. If anyone have broken (and unusable) driver with this part (AC3400, working) and is willing to send
it to me I will be most grateful.
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Komšo hvala za informaciju 
I have bunch of “generic” leftover drivers so I will check them…
Nema problema…
Just checked. No 3400 mosfet but I do have exactly the same driver :bigsmile: If you’re interested I will send it to you… Just leave address on PM.
What a coincidence 
Still can’t believe :bigsmile:
PM sent, THANKS
I’d just get a new driver. You can also from intl-outdoors buy a single amc7135 and attempt the repair yourself. That way if it works you have a spare driver, if you fail, well you really only lost 49 cents.
Maybe I’m missing something here but I would have thought an amc7135 =/= AM3400.
Once is a self contained current regulator, the other is a power FET, of which many are probably contained within the amc7135.
You need either the exact replacement, (or equivalent). Secondly, the AMC7135 has a different footprint to the one in question (thanks scaru for bringing this to my attention)
7135, is actually just 2 pins. The 2 on one side are connected and the 3 on the other side are connected.
I checked datasheets, they are not compatible, okwchin explained everything.
New driver is on its way
Thanks scaru for bringing it to my attention, I didn’t quite describe the 7135 correctly… oops.
The AMC7135 has 3 pins on one side and a heatsink tab on the other.
A different footprint to the AM3400 which is your typical 3 pin layout with 2 on one side, and one on the other.
Is the big one a heatsink pin? I'm pretty sure it just is one side is positive and the other side is negative.
(Picture of 7135 for reference)
The large tab on the "back" and the small in the middle are connected. Left one is output, right needs input to switch on. So there are 4 pins, 3 different types and all are needed.
Useful pic found via google:
