Can I Reverse The REALLY Stupid Thing I Did?

RBWNY

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Mar 10, 2011
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Several years ago, when 100 lumens was considered "awesome", I bought a SUREFIRE U2. For the past couple of years it's sat mostly un-used.

I recently began using 16340's as an alternative to CR123 primaries wherever I can. I was wondering what the workable voltage was for the U2, and strangely SUREFIRE does not mention it on their website. So here I thought, can I use RCR's in here? -- since the U2's runtimes aren't as efficient as most of todays' lights? Well, foolishly, I plopped a couple of AW's in the tube and turned it on low.

Level 1 & 2 were as usual. Level 3 ....whoa! Level 4 about the same. Level 5... I think it was just a tad brighter than level 4. Level 6, the same as 5. But, I didn't get to analyze that final brightness for more than a few seconds... then... :poof:... the U2 went to black. :eek:oo:

Now.... nothing. :ironic:

It doesn't appear to me that the led comes out, or can be replaced. Is it a "dead" issue now?

I'd do anything at this point to turn back time and prevent myself from doing what I did.
 

Yoda4561

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Your two best plans of action are to

A: Contact surefire, and tell them what you did, be honest and see if they can accomadate you somehow. You shouldn't expect anything but a polite "sorry, we don't cover that" from them, but it can't hurt to ask.

B: Take the opportunity to send your U2 off to a good flashlight modder, we have an entire section of CPF dedicated to them. Someone there should be able to replace and upgrade whatever you broke, though it might cost you as much as a new U2. The benefit is getting a better emitter than surefire is using right now, and perhaps a driver that would let you use RCR batteries. If you're lucky and if it's just the LED that died it might not even be that expensive.
 
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RBWNY

Enlightened
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Mar 10, 2011
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374
Your two best plans of action are to

A: Contact surefire, and tell them what you did, be honest and see if they can accomadate you somehow. You shouldn't expect anything but a polite "sorry, we don't cover that" from them, but it can't hurt to ask.

B: Take the opportunity to send your U2 off to a good flashlight modder, we have an entire section of CPF dedicated to them. Someone there should be able to replace and upgrade whatever you broke, though it might cost you as much as a new U2. The benefit is getting a better emitter than surefire is using right now, and perhaps a driver that would let you use RCR batteries. If you're lucky and if it's just the LED that died it might not even be that expensive.

Thanks. Ok, well -A- sounds like it's worth a shot! -B-... I'd have to find out what the $$$$ were going to be first. --- whether it's worth it to me or not. If it was equal to the price of new...well, you can guess the answer there :duh2:.
 

Justin Case

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Mar 19, 2008
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You probably cooked the driver. The older U2s used a boost driver to run a LuxV LED. You need to keep Vbatt<Vload for a boost driver. When you cranked up the selector to max, you sent Vbatt of nominally 7.4V to a Vload of probably around 6V. That put the driver in direct drive, and you probably cooked some component in the DD path, like the Schottky diode.

The problem with sending it to a modder is that the U2 driver is a complex beast. Sure you probably can fit some new driver board in there, but you aren't going to have selector ring function anymore. So you probably don't want to simply change out the driver, unless someone somehow happens to have a genuine, complete replacement SF U2 driver.

But if you are lucky, maybe there is a clearly cooked component on the driver board and replacing just that component will restore functionality. I suppose I'd try that first. Crack open the light, see if there are any obviously cooked components, replace them, and hope for the best.

Edit: If you can get the head open, the first and easiest thing to try is to test the LED itself for function. If that's dead, then I'd get a replacement (presumably a LuxV, or if ambitious, a 2S2P MC-E). If the light works with the new LED, you are one lucky person.
 
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Kestrel

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Oct 31, 2007
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Willamette Valley, OR
The only other decent option I could suggest is to acquire a used Surefire non-U2 head assembly in CPF/MP. Question for folks here: the U2 body is thread-compatible with what SF head assemblies? E-series?

Of course, by doing this you loose the selector ring from the U2 design, but for only the price of a used SureFire LED head assembly, at least you have a perfectly-operational flashlight, albeit with only one or two modes (depending on what type of SF head assembly you use).


Edit: BTW, it's actually easier to use the CPF/Google search function ("SureFire U2 RCR123") than it is to try experiments such as these, ya know. Lots of good answers in posts with folks saying, 'don't do it, use 1x17670 instead', like in this recent thread.
 
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RBWNY

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Mar 10, 2011
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Yes........ My impetuous side took charge for a few fleeting moments. :oops:
I KNEW I should've searched for the answer FIRST.

Good suggestions from all. Thanks.
 

turboBB

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Jan 16, 2008
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NJ, USA
The only other decent option I could suggest is to acquire a used Surefire non-U2 head assembly in CPF/MP. Question for folks here: the U2 body is thread-compatible with what SF head assemblies? E-series?

Unfortunately the SF U2 is a completely different beast than the typical C/P/Z and even E-series in that the bottom of the head is a male connector. I believe something like the LM1 or LM2 (not sure if that "extender" can be disconnected) would fit on a U2 body. There's also the LU60 adapter that'll allow you to use a C/P/Z/M2 head on the U2 body.

@OP, sorry to hear of your misfortune and best of luck w/the repair/replacement process.

Cheers,
Tim
 
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