U2 Strobe...

I whipped out my U2 tonight to look for something in the cupboard. well to my surprise the usual flood or brilliance was replaced with a 70's disco bash in a tube.

I am now stuck with a decision to return the light I love and possibly get a less powerful donut-hole version with bad tint, or keep this one with the option to annoy and "wow" my friends... hrmmm.


Watch the strobing!

Groovy! :rock:

Looks like the level controller has gone nuts. Any junk or anything under the ring that controls the intensity?

What does it do if you turn the selector ring?

PowerMatt said:

Looks like the level controller has gone nuts. Any junk or anything under the ring that controls the intensity?

Click to expand...

nope

My only U2 does this. Apparently, there is no hysterisis in the level select switch. When the switch is about 3/4 of the way from level 5 to level 6, the light can come on in a strobe mode. The tiniest dial movement will then switch the light from 5-1-6. Turn it back just slightly to strobe. I suspect the cause is the voltage/current changes effect the dial (hall effect?) position sensor. I believe this is a design defect, but don't have a lot of U2 hands-on, nor do I care to. I have been waiting to change my PayPal account before and finish some additional measurements before I put the "new" U2 on B/S/T.

Well, those in the U2 vs. Gladius debate have been talking about the U2's lack of a strobe mode. No longer! Now if it were just only available by deliberate action

Whoa. Sorry, that kinda sucks.

I hope you tried the obvious things, like replacing the batteries, tightening both ends, and turning the brightness selector ring. I think you're going to have to send it back to Surefire if you want it to be a useful light again. Most people seem to report that RMA'd lights come back bright, white, and relatively donut-free. I sent one in for RMA (bad tailswitch & lousy donut) and the replacement was really bright, had an ever so slightly noticeable donut, and an ever so slightly odd tint (cyan?).

I've seen my U2 flicker exactly like that if you turn the selector ring just the right way. I'd fiddle with that a bit before you decide to send it back. Good luck. You have my condolences.

Well, that was my first idea. Rings like that can be a problem if the contacts get screwed up, and it'll do something like that. Or the chip is screwed... either way it's probably RMA service for you.

Mine does that, but only when the batts are low. If I turn the level selector ring to the next lowest level, the strobe stops - it does return when the batts can't power the "new" power setting, at which point I dial down again, or replace the batts. IIRC, 2.6V is about where this happens in my light.

Wow, I've got to say that I'm quite concerned with all the problems I read about the U2, you would think for $270 MSRP, that they would be perfect.

I can control this, I found that it is in-between level 5 and 6. The batteries are well used so maybe its a common thing with low batteries. Kinda a nice feature if it is, lets us know the bats are running low.

Haven't seen anything like a "strobe" with my U2!

Just tried it with new batts, and i can still make it strobe. I have to dial it in carefully so its not like a gladius, but its pretty cool but im not sure if its doing anything negitive to the batts, circut, or LED.

greenLED said:

Mine does that, but only when the batts are low. If I turn the level selector ring to the next lowest level, the strobe stops - it does return when the batts can't power the "new" power setting, at which point I dial down again, or replace the batts. IIRC, 2.6V is about where this happens in my light.

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Weird. When the battery goes low in mine, it just drops to the next lowest level by itself. No strobing, no turning of the ring required. When the battery is almost completely dead, all six settings are exactly the same. You can sit there and turn the ring back and forth with no effect whatsoever.

Hmm... weirder...

I run a li-ion 18650 cell in my U2. If I pop in a set of spent primary cells, it strobes just as described above. No strobing on a flat li-ion, though.

Ty_Bower said:

Weird. When the battery goes low in mine, it just drops to the next lowest level by itself. No strobing, no turning of the ring required. When the battery is almost completely dead, all six settings are exactly the same. You can sit there and turn the ring back and forth with no effect whatsoever.

Click to expand...

Just what I needed...

I find that my U2 does this only when the batteries are running low and they are no longer to run the selected light level inside of regulation, it flickers back and fourth for a while then dropps out of regulation completely. i cant make it do this using the ring, just happens when Vbat runs low.

After reading TY_Bower's post, I decided to e-mail SF and ask them about it. Here's what I sent them:

greenLED via e-mail said:

I recently bought a SF U2. I've noticed that the light "strobes" when the batteries go below 2.8V or so. I select a lower output level, which fixes the strobing until the batteries are depleted some more (and I have to keep decreasing light levels).

However, I just read on Candlepowerforums.com that other U2's don't behave like that. Once the batteries can't support a higher output, the light apparently switches to a lower output by itself - no strobing involved. I'm wondering if there's something wrong with the selector ring or the circuit on my U2. Now that I think about it, it makes more sense for the light to power down, not to strobe.

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The bottomline of their message was "call us to get an RMA". That's exactly what I did earlier today. Seems like this strobing is not normal after all. :green: The CS rep I spoke with wan't able to provide more info as to what is the cause of the strobing. So, my U2 is packed and ready for an appointment with Dr. SF.

mine only strobed once but new batteries fixed the problem

Ty_Bower said:

Hmm... weirder...

I run a li-ion 18650 cell in my U2. If I pop in a set of spent primary cells, it strobes just as described above. No strobing on a flat li-ion, though.

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Green,

Before you send yours back, make sure you've read my entire post. I did mention that mine strobes on dead CR123A cells, but not on an empty Li-ion 18650. You might want to try a similar experiment yourself.

If you are happy with the tint/brightness/donut, I would keep it. Now, if you're not happy with one of those three, AND this strobing thing bugs you, then it might be a good excuse for an RMA.

Good luck!

Thanks for your concern guys. I know it doesn't happen with new batteries or li-ions, but it bugs me that it's hapenning. I've had one too many things not work as they should with my U2 (aside from tint & brightness). On top of that, the SF CS rep said this is not normal, so I'm sending it in for "repair" (whatever that means). It's a good chance to get that lint outta the reflector too :green:

Hopefully they *do* fix it and not exchange it for another head, in which case I might be hit by the lotto. I'll share the prize, promise :green: