Surefire UM2 Ultra

[AR_Shorty]

I just put two new primaries in the light...no change. Its still messed up on the highest two levels on the selector ring. It worked just fine the night before last and then when I went to use it last night, the glitch was present. :sigh:

 

[Vox Clamatis in Deserto]

Hmmm, about the only other things I would check before sending it to SF for repair are the contact areas in the current path.

Make sure the springs are properly seated at both ends inside and check that the three brass colored strips in the tailcap and the bottom edge of the battery tube are clean. The lockout tailcap needs to be fully tightened for these parts to mate. The head doesn't seem to be as critical, the light will still work if the head is slightly unscrewed.

I would double check that the black plastic washer that secures the clip is fully screwed down. Some of the old 47's Quark lights had a pesky retainer ring on the tube that would loosen just enough to keep the light from working properly.

Do you have a U2, P2X or other SureFire with a tailcap that you could swap to see if that makes a difference? Years ago I had a power hungry multi-LED SF 6P dropin that would not go to the highest level. After trying everything else, it turned out that the tailcap had just enough contact resistance to keep the light from going to high. Another SF tailcap worked just fine.

 

[AR_Shorty]

Good news! Thanks to Vox Clamatis in Deserto's post, I tried a tailcap from a U2 that I have. The light functioned normally then. So I fiddled around with the spring in the UM2's tailcap and put it back on. The light now functions properly. It must have not been making the proper connection. At least I know the issue (if there still is one) is limited to the tailcap, should I need to get a replacement. I'll see if I have any further problems with it. Thanks for the suggestions for troubleshooting!

 

[Sofastreamer]

since surefires seems to aim quite a bit at consumer products (sidekick, peacemaker, fire peak) they tend to get worse in quality control. if that is the path for surefire in the future... what a shame.....

 

[Vox Clamatis in Deserto]

Good news! Thanks to Vox Clamatis in Deserto's post, I tried a tailcap from a U2 that I have. The light functioned normally then. So I fiddled around with the spring in the UM2's tailcap and put it back on. The light now functions properly.

Great! :twothumbs

Earlier I made this observation about the UM2 and swapping tailcaps:

The bodies of the U2 and UM2 are very similar but not the same from I can see. Although the tailcaps appear to be identical, the tail threads are not exactly in the same position on the tube. You can swap the U2 and UM2 tailcaps and both lights work. However a Z49 tailcap works fine on the U2 (even thought the finish is shiny, not matte) but does not work on the UM2. The Z49 doesn't seem to tighten onto the UM2 threads far enough to get that last millimeter of contact somewhere.

Well, I just tried the very same Surefire Z49 tailcap on the UM2 again and it now works fine. The light also works great with a Z48 tailcap (similar to the Z49 but with a hard anodized finish). Did I just not tighten the Z49 enough when I first tried it?

Or is the threading on the UM2 tube indeed slightly shifted from the other SureFires and the spring doesn't press on the battery as hard? The spring in the Z49 that didn't work earlier is visibly bent slightly to one side but since it works, I know from past experience that it is best not to try to fix it.

 

[AR_Shorty]

Ok, so my tailcap is definitely a problem. Its flakey again. What other tailcaps will work with this light and have the same nice flat black anodizing? My U2 tailcap is too glossy. I can't imagine even if I contact Surefire that they have an inventory of UM2 tailcaps laying around that they can just send me a replacement.

 

[FPSRelic]

Ok, so my tailcap is definitely a problem. Its flakey again. What other tailcaps will work with this light and have the same nice flat black anodizing? My U2 tailcap is too glossy. I can't imagine even if I contact Surefire that they have an inventory of UM2 tailcaps laying around that they can just send me a replacement.

Id send it back. You pay all that money for the warranty, you may as well use it

 

[FPSRelic]

Just saw this on Surefire's facebook page:

https://m.facebook.com/SureFire/pho...9611.176428635720061/1383085388387707/?type=3

 

[Minimoog]

That sounds very nice. Same driver?

Yes, everything the same apart from the LED upgraded. Even I was surprised how good it made me the light and now I use it much more.

 

[Vox Clamatis in Deserto]

Ok, so my tailcap is definitely a problem. Its flakey again. What other tailcaps will work with this light and have the same nice flat black anodizing? My U2 tailcap is too glossy. I can't imagine even if I contact Surefire that they have an inventory of UM2 tailcaps laying around that they can just send me a replacement.

Id send it back. You pay all that money for the warranty, you may as well use it

Years ago I had a problem with a SureFire L2 tactical tailcap. I called SF product support to get an RMA and they seemed to be aware of the issue from other reports. They verified my address (I've had an account with SF for years) and sent me two new L2 tailcaps, both worked fine. I didn't have to send the light but they did have me do a test with a paperclip shorted from the bottom of the battery to the end of the tube. When the light came on bright it indicated that the problem was likely in the tailcap switch.

Maybe SF will send you a new UM2 tailcap and save both of you the trouble of a round trip RMA shipment. Since another tailcap works fine, you might try the paperclip test just to confirm in case product support still has this on the customer troubleshooting checklist.

I'm on the road at the moment and don't have access to my SF U2's to check the tailcap finish. I thought that one had a finish very similar to the UM2 tailcap. With SureFire's greater acceptance of clicky switches in recent years I would hope that another light still in production would have the same tailcap as the UM2.

Here's a list of SF tailcaps in this post from a few years ago:

http://www.candlepowerforums.com/vb...-with-IMAGES&p=2116454&viewfull=1#post2116454

 

[kssmith]

I've been wanting to reply to this for a few days, but have been busy. In reference to the tailcap problems. I used to have an EB2 that would not switch modes, when the paperclip test was done, the high mode worked fine. I contacted Surefire, and they shipped me a new tailcap without having to send in the whole light. Also, I swapped tailcaps on a P2X and the UM2, and think they look better. Here are some pics. Also, there is no function problems.

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[Vox Clamatis in Deserto]

What other tailcaps will work with this light and have the same nice flat black anodizing? My U2 tailcap is too glossy. I can't imagine even if I contact Surefire that they have an inventory of UM2 tailcaps laying around that they can just send me a replacement.

I'd say that the tailcap off a late model SureFire U2 is almost identical cosmetically to the UM2 tailcap. The WWW.SUREFIRE.COM is in a smaller font on the U2 tailcap and I've mentioned previously that the UM2 cap has a plastic collar around the spring inside instead of a metal one. The matte black finish is about the same on both caps.

A tailcap from an early Luxeon emitter U2 is more shiny and has a dark purple tint by comparison.

Judging from serial numbers, somewhere on the order of 100,000 U2's were made. I would hope SF customer service would have spare tailcaps and be able to send you one or two.

 

[the badger]

Does anyone know if it's safe to use a 17670 in this UM2 Ultra?

 

[Vox Clamatis in Deserto]

Does anyone know if it's safe to use a 17670 in this UM2 Ultra?

Both a Keeppower 16650 and an AW 17670 fit OK but they cycle up and down continuously on the highest selector ring setting. The 17670 is a little snug but can be pushed out since you can remove both the tail and head on this light unlike on some other recent SureFires.

AW and Olight RCR123A's work fine in my UM2.

I really like the light. I'd probably like it twice as much if it were half the price though.

 

[the badger]

Thanks for the reply Vox!

With regards to cycling up/down on the highest mode - does it drop from level 6 to 5 and back up to 6, etc?

 

[Vox Clamatis in Deserto]

With regards to cycling up/down on the highest mode - does it drop from level 6 to 5 and back up to 6, etc?

Yep, that's exactly what it does. And, the cycling seems to be very regular, as if the voltage is polled every second or so and the level is dropped if it is below some threshold. The single RCR cell voltage must be right on the low limit when on the highest selected setting. Kinda like a bistable multivibrator driven by a one Hz pulse signal. Not that there's anything wrong with that as Seinfeld would say.

Also, as the batteries run down, the light will cycle more than one level down until it reaches a steady mode. If the battery recovers somewhat, it will cycle up and start the routine again. It gives you plenty of warning to recharge or replace the batteries as they weaken.

 

[the badger]

That's great info, thanks a lot! I was just outside comparing my UM2 (2x 123A) to my UC30 (1x 18650). Pros and cons..

 

[WarriorOfLight]

Yep, that's exactly what it does. And, the cycling seems to be very regular, as if the voltage is polled every second or so and the level is dropped if it is below some threshold.

It is the same in my two UM2 lights. I assume this is a voltage observer in the driver. The brightness change between level 5 and 6 is very regulary. I have other SF lights they really flash (between on and off) if the battery is going low.
I think this is a battery warning feature in this light. At all it seems like the UM2 has a build in driver with a lot nice features. Maybe a thermal observation like the EB2 and E2DLU is also in this driver... !?

Currenty I did not found the courage to flip two "normal" LiIon cells in the UM2. I only tried K2 Energy LFP cells and they work perfectly in my UM2's.

 

[WarriorOfLight]

When I receivedd my UM2 I took some pictures and wrote a review (in german). But anyway it may also be interesting since it has some pictures:
http://www.messerforum.net/showthre...iew-Die-Lampe-die-es-nicht-gibt-oder-nun-doch

 

[RobertMM]

Price is down to 250!