SF 2 stage tailcap question (kroma or lx2)

First, does anyone know how much current these tailcaps are rated for?

Second, what resistor values do these have? I tried searching these tailcaps but couldn't find any specific information for both.

Wondering if these tailcaps can handle amps required on some of the new high power 6p drop-ins.

Good questions. Regarding maximum currents for that model of tailcap, I don't believe that a definitive answer has been posted in CPF. However, there are a few DD XM-L L1 configs running around (~4A), and nobody has reported an issue yet. I would like to know this as well. If I was to guess, I'd say 2 amps is OK, but I have my doubts about 3+ amps over long time periods. I would definitely like to hear a more authoritative answer on this one.

Regarding resistance values, the L1/L2/A2 tailcap was definitely 10 ohms. I don't know about the Kroma. I would have assumed that the resistance value in the LX2 tailcap was unchanged from the 10 ohm of the previous models, but there have been some anecodatal reports of differing outputs between the two tailcaps. Perhaps someone with an LX2 can chime in here.

Kestrel,

Thank you for your response. Hopefully, others also could chime in and shed some light on this, but good to know that these can take even 2 amps.

Just out of curiosity, could the resistors overheat significantly to cause problems on high current lights? Sorry, I just don't have any knowledge in these things.

On another note, do you think these reistors can be swapped out with higher valued ones for more space between the outputs? Just a thought.

euroken said:

[...] good to know that these can take even 2 amps.
Just out of curiosity, could the resistors overheat significantly to cause problems on high current lights?
On another note, do you think these reistors can be swapped out with higher valued ones for more space between the outputs? Just a thought.

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1) I don't know about 2 amps, I stated that I guessed that 2A is OK due to SF being conservative etc etc. I haven't heard of a high quality tailcap / tailswitch out there that can't reliably do 3A, but the specifics with this particular tailcap is unknown. There was a relatively recent report of someone frying this tailcap with a high-output incan setup, but I don't know the specifics of that particular situation.

2) I don't imagine that the resistors could overheat, even a relatively low resistance such as 10 ohms really cuts the current down, I don't imagine that the issue would be there. I'm guessing that the issue could be the high mode, bypassing the resistors - over the long term, the impact of unusually high currents on the 'high' mode is unknown - arcing at the tailcap contacts, etc.

3) The resistors can definitely be swapped out. I don't think there is a disassembly tutorial on CPF - I have yet to see one and it's something I've been interested in for years. I have heard it's a bit tricky, but Milkyspit has been changing out resistors for a lower-low with these tailcaps for a very long time. Send him a PM - he's very busy, but if you're patient, this would be a good option. IIRC the last time he quoted me a cost, I thought it to be quite reasonable, but haven't yet gone that route with mine.

Thanks again.

I see. I thought I'd take an attempt myself, but if it's complicated....then to the pros

euroken said:

I see. I thought I'd take an attempt myself, but if it's complicated....then to the pros

Click to expand...

Well, I doubt that it's complicated (particularly for someone who solders), but getting out that top plastic ring is a bit difficult from what I hear - the legendary SureFire loctite etc.

The nice thing is that Milky can use a resistor rated for high wattages, and he has the most experience on CPF with regards to spec-ing a correct resistance value to hit the 'low' that you might be going for. Otherwise it could be a bit of trial and error on your end. :shrug:

My perspective is that I don't mind paying someone for their time who knows exactly what they are doing (and can do a job efficiently), rather than myself messing about for hours on the 'learning curve' if it's something I'm not particularly interested in doing myself.

Good luck,

BTW, If you do get Milky to do this, here's a tip: I'm guessing that he gets LOTS of PM's & e-mails with folks saying, can this be done, what would the cost be, etc. Lots of people who aren't really serious about getting a custom job done. If you want this done, PM him saying that you're ready to mail the tailcap to him, just give the word, etc, and you'll get good service.

Most people have no idea how many non-serious inquiries custom builders get - in any field - cars, guns, flashlights, etc. If you're serious about getting the work done with minimum B.S., communicate that you're serious - don't waste their time. He'll take you seriously and the job will get done.

PM incoming in a bit ...

Kestrel,

Thanks again for all your input. I'll have to see how serious I'm with the pro modding I've contacted Milky for couple of light mods and I realize how crazy busy he is.

I might at least try taking the plastic ring off myself...

http://www.candlepowerforums.com/vb/showthread.php?312870-2-stage-switch-experimentsHere is an example of a thread where members discuss using SF 2 stage switches with Malkoff dropins. You will probably not be happy with the low unless you increase the resistance from stock.

Thanks mudman!

I would love to get a hold of few more sets of McE2s or McC2s. Thought Kroma would be the better two stage for SF C series these days, not that Kroma tailcaps are more readily available

I'm thinking something like Moddoo triple two stage :devil:

Sorry to bring almost a year old thread...

Did anyone try running AZ2 tailcap or Croma tailcap with higher current modules (like M91 or Triple XPG for example)... I tried AZ2 tailcap with Malkoff M61W and difference is just slight less brightness... so I'm thinking if I go with M91 module, the difference between high and low would be even more noticable... I don't have Triple XPG any more but if the tailcap can withstand that current, it would make even more difference in brightness making it more desirable setup...

So what setups were tried so far by members with similar lego ideas ??? If it can withstand 2 amps at 8.4V at tailcap, I'm thinking it could be safe even with single mode Triple XPG, Malkoff M91 for sure...

I have LX2 paired with M61 at home and the difference is more visible... so it's definitely interesting setup...

I have not tested this, but I would advise caution using the Surefire two stage tailcaps on a very high power light. All of them (that I have tested) are 10 ohm resistors and they are only 0.5Watt rating, so if you try running a 12 Watt drop-in with them, then if you spend too much time on low the resistor will heat up and burn up. You may have to modify the TC to put in a higher wattage resistor or put in a higher ohm resistor which will drop both the output on low and the wattage requirement due to the lower resulting current. If I were to guesss, I'd say you need over 30 ohms resistor to drop the Wattage down below 0.5 which is a common size resistor that can fit in the tailcap.

Different drivers have different resistor needs as buck v. boost do different things and have different demands on a resistored circuit. I would have to test what the resulting amps and voltage are on a given light to deterine the Wattage need, but IMHE (in my humble experience) modifying lights with resistors, if you go over 3W unresistored power, you are asking for trouble with a 10 ohm resistor. Fire type trouble. 5W is definitely risky.

Here is a good reference page: http://www.bcae1.com/resistrs.htm

But remember you don't know the current on the resistored low with a driver until you try it.

Lets say the module used has 3A buck driver that pulls 1.5A at 8.4V at the tailcap... If the module makes like 600 lumens OTF, what resistor would have to be used to drop low mode to maybe 10% of that OTF and be safe so it doesn't burn up or something?

Would this be enough information?

Now you got me worried... So even my LX2 body and tailcap with M61 seems to be pushing it, right ??? I't about 4W at the tailcap on high with both setups, 4.2Vx~1A with 1xLiIon or 6Vx650mA that Gene's modules pull...

Tana said:

Now you got me worried... So even my LX2 body and tailcap with M61 seems to be pushing it, right ??? I't about 4W at the tailcap on high with both setups, 4.2Vx~1A with 1xLiIon or 6Vx650mA that Gene's modules pull...

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I personally wouldn't worry about it - on high mode (i.e. the 4W that you cite), the tailcaps bypass the resistor completely. Of course, I defer to Blindasabat's hands-on knowledge on the tailcaps - the only other CPF'er who has re-worked these tailcaps besides him is 'Milky' AFAIK. However, remember that a stock LX2 on 'low' pushes its tailcap resistor approximately as hard as your Malkoff dropin. Furthermore, BigChelis has ran the stuffing out of his direct-drive L1 setups, and their tailcap currents are considerable with the 1xIMR123 cell. He's never reported any issues.

Honestly, I've read up on most every SureFire L1 & L2 modding thread on CPF over the past ~4 years and I've never heard of any instance where a tailcap failed due to too much current on the 'low' setting. Not saying it's not possible, I just don't think it's happened yet.

So the guts in L1, L2, LX2, AZ2... they are all the same (well, the connections and resistor used)?

Tana said:

So the guts in L1, L2, LX2, AZ2... they are all the same (well, the connections and resistor used)?

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At least the last three generations of L1's, the L2, and the A2 are the same exact tailcap - 10 ohms. The LX2 tailcap was restyled but still used a 10-ohm resistor, although it may be that the driver senses that and attenuates the drive current more than the 10 ohm would by itself. I am unsure on that last point. I'm not knowledgeable about the AZ2 tailcap but I don't see any reason SF would change the internals for it. :shrug:

Well, my LX2 is at home and AZ2 tailcap is here with me... but I think the difference on the low is noticable... but that's by the memory... And at home I have installed M61W 4500K version and over here I tried with newly acquired M61W 5000K version... it just seems that AZ2 tailcap low is higher than with LX2...

I'm guessing I would decide very quickly to mod AZ2 to withstand 10W and lower high on any amp down to current that would give around 50 lumens (gotta remind myself of all those formulas now from school)...