# Help with M6



## jamesmtl514 (Nov 16, 2011)

Hi all.
Here is a pic with my M4 with Nailbender High CRI LED dropin running off 4x SF123, M6 MN21 with 6 fresh SF cells and my C2 with 3x 16340 with MN60.
Why is the output so much less out of the M6?





C2 with MN60 on LEFT M6 with MN21 on right.


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## angelofwar (Nov 16, 2011)

Maybe a bad circuit in the MB20? Do a voltage check on the MB20 with the batteries loaded. That's my best guess...hope this helps James!


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## jamesmtl514 (Nov 16, 2011)

Thanks for the suggestion.
The MB20 reads 9.0v. I popped in true fresh cells and they read 9.7v Same output.
I pulled my C2 out of it's pelican case, and it slipped out of my fingers and landed on a tritium sphere making it go  :mecry:

and the C2 was still significantly brighter.


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## ampdude (Nov 16, 2011)

Are you sure it's not an MN20? Maybe a bad bulb though. An MN21 should smoke both of those setups by a wide margin.


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## jamesmtl514 (Nov 16, 2011)

Yup, for sure it's the MN21. Triple checked. Bulb looks (to my eyes) to be fine.


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## angelofwar (Nov 16, 2011)

Hmmm...check the resistance (ohms). Do you have another MN21 to compare it to (resistance wise). I'll check mine real quick if you don't, so you can compare it. Also, is it a new or older MN21? Or is there a way to check the amps it's drawing?


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## HotWire (Nov 16, 2011)

my My M21s (I tested 2) measured 0.5 ohms on my Fluke. I swapped them out real quick and they both have about the same brightness: very bright. You could have a slightly dirty connection somewhere or you might have a substandard bulb. Try another M21.

Edit: If you use alligator clips on your VOM it will help settle the range of resistance to one number. With just probes readout moved around like yours did. 

If you know someone else with an M6 could swap the MB20 and see if that is the problem. Then swap the M21s. I don't think your batteries should sag to 4.4v. I'm not an expert, but you either have bad batteries or some extra resistance in the M6.


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## jamesmtl514 (Nov 16, 2011)

I tested the resistance. It jumped around a lot, but finally settled at .3 It stayed there for about 3 seconds then bounced around between .3 and .6 for a bit.
Unfortunately, I don't have another MN21 to test. _Checked with my Ideal model# 61-732_


Here are some non scientific tests.

at about 2 inches from the wall, examining the hotspots.

The M6 is just slightly brighter than my M91W. 
The C2 with MN60 3xIMR16340 is SIGNIFICANTLY brighter than the M6. It hurt to look at the hotspot.


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## fivemega (Nov 16, 2011)

angelofwar said:


> Do a voltage check on the MB20 with the batteries loaded.


*Voltage reading might be good to test batteries (if any) but meaningless for mentioned situation.*


jamesmtl514 said:


> I popped in true fresh cells and they read 9.7v Same output..


*You may try reading voltage (as close to bulb) and  UNDER LOAD or read tail current.*


jamesmtl514 said:


> The C2 with MN60 3xIMR16340 is SIGNIFICANTLY brighter than the M6.


*This means, you definitely have some problem in your M6.*


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## jamesmtl514 (Nov 16, 2011)

Thanks for the input, how would I go about testing under load/ tail current?


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## angelofwar (Nov 16, 2011)

You would have to run the light while "disected"...if you have some alligator clip and wire you can do it...this will allow you too measure AMPS, etc. You can do it piece at a time. Run a "lead" from the tip of the MB20 to the MN21 while installed in the turbo-head, and use a multi-meter to measure the amps being "consumed"/drawn by the MN20. And do the same for the tail-cap, if you suspect it. The amps should be about the same...if you're getting significantly less from either, that's where the problem is...

Do you have any other Turbo-head lamps? If so, you could use one of those to determine if the lamp is the problem, or if it's in the M6 itself. An N1, N2, or MN15 would work.


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## oldways (Nov 16, 2011)

Remove tailcap and clean the shoulder at the end of the body threads. Pop out the disc in the tailcap and clean.


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## jamesmtl514 (Nov 16, 2011)

I don't think my multimeter has an amp option. I dissected and connected, made it light up. all i got a reading from was the volts. It was at 4.4v when lit, 8.9v when just the MB20.

I cleaned the threads and removed that disc, cleaned there too. The cloth was removing a little black residue, which just seems like the usual surefire lube (based on the smell and me having owned 30 SFs) This flashlight is in pristine condition. Not even the slightest hint of a blemish. 

MN60 is still much brighter.

I have N1, MN60 lamps on hand, What do you suggest I do with those?


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## ebow86 (Nov 16, 2011)

Hello James, sorry to state the obvious but are you sure their isn't a issue with the batteries your using? I know we can eliminate the bulb being the problem, as these bulbs either work properly or they don't, and this one obviously works.

To be honest I am a little perplexed and confused, as you say the "M6 is just slightly brighter than my M91W". That would indicate to me that the M6 is functioning correctly, as the M91W is conservatively rated at 450 OTF lumens and your saying the M6, with it's 500 lumen rating, is slightly brighter, which is exactly what the results should be when comparing them. 

But at the same time your saying the M6 is dimmer than your C2 with MN60, but then you go on to say that the M6 is still brighter than the M91W?. The M6 is dimmer than the C2/MN60 but still brighter than the M91W? I don't understand how the M6 can be brighter than the 450 lumen M91w but at the same time be dimmer than the C2/MN60? That seems contradictory to me. Ok, now I'm getting confused, just trying to understand the comparesons you've made here.

Sometimes comparing the output of different lights can be confusing, as the beams and color temperature can vary greatly, and that can make it difficult. Also the first photo you posted looks very much like weak cells to me, the yellowing is typical of what happens when the cells are weak. That MN21 really sucks the life out of the cells, and runtime is painfully short.


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## jamesmtl514 (Nov 17, 2011)

I know... I'm confused too. 
The cells that I used for the above pictures had about 2 minutes runtime on them. I even replaced them with cells that I individually tested to be fresh, and I got the same output.

As you see in this picture.




The MN60 is white and really bright. The MN21 looks very weak.
Last night Before going to bed I shined both of them into the night sky and the MN60 produced a very smooth, bright beam. The MN21, not so much.

I'm in talks with someone in the MP, trying to get my hands on other MN21 bulbs to see if that helps.


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## angelofwar (Nov 17, 2011)

James,

Do a search on running an N1 bulb in the M6...I did a thread up a few years years ago. If the N1 isn't as bright as a P60 (approx.), then we know it's not your bulb, but something with the light or the battery holder. I'll try to find the thread and will post it if I do.


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## angelofwar (Nov 17, 2011)

Bumped it to the top of the incan thread, but here's the link JIC:

http://www.candlepowerforums.com/vb/showthread.php?236279-N1-in-an-M6


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## ebow86 (Nov 17, 2011)

FWIW I have run the MN60 on 4 primaries and done several comparisons with the M6+MN21 on primaries and there is no comparison, the M6 easily was significantly brighter and whiter every time. I have seen both lights in person and I would completely agree with the assessment that "The M6 is just slightly brighter than the M91W. See this post here http://www.candlepowerforums.com/vb...-Surefire-M4&p=3739731&viewfull=1#post3739731 You can clearly see where I mention the M6's output is brighter and whiter than the M4's. 

That still doesn't explain to me why the M6 is supposedly brighter than the M91W, which sounds perfectly normal, yet it is not as bright as the C2/MN60? Again that doesn't seem to make sense to me, as your M91W should easily output more light than your MN60. Any chance of a beamshot of your M91W vs M6? The M91W should appear to be dimmer or slightly less bright than your M6, correct? That would be hard to beleive judging by the beamshots you provided, yet you have already confirmed that the two are similar in brightness with the M6 being slightly brighter. So with that said, we can determine that your MN60, rated by surefire at 225 lumens, is brighter than your M91W rated at 450 lumens, correct? Wow, very confusing.


Lamp Assembly's either work or they don't. I've never seen it when a "defective" lamp assembly was significantly dimmer than a normal one, it's always either they work or they don't. There are rare occasions when the gas can escape from the globe and cause the output to be extremely dim and yellow, and then the bulb proceeds to burn out fast and die, but that's obviously not the case here. Lamps darken with age and the output can be reduced, but typically it isn't very severe.


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## ebow86 (Nov 17, 2011)

angelofwar said:


> James,
> 
> Do a search on running an N1 bulb in the M6...I did a thread up a few years years ago. If the N1 isn't as bright as a P60 (approx.), then we know it's not your bulb, but something with the light or the battery holder. I'll try to find the thread and will post it if I do.



AOW, isn't the N1 a 6 volt LA for the KT1? Won't it burn out or explode in the 9 volts the M6 is going to give it?


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## angelofwar (Nov 17, 2011)

Yes, but when I decided to run it in my M6, I used two CR123's and a spacer. If you do a continuity check between the connections on the MB20, you can arrange them right, and get 6 volts out of it. I explain it in my M6/N1 thread...the best I could explain it, anyways.


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## ebow86 (Nov 17, 2011)

angelofwar said:


> Yes, but when I decided to run it in my M6, I used two CR123's and a spacer. If you do a continuity check between the connections on the MB20, you can arrange them right, and get 6 volts out of it. I explain it in my M6/N1 thread...the best I could explain it, anyways.



Gotcha, sound's like an awesome setup, those N series LA produce such beautiful round hotspots.


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## jamesmtl514 (Nov 18, 2011)

Just got in, here are some photos for your consideration.
M91W with 2x 18490 vs. M6 with MN21
M91W is about an inch from the white molding. The MN21 is about 3 inches away. you can see the tip of it at the bottom of the photo.






C2 with extender and KT 3x 16340 with MN60 in vs. M6 with MN21. M91W with 2x 18490 on the floor.
Both incas are about 4 feet from the wall.





Reversed this time.
MN21 on left, MN60 on right. Pointed at the ceiling. about 8 ft away.(~9 ft ceiling, 12" light)


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## DM51 (Nov 18, 2011)

james, the MN21 pulls about 5.0 amps out of 3s2p CR123A primaries. It works them about as hard as they can take, so it is essential to use top-quality cells. 

The voltage under that load drops to around 7.0-7.5V, so I'm a bit puzzled by your reference in post #13 above, where you measured 4.4V. How did you measure that?


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## jamesmtl514 (Nov 18, 2011)

I have only used Surefire batteries.
I achieved the 4.4v by running wires from the MB20 to the MN21 forgoing the M6 body.
I placed my multimeter leads on the outer and inner springs while the light was lit. It gave me 4.4.

**************************

If anyone here can post beamshots of their MN60 and MN21 side by side like I have that would be greatly appreciated.


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## DM51 (Nov 18, 2011)

At 4.4V the MN21 will definitely under-perform, with the result you've seen. Either the cells are old or used, or the MB20 has a bad connection that bypasses one of the cells.


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## jamesmtl514 (Nov 18, 2011)

I tried 2 sets of new cells. I'm leaning towards a bad MB20 at this point. How would I go about testing it?
(I will attempt AOW's N1 vs P60 method when I get my multimeter later on this evening)


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## angelofwar (Nov 18, 2011)

I'm with DM51 on this one...Bad MB20...I'm Sure SF will swap it out for ya.

At 8' the MN21 should appear a little brighter than the MN60...and "white" for that matter.

Here's a quick diagram I did up showing how your MB20 should be wired to make up the two parallel 9V stacks.


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## DM51 (Nov 18, 2011)

I'm not sure exactly how the MB20 is wired up. Just looking at it would suggest it is 2s3p, but it's 3s2p. What order the wiring goes inside, I'm not sure. 

I may be wrong, but I think someone has taken one apart before - probably LuxLuthor. I think I recall seeing something about it a long while ago.

Try various combinations of just 3 cells to get a reading of 9V at the +ve and -ve terminals of the MB20, then take those out and put 3 cells in the other 3 spaces. If there is a faulty connection, a reading of 0.0V will reveal it.


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## DM51 (Nov 18, 2011)

BTW in post #28, take those readings open circuit, _without _a bulb connected...


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## angelofwar (Nov 18, 2011)

Ha-Ha! just did that diagram up while you were typing yours, DM!



DM51 said:


> Try various combinations of just 3 cells to get a reading of 9V at the +ve and -ve terminals of the MB20, then take those out and put 3 cells in the other 3 spaces. If there is a faulty connection, a reading of 0.0V will reveal it.



If you do this, just make sure you do it in a timely fashion. There's a "loop" in the circuitry...if you just put 3 in, or 4, etc., and they're not right (say you put batteries in A1, A2, and B2), and you accidentally leave them in there, they can get extremley hot (and probably go poof on ya)...it's either 3 in the right spot (A1, A2, A3), all, or none.


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## Justin Case (Nov 18, 2011)

I'm not quite clear how inserting the wrong combination of cells can result in a "loop" in the circuitry, i.e., a short. The cells are wired 3S2P. Unless you connect the MB20 + to the -, how do you short the cells?

Also, I'm not clear on your battery topology. I put a meter to the MB20 to test continuity for all of the connections. I get the following:

```
MB20+
      |
   --------
  |        |
--^--    --^--
|   |    |   |
|   |    |   |
|   |    |   |
----     ----
  |        |
--^--    --^--    These two pairs of cells are lined up on either side of the + sign on the top of the MB20.
|   |    |   |
|   |    |   |
|   |    |   |
----     ----
   |______|
      |
  |--------|
--^--    --^--
|   |    |   |
|   |    |   |    These two cells are the two on top of each other, lined up under the www.surefire.com writing.
|   |    |   |
 ----    ----
   |______|
       |
     MB20-
```


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## jamesmtl514 (Nov 20, 2011)

I just performed the 3 battery test on the MB20.
With all 6 batteries I get a reading of 9.1 (i've used the cells for my tests in this thread)
With the 2 on top 1 on bot I get 8.8v
With 1 on top 2 on bot I get 8.8v.

I bought 3 new MN21 bulbs. Maybe It's the bulb at this point...


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## DM51 (Nov 21, 2011)

Intriguing problem... very helpful input from AOW and others above... it will be fascinating to know what caused it. 

If the new bulbs don't work any better, you should give SureFire a call and send it back - they'll definitely fix it / replace it under their lifetime no-quibble warranty.


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## Justin Case (Nov 21, 2011)

jamesmtl514 said:


> I just performed the 3 battery test on the MB20.
> With all 6 batteries I get a reading of 9.1 (i've used the cells for my tests in this thread)
> With the 2 on top 1 on bot I get 8.8v
> With 1 on top 2 on bot I get 8.8v.
> ...



If you look at the MB20 topology shown in my post #31, there are four ways to obtain 9V nominal using three cells. It's possible that the two 3-cell configurations that you tested both tested only the left side of the topology I drew (for example). If the other parallel path wasn't tested and is defective, that would explain why the cells sag so badly under load. Your MB20 gives you essentially 3S1P instead of 3S2P.

Do you have a dummy cell to use in your M4 to test the MN21?


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## jamesmtl514 (Nov 21, 2011)

I do have a dummy cell. Good idea.

I just tried the MN21 in my M4 with the dummy cell. The light output was the same as when it was in my M6.
MN60 off 3 16340 was still much brighter.


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## Justin Case (Nov 21, 2011)

The M4 test is a 3S1P test. If it produced the same output as with your M6, I would suspect a faulty MB20, especially since you measured 4.4V under load in your M6. An MN21 draws almost 5A in an SF M6. SF123 cells probably can hold 2.0V-2.2V at a 2.5A draw. So at 5A, I can believe that the cells might sag to 1.5V each. If the MB20 were working properly and giving you a true 3S2P configuration and assuming identical banks of 3S cells as an approximation, then each bank of 3S cells should see about 2.5A draw and the total voltage under load should be closer to 6.0V-6.6V.

I would re-test the MB20 to make sure that you check both banks of 3S cells.


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## DM51 (Nov 21, 2011)

Excellent thinking, Justin


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## HotWire (Jan 6, 2012)

Please let us know what you found out! We are all interested in your success with the M6. Right now I'm guessing you have a bad MB20.


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## JNewell (Jan 26, 2012)

Interesting thread. I don't recall many reports of MB-20s failing.


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## Kif (Jan 26, 2012)

Wow, a faulty MB20!? 
It's time to take out all my MB20s and make sure they are good :duh2:


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## HotWire (Feb 11, 2012)

Just curious. Did you discover the problem?


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## 325addict (Feb 14, 2012)

Got an MN15 lamp assembly? Put this one in, then test again. If this one gives at least a bright WHITE beam, then most definitely your battery holder has a bad connection between the two series stacks. It then uses a 3S configuration instead of a 3S/2P configuration. Only three of the six batteries are used.
This will work fine for an MN15 lamp, that only draws 1.15A but will definitely not work for an MN21...

Another way to test it: load either an MN15 or MN20 lamp (in this stadium I woudn't use the MN21 anymore - you may be overloading the cells severely!) and take six NEW cells. Measure their open voltage, of all six. Mark the voltage on them.
Let the light run for 10 minutes, then measure all voltages again.
If three of the six batteries have an unchanged voltage, then your battery holder is DEFINITELY bad!


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## jamesmtl514 (Feb 16, 2012)

Hi everyone!
I have just received my brand new sealed MB20 from SF. I popped in fresh cells, lit it up and was_ underwhelmed_. I lit my MN60 light beside it and it still produces a brighter, whiter beam. 
I can't perform any tests or take any photos as I'm extremely limited for time lately. I just wanted to keep you guys informed and let you know that when I have more time I'll try to work this out.

THANKS!


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## HotWire (Feb 18, 2012)

I just finished taking my M6 apart and studied all the places that allow current to pass. All the the places where contact is made should be cleaned with alcohol, rags, Q-tips, then coated with DeOxit Gold. If it's not the bulb, and not the MB20 I asked myself what else could it be? Clean the inside of the tailcap especially well. Make sure the spring is tightly fitted to the tailcap. 
One of those things should help. After all that cleaning and polishing try this: Install the batteries and bulb, load the MB20 and insert it. But don't put on the tailcap yet. Take a paperclip and bridge the _end of the body_ (a connector) to the _appropriate area of the MB20._ You should get full light. If you do, then the problem is in the tailcap. If it is not bright, the problem is forward of the tailcap. Good luck!


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## jamesmtl514 (Feb 19, 2012)

Thanks for the help. I'm really anxious to get this light running up to par.


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## Justin Case (Feb 19, 2012)

I'd first get a DMM that can measure amps and check the tail current draw for the M6 with MN21. It should pull almost 5A. If the draw is more like 4.5A or less, then that explains why the output is weak (with the potential complication that your DMM might present enough resistance to drop the tail current). HotWire's suggestion to bridge the tail of the M6 is a good one. If you get full output, as determined by eye, then even if your DMM measures low, I'd say that all is else well and your tailcap is suspect.

If the DMM measures about 5A, then for whatever reason, your MN21 is "off". It is pulling the expected current but not delivering the expected lumens. Swap lamps and re-test.

If your DMM reads low and bridging also gives you weak output, then the problem could be one or more of the following:

- Bad MN21
- 123A cells can't deliver the goods
- Defective MB20 holder
- High resistance path in the remainder light (excluding the tailcap)

Did you ever test the M6 with the other MN21 lamps that you have? If all of the lamps give weak output, then the problem is probably not with the MN21.

IIRC, you've said that you have tried various sets of fresh 123A cells. I forget if these were quality cells such as Duracell or SureFire. If they were, then that possibility is also eliminated.

You've gotten a second MB20 and you still get weak output, so most likely the battery holder is not the cause.

If it is a high resistance path in the M6, I'd check/clean all metal-metal contacts, e.g., MB20 contacts, springs, bottom of the M6 "neck", and back edge of the M6 tail threads. Then re-test with the DMM and bridging. If you get full output, then add the tailcap back and re-test. If you still get full output, you're done. If output is weak again, then remove the tailcap, disassemble it, and clean it.


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## jamesmtl514 (Feb 25, 2012)

I had a few minutes to conduct some tests. 
I cleaned the light, although it's just about new.
I tried all 4 of my MN21 bulbs, always the same result.
The MN60 was still whiter and brighter. 
The only bulb that was brighter than the MN21 was the 11185.


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## Justin Case (Feb 25, 2012)

I would get a DMM that can measure high current and test the current draw when using the MN21 lamp. If it is up to spec, then all is probably well and the problem is that your Mk 1 Mod 1 eyeball is uncalibrated.


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## jamesmtl514 (Feb 26, 2012)

Justin. I'm leaning towards agreeing with you. I more or less came to the same conclusion yesterday.
The other one being that my MN60 is some rare gem. 
I turned on the MN60, aiming it at the wall behind my computer screen and I auto squint. It's that brignt. I waited, fired up the MN21 M6, and no squinty action. light up the MN60 right after, and I squint.
I don't know if it's the whiter beam, it's tighter profile or... some other variable. I just feel that the MN60 is much brighter.


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## jayflash (Feb 29, 2012)

Where do you recommend buying replacement MN21 lamps and what do they sell for now?


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## Snacks (Mar 24, 2012)

hi
was just curious to find out if the issue was sorted out. i don't have an m6 myself but i am anxiously awaiting to get one. Just wandering what the fix was for this issue.


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## jamesmtl514 (Mar 24, 2012)

I haven't had time (nor really cared to look into it as I have a lot of other throwers and as mentioned, haven't had a lot of time to play flashlights..)
I will try to make a point of cleaning it up properly and seeing if that fixes anything.


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## jamesmtl514 (Apr 14, 2012)

I didn't bother cleaning it yet. I did get the MD60 thanks to an awesome member. 
it changes the light for the best. It would have been nice if it were a warmer tint, but I don't really care.

My MN60 is still a monster thrower, but the MD60 is nice and useful with it's 3+ hours runtime.


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## HotWire (Apr 14, 2012)

I have the MD60 from Malkoff in one of my M6s. Great setup. Long runtime. The other M6 runs 3 X 17650 IMR with LF 1000 lumen IMR M6 bulb. Bright incandescent light! Both are good. At home I tend to use the incandescent M6 more because it's easy to recharge it. Away from home I take the MD60 version for the long run time.


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## Justin Case (Apr 14, 2012)

Post deleted.


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