MN21 life?

Hey guys, I know many of you with M6s have moved onto rechargeable solutions and alternative bulbs. But I like the MN21, and for now so does my wallet, but eventually I will go the rechargeable route. Now I estimate that I have only used it for about, total on time, maybe an hour.

It has always been just turned on for a few seconds, no longer than a continuous minute, but multiple times.

I went to SF and bought an MN10 for my M3 head. I swapped the M3 head and MN10 to try out my "tactical sea cucumber". I swapped the heads a couple more times back and forth. I then settled on the sea cucumber and left the M3/MN10 combo on my M6 and put the MN21 in my spares carrier SC2.

The next day when i tried to use the MN21 again, nothing happened. Im guessing the bulb may have burnt out? but it worked just fine the day before when i was shooting it at night and taking pics of the beam pattern and comparing it to the M3/MN10 combo.

I looked at the filament and it doesnt seem broken. Do MN21 filaments break like normal lightbulbs do when they burn out?

I did buy my M6 on clearance but shoudl the bulb only last for such a short time?

The MN21 should last 25+ hours.

Make sure you don't have a contact issue.

You MN21 may have been on clearance with 24+ hours on it .

Use a DMM to test the resistance of the LA. Set it to "Ω" (ohms), put one probe on the large outside (-ve) spring and the other on the small central (+ve) one.

You should get a reading of ~1.2Ω if the bulb is OK. If you get an open-circuit reading (i.e infinite resistance) it is dead.

What are you running for batteries? If you are trying to light the MN21 on Li Ion rechargeables, you may be tripping the protection circuit. If the LA checks out OK, try fresh batteries - primaries or charge yours.

yeah im running primaries. I already tried a fresh set of 123 and still nothing on the MN21.

Is there any physical evidence that a bulb has burned out? normally the filament would be burnt down. But this one looks just fine.

Sometimes the filament might be visibly broken, or there might be a smoky deposit on the inside of the glass. Sometimes there is no visible damage.

Did you try using a DMM as I suggested in post #4? That is the only way to tell for sure.

I dont know what a DMM is nor do I have one. But I called SF and they said it might be defective after explaining:

I swapped heads M3-MN10/M6-MN21/M3-MN10. In that order they all worked I put the MN21 in my spares carrier and when I put it back in with the M6 head, it didnt work. so I dont see how it could stop working when it wasnt even in the light.

Sorry - jargon. DMM = digital multi-meter. Useful if not essential flashaholic equipment - use it to test voltage, current, resistance etc. Good idea to get an electrician friend to explain one to you. You can pick up perfectly good basic one for a few $, and it will be useful for numerous purposes, especially if you are going to be using Li-Ion rechargeable cells as you say in post #1.

However, if you don't have one available, I would agree - just send the bulb back to SF, as it is most likely dead anyway. They should send you a new one under warranty.

Will SF replace the bulb? I thought bulbs are one of the few exceptions in the SF warranty? Then again, if the bulb is determined to be defective, that's another story...

yeah I dont think so. but in my particular case, i havent even used the bulb that long.

But what adamlau suggested could be true. I bought it on clearance, and it might have had more time on the bulb. I dont know that though. It isnt used though. but for all I know it might have been the actual store's display.

Solscud007 said:

yeah I dont think so. but in my particular case, i havent even used the bulb that long.

But what adamlau suggested could be true. I bought it on clearance, and it might have had more time on the bulb. I dont know that though. It isnt used though. but for all I know it might have been the actual store's display.

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Unless the store was constantly putting new batteries in the light for display purposes....like a couple hundred dollars worth, then it's unlikely that the bulb failure was due to it's normal life span being exceeded. It was most likely just a fluke and Surefire will probably replace it for you if you explain to them how long you've had your light.

Actually now that I think about it, I recieved the packaging and all, when i bought it.

And I recall that the MN21 was still in the poly bag, never opened. so the thought that it could have been a store display is not disproved, but the idea that the MN21 might have been used is bunk.

No one has mentioned that perhaps the oils from your hands/fingers may have gotten onto the bulb, which would definitley shorten the life. When handling the bulbs, always make sure NOT to touch the them and if you accidently do, wipe it down with alcohol.

thanks. yeah I treat them like halogen bulbs. I only touch the metal springs or the base of the bulb.