Leupold MXc 421/621 Flashlight Upgrade Advice (pictures included)

Hello all,

First thread here, so pardon if there are errors. I have a few Leupold MXc 421 (and 621) flashlight(s) and love these lights even though they are now eclipsed lumenswise by a few lights i have recently acquired in my last wave of flashlight buying. They are better built though and are incredibly waterproof. I have been looking up a little on drivers and LED upgrades and must admit the more i look the more questions i have. First the light particulars:

Pic of the assembled light:

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Taking off the head:

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I unscrewed the retainer and removed the metal cap/clamp holding the driver in place:

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I then gently pried the driver and got the driver (measured at 22mm diameter) out of the head:

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At first I thought I'd modify this driver by replacing the LED. However, since it was originally meant to be run off of CR123 primaries AND it says 6V on there, i've begun to rethink that and want to run it efficiently with the 16650s i bought for it. Anyway, couple questions:

What type of driver is this?
What replacement driver would you suggest for this light?

I have googled the name and model on the driver, but can't come up with much more than the company that made them. I looked over at kaidomain and found a few drivers that are similar in diameter and look like they may work, but they are 3 to 4.2V drivers. I think they are linear drivers, but i would prefer a buck driver so i could also run CR123 primaries or the 16340 rechargables i bought for it that started me on this recent flashlight buying spree. Oh yeah, only recent research has led to these new to me terms, so if a different type of driver would work for this application, please feel free to tell me i'm way off in my assumptions

Anyway, any advice would be welcome.

Thanks,

David

Although I've ordered some LEDs at Kaidomain, I am open to buying a premade driver (that includes the LED) as well if they are reasonably priced. I would like to learn a little about putting together some of the components myself though as i've done some soldering in the past. I saw one premade "drop-in" the other day that appeared to be able to work if the diameter wasn't too large. BTW, The diameter of the inside of the head is around 7/8 inches (22mm).

As far as mode preference, the MXc 421s have two levels and a strobe, the MXc 621 has two level and SOS. For my wish list, I'd like to have a three level mode with both strobe and SOS function hidden. One of the site i went to the other day had programmable drivers that looked interesting.

Anyway, i appreciate any guidance.

If your driver is 17mm in diameter, then there are tons of options. I've purchased many drivers from Mountain Electronics, and they offer variations on them, so you can specify modes, incoming current, things like that.

If you are changing the driver, then you will have full control over what type of battery you use. If your torch used (2) CR123's, then the driver was originally set for 6v as you've mentioned. You can get a driver optimized for one cell, a 16650 would be fine. Then, you can choose an LED. Or of course you can work backwards, start with the LED you'd like and design the system to drive it properly.

Keep us in the loop on this build, it looks interesting~

Hey Dan,

Yeah, i think Mountain Electronics was the store i was looking at that had the drivers that were programmable (guppydrv they call it) to where i could pick which programming i want. I was looking at one of their buck drivers (so that i could still use two CR123s in it), but it looks like the driver i wanted was thicker on the opposite side. As you can see, the original driver on this flashlight is flat on the side facing the reflector. The LED is sticking out and goes into the reflector. I emailed them to see if they had another option that would work though. So i guess i was on the right track, thanks for the help.

I think you have a big issue with the LED being on the same PCB board with the driver...you got to find a way to mount the LED else that has metal contact too.

Best i can tell, the Emitter is soldered to the PCB which in turn is connected to the driver. The driver and PCB are glued together with a little space between them where the "glue" insulates the board from the PCB. The "cup" shaped piece of metal that the retaining screw presses hold the PCB with the emitter against that "ledge" of aluminum (Picture 5) in the bezel that transfers the heat to the bezel/head. If i upgrade the emitter, i guess it will drive a lot more heat than the original design did though, huh? Am i missing something?

If i make it too thick in there, i impact the battery length. They name this the MXc, the 'c' standing for compact...maybe too compact?

that may be crazy but i will suggest it anyways..

make this stack
new led in copper PCB
metal cap with flat surface up
new driver
plastic retainer

Assuming you are talking about the metal cap in the picture, that metal cap actually is the battery contact. I agree though that maybe i need to think outside the box (what is there presently) here and insulate the driver from the PCB. :thinking:

Since that cap has a taper to it, maybe a stack as follows:

LED on PCB, Plastic/insulating spacer
17mm driver


Then make sure that fits in the metal cap that is retained by the screw pin (and has to make contact for the ground). That way, i get back to more options with a 17mm driver like Dan pointed out. Back to research it a little to see what components i can get for that configuration. Much Apprieciated! :thumbsup:

No! you need a metalic surface for the led to absorb the heat...Alot.

Assuming the heat transfer system works as it appears the original system did (with more heat to transfer most likely), the side with the PCB with the emitter (pics 6 & 7 for the original emitter combo) would be facing the aluminum ledge (with the emitter through that glass emitter window into the reflector shown in pic 5) and pressed against it by the threaded retainer transfering the heat to the aluminum (shown in pics 5 thru 7 in various angles which acts as a heat sink) which further transfers it to the flashlight bezel, correct? The plastic/insulator would be on the driver side of the PCB/emitter acting as a heat barrier between that and the driver keeping the driver as cool as possible. Of course, the setup shown has the cup-shaped retaining clamp (best shown in the top right in pic 4) creating the ground connection (which some of the heat can come around i guess). Haven't got that worked out yet...I guess i need to draw diagrams showing this to clearly illustrate the intent. BTW, that cup mentioned above also makes the battery connection in the front of the flashlight (can be seen in the center of the screwed in retainer through the center hole in pic 3).

I think i get what you are saying though...surround the PCB with metal (on both sides) that takes the heat away from the PCB and to the flashlight bezel. Maybe that and then a insulater before the driver to shield it from the heat? The plastic and then something that connects to the battery/ies positive end.

Man, and i thought this wouldn't be that difficult as it probably was something standard that i could get off the shelf. I guess this light is anything but standard.

I just noticed my account is now "enlightened" but the more i post, the less enlightened i feel...Can i change it back to unenlightened