A2 White 5mm LED's - help needed

Hi guys,

Background:
Recently I got myself a SureFire A2. Thanks to SF
policy I've been forced to get a second hand one.
It's the RED LED version. I thought myself that I
could live with that, but I can't. What I'm also
not able to do, Is to get a White LED ring for it.

So, swapping the LED's seems to be the only option
for me. And I'd like to do it myself

I've already found out how to do it. But now I have
to choose some LED's, unfortunately I'm completely
unfamiliar with that market.

What I'd like to get, is a warm 2 to 6 lumens white
floody beam. The LED's should be far from overdriven
(if possible).

The red led ring uses 100.4 Ohm SMD resistors, that
as far as I've found are responsible for the ca. 25 mA
current flowing through the 5mm LED (I might be wrong).
I must say, that I would like to keep the stock resistors
and swap the LED's only. But if a needed....

Can You propose me a good 5mm LED for this task, and
a source where I could buy it ?

Whats with the surefire policy....why did you have to get a secondhand one? Just interested, cause I own a few and don't want any surprises down the road. Please share.

AAAHHHH.....I see you live outside the USA....is that it?

Yep, that's it.

It's hard to gat a new A2 here.
And even if, the price would be a killer.

I don't know anything about A2s with red LEDs, but typically, red LEDs have a lower Vf than white LEDs... Lower by about 1.2-1.4 V. If Surefire has a different driver for the red LEDs than for white LEDs, then you might not be able to use typical white LEDs.

There are some LEDs that are quite bright called SMJLEDs that require less voltage to operate at spec. They are available both 'cut' and 'uncut'. The cut ones are intended for use in reflectors so I would assume the uncuts would work better in the A2.

The drawback is I think that they are qiute bright. I think one direct driven on 2 E2 lithium cells is about 15 lumens. So assuming they would be under-driven with the A2 booster intended for red cells, maybe they would be 5 lumens but that's a random guess. But I'm sure that three of them would be well beyond 6 lumens.

I'd imagine if you wanted something in the 2-6 lumen range, you'd be looking at VERY low output LEDs. Even the Nichia CS LEDs are about 7+ Lumens each.

I'm just sort of thinking out loud here. There are many other variables and I've never modded an A2 anyway.

Esthan said:

...now I have to choose some LED's, unfortunately I'm completely unfamiliar with that market.

What I'd like to get, is a warm 2 to 6 lumens white floody beam. The LED's should be far from overdriven (if possible).

The red led ring uses 100.4 Ohm SMD resistors, that as far as I've found are responsible for the ca. 25 mA current flowing through the 5mm LED (I might be wrong). I must say, that I would like to keep the stock resistors and swap the LED's only.

Click to expand...

Esthan, I assume you've seen my A2 LED shootout? The only white LED in the lot with a "warm" tint is the THC3. IIRC, their VI is around 80mA so, judging by the numbers you posted, you'd be far from overdriving them in the A2. I'd double-check with Milkyspit, as he's the one with actual experience doing that particular LED transplant.

As far as what the lumen output is with that mod... I have no idea.

So greenLED, has it been determined for sure if there is a different circuit for the red LED A2s than for the white/blue/green A2s? Or do they just use some version of red LEDs that can deal with the extra voltage?

That's an outstanding thread, by the way. I hadn't seen it because I don't own an A2. But just the info on the different LEDs is excellent.

cratz2 said:

So greenLED, has it been determined for sure if there is a different circuit for the red LED A2s than for the white/blue/green A2s? Or do they just use some version of red LEDs that can deal with the extra voltage?

Click to expand...

I honestly have no clue, and now that you mention it, I didn't even take a peek to see what the different R values were on the LED rings.

Thanks for the kind words, and for bringing that issue up - I'll see what I can do.

Your Shootout was indeed helpful. I'd like to thank
You for it :]

After reading it, I got convinced hat people were trying
to drive the 5 LED's as hard as possible to get some
more brightness.

I'm, on the other hand looking for a long runtime,
with moderate output (bright enough to protect
me from tripping in a forest at night).
Something like factory set secondary mode in HDS
lights, which I find more than sufficient for my needs.

Those are different reasons to do a mod, and I do not
know, how do the 5mm LED's behave when not driven
very hard :]

Hrmm. Well, if you want that much less output than stock, you'll probably either need to look for some VERY ineffecient LEDs (and there's a lot more information on CPF concerning bright and effecient LEDs) or actually change the LED circuit on the A2.

I hear you on wanting a dimmer light though. Sometimes it seems I'm the only one on CPF that actually uses the lower modes. Heck, the reason I haven't bought a Fenix with a Cree is because the low mode is too bright with a LiIon cell.

And HDS is my primary carry light and I use the secondary/low mode quite often.

But for your situation, it would be cheap and easy enough to try some white LEDs. If the circuit is in fact driving the red LEDs properly, then that same circuit should under-drive white LEDs.

Might try PMing member Milkyspit if he doesn't chime in on this thread.

First off---this is very simple, but involves very precise soldering---I can explain it to you but can't help soldering the surface mount resistors.

First thing you'll want to do is remove the little circuit ring that holds the three LEDs on it. If you look between the leds, do you see those little black rectangles? Those are surface mount resistors. They currently are the larger resistor values for red than you will want for white due to differing vfs, so you'll need to swap those out for higher value resistor values, or else you'll end up with pittiful dull LEDs. I can't tell you the exact resistor value, without playing with your leds, but using a meter you can find what will make these new values, which will be lower than they currently are.

The concept is simple, and the parts are cheap, but the pain is how small those things are. Once you swap those, and the LEDs, you're good to go. This is very straight forward, but the precision in soldering and selecting proper resistor values will be your only obstacles. Good luck.

When I get the THC3 LEDs, I'm make some experiments
with potentiometers before I attempt to make this mod.
It'll take some time, but I'll post the results :]

What is this vfs ?

If you need small, SMT, 1 Ohm resistors, PM me.