Is this L4 LED OK???

A while ago I sent back to SF my L4 for replacement as the LED dome was full of air bubbles and the light output was nothing to write home about.
When I received the new head I found out that the LED has a sort of slightly frosted "halo" around the dome, it is hard to say wether it is inside or otside the lens.
Is this OK and I am being too anal or...?
The light output appears to be lower that the old one - but I have to admit that this is subjective as I have no way to make a comparison.
Thanks everybody for the advice.

The LED on my L4 is completely clear/clean..

Alexgian:

My L4 is clear also. What is the S# of your KL4 head. If its below 5000 you may have an older production run.

Larry

I have 3 R2H LED's that either have scuffed lenses or one large bubble in them. I can't really tell what's going on although I didn't subject them to a microscope. I first noticed this when I had installed one in a light and I didn't see the typical "gold" in the reflector. Since this light was already made, I fired it up and did have a reasonably bright beam. I ended up swapping out the LED anyway since it just didn't look right! The good news is that the LED's receive a high bin rank regardless of the lens imperfections, I believe. It would be comforting to know that the LED's are tested for flux at the final step after becoming complete LED's. If the bin sorting is done on the die before packaging, all bets are off. Does anyone know?

- Don

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McGizmo said:
It would be comforting to know that the LED's are tested for flux at the final step after becoming complete LED's. If the bin sorting is done on the die before packaging, all bets are off. Does anyone know?

- Don

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Don,
I don't really know for sure, but the Lumileds Applications Brief AB08, Optical Testing, seems to suggest that the flux sorting is done as a final step. For the 5W units, I can think of a reason to do die level Vf testing prior to assembly. In a 5W, the two series strings of dice need to have a balanced Vf or one string may tend to hog most of the current.

I just checked my L4 (KL4, serial number A00531), and the LED appears perfect. Well, "perfect" might be a bit anal, but I can't see any imperfections in it other than a tiny black speck near the bottom of the lens at one corner. I hit the head of the flashlight on my desk a couple of times, but the speck is still there. The speck is very tiny, and you need to use a magnifying lens to see it unless you know exactly where and what you're looking for. I'd venture to guess that it obscures around 0.01% of the light. /ubbthreads/images/graemlins/eek.gif

Larry,
The sn is A01XXX, any hints?

I don't think a serial number is going to tell you squat. I believe that some of the Luxeons just fall short of what we would accept and unless everyone is looked at by somebody, somewhere, on occasion, you might get one like this R2 I got and have shown below:



I don't know if this was binned before or after packaging but I don't think this LED is one I would *pick* as my selection! There were three of these in a tray of steller R2H's.

- Don

Don,
This is *exactly* the same "halo" I have in my L4, same crescent shape, same appearance, the only difference is that mine is slightly larger.
Either this is a common fault or they must belong to the same batch...
Now the question is: what should I do with this light considering that this is already a replacement of an even worse one...
Thanks for the advice.

alexgian,

I don't think this is that common and these aren't from the same batch since yours is a 5W and this is a 1W.

In a perfect world, this is where the Lumiled rep steps in and tells us what's what. In a less than perfect world, perhaps third time is a charm? I can't imagine what response you will get from SF CS. It will probably depend on how well you describe your situation and how receptive the CS person on the other end is.

Frankly, I don't know if these anomolies make a real difference or not. I don't expect SF to QC 100% of the components they use and I can easily see how something like this could get by. On the other hand, since SF likely doesn't QC 100% (speculation here!) it would seem reasonable that they would accept that some of their parts are not up to standard; especially a component like the Luxeon which they don't manufacture themselves.

Why don't you give CS a shout if you're game and explain the situation to them and see what they say. If you get blown off by them, perhaps I can replace the LED for you if you want. I have some good high bin LED's that came out of some KL4's that I modded with 1W's. I would only ask you to pick up the postage but the LED and change out would be free. Let's consider this a last ditch option.

- Don

Don,

Thank you very much for the info and the generous offer, I *really* appreciate it.
I will contact SF CS tomorrow and will let you know the results...
Thanks again

[ QUOTE ]
alexgian said:
Don,

Thank you very much for the info and the generous offer, I *really* appreciate it.
I will contact SF CS tomorrow and will let you know the results...
Thanks again



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I'll be waiting on this also... I have a KL4 S/N 00163 that's a greenie and I haven't wanted to hassle with C.S. for this very reason, not to mention downtime.

Rich