Fading L4 -mechanical or psychological?

Pydpiper

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Jan 4, 2005
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Part of me thinks I may be losing output from my KL4, I want to think it is just my imagination but I can't be sure.
I EDC it on my Kl1 body with a protected 123, also in the original body with a pila. I try not to let it get too hot, but it happens periodically. Other than that it's just a day in the life of a typical flashlight. /ubbthreads/images/graemlins/smile.gif
I have read threads of a similar nature to this in the past but I am hoping some new discoveries have been made since, I am confident there are people out there who use their lights more than me.
 

Ginseng

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Feb 27, 2003
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Py,

Two things to check first.

1) Check all your electrical contact surfaces for insulating crud. I always do a full clean whenever I replace O-rings about every 6 months.

2) Look at the LED through a few layers of window tint or other transparent but dark material. I've had a 5W go bad by losing a few of the glowing strips on three of the dies. The overall effect is one of visible dimming and distorted hotspot.

Also, if you can do it, remove the tailcap and touch the bottom of the battery and the rim of the body tube to check your current. On a fresh Pila it should read around 1.2A.

Wilkey
 

Ginseng

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Feb 27, 2003
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Oh,

And I used my last L4 alot for over two years and subjected it to plenty of hot runs. My sense is that very little brightness was lost after dozens and dozens of cycles of Pila 168S cells.

Some guys will quote you the Luxeon Lumen Maintenance curves but in reality, you'd have you use the living heck out of a light to see noticeable dimming.

Wilkey
 

Pydpiper

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Ginseng, great advice! I didn't realize that some of the glowing strips could go bad without all of them following behind, I will try that today.
I keep the contacts clean, always. I strip down the lights I use weekly to clean the threads and contacts, so we can rule that one out.
Thanks again!
David
I have a cheap welding helmet that may work to get a close look at this thing lit up.
 

JanCPF

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Oct 17, 2003
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Denmark
Those cheap solar eclipse gogles also works great for checking out Luxeons.

FWIW I've run my L4 for well over 100 hours on a Pila(constant on for 50 min. at a time) with *no* measurable output degradation.

Jan
 
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