led turns blue

[jbieszke]

I just purchased a ssc p4 and the gd 1000. The first thoughts were WOW! but after 1min my led turns blue, after 3 min output is very low, I presume its from low current, but when I put in a fresh 17670 the same thing happened, what could be wrong?

Thank you

 

[lasercrazy]

You need to isolate the emitter, your led is shorting out and over heating.

 

[Tubor]

I think that is from overheating - they need to be well heat-sinked, or they will turn blue (don't forget that the base needs to be isolated or it will cause a short circuit). Also you may have damaged the LED by now as the excessive (over 100C) heat isn't good for it.

 

[ZuluWhiskeyFox]

I concur with the lack of heat sinking. When they get hot the first thing they do is turn blue. After which if you keep it up it will let out all it's majic smoke. Once that happen it's all over but the crying. At those power levels that you speak you will need a good heat sink to keep it happy.

cheers,

zwf

 

[Changchung]

This Led is dead...

 

[jbieszke]

thanks for the advise, is there anyway to test the led? right now the led has appx 6 min on it and about 4 are while it was on the blue side, as far as I know heat didnt really build up, the head wasnt hot at all. Tonight I will re isolate the led and post later. any other words of advise?

thank you for you input

 

[Changchung]

thanks for the advise, is there anyway to test the led? right now the led has appx 6 min on it and about 4 are while it was on the blue side, as far as I know heat didnt really build up, the head wasnt hot at all. Tonight I will re isolate the led and post later. any other words of advise?

thank you for you input

If you have another new try the same volt and current and compare with the damage one...

 

[jbieszke]

heres what I believed happened. last night I took the light apart and ohmed everything out, I didnt have a short anywhere, but what I did have, I didnt isolate the led enough, I isolated the led with artic silver checked for any shorts, now my problem isnt the blueness (which I believe was due to heat not a short) its runtime.. my components are KL4, w/stock heatsink, AW17670 2wks old, gd1000 driver (specs 85%-93% efficient) and the SSC P4, by my estimations runtime should be about 1.5 hrs with a very flat curve. my realtime runtimes are about 20 min. could it be a bad driver? does the SSC have a break-in period? I thought about the batteries, but I have 2 17670's and its with both that I ma having this problem.

Thank you

 

[chimo]

as far as I know heat didnt really build up, the head wasnt hot at all.

There's your answer. You *want* the head to heat up. That means the heat is getting transferred from the emitter to the body instead of roasting in the little flashlight "oven". Some of those SSCs did not have good thermal contact with the star heatsink.

 

[FlashCrazy]

...by my estimations runtime should be about 1.5 hrs with a very flat curve. my realtime runtimes are about 20 min. could it be a bad driver? does the SSC have a break-in period?

The LED's heatsinking is definitely the issue here, either from the LED to the heatsink, or the heatsink to the flashlight head/body. What kind of light is this installed in? You should only use enough Artic Silver to isolate the LED electrically... more isn't better.

As far as the runtime, when LED's overheat they can get into a "runaway" situation, which can cause them to draw very high current levels. I'm not sure if this is the cause of the 20 minute runtime... I would think if it was in a runaway situation the LED would've died way before then.

Also, are you using a bare LED, or is it mounted to a star board? If a star board, the ones from DealExtreme or KaiDomain had mounting issues... they just use some heatsink compound. The stars from SSC have the LED soldered to the base, no problems there.

 

[kongfuchicken]

The led is dead; there is no question about it.
It had nothing to do with shorting or lack of power. In fact, it sounds like you wired it correctly and calculated your estimation perfectly well but just omitted heatsinking. Leds don't have break in periods; they work the best the minute they came out of the factory and it all goes downhill from there (although it's a long long, 50k hours long hill).

The led overheated to death. The thermal path from led die to slug, slug to star, star to heatsink and heatsink to body must be as good as possible, especially since you're driving it at a huge current.

I'd recommend using artic alumina epoxy and pressing the led on its heatsink tightly to remove any possible air bubbles and then artic silver it in the body. Make sure nothing rattles and everything makes good contact. Anodized surfaces conduct heat better than bare surfaces and the less part junctions there are, the better it'll conduct heat.

If you did everything correctly, the body should become very noticeably warm within 1 minute of the light being on and burning hot within 20 minutes. Otherwise, you'll probably fry another led and so on...

If you don't want the light to heat up that much, I really recommend running it at a lower current; you'll lose much less brightness than you'll gain in runtime, reliability and lack of "Caution Hot Surface" tattoo'd on your hand.

 

[jbieszke]

I just wanted to say thanks to everyone for all your input, it really helped, and it looks like (from my opinion) that the led didnt burn out, I was one of the lucky few. Here are the facts of my build, I did get the led hot, but apparently not hot enough to burn it out (phew) the runtimes are near expected, and color stays a wonderful white and very bright, I dont have meter to give true results, but against my luma M1R on high, the L4 outshines, the head gets warm and becomes hot near the 15 min mark, led took me appx 1 hr to get perfectly centered. I will have a few beam shots in the very near future (my son loads the pics for me). The details of this build, SF L4, stock body, stock reflector, stock lens, GD 1000 driver (sandwich shoppe $20), SSC P4 (sandwich shoppe $12.50), copper slugs (sandwich shoppe $.50) and about 4.5 hours start to finish. This was my first KL4 build, not a really difficult build, if I were to isolate the led correctly the first time I would have about 2 hrs into this build. If anyone would like info on the KL4 (apparently this is a hush hush subject because it took many hrs looking for help) well I would be glad to help anyone who wants to take on this project, including how to disassemble this head without damage, PM me I would be glad to help in anyway possible.

Good luck
Thanks again
Jeff

 

[Nitroz]

If the heat sink is anodized then you do not have to worry about isolating the Seoul LED.

 

[jbieszke]

nitro you are completely correct about anodizing, anodizing completely removes the conductivity of electricity, but, I was using a bare copper slug. nitro, do you have a source for anodized slugs?

Jeff