Replacing the Emitter in an ARC LSH Rev 2

Anyone have some screenshots/instructions on replacing the emitter within an ARC LSH Rev 2 ? 1/3 of my hotspot went baby-poop green recently and I'd guess that the phosphor is probably detaching from the die. It looks like it's time to replace the LED if someone knows how to do so w/o damaging things (and hopefully has some pics of the process to boot ! )

/ubbthreads/images/graemlins/smile.gif

It's fairly easy. The aluminium ring holds the circuit board in place. It unscrews counter clockwise when the locktite is heated enough. A pait of ground down needle nose pliers fit the holes in the retaining ring.

The circuit board has the emitter in the middle of the back side. Mine had thermal tape under the emitter. Replacing the emitter with an SWAK Lux III gave a beam twice as bright as the original and nicely white. I left the driver circuitry stock.

Be careful to center the new emitter exactly where the old one was. The optics being held by a seperate retainer, don't seem to move at all.

Daniel

You will still need to center the board before tightening everything down. Also if your light has a copper ring between the retaining ring and the board you should put it in the way it was. so be sure to make note of which side is which. The side with the smoother edges faces towards the board to prevent damage.

HINT: If you feel you absolutly must get the optics out then I advise you wear latex (as in made of latex not vinyl) gloves. Latex is the only material I know of that will not mar the optics. I wear them all the time at work.


Good luck.

How do you go about heating the locktite ? will a hairdryer do the trick?

gadget_lover - Thanks that was just the info I was looking for... I plan on putting a TX1J into mine and was hoping the ARC board could drive it..sounds like it should be fine.. how did it affect the run time on yours? and does it get any hotter than normal?

Thanks

stan

I think I read somewhere on the Arc thread that your problem with the led is covered under warranty.

[ QUOTE ]
H00D said:
How do you go about heating the locktite ? will a hairdryer do the trick?

gadget_lover - Thanks that was just the info I was looking for... I plan on putting a TX1J into mine and was hoping the ARC board could drive it..sounds like it should be fine.. how did it affect the run time on yours? and does it get any hotter than normal?

Thanks

stan


[/ QUOTE ]

To loosen the loctite I used a heat gun set on low and held over a foot away. I tested it frequently. You don't want to melt the optics or the optic retainer. A hair dryer should also work. Others have suggested a ziplock bag and boiling water. I've not tried that myself.

The current draw is the same as my LSH-P, so the run time should be the same. I don't notice any extra heat, but my usage pattern is to turn it on, look at something and turn it off again. I seldom need to have it on for more than 5 minutes at a time. I slos have mine set up with a hi/low switch, so most of the time it's on low mode.

The heat should be the same as the original LED because the power consumption is the same.

Daniel

It's a real hard decision at this point, whether to send it in and keep the warranty or go 'balls to the wall' and put a T-Bin III Watter in the thing. One part of me just doesn't want to cause Peter any expense in replacing the LED (as the problem was with Lumiled's quality control, not Peter's), but then if I'd ever want to sell it, the value would be decreased from opening it up and voiding the warranty.

I'm still tossing around the idea of whether to send it in for a warranty repair, then sell it on eBay, or see if a T-Bin will breathe some new life into it and make it worth keeping a little longer.

Also, mine seems to have an aluminum retention ring glued/welded into the head in addition to the copper snap ring - not sure how to get that off safely.

........................

I'd sent it to Arc, that's what the warranty is for. Peter will probably be happy to see one that actually is returned for the right reason. /ubbthreads/images/graemlins/smile.gif

If you're looking for someone to do the swap for you, send me a PM. If you want to sell it, I'd give you $45, assuming it's in very good to excellent condition.


Peter

Peter has mentioned (in this forum) putting T bin LEDs in some lights as special favors for people. I wonder if he would consider replacing the LED under warranty with an LED you supply? That cuts his cost to just labor, and it allows you to benefit from the continued warranty.

Daniel

I was wondering about that - if I don't sell it to THE_dAY, I might run that idea past Peter.

Will the Vf of the replacement led matter when replacing the stock led without tweaking the circuitry? If yes, in what way will it affect it.

Let's see... It's very late but I'll give it a shot anyway.

Will the Vf of the replacement led matter when replacing the stock led???

The LEDs are really rated by maximum current, not maximum watts. 1 watt LEDs are rated for 350ma with proper heat sinking. The Vf is the voltage at which it draws it's rated current. The bins give ranges for the Vf.

A lower Vf means that the LED will draw it's rated current at a lower voltage.
An LED that draws 350ma at 3.03 volts (low end of H) will generate less heat (1.0605 watts) and use less power than one at the high end of K which draws 350ma at 3.75 volts (1.3125 watts). This assumes a constant current driver.

If the driver is constant voltage, on the other hand....
Assume the voltage is maintained at 3.5 volts and you add a LED with a Vf in the H range. The LED will be drawing MORE than 350 ma. It will be brighter but the light will generate more heat and the LED will deteriorate over a long period of time. Add a LED with a Vf in the L range (3.75V - 3.99V) and it will draw less than it's rated 350ma and will be dimmer.

A last consideration for lights in general is that the battery voltage should be equal to or less than the Vf because many UPCONVERTERS (boost converters) will be in direct drive (more or less) if the battery voltage exceeds the voltage needed to meet it's current or voltage specs. So adding a low Vf LED (in the 3.03 volt range) to a light powered by a pair of lithium AA (around what? 3.5 volts???) will likely overdrive the LED. This, of course, does not apply to buck+boost circuits or buck converters.

I don't remember if the ARC LSH is constant current or constant voltage. Blame that on the jet lag. Please correct me if I'm off base on any of this.


Daniel

I think the Arc LSH is current regulated at 350ma but I don't know the vf of the led. If I were to replace the led with a TWOJ for example without tweaking the current settings, would it result in a brighter light or would the brightness stay the same? I'm assuming it should be brighter even by just a little bit because of the bin variations. Q vs T.

The reason I'm considering not changing the current is because I want a brighter light without sacrificing the runtime.

Billson,

The LSH is current regulated at 333ma. Emitter Vf will not effect the current as it is regulated by the ciruit and set by a sense resistor.

According to Lumileds spec sheets and many posts by CPF'ers a T is about equal to a Q or R at these current levels. You don't gain much until you increase the current level.

Steve

I should have checked the LED volatge of my LSH-s before I replaced the LED. It would have let me determine what the original Vf bin was. The advertised output would suggest that it was an 'M' output, with a color that suggested a tint 4 or maybe a 3.

The jump to a SWOK Lux III was very dramatic even when driven at only 333ma. According to the lumileds data sheets it should be doing about 55% of its total output at 333ma, so at ~35 lumens it's squarely in the same range as a 1 watt Q. It's pleasantly white, even at lower current (30 ma).

Daniel