xp-g failures

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RoyalFizbin
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xp-g failures

Anybody else had an xpg fall off it's heatsink?  I have the dx 5 mode xpg drop-in.  I've had it for a while but havent used it that much.  The light turned on but as soon as i went to swich modes, the thing died.  I took it out and removed the reflector and while peeling back the isolating sticker disc, the emitter fell right off.  I'm reasonably sure that this is where the failure happend.  Checking through the dx reviews, i found that this happed to black_rose twice.  His were the single mode version. 

Since I really like the driver on this drop-in, I ordered another mounted xp-g emitter from dx to fix it.  I purchased http://www.dealextreme.com/details.dx/sku.44305.  It looks to be the exact same disc that im replacing.  Checking ebay and everywhere else, it seems they're all mounted on this disc which probably means all our budget xpg lights are getting from the same source and all our xpg lights could have the same failure.

 

I tried to reflow solder the emitter back onto the disc using a frying pan but there was never enough solder on there in the first place so that didn't work.   Having no soldering paste i tried to tin the back of the emitter with a soldering iron first and then try the frying pan again.  It bonded but i damaged the led with too much heat.  The light works in lower modes but switch it to high and it instantly turns super blue.

SPAMBOT
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Some of those drop ins had or has a sense resistor that makes the regulator dump up to 2.5A into the emitter. Since XP-G's are only rated for 1.5A the added current makes the LED overheat, turn blue and in some cases even unsolder itself from the mcpcb. It isn't really an XP-G failure as much as a driver configuration failure. Try changing the sense resistor from 100mOhm to 200mOhm to prevent further damage.

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agenthex
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spambot, do you have a link/photos?

 

I have the same issue with the cheapo xp-g dropin I got from KD (2A draw).

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board

 

Ax2002 chip, to calculate Rs: 0.25/I=R (ex. 0.25/1.25=200mOhm)

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agenthex
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Thanks. But that spot looks unpopulated? Did the owner remove the existing resistor?

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R3=Rs in this case so there is where your sense resistor goes. The original 100mOhm resistor chills out with a pt4115 regulator, it was way too cool for the ax (or is it an ax clone?) : )

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RoyalFizbin
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I haven't removed the driver from the pill yet so i don't know what it looks like from the other side but I know mine is green and it's the 5 mode.  I don't think it was getting too much current.  When it was working, the light was bright but not exceptionally bright nor was it extreamly hot or blue.  The emitter was mounted very poorly.  If you look at the bare mpcb, you see that it has an exact orientation for the emiter to be mounted.  My emitter was rotated about 30-35 degrees.

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Was the emitter rotated before you first used it? You could measure the tailcap current, it is a good indicator of overcurrent. The 5-mode regulator is based on the same design but with the addition of a extra pcb with a uC for pwm modes on top.

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RoyalFizbin
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The emitter was always crooked to begin with, I noticed it the first day I got it.  Tail cap measurements  1.24amps with 1x18650, 0.9amps with 2x18650 and .67amps with 3x18650.  These are all for the high mode.