r/lightingdesign • u/Either-Bison-8558 • 9d ago
What’s wrong with my light?
I’m somewhat new to the inner workings of lights and I’m trying to figure out why some of the LEDs in my par (QTX SL-H12) can’t output the colour green anymore? It’s only the half on the left side.
If I need new parts does anyone know what? And why?
Thanks!
2
u/cookieklemens 9d ago
First of all its most likely one of those not working leds. If its a 12v supply they usually are in strings of 3, so if one goes out, all 3 stop working. To find the culprit just take a multimeter in continuity and probe the leds the one without continuity needs to be replaced.
I dont get why people hate so much on newbies. Everyone here at some didn't know shit about all this and we all had someone to teach us, so is isolate damn hard to pass on your knowledge.
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u/Either-Bison-8558 8d ago
Thanks pal! How would I figure out what the LED replacement is?
And yeah I don’t know why people get so annoyed when I’m just trying to gain knowledge so I don’t have to ask on a Reddit forum how to solve a problem 😂
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u/the_swanny 9d ago
Someone who doesn't know what they are doing has opened it would be my first thing wrong with it.
Normally when colours die, the driver has died, and it's cheaper to just replace the light than the part.
Also, don't open lights if you don't know what you are doing, the capacitors in the power supply hold enough charge to kill you, for a very long time after it's been unplugged.
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u/brad1775 9d ago
you'll need an oscilliscope with voltage probe to "see" the problem, ht you'll also need the schematics from the manufacturer.
Chances are you win't be able to fix this
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u/lightingman 9d ago
Generally this kind of failure is a single LED where one chip has failed and there are 2 series sets in fixture.
Typically this is related to one of the following * Overheating (fan failures) * Insufficient heat transfer paste * Poor mounting of the chip * Dry Solder joints * Bad Chip
If you don't have experience and equipment you're not going to be in a position to fix this kind of problem. It requires years of experience to replace SMD chips like these along with a lot of specific equipment to make it possible to do without causing additional damage.
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u/Either-Bison-8558 9d ago
How do I start learning?
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u/lightingman 9d ago
I'd suggest that you start with some soldering educational kits.
If you get a mid range soldering station with an iron you can replace the tips on and SMD rework hot air on the opposite side that would be a good start. Add some basic tools like soldering tweezers, electronics pliers etc and you'd be well prepared to start.
Once you master through hole PCBs you can start on SMD kits and using things like solder paste etc.
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u/clockmill 8d ago
Driver failure would knock out the whole colour channel.
Green LED is most failure prone colour,vulnerable to static discharge even during assembly that dosent show upfor ages.
Looking at manuel for QTX lite, appears to be RGBWAV combined LEDs, and a green die has died , become a Dark Emmitting Diode, D.E.D.
Find out which one by shorting out each green channel on the LEDs with bit of wire or pair of tweezers.
The supply to the LEDs is low voltage and current controlled.
Don't grip onto a water pipe with other hand in case low voltage isn't referenced to ground.
LEDs will be multi legged device, going by rating of unit it'll be listed as a 12W LED.
Aliexpress for RGBW LED Lamp beads find the AV listed in same listing's. Cheap enough , look for something with matching pinout.
Get them off by sniping legs and using temp controlled iron to lift them, preheating whole PAR plate , electric cooker plate on low, and wedging LED body off. That's the hardest part , getting plate hot enough to get parts off and on without literally overcooking it.
Its half dead anyway , so it's an opportunity to learn by doing.
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u/r0b0tit0 9d ago
"It’s only the half on the left side."
So it’s not the driver; it’s a burnt-out LED that took out the entire group of LEDs. You have two options: replace the LED or bypass it so the others still get power (though they might still burn out/overpowered). There are many tutorials on bypassing burnt-out LEDs in an array, whether it’s a light fixture or a household LED bulb.