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Please help with repairing my LED light bar there are a total of 60 1w leds but 2 sets of 3 LEDs are dimmed.

I was wandering if you could give me a bit of advice on repairing my LED roof light bar, there is issue with 2 sets of 3 LEDs. there are a total of 60 3w leds and for some reason (probably condensation) 2 sets of 3 LEDs (one in the middle and one in the end) get dimmed. Any advice would be greatly appreciated.

Picture of Please help with repairing my LED light bar there are a total of 60 1w leds but  2 sets of 3 LEDs are dimmed.
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AntonD201 year ago

does anyone know the part number is for the 3 pin trans transistor??

-max-2 years ago

Can I get a part number for the small 5-pin device next to the inductor? That will make it easier to reverse-engineer the circuit.

survivel82 (author)  -max-2 years ago

Thank you for your help, I just ordered new 3w LEDs will try replace one by one in these 2 groups.

The part number for 5pin chip is: PT4215 412THT

I just saw that a youtuber that I am subscribed to had posted a video discussing some possible repairs for what appears to be a very similar LED bar light! I presume he will post another video shortly on repairing it as well.

Second that, the 5pin chip will be what actually controls the voltage/current to each set of 3 led's(it's the only IC that's part of every Led group) The transistor you tagged in the photo is most likely a voltage regulator, or bring used as one. I also noticed max here mentioned rubbing it with alcohol, Worth a shot. If it's contamination the alcohol will remove most if not all of it.

madhavdivya2 years ago

Well Survive182, and then what happened.......I am eager for the next part. Did the new replacement LED's solve the problem and restore your LED bar ? Who was the culprit ? Did you have to replace any other components ?

iceng2 years ago

It only takes one LED to cause three to get dim.

Condensation (moisture) affects the LED phosphors that change some blue to red and green resulting in white light.

My point is it is more likely moisture LED damage then semiconductors.

Any way, as -max- says do test voltages.

-max-2 years ago

We would need to know how the LEDs are wired together, I am not exactly sure what would cause that problem, but it seems like they are pairs of 3 LEDs are wired in series, then those pairs are wired in parallel.I cant be sure though. Perhaps a current-limiting resistor has been damaged in some way for those 3-LED pairs.

survivel82 (author)  -max-2 years ago

Hi Max, thanks for you answer! just added few more "inside" pictures.

Golden rule of electronics, Thou Shalt Test Voltages! See if you can see any of the silkscreen and factory test points that are labeled, and see if they measure anything. See if swapping off the components with some rubbing alcohol will clean off possible contamination on the parts.

There is certainly some proper switching regulation used to regulate power to the (what appear to be 1W) LEDs. Switch mode regulation would be more efficient, but the downside is the greater complexity. Also, I bet it is has a constant current output so the voltage seen across the LEDs will vary depending on the impedance of the LEDs. (it is probably around 9-10V ish)

To make sure it is not one of the LEDs in the series, use a 9V battery connected directly across the three LEDs, and see if they glow with the same brightness as and other three in another series. I wouldn't worry about a resistor since A, the small 9V batteries already have big ESR, and the 3 LEDs would require at least 9.9V to light up full brightness anyway, it shouldn't matter.