LED Diode repair help

[bjlasota]

I'm seeking some electrical help to replace a bad LED on the board from my tv. Pictured below is a zoomed in picture of 2 diodes from the LED strip taken from my tv. I've exhausted all online resources to find a simple replacement, so now I'm moving onto the repair stage. I'm a mechanical engineer, and as such, don't know the proper and tricks to working everything electronic. I've had 2 suggestions come to me on this board. Replace the LED diode or simply smash the diode and bridge the +/- connections. So which is easiest and how to I do it? As you can see, the diodes are really, really small. They're also very thin as the board is sandwiched between the mounting plate and the glass panel in the tv. I understand on how to solder PC boards that have thru holes, but have 0 experience with boards like this that have an aluminum backing that prevents access to the bottom of the board. Any help would be appreciated. Thank you.

[eccerr0r]

Re: LED Diode repair help

If you have a dremel and a steady hand you could just slice the LED off, leaving enough space to solder another or a few diodes to make up for the lost voltage drop.

If your LED PSU is constant current, you could just bridge the pins on top and just leave a dead spot, this probably is easiest.

[bjlasota]

Re: LED Diode repair help

If you have a dremel and a steady hand you could just slice the LED off, leaving enough space to solder another or a few diodes to make up for the lost voltage drop.

If your LED PSU is constant current, you could just bridge the pins on top and just leave a dead spot, this probably is easiest.

So would I just be dropping a line of solder to bridge the pins? I see 4 pins around the diode. Am I bridging them all together, or do I need to trace a +/- post?

[nicam49]

Re: LED Diode repair help

Hi, there's are 2 youtube videos from a badcaps member called ReeceyBurger123 showing how to replace leds, not exactly what you've got but might give you some ideas. btw, I think if you short the led out, the psu will detect more current being drawn than normal...and might cut out to protect the circuit.
https://www.youtube.com/watch?v=RxwdC7V5Ue0
https://www.youtube.com/watch?v=0uBhca7zyXI

[diif]

Re: LED Diode repair help

Does the strip with the LEDs on not come out from the screen ? You could then use hot air from the top.
What TV is it ?

[bjlasota]

Re: LED Diode repair help

Thanks for the replies folks! The strip is removable. I figured mine might be similar to Burgers way of removing them, however, it looks like the diodes have leads on them that were stuck through holes on the top of the board, and soldered under the board before the heatsink was installed. The heat sink is the aluminum strip I'm referring to in the original post. I used the heat gun method and had the board pretty toasty and still couldn't get the sucker off.

[bjlasota]

Re: LED Diode repair help

This is what I have when I rip the plastic off. 4 posts appear to be visible, which is quite different than the videos posted on youtube. These posts also don't appear to be soldered on, rather passed through the board and connected under the board between the heat sink board. Thoughts on how to get this off and bridge the connections?

[eccerr0r]

Re: LED Diode repair help

interesting, the 4 pins are all tied to the metal part? I've never worked with that kind of diode before, thought that usually 4 pins = 2 anodes, 2 cathodes, and if you want to bridge it, just connect anode to cathode. You can try a working diode to see which are the cathodes and anodes. Now I haven't seen where all four pins are cathodes or anodes, and the heatsink is the anode/cathode depending on the pins... I suppose this is possible. Then maybe the job's done already with the pins shorted to the heatsink?

[budm]

Re: LED Diode repair help

It looks like it is 2-LED in parallel in one package, the big pad is the Anode where the die is attached to to dissipate the heat to the strip.
What is the Vf reading of the good LED?
Can you remove those two terminals to expose the solder pad?
This is how I removed the bad LEDs:
https://www.badcaps.net/forum/showpo...&postcount=255

[stj]

Re: LED Diode repair help

looks like 3 things in the package actually - i wonder what it is.

[budm]

Re: LED Diode repair help

I see two large dots and one small dot.
The third one may be the protection diode which is connected in anti-parallel fashion.

[Brian_STI]

Re: LED Diode repair help

These have traces, the aluminum is just a heat sink. The traces are visible in the last picture, one on top and two on the bottom. You can trace these from the board input. The best way to remove these LEDs are with a hot air station, I heat up the underside of the board then heat the LED side of the board while holding the LED with tweezers.

These LEDs will be in series, so right now the strip will not work. You need to complete those traces to complete the circuit.

Source: I have fixed well over a dozen bad panels in several brands of TVs.