Chosen Solution
The backlight of my Mackbook pro A1502 model is not working. Earlier it used to come on after closing lid and opening again. Now it has completely stopped. However display works perfectly on connecting to external monitor. I had given it for diagnosis at apple center and they said it was logic board issue. I have opened the mac and seen but i am not sure where the wled chip is located in this model and what is the chip number?. I have bought WLED chip LP8550 but not sure if that chip is used in this particular model I am really stuck on this issue for more then a month now :(:( any help would be highly appreciated.
@deepalip5 this answer is not to diagnose your backlight failure. It is to show you the fuse and the WLED IC. The reference designator is F7700 for the fuse and it is a 3A 32V fuse in a 0603 package and the driver is U7700 and it is a LP8548B1SQ_-04 IC. Start with that and see what voltage etc. you find when checking your board. You are looking for 2.7V to 3V on pin 17 and 5V on pin 5 and 18 of the WLED driver. you also want to check the voltage on pin 1 of the LCD connector. Let us know what you find in case somebody can help you out more. Or of course, like Bradley suggested just get a logic board ;-)
From the sounds of it apple is correct and it is the logic board, I have dealt with a few of these, most of them from liquid spills, although apple would have told you if it was a spill when they opened it. I think a new logic board may be in your future.
Same problem. A display corrected the issue.
