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Hello! I have a mid 2015 MacBook Pro 15’’ with Dual Graphics. I stumbled upon a display whose backlight no longer works. I’ve performed an SMC reset and NVRAM reset, but they did not help. The logic board had been replaced with the one provided by iFixIt, so I suppose that the logic board may not be an issue. The LVDS cable that connects the display does not show any signs of corrosion or damage. I also wanted to point out that the MacBook doesn’t seem to detect any monitor I hook up to via HDMI either. I don’t have a Thunderbolt 2 compatible monitor yet to see if it’s also being detected. Did parts of the I/O board became faulty? Was the display the issue all along? UPDATE (12/2/19): Here are two pictures of the display connector and its socket:
I also shined a light source at the Apple logo and I can confirm that there is something being shown on the display.
One issue I’m currently facing is that the HDMI port doesn’t want to output anything, although the external monitors that I use do detect the MacBook. Haven’t tried the Thunderbolt 2/Mini DisplayPort yet.
Sorry for not seeing your question sooner The retina series have a complex video mux logic to send the video signal to multiple pathways. You have the internal display, but you also have two Thunderbolt ports and a HDMI port. For starters you do need to validate if the video signal is working properly. What happens when you use the HDMI connection? What happens when you use a mini DisplayPort connected display to the Thunderbolt ports (or an adapter to VGA display) As far as your backlight issue with the internal dispaly you really need to check to see if the video signal is even getting to the display. Take a flashlight and aim it through the Apple logo on the backside of the display it will allow you to see a faint image of your desktop and its icon’s do you see them? If you do then you know the display is getting its iDP (also known as eDP) signal this is a very different signal than the older non-retina systems which use LVDS. The backlight logic is on the main logic board. Things like liquid damage of the video connector and the area around it could effect things. A damaged display connector is also a possible issue. If you can disconnect the battery and then disconnect the display connector taking some nice tight in focus pictures of the cable connector (both sides) as well as the logic board connector and the area around it. Post them here of us to see Adding images to an existing question
