Chosen Solution
I am trying to fix an early 2015 13" MBP. Got it working (mostly) except on wake from sleep (or when rebooting during an install) I lose video output on the LCD. Backlight is on (verified by turning bringhtness all the way up, I get a light vertical display output from second lvds channel) If I don’t close the clamshell, use screen saver with “never sleep” timeout, it works fine (except needing hard power down if I update OS) Unfortunately due to cats who love walking on keyboards, I need to close the lid. I have tried: SMC and P/N VRAM resetunplug/replug battery (battery is “normal”)safe modebooting external SSD (same problem)reinstalling OSgoogling many hours for answers I suspect something with LCD voltage rails coming out of sleep, but I need to find the schematics and board view to check. I will try an external hdmi monitor, which I suspect will work, but that does not help with getting sleep working. Any/all help much appreciated, Bill
@mikronauts - Let’s back up here a bit… What happened on your repair journey? You talk about your cat loves walking across your computer is it possible it marked your system? As far as your video retina systems use iDP signaling while the cable is similar to the older LVDS cable the signals are very different like the older analog TV and our current digital TV signaling both use an antenna so we can’t assume the conduit is the same just like how water and gas both use pipes. As far as what the external display uses. It uses either DP or Thunderbolt connection (the video in both is DP) The logic board uses a MUX to spilt out the video to the internal and Thunderbolt ports. If you are getting a good external image via both TB ports then we know the issue is strictly within the internal displays path if it doesn’t offer a good image. As far as wake/sleep that is a different circuit which would need to be independently tested and repaired. While from the use perspective they do fit hand to glove they are not one in the same.
