Chosen Solution
I installed a new screen, everything went smoothly. Boots up with no startup sound and it’s just a black screen. It’s a known good screen.
Aha! I had this problem the other day. Here’s how I got my screen to work again. With the MagSafe and the battery in, home the power button down for 10 seconds.Remove the battery and MagSafe charger and wait 2 secondsAfter 2 seconds is up, put the MagSafe charger in, you should get a spontaneous reboot. That somehow solved my issue with my MBP’s screen not working after replacement , hopefully it solves your issue.
