Chosen Solution
Hello guys, first of all, I’m an idiot. I have replaced the keyboard on this MacBook Pro but made a terrible mistake while doing it. When connecting the display cable, the bar of the cable made contact with the connector itself and shorted it. that resulted in some smoke in the area of the first couple of pins on J9000 after turning it on. Now the system turns on but it doesn’t show an image on the screen or external monitor. After further inspection, I found out that U9000 doesn’t put anything out on pin 4/5. it receives 3.3V on pin 2/3 but LCD_IG_PWR_EN shows 0V. J9000 to gnd: 1:2:0V3:0V4:3.31V 5:6:3.28V7:3.28V LCD_IG_PWR_EN seems to come directly from U1800. Has someone an idea on how to continue?
You’re right, enable signal comes directly from U1800. There’s not much to do other than replacing it.
Ok so a few things: Have you tried a known good screen? If so, do you have an image if you shine a flashlight through the Apple logo? If YES, then what is your voltage on PPVOUT_SW_LCDBKLT? If NO, then do you have 3.3 volts on both sides of L9004? If yes, my guess would be bad LCD connector. If 3.3 on pin 1 but zero on pin 2, then blown L9004. If 0 on both sides then troubleshoot back to U9000 to see if you get any outputs with the screen attached of course.
