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This board has problems when external Display is hooked up to Thunderbolt port. Internal and external displays stay black until you close and open the lid a few times. Then they both work properly.
I?m not sure what customer uses. I do have 85W.
I only have board and display for this one. I guess SMC_LID won?t work without housing or I could use a magnet somewhere?
Sorry, wrong information. Just got the board in front. It actually doesn't show picture when starting, but it does when lid is closed and opened a couple of times, while Thunderbolt is connected.
SMC_LID 3.42V with display only connected, outside the housing.
SMC and PRAM no luck.
Do I still have to try El Capitan? I don't see how that would be connected to no image and no backlight. I would be happy with a question mark folder screen.
Laptop starts with black screen, nothing can be seen using flashlight.
For backlight LCD_BKLT_EN is missing. Goes straight to U9100 (eDP MUX sheet). So something with MUX then since I see HDMI and DP involved on this sheet?
Understood now.
For the repair, continue with internal LCD only.
Check SMC_LID and voltage for pins 28-30 of J9000.
In the first few seconds, you must get 5V there; even without LCD connected.
If LCD is connected, LCD_HPD should go high.
Once LCD is recognized by PCH, all these should stay high and also image/backlight must come on.