Macbook Pro A1398(820-3787-A) Backlight problem

[2informaticos]

54V means no connection with LEDs strip.
Did you measure voltage at the LCD connector pin?
Be sure connector is not damaged and has good contacts.
Test with known good COMPATIBLE LCD assembly.

Just in case, do PRAM reser 2-3 times.

 

[Ictc]

Just digged around and found EDP_IG_BKL_ON =0
Is there a problem with the PCH? In wich situation this signal should be provided by the PCH?

 

[2informaticos]

If you get 54V on backlight output, backlight circuit is enabled and working.
Of course, EG_BKLT_EN is high, true?

 

[Ictc]

Yes EG_BKLT_EN is 3,3V as it should

 

[Ictc]

For your experience do you think the 13" display should have worked with this 15" logicboard as the pinout is the same? Am I assuming this incorrectly?

 

[Ictc]

PRAM reset didn't change anything.

 

[2informaticos]

"For testing, 13 and 15 inch retina screens of the same generation are compatible."
Did you test with 13" screen from same generation?

 

[Ictc]

Yes I did it but what sound strange to me is that the 13" display backlight works on the 13" MBP but not on the 15" one. I tought it should have worked on the 15" as well at least for showing backlight. If I connect the 15" display on the known working 13" MBP I also do not get any backlight. ???