820-3787 No backlight or image

[PPVCC_S0_CPU]

no liquid damage, board is clean and no signs of corrosion, display comes on external monitor but its no image or backlight on lcd, checked l8300 and lcd_bklit_en_l is 12.40volts, so no voltage is passing it, r7742 is 0 volts, so i removed it and hooked that line to pp3v3_s5 and then backlight started working, but there is no image..can it be u9600, i have already replaced u7701 and u7750.

 

[2informaticos]

PRAM reset done?
Post voltage at J8300, pins 9 and 28/30.

 

[PPVCC_S0_CPU]

Pram reset done,
pin 9: 0v
pin 28,29,30:5v(even without lcd connected) i have seen in other board that pin 28 goes high for few seconds then it goes low, but this one stays at 5v all the times

 

[2informaticos]

Pin 9 should go high.
If not, 28-30 should also drop...
HPD signal comes from LCD, so check another known good assembly from same year.

 

[PPVCC_S0_CPU]

Yeah, tried with 3 good lcds from same, but same result, removed u9600 and its pin 1 is corroded on chip itself, i have a board with same number, can i replace it from there?

 

[2informaticos]

Yes, it has firmware, so needs donor board same model.

 

[PPVCC_S0_CPU]

Tried it, still same issue

 

[PPVCC_S0_CPU]

Hi, it was l8300, that fucker had 5 volts on one side and 2 volts on other. Replaced and machine is working fine now