820-3115 video issue

[jgraffis]

I've got this 820-3115 that doesn't post video on internal display. video works great threw the thunderbolt port. i can see that the back light is very dim and no picture. the machine did have very minor liquid damage around c3888 and r3880.

ppvout_sw_lcdbklt-- 27v
L9080 pin1 and 2 are 1.4v
pp3v3_lcdvdd_sw is 3.32v
pp3v3_s0 3.32v

i have changed the lcd connector as i had the pins smash and touching each other.
not sure what I'm missing any ideas would be great.

 

[jason_microsoldering]

Is the screen white or black?

 

[2informaticos]

27V is sufficient for normal backlight.
You probably have problem with LCD connector, video cable or display itslef...
However, check return resistors.
NVRAM reset done?

 

[jgraffis]

screen is black. have already changed connector, lcd cable and screen already swapped from known work machine. ill check resistors though. smc was reset and pram.

 

[dukefawks]

Measure all LVDS lines on diode mode

 

[jgraffis]

pin-1 0.0
pin-2 0.413
pin-3 0.413
​​​​​​​pin-4 0.311
pin-5 0.312
pin-6 0.488
pin-7 0.456
pin-8 0.457
pin-9 0.503
pin-10 0.00
pin-11 0.00
pin-12 0.056
pin-13 0.00
pin-14 0.00
pin-15 0.008
pin-16 0.00
pin-17 0.060
pin-18 0.106
pin-19 0.00
pin-20 OL
pin-21 0.565
pin-22 0.565
pin-23 OL
pin-24 0.606
pin-25 0.605
pin-26 0.604
pin-27 0.602
pin-28 0.602
pin-29 0.603
pin-30 OL

 

[jgraffis]

pin 12 pin15 pin 17 seem like problem with u1800