820-3536 came back from the dead but no Backlight (although PPVOUT_S0_LCDBKLT = 52V?)

[george-a]

Hi guys,

this one came with with liquid damage with lots of corrosion near the SMC but rest of the board seemed unaffected. After UC I found a couple of broken lines and jumped them.

The system now gives green light, chimes, can see boot options with USB drive (the owner did not provide the internal SSD) but there is no backlight.

I measure PPVOUT_S0_LCDBKLT = 52,4V at pin1 of the LVDS connector.

I also booted with USB drive to Yosemite without issues and the external monitor properly shows the desktop.

Any ideas?

br,
george

 

[aprendiz]

52V means no load detected, could be a bad display cable and/or connector, do a continuity test from pin 1 of J8300 to the other end on the display cable....

If you use a flashlight are you able to see any image on internal display??

 

[george-a]

yes internal display shows image normally. just no BKL... I need to pry open the LCD assembly for that test right?

 

[george-a]

well after looking closely with the microscope the 1st pin seems loose... glad it didnt short. was not obvious with naked eye and also the connectors had no problem sliding in...

 

[aprendiz]

Just replace cable then and before you connect magsafe check for short on pin1 from J8300 just to be sure there is no problem inside the connector...

 

[dukefawks]

Replace connector AND cable!