820-00281 No image/backlight. But...

[ajdoc]

Very small liquid damage near jack connector on board.

When is turned on with charger I see Apple logo to 1 second and then there is no backlight. I see image. Can log in but no backlight.
As soon charger is disconnected there is no image on display. When charger connected again no backlight but image works.

Tested on external display and when charger is connected all works great on ext. display. Charger not connected and there is no image/backlight on ext display.

Any idea where start?

 

[ajdoc]

There is short to ground on backlight fuse (fuse not blown) so removed it and short in on F8400/1 which is PPBUS_G3

 

[2informaticos]

Let me guess; you are measuring continuity on a powered board
Cannot have short on PPBUS_G3H if machine works; even if backlight is missing.

Post SMC_LID value.

 

[ajdoc]

Got 3.40V on J4501/1

D8410/K at 0.2V
F8400/2 at 12.95V
R8442/2 at 0.00V

 

[2informaticos]

"I see Apple logo to 1 second and then there is no backlight"
Do you get backlight for 1s?

PRAM reset done?
SMC_LID measured with LCD connected and both situations, charger yes and no, same 3.4V?

What happens if start in SMC bypass?