820-3437-B no back light

[Dewanbd]

This was pure water damaged around video connector and some other place too. After ultrasonic turn on but no backlight.
Backlight out was 8.5 v so
Changed bklight driver and got the back light back but after few minutes again bklighet gone. changed bklight driver again

now bklight out is 20.9v. Bkl-EN=2.8v, bkl-pwm=1.46!!!!

but no backlight. I did all reset and this is good know screen. what next, any help please?

 

[2informaticos]

I recommend to reflow U7701; bad solders I think.
Be sure to have good continuity from A5 ball to D7701.

You can also make a "force" test.
Remove R7704 and bring BKL_EN to C7704.
If you get max backlight, then turn off and do PRAM reset.
Next, restore the board components and check if it works...

 

[JohnB8812]

20 volts should be backlight. Replace driver again MAKE SURE it’s soldered well

 

[2informaticos]

20V is insuficient; can only get very dim backlight, almost nothing...

 

[Dewanbd]

Replaced again bklight driver and fix the path A5. Thanks a lot, you guys awesome.