820-2936 no backlight

[Hermann Neupert]

Board is water damage, on inicial inspection I detect that R0910 is bad, I also replace the BL driver U9701, tons of crap under the IC.

Now I have 12.5V in PPVOUT_SW_LCDBKLT all the way to pins 21 and 22 of J9000.

Have measure all resistence around the driver and all readings are fine.

Line LCD_BKLT_PWM in 0V, not sure what value I need in that line.

Any ideas?

 

[2informaticos]

Do you have image, only missing backlight?
Do few PRAM resets first.

Post BKL_EN level.
If OK, then remove R9704 and run a wire from R9715 to C9704.
If still no backlight, post diode mode to ground on all (6) return pins of LCD connector.
Be sure both pins of D9701 have continuity to U9701; especially FB line.
Also check if D9701 is not shorted A-K.

 

[Hermann Neupert]

Mark as solved.

R9731 was bad and rolling me, because for some reason when I measure resistance it read 300K ohms, but BKL_EN was OV, now is 3V and BL is working fine.

As always thanks, was your suggestion what repair this mac.

Muchas gracias.