820-00165 No backlight [solved]

[nik1981]

Hi I have a liquid damaged Air with no display.

I've changed over a slightly burnt LVDS connector, change a couple of ugly looking caps and replaced U7701 and tried another screen also.
I'm still getting no backlight and I'm stuck.

I'm getting a display though

8.5v on L7701 LCDBLT_BOOST
8.5v on PPHV_S0SW_LCDBKLT
2.8v on LCDBKLT_EN_DIV_L
3.2v on EDP_BKLT_EN
3.2v on BKLT_PLT_RST_L

R7717-R7722 all 0 ohm

On U7701:

PP5V_S0 on C7710 = 5.02v
BKL_EN = 2.8v
BKL_PWM = 1.45v
R7731 = 198k
R7715 = 91.6k

Any help would be really appreciated

 

[2informaticos]

Try 2-3 times PRAM reset first.

Did you inspect XW77200?
Some pictures available on the forum.

Be sure to get (very) similar diode mode readings on all return resistors.

If still the same, remove R7704 and run a wire from C7704 to R7715.

 

[nik1981]

I searched XW7720 on the forum but couldn’t find a picture of it.
I’ve attached what I think might be the correct trace but I’m probably wrong.

 

[nik1981]

Yeah on closer inspection, I’d say that was f’d

 

[nik1981]

Fixed and I now have a backlight. Thank you @2informaticos