820-3747 BKLT_PWM Low.

Ryanlen2

Member
Macbook air no backlight with no real history. Board has been cleaned with liquid indicators tripped.

There is an image on screen, just no backlight

BKLT_PWM (With Screen) - 1.47V

BKLT_PWM (Without Screen)- 2.6V (without screen)

BKLT_EN - 2.7V

Changed driver with no change. Also replaced r7704 and c7704 with no change.

Diode mode on BKLT_PWM - .526

Should I assume bad CPU/PCH on this...?

Thanks!
 

JohnB8812

New member
Nah I don't think so. What voltage are you getting on backlight currently? Also diode mode on backlight output?
 

2informaticos

Administrator
Staff member
Check continuity between D7701 and A5 ball of U7701.
Pay atention to XW7720 bridge.
Search the forum for that and you will find some recent threads with detailed explanations...
Post voltages for D7701 pins.
 

Ryanlen2

Member
There happened to be a slight crack on pin 1 side of L7701. No sure how that would cause BKLT_PWM to be low, but it works.

Thanks, have a good one.
 
Top