Hi again.
I'm working on a 820-00165 with no backlight.
Originally came in with signs of liquid ingress, primarily around F7700 and U7701 areas.
After cleaning, I've confirmed its working on an external monitor, and can faintly see the image on screen, so its outputting data, just no backlight.
Tried with two known good panels.
All measurements are with screen connected to J8300.
Backlight fuse F7700 is OK.
Only getting 8.6V on F7700, and, according to your sticky "Macbook Air no backlight troubleshooting guide":
"If you have 8.5v on backlight, that means no boosting is occurring. This can be bad LED driver, this can be feedback line from backlight output to ball A5 of the LED driver for feedback being destroyed(VERY COMMON). Also BKL_EN voltage divider being bad - you need at least 2.7v on BKL_EN or you get no boosting and wind up with 8.5v on backlight, which is just PPBUS_G3H being passed through the circuit."
I've replaced the LED driver, with no change.
However, I just noticed that BKL_EN is 0 Volts.
R7730 is 200 Ohms
R7715 is 100 OHMs, both as per schematic...
As BKL_EN shows 100 Ohms to ground, it is not shorted to ground.
PPVIN_S0SW_LCDBKLT must therefore be missing, I'm assuming?
I'm a little confused as to the source of BKL_EN - there is only one single reference to it in the schematic.
It appears to be created by PPVIN_S0SW_LCDBKLT.
Any suggestions appreciated.
I'm working on a 820-00165 with no backlight.
Originally came in with signs of liquid ingress, primarily around F7700 and U7701 areas.
After cleaning, I've confirmed its working on an external monitor, and can faintly see the image on screen, so its outputting data, just no backlight.
Tried with two known good panels.
All measurements are with screen connected to J8300.
Backlight fuse F7700 is OK.
Only getting 8.6V on F7700, and, according to your sticky "Macbook Air no backlight troubleshooting guide":
"If you have 8.5v on backlight, that means no boosting is occurring. This can be bad LED driver, this can be feedback line from backlight output to ball A5 of the LED driver for feedback being destroyed(VERY COMMON). Also BKL_EN voltage divider being bad - you need at least 2.7v on BKL_EN or you get no boosting and wind up with 8.5v on backlight, which is just PPBUS_G3H being passed through the circuit."
I've replaced the LED driver, with no change.
However, I just noticed that BKL_EN is 0 Volts.
R7730 is 200 Ohms
R7715 is 100 OHMs, both as per schematic...
As BKL_EN shows 100 Ohms to ground, it is not shorted to ground.
PPVIN_S0SW_LCDBKLT must therefore be missing, I'm assuming?
I'm a little confused as to the source of BKL_EN - there is only one single reference to it in the schematic.
It appears to be created by PPVIN_S0SW_LCDBKLT.
Any suggestions appreciated.
