820-3787 no backlight, LCDBKLT_EN_L: HIGH, LCD seems to be detected.

george-a

New member
Hi guys, this one just came in with very little signs of LD - the owner sais it was not spilled on. I UCed it before starting with it.

I measured:

LCDBKLT_EN_L to be HIGH which means Q7706 does not produce PPBUS_SW_BKL

LCD_PWR_EN is HIGH which means the LCD is detected (?)

Also PP5VR3V3_SW_LCD_ISNS is ok

PPVIN_S0_LCDBKLT at 13V

Also PP5V_S0_BKLTCTRL present at C7750 and R7743 - R7744.

There is continuity from R7700 to Pins 9 & 10 of U7701.

External monitor shows image without issues.


(Irrelevant question: This one turns on only when the battery is connected - is this normal behavior?)


Please kick me to the right direction. Or punch me or use a 9mm and aim the shoulder.


george
 

dukefawks

Administrator
First hold a flashlight to the Apple logo and check if there is an image for sure.
It only powers on from battery because probably you are not using a real 85W charger
 

george-a

New member
First hold a flashlight to the Apple logo and check if there is an image for sure.
It only powers on from battery because probably you are not using a real 85W charger


ok duke, checked with flashlight, no image. External monitor stil working...

also you re right I was using a 60W one, switched to the 85W and works ok.
 

george-a

New member
Check 5V on L8300 and to eliminate the LCD try a known good LCD assembly.

ok duke back to this one - 5V checks ok at L8300. Can the symptoms in this case explain a bad LCD? I am asking since I do not have a spare one at the moment but I can try and source one if there is meaning to it.

thank you for all your help.
 

dukefawks

Administrator
If there is 5V at L8300 I'm pretty sure there must be an image on the LCD, check again. LCD actually controls the backlight through serial bus to backlight chip. Before messing with the board you should eliminate a bad LCD assembly. Or if there is obvious corrosion on the backlight chip then you can look there first of course.
 
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