no screen backlight in MacBook Pro retina 820-3536-A
my macbook pro A1502 with motherboard 820-3536- A does not have backlight but it have video display.
pin 1 in display connector is 0V
pin 3 and 4 have 4.8V and 5V
i have been testing all caps, resistors, and fuses seems all are working fine.
F7700 is fine and is 12.6V in both sides
the issue that i see is that:
11.6 V in pin 3 (GATE)
12.6V in pin 4 (SOURCE)
0V in pins 1,2,5,6 ( DRAIN )
i dont know how much voltage it needs to open, but those voltages are what i am getting from U7700 ( backlight driver) hence line PPVIN_SOSW_LCDBKLT is 0V , it means zener diode, caps, resistors on that line are 0V because of Q7700.
checking Q7700 with multimeter seems is fine, it appears the drain is not open because U7700 does not send correct voltages to open it.
U7700 pin 5 & 18 have both 5V
SMC_LID is giving 3.4V which is ok, should be backlight
i have same measurement even if the display is connected or not.
i also dont have voltage in pin 2 & 4 of U7700 which is feeding Q7701 mosfet on pins 1,2,3 & 4 which are source and gate, hence it never opens
my conclusion is that U7700 and/or Q7700 may be the wrong components. ( mostly U7700)
do you have any idea what else can i check just to discard above components?