ytesfay80
Member
This board had liquid damage in the area of the LCD Connector and had no backlight. I cleaned up the area and replaced all the components around it. Fortunately the other side of the board is spotless including the LP8550 area. I ended up having to replace the screen and I also replaced the LCD connector. Now I am getting 8.55v on Pins 3/4 of LCD connector and I can see the question mark folder.
I noticed that BKL_PWM was 0.17v so I plugged the keyboard in and did a PRAM reset and it went up to around 1.6v. It seemed like the screen was less dim and I could see the question mark folder better. I tried putting the brightness up with the keyboard and that didn't work.
I removed R7704 and ran a wire to C7711 and 3v now is on BKL_PWM but still 8.55v is on backlight.
This board is a little different from the 820-3437 so I'm not sure how I can check if the feedback trace is fine. The feedback ball and the entire chip look perfect. Here are some more measurements
C7799 in diode mode - 0.614v
Pin 1(D7701) in diode mode - 0.419v and Pin 2 is 0.614v
BKL_EN - 2.85v
SMC_LID - 3.4v
There is continuity from Pin 2 of D7701 to Probe 1155 on the other side of the board
I noticed that BKL_PWM was 0.17v so I plugged the keyboard in and did a PRAM reset and it went up to around 1.6v. It seemed like the screen was less dim and I could see the question mark folder better. I tried putting the brightness up with the keyboard and that didn't work.
I removed R7704 and ran a wire to C7711 and 3v now is on BKL_PWM but still 8.55v is on backlight.
This board is a little different from the 820-3437 so I'm not sure how I can check if the feedback trace is fine. The feedback ball and the entire chip look perfect. Here are some more measurements
C7799 in diode mode - 0.614v
Pin 1(D7701) in diode mode - 0.419v and Pin 2 is 0.614v
BKL_EN - 2.85v
SMC_LID - 3.4v
There is continuity from Pin 2 of D7701 to Probe 1155 on the other side of the board
