820-3787-a (a1398) no display

[dam1inc]

have a 820-3787-A with no display.
no signs of water damage.
On the LCD FPC (J8300)
PPVOUT_S0_LCDBKLT is missing
PP5VR3V3_SW_LCD = 5V

Q7706
PIN 4 -PPBUS_SW_LCDBKLT_PWR = 12V
PIN 3 - LCDBKLT_EN_L = 12V
PIN 1,2,6,5 - PPBUS_SW_BKL = 0.065V


Followed PPVOUT_S0_LCDBKLT to Q7706 and a few pins aren't getting the proper 12V and so im not sure if Q7706 is bad or if PPBUS SW BKL is generated somewhere else. the schematics are a little confusing as i'm not sure what is Q7706 and how it works. If anyone can give me a quick explanation i'd really appreciate it.

thanks

 

[dukefawks]

Is it no backlight or no image? Hold flashlight on Apple logo and check that first.

 

[dam1inc]

oh sorry its no backlight

 

[dukefawks]

PRAM reset done? Correct LCD assembly? For testing you can use 2012-14 LCDs, 2015+ is different!

 

[dam1inc]

Yes PRAM reset done and just tested lcd with another board and lcd works.

 

[2informaticos]

Check resistance to ground on both sides of D7701.
Also check if D7701 is not shorted.
Q7706 requires 0V on its Gate to work...
Measure BKLT_EN_R on U7701, also VDDD/A.
Keep LCD connected when you measure backlight area.

 

[dam1inc]

PPVOUT_S0_LCDBKLT is short to ground. all caps look good does that mean d7701 is the issue?

 

[dam1inc]

FPC Connector was shorted, removed and short gone, need to order this part. thanks guys, i really appreciate it...