820-3330 no display

[Yoel Ren]

So this came in with corroded lvds pin, pin 5, 37 and 38 and 40 blown away, but its okay right? Because pin 39 is still there. At first, there's image but no backlight, i tried to change lp8550 a few times but suddenly there's no display anymore, but macbook still turn on, connect to external video is working fine, so looks like not an gpu issue
Ppvout_s0_lcdbklt is 0v
Lcd_power_en 0v
I got 12.6 on both side of F7700
Pin 2 3 4 7 of lvds connector is 3.3v

 

[2informaticos]

Did you change LCD connector?
Also check if video cable has good connector.
Be sure to rebuild any broken trace.

 

[Yoel Ren]

Yeah i change lcd connector, the only relevant pad is pin number 38 and 40, but can I just make a solder bridge there?
Anyway the problem now is no image..

 

[2informaticos]

Do you mean traces for pads 38/40 on the board, or the pads of video cable?

Check continuity for L9000/10/11.

 

[Yoel Ren]

traces 38 39 40 is gone now, so i jump from c9000 to there..
continuity is good on L9000/10/11 , no o.L
I solder pp3v3_s0 to bkl_pwm , so I can bypass if gmux is the problem.., when i press lp8550, I have backlight, but still no image, but i will clean up the backlight problem once i have image later..
i notice the ddc data line r0910 and 0911 is 4.5k, should be 100k ,but when I solder known good 100k resistor, the value will become 4.5k again..

 

[Yoel Ren]

for info, i use 15 2011 style lvds connector ( the golden ones ) to this 820-3330 ( 15" 2012 ), and I use 15 2011 LCD there, because I don't have 15 2012 lcd , I have tried resetting pram everytime im testing.. sometimes I will have image, if image is present, backlight is usually present without me putting pressure on lp8550

 

[2informaticos]

I cannot locate R0910/11 into 820-3330 pdf.

Image must come on before backlight.
Do you always have 3V at pins 4/6/7 of J9000?
Be sure to have good contacts on LCD connector; try another LCD assembly.

 

[Yoel Ren]

sry I mean r9010 and r9011..i always have 3.3v at pin 4 6 7, i have used known good lcd assembly, and i have tried another..

 

[Yoel Ren]

i don have pp3v3_sw_lcd or lcd_pwr_en trying to enable when i plugged in magsafe.. pch?
r9010 and r9011is 67k and 100,5k, so good value, has continuity with the lvds pin

 

[2informaticos]

You should have some corroded traces, or bad contacts.
Be sure J9000 pins have contact with corresponding components.
Image should appear before backlight.
If PCH cannot communicate with display theough CLK/DATA lines, no image, nor backlight possible.
Be aware, all voltages around J9000 must be measured with LCD assembly connected.