MacBook Pro A1398 820-3787 no video on display

Chip Chip

New member
First i want to say that this forum is awesome. Thank you Duke!!!

I am working on a 820-3787 board

When i start the machine i got no video. The backlight is there. The machine is booting but i cannot see a picture. When the machine boots i can hear a sound when pressing the enter key for example. This means that the machine is booting fine. There is no video on HDMI and no video on DP.

i meassured all the voltages for GPU rails. They are all fine. Don´t know what to do next. I know that there are two graphic cards and that the Mux is controlling them. But no idea how to make the next step.
I forgot to mention that the board is not water damaged and looks abolutely fine. No corrosion at all.

Any ideas?
 
Last edited:

dukefawks

Administrator
You sure the backlight is there, is the Apple logo lit up? If backlight is present the LCD should also work so I suspect a bad LCD assembly.
 

dukefawks

Administrator
Disconnect internal LCD and boot with LCD connected to DP port through VGA/DVI adapter. Should have boot screen then
 

dukefawks

Administrator
I still think a bad LCD. If backlight works it means eDP interface to LCD is ok. Find a test assembly for the correct year of the machine.
 

dukefawks

Administrator
Don't know how 3787 behaves with boot screen through DP. Sometimes the OS needs to fully load the drivers for it to work.
 

Chip Chip

New member
Ok, thank you Duke ! I´ll try to find a known good Display and try my best. Maybe even the HDMI is working only when the OS is fully loaded
 

Chip Chip

New member
OK, thank you Duke! I´ll try to find a known good Display for test. Maybe even HDMI is only working when OS is fully loaded.
Ohhh, i posted this twice.....hehe
 

Chip Chip

New member
Just an update...... When i plug the HDMI cable in i can see the extern LCD Monitor looks like the internal LCD. It´s just the same. You can see a black screen and it´s shining like the backlight from the internal LCD.
 

Glenn

New member
I hade the same problem with a3115 card and change the lvds connector after that i got pictures
 

Chip Chip

New member
Hello Duke,

ok, now i tested with a known good display. No screen. Than i tested my display on the other machine. Working fine. Now it´s 100% sure that the Logic Board is faulty.

Any ideas?
 
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