A1990 2019 touchbar weird behaviour

[arashmoayyedizadeh]

Hello to all of you engineers
i have a macbook pro a1990 in no power condition
another shop had done some works on it with no success (pm ic was reflowed, a little bit of flux around one of the type c rom ic, changing the charging ic)
initial state: 5v 0amps on all 4 type c sockets
after some inspections i realized the charging ic that another shop installed is isl9239
I changed it with right one (isl9240) and the machine turned on and booted into macos
weird behaviour:
Lcd works ok until it boots to os and as soon as you see login page it goes black but if you connect to external monitor both internal lcd and external monitor work very fine,if you disconnect the external monitor , after a couple of seconds the lcd goes black too
reconnecting the external monitor doesnt work any more untill you turn off and turn it on again (it should be connected during boot)

What i did: reprogram the type c rom ic that i mentioned above (it was identical with good dump and may be just was reflowed)
perform a dfu restore successfully
re install latest mac os on device (during installation it was ok until the section you should insert information and costomizing os and in this moment lcd went black
i connected to external and both internal and external was ok as i mentioned and i completed the instalation
So far the problem persists

I would really appreciate ane guidence or clue
thank you very much

[reformatt]

Lid sensors checked?

[arashmoayyedizadeh]

Lid sensors checked?

Yes, lid sensors are ok
i booted the machine into safe mode and lcd worked perfect , closing the lid will put the machine into sleep and it will be ready as soon as you open the lid
in normal boot another thing i realized is: only the image will go blank , the backlight is activated an on
i dont know why the lcd works perfecf in safe mode

[reformatt]

Being an A1990 it has CPU and GPU graphics and sounds like one isn't working properly when it's flipping from one to the other or or when the kext is loaded. The MUX chip comes to mind (U9850) as that's commonly damaged when you have liquid damage in the LCD connector. Might be a bad GPU.

[arashmoayyedizadeh]

Being an A1990 it has CPU and GPU graphics and sounds like one isn't working properly when it's flipping from one to the other or or when the kext is loaded. The MUX chip comes to mind (U9850) as that's commonly damaged when you have liquid damage in the LCD connector. Might be a bad GPU.

Thank you so much
The interesting thing is when the external monitor is connected you can use all the options in display settings (main,extend,mirror) without any problems
btw i will do some inspection around u9850 and will inform you if i find something

[arashmoayyedizadeh]

Today i was searching around and i realized that macbook pro uses discrete graphics when you connect it to external monitor (amount of graphical load doesnt matter) and when you disconnect the external monitor it will be switchable due to load

I was thinking in my case may be an issue with igpu , so i diged deeper and found a terminal command that will set gpu on discrete mode permanently

Guss what !!!!

The image didnt go blank and now the machine works very good on its internal lcd (with or without connecting to external monitor)

In this way consequences are: more heat and faster battery drain

I will appreciate if something comes to your mind