Hello. I have A1990 emc 3215 (820-01041-A) macbook pro. Apple logo comes on at startup. I come to the password screen. After I enter the password, the desktop does not come on. There is a light on the screen, but there is no image. displays an external display. Does anyone know about this problem? There is no liquid damage on the motherboard.
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Re: Macbook pro 1990 help
Try pram reset.
Check if there is a mux on the video signals. Check the voltage of the select pin of the mux.
Check voltage of the lid. This is a hall effect switch in the trackpad.
Test without the trackpad but use an external keyboard and mouse. -
Re: Macbook pro 1990 help
Thank you for the reply. I tried pram, no result. During the software, it displays on its own screen, comes up to the user password, after that, there is no light and image on the screen. Which pin number should I check?Comment
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Re: Macbook pro 1990 help
Since you do have the display working during boot, first confirm that the issue is not software related. Try to do a boot from a USB key or internet. See if the graphics appear normally. In this case, the OS is corrupt.
Otherwise, review the mux at U9850 to check the voltage of GPU_SEL (R9819) to ground when the display is working and after the display is not working with your login.
Suspecting the fault is software related.
See here for more details of this mux:
https://repair.wiki/w/A1990_2018-201...ar_MacBook_Pro
* see no image
Do attempt to boot another OS image first.Comment
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Re: Macbook pro 1990 help
I'm trying now, after the password screen, the image goes out, I see a light on the screen. When I close the cover of the screen and lift it, the desktop comes and stops and goes again. It's like a sensor is kicking in.Comment
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Re: Macbook pro 1990 help
Perform a SMC bypass and test again:
https://logi.wiki/index.php/SMC_Circ...%20max%20speed.
https://www.ifixit.com/Guide/How+to+...ar+2018/113258Comment
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Re: Macbook pro 1990 help
Since it is a 2019 model, SMC does not reset. I can pram but the result is the same. When I lower and lift the screen, the desktop comes, waits and goes, the light continues. I installed a new system from external usb catalina but same result.Comment
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Re: Macbook pro 1990 help
Review this article, you should be able to perform the SMC reset:
https://osxdaily.com/2019/01/14/how-...ro-2018-later/
Closing / opening lid is the lid sensor in the trackpad.
Check the voltage to ground of IPD_LID_OPEN.Attached FilesComment
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Re: Macbook pro 1990 help
The 4 pin IPD_LID_OPEN R5102 resistance of the cover sensor goes, and 1.8v goes through both measurements when there is an image on the screen and when the image is cut off. I get 3.38v when the screen is on and the screen is gone in the R9819 measurement. I try SMC reset but the result is the same.Comment
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Re: Macbook pro 1990 help
I reinstalled the software but the result did not change.Comment
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Re: Macbook pro 1990 help
Once you are at the login screen, if you close / open the lid, does the display continue to function ok?
If you close the lid, the display turns off?
And then on, when open, everytime?
After you login and the display is off, take a flashlight or phone in torch mode and apply to the front face and sides. Can you see the usual graphics? The backlight maybe the fault if you do.Comment
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Re: Macbook pro 1990 help
During the software, the screen works smoothly. When I come to set a password, the screen goes out and I see a light. I connect it to the external screen and finish the installation. When I restart, there is an image on the screen until the password screen. When I close and open the lid, the screen comes on and after 10 seconds the screen goes out again. when i hold the phone light, nothing shows up, it's not related to the backlight. I can dim the screen light from the touchbar, but unfortunately there is no picture.When I close and open the cover, the image comes on and goes out again.Comment
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Re: Macbook pro 1990 help
Hi . The problem is in the lcd board. the motherboard was tested with another display and the motherboard is OK. At the end of the installation with the screen on the motherboard, when the motherboard recognizes the screen, the screen turns itself off. When I open and close the lid, the screen comes on and goes out again. In the card section under the lcd, which integrated do you think is causing this problem?Comment
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Re: Macbook pro 1990 help
So you have confirmed that this motherboard with another display works without this fault?
The issue is with the display only?
Is the display the correct model for use with this logic board?Comment
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Re: Macbook pro 1990 help
Yes, the problem is the screen. I have now repaired the bottom board of the screen and it is working properly. Thank you for your support my friend.Comment
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