820-01814 Screen and touchbar flickering

[Sr. Robot]

Hi, got an 820-01814 with flickering backlight on both the LCD and the trackpad.

It had corrosion on C9081 and its PPBUS_G3H_SSD0_SNS line was blown.

C9081 is now replaced and the line restored.

I dont have another A1990 to try and see if its a hardware issue. I was wondering if its possible the two issues are related. Thanks

 

[2informaticos]

Start in diagnostic mode; lets see if any error pops up.
You can also discard software issue.

 

[Sr. Robot]

Diagnostics says no issues found. I also updated the OS, and tried in safe mode.

 

[2informaticos]

Check the lid signals, if stable.

 

[Sr. Robot]

Is is safe to test the motherboard without the fans? Since the fans seem to run through the keyboard, i am afraid of heating the CPU too much.

 

[2informaticos]

Don't worry, you have sufficient time for test, without fans.

 

[Sr. Robot]

LID_OPEN_RIGHT
LID_OPEN_LEFT
IPD_LID_OPEN
IPD_LID_OPEN_R

All stable at 1.8v

DFR_LID_OPEN_L stable at 0v

 

[2informaticos]

Test the machine starting in safe mode, w/ and w/o touchbar connected.

 

[Sr. Robot]

In safe mode with touchbar connected and disconnected theres no screen flickering

In regular mode with touchbar disconnected theres screen flickering.

The touchbar flickers in safe mode.

 

[2informaticos]

Just in case, try known good touchbar and flex.
Or test this one with other MLB.

Also check if screen flickers in Windows; after installing graphics driver.

 

[Sr. Robot]

On windows with driver installed theres no flickering on the screen. However, i erased the disk to reinstall and now it wont boot in to recovery (not even with option+command+R), it gives error -2003f.

In DFU mode it gives me a padlock symbol, and of course it wont let me boot from USB. The mac didnt have any icloud account

 

[2informaticos]

Did you try both revive/restore in DFU?