820-00850 Touchbar works on and off

[No-Clean]

Clean board, already tried 2 known good top cases and same behavior, touch bar light comes on and off, more off than on, touch seems to work even when there is no light or icons, sometimes when it works only about halve the icons/light works, but more often than not touchbar has no light at all most of the time.

J5100 and J5110 look clean, U5111 and U5100 are doing their work.

 

[2informaticos]

Keyboard backlight works correctly?

 

[No-Clean]

No, I just realized that when one fails the other one does too, the keyboard was replaced on this MacBook with aftermarket, but I tested this board on another know good top case and does the same thing.

 

[2informaticos]

Then you have a problem with the ALS, embedded into webcam circuitry.

 

[No-Clean]

Thanks, if I am understanding correctly this is not a board problem, but rather a screen issue since the webcam is part of the screen?

 

[2informaticos]

ALS I2C bus has two pull-up resistors (R5315/16), but I doubt that any fails.
Check them, just in case.

 

[No-Clean]

Both those resistors are fine, screen connector and cable are fine, screen looks good, what causes this issue? T2?

 

[2informaticos]

Try known good working LCD assembly; ALS is placed on the screen.

 

[No-Clean]

I put this board on a know good case, worked fine on first reboot, second reboot and same problems, I restored T2 and now I am installing clean OS to try, will report back.

 

[No-Clean]

I restored T2, installed macOS via internet recovery because it would not let me restore or bootup from USB, after I installed macOS (for some reason it downloaded and installed Mojave) but it did not work either, however when I was working on restoring macOS the keyboard light and touchbar was working, but not inside the user on Mojave, so I now installed Big Sur from USB and all is working fine.

Takeaways:
First try to revive T2 instead of restoring.
If you try to restore T2 make sure you have a backup since restoring bridge OS will erase all data.
After installing macOS via internet recovery make sure to then later update to the latest OS.

Thanks @2informaticos

 

[No-Clean]

I restored T2, installed macOS via internet recovery because it would not let me restore or bootup from USB, after I installed macOS (for some reason it downloaded and installed Mojave) but it did not work either, however when I was working on restoring macOS the keyboard light and touchbar was working, but not inside the user on Mojave, so I now installed Big Sur from USB and all is working fine.

Takeaways:
First try to revive T2 instead of restoring.

Have the Apple ID of the Mac handy or have your customer remove it from iCloud before restoring T2, otherwise after your restore it wont let you install macOS via internet recovery untill you enter the Apple ID and password of that Mac.

If you try to restore T2 make sure you have a backup since restoring bridge OS will erase all data.
After installing macOS via internet recovery make sure to then later update to the latest OS.

Thanks @2informaticos

 

[No-Clean]

Well machine is back again, same problem.

We have narrowed down to installing the cover, once the bottom cover is installed the touch bar starts to have issues and after a restart it will disappear, removing the cover and a couple SMC resets and it is back until cover is installed again, this is the second machine I have do this, last one I did not solve, this one since it is a second one and same problem then I will like to try to solve.

I understand that at this point this is not a board issue, and the forum may not be for this problems, but it will be nice to get to the bottom of this and solve it for future users of the forum, any tips are welcome.

I already tried covering some parts of the board with Kapton tape but no luck so far.

 

[2informaticos]

Look where the bottom cover can make pressure to MLB.