Macbook Air A1466 - 820-00165 Display flickering

[miranda_ss]

Hi guys, first post here.

This A1466 - 820-00165 display starts flickering and blinking a few moments before the end of system bar startup running. When the login screen appears, I almost can't see. This is not happening with the external monitor. Tried a new display and the same happens. If I log in and activate the Colors filter, everything works fine again, but the screen gets dark if I don't touch the mouse or keyboard after a few seconds.

After a few days checking this board, I noticed that this flickers starts when vcore drops on both inductors L7310 / L7320. Any Idea?

 

[miranda_ss]

Thanks!

SMC_LID is 3.3v stable. Checked on R5171.
U7701 replaced, nothing changed.

No liquid damage, board is nice and clean.

 

[miranda_ss]

The backlight is working good every time, no instability. That was my first guess too.
The U7200 is where things are strange to me. CPUVR_FCCM, CPUVR_PWM and CPUVR_PWM1 are stable until flickering starts.

 

[2informaticos]

Do PRAM reset 2-3 times, also SMC reset.
Just in case, disconnect internal SSD and test with known good USB macOS.

 

[miranda_ss]

Made PRAM reset 5 times, also SMC, no news
Tested with known good USB macOS, no news
Tryed to reinstall on a new SSD, impossible. Black screen or image flickering after apple logo.

 

[2informaticos]

Be sure to use original Magsafe 2 charger.
Problem appears w/ and w/o known good battery connected?
Also test starting in safe mode and SMC bypass.

 

[miranda_ss]

- Used 2 different known good original magsafe 2.
- Yes, it appears w/ and w/o known good battery.
- No news in SMC bypass or safe mode.

Why that problem "go away" temporally when I enable color filter? What really change on screen?

This machine is really testing my patience!

 

[2informaticos]

Check all resistors and traces around U7701.
Be sure XW7720 is good.

You can try changing video connector; at least clean it.

If external video is OK, shouldn't be iGPU related.

 

[miranda_ss]

Thanks for your help, but its taking too much time and I give up. God bless y'all