A2779 no backlight, incomplete boot after replacing Display

[Dozer]

I got an A2779 which has a black display. External monitor works.

I connected a working display that works fine. of course it has the ghost problem.

So I thought the display was defective. I ordered two displaypanels then I disassembled a display of this series for the first time and replaced the two chips in one display

the angel sensor is connected and with the calibration tool i checked that it works

now I have different results.

1. foreign display
everything works except for the usual misrepresentations

2. display with original china chip without any changes
it comes the dong
backlight does not work
the apple appears, nothing more, it goes out. this is repeated a few times, then the circle with the exclamation mark appears

3. display with re-soldered original chip
it comes the dong
backlight doesnt work
the apple appears, the backlight does not work, it goes out. this is repeated a few times, then it stays off

now i have reflowed the two original chips again but there is no other result.

unfortunately there are so many factors that i cannot find out what exactly is defective.

i thought the display cable was faulty but when the apple comes it should work.
then i thought maybe the two chips are not soldered properly or defective but even then i thought could it not be the apple sign?

i thought with the display without changes, i.e. still with the chip from china, at least a picture and backlight should come, even if only as a ghost picture.

the device boots up fine without a display. until the keyboard backlight lights up i can click the trackpad.

with the original replaced chip variant, where only the apple is present, the keyboard does not light up and the trackpad cannot be clicked.


need some help please

 

[2informaticos]

The MacBook should boot with new screen, even without changing the chips.

I don't have any experience with these new screens...

 

[ronaldo]

Most likely it's a faulty LCD, a few times I found that numerous LCDs coming from China are faulty on arrival and cause all manner of issues; no boot, LCD test mode, etc.

The LCDs for 14"/16" Apple Silicon models are pretty much all factory rejects, could be as basic as colour temperature, to dead pixels, to not booting. I had to go through a few suppliers to find a good one.

 

[Dozer]

ok, i will try another one

 

[Dozer]

I now have a display from a known good supplier
The chips have not yet been re-soldered, the display is out of the box


the backlight does not come on

the dong can be heard

the apple can be seen after a few seconds it boots up again and after a few more attempts a circle with an exclamation mark appears. That's it.

All cables are plugged in, including the angle sensor.



with a display assembly from another device(from A2442) I get a normal picture with backlight etc on this A2779

has anyone already replaced a display like this? do you have to do anything else?

 

[Dozer]

I have now found out the following.

1. the displays A2442 and A2779 are fully compatible.

2. if I connect the good complete display to the patient mainboard, everything works perfectly. if I now unplug the backlight, I have the same as with the purchased displays. It does not boot

3. if I connect the good complete display ONLY the backlight and the purchased display then everything works perfectly.

my conclusion is that the backlight board is defective. i have now ordered a new one and will get back to you.