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Random black screen and difficulty to boot after a small fall

I dropped my 15″ MacBook Pro Retina mid-2012 from about 2 feet on the carpet while it was running. It felt flat on the screen side.

I closed it when I got it back from the ground and then I was unable to awake it.

The fall was so small that I didn't think one second it would damage the computer.

On the outside, there is absolutely no visible damage, the screen is ok.

Symptoms:

I am unable to wake it up systematically. I have to try 20 times before the screen shows up, the other times, the screen remains black

(the backlight remains off, I can see no light on the apple on the reverse side of the screen) but the fans are working.

After a reset of the PRAM (Command + Option + P + R key, I can hear the second startup sound) and SMC (Shift+Ctrl+Option+power button), I can hear the boot chime but most of the time, the screen is black (totally off, no backlight)

I have to force the shut down (by a long press on the power key until the fan off) and try again until the screen shows up.

I figured out to run the diagnostics tool (boot with R key) and it shows no issues.

Sometime, when it boots, the screen turns off during the loading bar.

When it boots properly, it looks like everything is working fine. I could do a full TimeCapsule backup on a USB drive.

I can close the clamshell with the machine awake, it goes to sleep, when I open it again it works few times until completely off.

Anyway, when it is running properly, after a variable amount of times (1 min to 2 hours), it finally goes to black screen (screen off, no back light, fan on).

Other details:

I went to an Apple authorized repair center, they opened it to check if the screen wire/socket was well fixed. It was ok.

They also tried to connect a monitor when the screen was black and the monitor was not working too.

They said that it is probably the motherboard (>500 euros) but I am not very sure about that as it looks like a bad connection of something.

I went back to my home and I bought the specific screwdriver to open it myself. Everything looks OK except one little magnet that was stick to the lower case.

I put a photo here: https://screenpresso.com/=1LP1c

I have put it back to its place but it looks like it was only there to hold the lower case. Can someone confirm ?

(is it the same as http://www.powerbookmedic.com/Macbook-Pr... ?) Do you think it can linked to the reed switch/hall sensor ?

The battery of the MBP works properly, there is no sign of failure on that side.

Somebody knows what is happening? Any clues ?

Thank you very much for your help!

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The magnet which fell out is just to support holding the bottom cover in, it is not related to the sleep/wake function.

If it is an issue with the MacBook thinking the lid is shut, the screen will not light up (as you describe) and the trackpad click will not respond, since this is disabled when the SMC_LID signal drops below 0.5v, when the lid is shut.

If the trackpad click is still responding (shine a light on the screen to check), it would indicate an issue most likely related to the trackpad cable inside the screen assembly. You will need to remove the assembly and remove the hinge cover, then wifi antenna. The wifi antenna covers the backlight cable and can partially hold the backlight cable in enough to light up the screen, but then sometimes cut out. This commonly disconnects when the MacBook is knocked or dropped.

If it is not outputting video, this more likely indicates the MacBook thinking the lid is shut. If this is the case, you would need to diagnose the logic board at this point, which is where it gets more complicated, and you will need soldering equipment, multimeter, schematics, board view, etc. Hope this helps :)

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Hi Reece, Many thanks for your response.

"shine a light on the screen to check" => The screen remains completely black so there is no video at all. When the pb occurs, the keyboard backlight remains even if I close the clamshell so it looks like the mac crashes. So I don't think now the lid switch is the problem.

When it starts properly, I can shake the mac (or move the screen) and it keeps running. However when I ask for a "restart", the screen is frozen 1 second (or display a small artifact) and it crashes systematically (screen black, keyboard back light on, fan on).

So I think the pb is not the screen itself.

da

Sounds like a GPU issue. See https://www.apple.com/uk/support/macbook...

Unfortunately you have just missed their cutoff, but if you make an appointment and get it to them ASAP, hopefully the will make an exception.

da

Thank you. I have contacted Apple support, I have to leave the MBP to an Apple Authorized Service Providers to validate the diagnostic and then contact them again to see if they make an exception.

da

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How can I fix this???

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JeanChristophe sarà eternamente grato.
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