820-00923-A - Boot Loop

[GoodguyFR]

Hi !

This board come from a A1706, not turning on, that has been lightly liquid damaged, but at the wrong spot. Indeed, oxydation was on right side of U7210 (pin 1 to 5), and also on C7433, nothing too big here. The rest of the board was in good condition.

I replaced U7210 and C7433, then the Mac turned on, Apple logo for few sec, progess bar appeared and then froze for 10 sec. The MacBook boot loop, again and again.

I replaced U7430, I though it could have been also damaged, no change. Then I cleaned ME Region, no change. I replaced BIOS with know working one, no change, I put the original one back.

Last step, I put the board in ultrasonic cleaner, it could have crap under CPU, still same behavior.

What could cause a freeze while loading OS, and what could I check next ?

Thank you for your advises.

 

[2informaticos]

Any error pops up starting in diagnostic mode?
Also test if boots in safe mode.

Did you try Internet Recovery?
If there is important data, check if can save it in Target Disk mode.

 

[GoodguyFR]

I've tried none of these so far.

So, diag mode freeze after 1 minute, can't finish it, as the internet recovery. Boot in safe mode has same result as normal boot, crash immediately at the beginning of the loading. Finally, Target Mode does not work, I have 2 logos on target screen (power and USB), but nothing on host. I tried with 2 different official thunderbolt cables.

When the Mac is waiting for internet network selection in recovery mode, it is able so stay on w/o any problem, but as soon as I enter password and it start downloading OS recovery it freeze and shut off.

One more thing I did not mention before, I've tried the board in an other casing to rule out the possibility of bad screen, battery, trackpad or keyboard, same result.

 

[2informaticos]

Try full known good (clean ME) BIOS.
Corruption into pure BIOS area, can't be solved cleaning ME Region.

Also check if you can install Windows.
If yes, check if crashes after installing GPU driver.