A1989 820-00850-A no boot

HI,

I have an A1989 820-00850-A that with the battery connected, it only shows 5V on the ampmetter, but without the battery, with the board only, it shows 19.5V on the amp metter and stays in the Apple logo and has no boot, and no progress bar.

Can you help?
 
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OK, thanks. I didn't know that.

Any USB-C to USB-C cable do it, or is a special cable? If so, can you give a link to any one?
 

2informaticos

Administrator
Staff member
Follow the tutorial...
 
No error, except the error / warning saying that a restore must be made, at the end of the restore / revive procedure.
However, right now, whenever i try do dfu again, i can't because it is stuck in recovery mode (but no image on scrren). Even when force shutdown, it always comes back in recovery mode
 
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2informaticos

Administrator
Staff member
Did you read this (recent post, no escuse)?
He managed to switch from recovery to DFU...
 
I haven't read it before.

However my problem is different, because i can force the DFU mode, from the recovery state. However, no recovery logo is showed, and when the restore is tried, it gaves an error saying:

"The system canot be restored on this device. Device added from an invalid state Restoring"

And then goes to recovery state again by it self
 

2informaticos

Administrator
Staff member
Try other USB cable, or use another T2 machine.
Test both Catalina and Big Sur on second machine, if you don't know what version was installed on T2 one.

Can you access it in Target Disk mode?
 
I can't do nothing on the mac.
The screen is black, and even when I disconnect the batery, i cant select disk or enter in the installation screen (complete black screen), and whenever i conect the cable to the other machine, it is alreay in recovery mode. The second machine, with the Apple Configurator 2, already is with Big Sur
 
After a while it managed to go to DFU (I don't know why), but when I do the DFU restore, after finishing, it shows a padlock logo and gaves an warning that says:

"Apple controller is not booted. Click restore to update the device to the latest firmware version. This cannot be undone."

When I do the restore again, it happends all the same
 
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Hi,
I always get the same error after the DFU restore:
"Apple controller is not booted. Click restore to update the device to the latest firmware version. This cannot be undone."

Shall i give up on it?
 
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