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Model A1502 / 2.4, 2.6, or 2.8 GHz dual-core Intel processor / Released October 2013

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OS X Big Sur lost afyter battery replacement. HELP!

Following your excellent video to the letter, and being used to working with electronic domestic appliance repairs, I found after calibration the Mac shows the grey '?' file. Apple Support advice did not fix the problem. It seems I cannot reinstall from Time Machine as there is NO OS X Big Sur to reinstall. Various fixes just could not find it, or the link I needed was greyed out. Is my Mac now terminal, or can I install from a disk? Your help and advice woud be much apreciated.

Thank you.

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If the Time Machine copy is complete you should be able to boot up under it. With the drive plugged in, restart and press the Option (⌥) to get to the startup manager so you can select it. Then go to the App Store using the link from here Big Sur

Reference Mac startup key combinations

If that fails you’ll need to use internet recovery to first format your replacement drive and then reinstall the OS. This gets tricky! As you’ll likely get the older OS that came with your Mac which will require upgrading. After you get the system working you’ll need to get Big Sur from the Apps Store and go though the upgrade process.

Reference How to reinstall macOS

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