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How do I make my microSD card writeable so I can reformat it? I was previously using it for time machine backups.

Disk Utility keeps telling me the partition has an issue and the disk is not writeable.

Also, windows says it is read only and I cannot format it on Windows 7 either. I tried Diskpart on windows and it just gave me errors. It seems I need to low level format it somehow to fix the partition table or find a way to force that operation.

MacBook Air

Posted on Dec 20, 2022 6:31 PM

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Question marked as Best reply

Posted on Dec 21, 2022 2:28 AM

Two things jump to me.


1 - Some MicroSD drives have a Slider Lock ' Unlock on the side of the MicroSD card.


If in the Locked Position - neither Windows for macOS can do anything except read from the card.


2 - MicroSD Cards are useful but Not for " I was previously using it for time machine backups."


Regardless of how big of a Drive Capacity it may have, MicroSD cards are prone to failure and are very unreliable for TM Backup drive


It is suggested to get a reliable External Drive with at least 2 1/2 Greater Drive Capacity than the Internal Drive of the computer and use that drive for TM Backups


Refer to link below


Time Machine Backup 


5 replies
Question marked as Best reply

Dec 21, 2022 2:28 AM in response to steve5n

Two things jump to me.


1 - Some MicroSD drives have a Slider Lock ' Unlock on the side of the MicroSD card.


If in the Locked Position - neither Windows for macOS can do anything except read from the card.


2 - MicroSD Cards are useful but Not for " I was previously using it for time machine backups."


Regardless of how big of a Drive Capacity it may have, MicroSD cards are prone to failure and are very unreliable for TM Backup drive


It is suggested to get a reliable External Drive with at least 2 1/2 Greater Drive Capacity than the Internal Drive of the computer and use that drive for TM Backups


Refer to link below


Time Machine Backup 


How do I make my microSD card writeable so I can reformat it? I was previously using it for time machine backups.

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