To restore MicroSD card of Antminer S4,

Please download a bootable image
https://bitmain.zendesk.com/hc/en-us/articles/203558329-Jan-29-Image

Please use this software called HDD Guru Raw Copy Tool (Free)
http://hddguru.com/software/HDD-Raw-Copy-Tool/
http://hddguru.com/software/HDD-Raw-Copy-Tool/HDDRawCopy1.10Setup.exe


If you need assistance with step by step how to, please view below.
https://bitmain.zendesk.com/hc/en-us/articles/204339655-How-to-create-a-bootable-MicroSD-card-with-factory-setting-