Did you replace the hard drive or add an SSD card to the logic board? How was the drive formatted and system installed? What are the diagnostic LEDs telling you?
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Was it this SSD? https://www.ifixit.com/Guide/iMac+Intel+21.5-Inch+EMC+2544+SSD+Replacement/28992
Did you replace the hard drive or add an SSD card to the logic board? How was the drive formatted and system installed? What are the diagnostic LEDs telling you?