Aporte original por: Wizbang FL ,
You may have inadvertently blown out a component with the 6tb hard drive as it isn't supported by iMac and the power requirements may be beyond capabilities. Also if you used a sata blade it would need to be positioned so that none of the soldered metal components make contact with external casing or other metal components within the mac (resulting in a short). I would check that all the SATA connectors are properly seated on the back of the motherboard and they have not been pinched during the prior installation. If one is pinched it will need to be replaced. The failure to have a tritone is an indication that the firmware is not communicating with one or more required components necessary to boot the system. (such as HDD, SSD, Video, etc) some components will result in a 3 beep sound indicating a problem such as keyboard, wifi, webcam are not connected. Have you attempted to boot from an external HDD (hold down alt during power on to obtain boot drive options.) Note that the first time you put new hardware in the iMac it will take anywhere from 3 to 5 minutes to inspect and identify the hardware prior to the tritone. I just upgraded my iMac with a SSD and it took 3 minutes before the tritone played and then took what seemed like a long time to actually start he boot progress bar. But after that initial boot it runs quickly. Hope this helps.