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hi friends I have a iMac 27’’ middle 2011 with 2 disks one ssd evo 250 (A) and the iMac disk (B). Startup disk is the samsung evo 250(B) . I decided, to change samsung(A) because the fans made a lot of noise and restoring the imac in its former state. I isolated the ssd (A) and made a boot from an external hard drive that I had time machine copy, to put new system in iMac disk(B) . Then the problems started. At the start of the boot, black screen (the fans loud to maximum constantly) for 1min and 40 sec, after this time , the gray apple , the startup line began fast but in the middle to full slow, and when the startup line went full, again black screen and the fans to loud. When i hit on keyboard any key, I hear a Basso sound I tried with ⌥ , I saw the disks but when boot, the same I tried with ⌥ +R I saw after 1 min and 40 sec the earth but after black screen I tried PRAM, first chime, the second chime after 1 min and 40 sec and the 3d 2 min Today I have isolated both disks, but the problem remains. I ask for your help.(sorry for my poor english). Nicolas
OK! So we have a dual SSD drive setup. You swapped out the HDD for a SSD and added a second SSD under the optical drive. So your issue is the fact the HDD has a thermal sensor the system needs to manage the systems cooling. As you took the drive out you’ll need to put a replacement sensor in. Here’s the needed part: OWC In-line Digital Thermal Sensor for iMac 2011 Hard Drive Upgrade
