Chosen Solution
I replaced the internal HD with a 1TB Crucial MX500 SSD and used the OWC Complete Hard Drive Upgrade Kit and NewerTech AdaptaDrive to complete the upgrade. This was the fist time I opened my iMac and I was careful to follow the steps from both iFixit and OWC. Got every thing back together but when it boots I hear the startup chime and only get a black screen and a very loud fan (never heard it that loud before). I’ve tried the following keys at startup: Option (Startup Manager, with a bootable USB thumb drive plugged in)D (Apple Diagnostics utility)Command-R (built-in macOS Recovery)Option-Command-P-R (reset NVRAM) But the screen never comes on. The new SSD should be fine — I used Carbon Copy Cloner to make a bootable clone of the previous internal HD and booted from the cloned SSD using an external USB enclosure to make sure it worked. Is there anything else I can check before I pull the screen off again and start checking connections? Once I’ve done that, what should I do to make sure it boots before sticking the screen back on (don’t want to keep buying adhesive strips)? Thanks!
iMacs have a very delicate video cable that connects to the logic board. I would say, hold down “Option” when turning on the iMac. If you still don’t see anything, not even a gray screen, it is highly likely that the cable is loose or damaged. Start with these, and maybe we can eliminate these as the issues. Also, the kit comes with the special hard drive cable with thermal sensor, so I am not sure why you are experiencing the loud fan, unless the cable isn’t in right or something else is wrong.
Not an answer but a question bc I have the same problem.Which connection is the screen’s cable? Is it the one near the ribbon? Would it not work if slid in up side down? That ribbon connection is the hardest and last one I do.
There are two connections: the Power and the LDVS Display connector. Disconnect the display data cable. This is a delicate connection that can easily be broken. Be sure to pull the display data cable connector straight out of its socket, toward the top of the iMac. Check the video (take apart) to view the how to. As this cable is 30 pin, you might put it in backwards, but the cable (attached to the Display) should not be twisted. Most likely you damaged that cable. There are small divots on each side that go “up”.
