Chosen Solution
I swapped out the mechanical hard drive in my iMac for an SDD, as the iMac was worse with the SSD (due to the 32gb NVME drive already installed for Fusion) I removed the SSD and put the mechanical drive back in. On doing so the iMac will now not display anything when booting off the hard drive, strangely enough though, it will display booting off the Bootcamp partition and an external drive with Windows 10 on it! So far I have tried…. A different display. Re-creating the Fusion drive (wiping the mechanical drive in the process). A different/new display cable. Trying to boot off an external drive with Monterey installed on it. SMC reset PRAM reset None of these things seem to kick the display back into life. I can get the Mac OS to work using an external display, but not the 5k display. As I’ve mentioned earlier, Windows works fine on the 5k internal display!! Any suggestions please, as I don’t think replacing the display will fix the issue (and is rather expensive to find out it doesn’t!)?
The drives partitions are getting you in trouble! You have two partitions the macOS and the BootCamp which is visible when you use a Windows OS drive. What is confusing you is the macOS partition is not one drive! It’s a marriage of two drives! With the newer macOS’s you need both drives present to access the volume. When you break the Fusion Drive set you can’t gain access to the HD’s macOS partitions data. To add to this Apple has altered things a bit so now so the blade SSD when present gets in the way when you replace the SATA drive as its expecting its partner to be present. Now we need to pull the blade SSD out. Basically, you need to fully remove the Fusion Drive set (both drives) to either replace the SATA HDD or blade SSD!
Press and hold the power button for about 10 seconds. Press and release the power button, then immediately press and hold Command (⌘)-R until you see an Apple logo or other image. If you still see a blank screen after about 20 seconds, contact Apple Support Regards, Will
