I had the idea to attach a Thunderbolt 3 drive (or an external SSD with an USB-C interface) to my iMac 27" Retina Late 2015.
So I took my Apple TB3-TB2-adapter, a TB2-cable and a LaCie Rugged Pro Drive as well as an Icybox USB-C Case with an SSD containing bootable volumes and happily tried all ways of connecting, putting plugs in and out an into each of the two TB2-ports. Whithout success, though.
Restarting to double check whether it might eventually recognize an external drive, my Mac would suddenly start in installation mode trying to reinstall Catalina on the internal volume (running on Catalina). This happened twice and I shut down the computer both times (forced by long power button press first time and then by unplugging the computer from the socket).
Since then, black screen, no chime, no boot menu. Checked RAM and reset PRAM/SMC, disattached all external stuff, tried all keyboard shortcuts. When pressing power button, it starts, after a second restarts, after 10 seconds restarts again, then it remains.
Can see some white LEDs from RAM tray, can hear something spinning in the upper left corner, USB ports power external devices.
Any explanations, anyone?
So I took my Apple TB3-TB2-adapter, a TB2-cable and a LaCie Rugged Pro Drive as well as an Icybox USB-C Case with an SSD containing bootable volumes and happily tried all ways of connecting, putting plugs in and out an into each of the two TB2-ports. Whithout success, though.
Restarting to double check whether it might eventually recognize an external drive, my Mac would suddenly start in installation mode trying to reinstall Catalina on the internal volume (running on Catalina). This happened twice and I shut down the computer both times (forced by long power button press first time and then by unplugging the computer from the socket).
Since then, black screen, no chime, no boot menu. Checked RAM and reset PRAM/SMC, disattached all external stuff, tried all keyboard shortcuts. When pressing power button, it starts, after a second restarts, after 10 seconds restarts again, then it remains.
Can see some white LEDs from RAM tray, can hear something spinning in the upper left corner, USB ports power external devices.
Any explanations, anyone?