Mac mini not booting, no safe mode, no recovery, no target-disk-mode, etc.
My Mac mini (mid 2011) is not booting. When I try to start, the power light turns on for about a second en I hear the disk spinning up for 5 to 10 seconds. Then it spins down again. There's no apple logo, no startup-chime-sound. It doesn't even gets far enough in it's boot-cycle to start up in safe-mode, recovery-mode, target-disk-mode or try to reset PRAM/NVRAM or SMC. (using a wired keyboard)
The last time I was able to get into recovery-mode by luck, I ran the extended hardware check. But no errors were found.
When taking the harddrive out and connecting it to my MacBook with a SATA-dock, I have no problem using the disc. Running some checks seem to point out that there is no hardware problem with the disk.
I also swapt out the RAM. No change.
Any ideas what could cause this problem and how to (try) fix it?
Thank you in advance for any suggestions.
Mac mini, macOS 10.13