I finally got around to check what happened to the Sam440 computer and opened up the PSU to at least check the fuse. Seeing the light show I had it probably was not something a fuse could have handled. And indeed it looked very much beyond repair:
I cannibalized the PSU of my AmigaOneXE system and voila:
You can imagine I cheered when the computer came back on :-) And now back to work.