Hi,
I have a old UR-6-85-5-A that has been running really well for a long time however yesterday we had a black-out and after that I cannot start the system up. When turned un i briefly see the universal robots logo but after five seconds the system turns it self off and I get a black screen. Is this omething you have seen before.? Is there possibly a fuse or something else I can check?
regards
It’s very likely the motherboard that’s faulty. There have been a lot of cases, where the CMOS battery on the old CB2s dies, which resets the BIOS when the robot is shut off.
Then the robot does not know which drive to boot from or to assign the touch screen correctly. 
You can read here how to fix it: https://forum.universal-robots.com/uploads/short-url/yGyv0osV4nsxl81Sx2xZ0JQtrhA.pdf