Power supply if plugged into outlet always has power on +5(standby) routed on motherboard to the "power switch" and to keyboard. The standby voltage also enables the microcontroller in the Power Supply, hence if standby power circuit on motherboard is shorted then nothing works. Dumb question, you said this was cpu upgrade, so does the old cpu still work? How do you know the cables don't work?
Did you check for voltage in the sockets that don't work? When you changed cpu, did you remember to unplug the motherboard from all power (wall outlet, battery)? (Because modern power supplies still power the motherboard even when turned off.) Static electricity damage is likely working in an unshielded technicians'
workstation.