I have a UR5 controller and do not have DC controller power because the DC power supplies are not receiving AC voltage. The relays controlling the power to these boards are not switching on meaning I have AC power on the pole side of the relay but not on the supply side to the DC power supplies. There is a cable connected from this relay board to the I/O board, which likely activates the relays. There is 12 VDC to the I/O board. Question: Is this normal, meaning that removing AC power to the DC power supplies is the safety mechanism for shutting down the robot? Or, is this a problem with the I/O board? Any help is appreciated.
Perhaps you need to describe what is happening when you are observing this condition.
Start up sequence should look like this:
Plug in robot - no power on robot arm
release eStop - no power on robot arm
press power button on top of Teach Pendant (TP) face - no power on robot arm
press red button on lower left of TP screen - no power on robot arm
press ON on TP screen - 48V is applied to robot arm (power supplies are turned on)
press START on TP screen - brakes are released
press eStop - power is removed from robot arm
release eStop - power is reapplied to robot arm
If this is not how your robot is behaving, you should contact the UR service department for assistance using the myUR portal https://myur.universal-robots.com/ or contact your UR distributor for assistance.