I’ve been troubleshooting and haven’t been able to narrow it down since it is an intermittent problem. Can someone tell me if the following assumptions are correct:
Following the circuit diagram, it look like:
Green power LED lights when EBB is connected to the computer (USB) and disconnected from the power adapter.
Green power LED lights when EBB is connected to the power adapter and disconnected from the computer.
When Inkscape is sending commands to the EBB:
Red LED lights when commands are being sent to the individual steppers. The red LEDs will still blink on and off during this process even if the power adapter is not connected.
The steppers hum when they are active but not moving.
Like you, I also suspect something is wrong with the power connection to the board. The plug on the power supply, the socket, or the connection between the socket and the board.