How do you connect the power to the Arduino directly from line power? So the printer can be turned on and operated from the LCD without using the USB? Of course the USB option must still be there.
The only way I know how is to use a PC PSU. It is supported in Marlin.
USB is not required, it runs off printer p/s.
Same issue here. When I have the usb connected, the system seems to work ok, but when I pull the plug the LCD shuts down
Sounds like you have blown the 5v regulator on the Arduino board. Very common issue as they are not spec'd very well. Same with the authentic units.
So a late followup, but yes fixing/changing the mega's regulator fixed the problem. Imagine that - ever since I started printing this had never worked and it was such a simple solution.
