Hi, I am having a minor problem with the Polargraph. It draws fine from the sd card as long as the usb cord is plugged into my laptop, but as soon as I take the cord out, the drawing stops. I have the Arduino Mega connected with the Adafruit motor shield on top. I am using a 12V 1A power supply which is plugged in to the Arduino Mega. The jumper is still on the shield.

It used to work fine previously before I replaced my old mega with a new one. Everything else works perfectly. Does anyone know what the problem could be?

Also, I have noticed the the LEDs on the microcontroller itself is very dim when the external power supply is connected but returns to normal brightness when I connect the usb. I don't know if this helps in any way.