Arduino uno will not start

Arduino uno will not start sketch after removing USB cable with external 12 volt power supply connected to board.

Please tell us how you know the sketch will not start. Where did you connect the 12 volt power to the Uno? Do any of the LEDs on the Uno light up? What sketch did you down load?
Paul

Thanks Paul. From your reply I determined that I did not have a way to really know if the uno was working. So I added some led's and now I can tell that it was working.

Great news! Now on to the next step.
Good luck
Paul

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