I have an Arduino Mega 2560 board running a ramps 1.4 shield for a 3D printer. For some reason, I can only power the Mega with USB. It does not get power from the ramps shield and it also will not power on when plugged in to a 12v wall adapter. I know all power sources are working because I have a second Mega that works fine on all. What could I check on the Mega board to help figure this out. Other than being powered only by USB, everything else works as expected with no problems.

1 Answer 1


Looking at this Arduino Mega 2560 schematic, if IC1 or IC2 failed (assuming only one or the other is installed for a given board), then you would only be able to power the board using the USB port.

Looking at this ramps 1.4 shield schematic it is assumed that the RAMPS 1.4 shield is providing 12 volts through D1 to the Arduino Mega 2560. And that testing included using a known good Arduino Mega 2560 board with the RAMPS 1.4 shield board with good results. Thereby eliminating the possibility that D1 on the RAMPS 1.4 shield is damaged.

If these assumptions are correct, this reinforces the likelihood that either IC1 or IC2 has failed on the Arduino Mega 2560 board.

  • D1 sends power from the shield down to the Arduino. I will look into the IC's on the Arduino. Aug 6, 2016 at 6:49
  • st2000 In the bottom left there is the power section, where you can see that D1 puts 12V on the net labeled AM_Vin; this net is then redirected to the mega Vin pin. @JeffThomas follow the wires with a multimeter, then share the measures..
    – frarugi87
    Jan 3, 2017 at 10:59
  • I will add a comments that it is assumed the shield is providing 12 volts through D1. And that it is assumed testing included using a known good Arduino Mega 2560 with the RAMPS 1.4.
    – st2000
    Jan 3, 2017 at 16:30

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