I'm trying to use my Arduino Leonardo with an external power supply.
I tried various power adapters as shown here: http://playground.arduino.cc/Learning/WhatAdapter
One with 12V/1.7A, another with 9V/0.8A. Also a 9V block battery (http://playground.arduino.cc//Learning/9VBatteryAdapter
+ is in the center like it's supposed to be.
If one of these power supplies is plugged in, the L-LED on the board blinks a short time or sometimes not at all, and both LEDs (L and ON) flicker or are on constantly. After that nothing happens (the program on the board doesn't load). Connecting to the USB port or even a DC USB adapter works fine.
I tested it with another Leonardo board and it's the same, so it's not a problem with the board, I think.
Does anyone have an idea why none of these power supplies work?