I have a 12 volt supply that does 2.5 amps. When I plug in the supply the Pi never seems to try and boot (no text is shown on a connected HDMI monitor in fact the monitor claims there is no input signal). If I disconnect the 12 volt supply and power up the PI by the Micro USB the Pi will boot all the way to the bash prompt.
I suspected the power supply was the problem but I have tried 5 different power supplies and all behave the same way.
Any ideas on how I should trouble shoot the boot problem?