lcd only works when plugged into usb

Hi guys...I have a LCD 12864 Graphic Smart Display Controller

When I first built my printer I installed and set the controller up and it worked fine...It stayed on and worked properly.
Then one day I plugged my laptop into the printer as usual doing some tweaking and when i unplugged my laptop the lcd shut off. Now The lcd will only work when my laptop is plugged in via usb but as soon as i unplug it is as if I have lost all power to the lcd though nothing else seems to be affected. Unfortunately i dont remember what i "tweaked" as i was still a newb to printing. Could I have blown something by leaving it plugged in overnight? The controller still works as normal and has full functionallity when usb is plugged in...does anyone have any ideas whats wrong or more importantly how to fix it?????

you never said which controller so am assuming its the RAMPS 1.4?. if it is, is the D1 diode been added to the ramps. [www.reprap.org] scroll half way down there mention of the diodes

hi...yes its a ramps 1.4....but how would this diode cause the lcd controller to work for a few days and then kill the power when not plugged into usb??

One of the problems with Arduino Mega/RAMPS is that the voltage regulator in the Arduino tends to overheat if you add a load to the 5V rail, such as your GLCD. I expect that is what has happened. If so, you can get a new Arduino Mega (but the same thing will likely happen again), or remove D1 from the RAMPS and provide an external 5V power source to the Arduino and RAMPS.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

that sounds way above my capabillities lol...would a fan on the board help? Though I would doubt it if the problem lies with the arduino Mega, which is UNDER the ramps board....