Lcd stopped working

Hello everyone my problem is.. I have 2 arduinos Mega and uno... I connect to mega leds buttons and potentiometers and connect to the uno lcd display... When I plug any arduino alone everything is very good but if i connect them together the lcd screen work 4-5 seconds and he stuck... I'd love to help I tried everything...

Thanks!!!!!

How do you power the two Arduinos and the LCD display?
If via USB cable it might draw too much current (LCD backlight is very hungry) and then the capacitors which stored a bit of power are empty and the USB interface doesn’t deliver enough to care for everything.

So, either use another USB port with more power or, the best solution: attach an external power supply (e.g. 7.5 … 9V wall wart which can deliver 1000mA or more).

rpt007: How do you power the two Arduinos and the LCD display? If via USB cable it might draw too much current (LCD backlight is very hungry) and then the capacitors which stored a bit of power are empty and the USB interface doesn't deliver enough to care for everything.

So, either use another USB port with more power or, the best solution: attach an external power supply (e.g. 7.5 .. 9V wall wart which can deliver 1000mA or more).

Thank you my friend for your help.. I connent each arduino with its own cable, only the screen connected to the uno and when I connect the uno and the mega (each its own cable) the screen work 2-3 seconds and stuck...but if I connect only the uno without the mega its work very good...You think an external power To UNO will help?

You think an external power To UNO will help?

Before I encourage you, would you please post a schematic (handsketched is ok) of all of your devices and how you connect them together when the display stops working after a few seconds.