Hi, i'm using a nokia 5110 LCD with arduino uno. it was working fine for quite a while, and then suddenly, it stopped displaying. there's only the blue background. it does not write anything on the LCD.
Can anyone please help in troubleshooting? Help 
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Don
If you haven't changed the code, your problem is mechanical.
These displays are factory surplus and some may have a short life.
If you squeeze, fiddle, or jiggle, it might work - for a while.
It could be slack installation on your part, and a better job at that might fix the display permanently. If you have been running it off 5v it may have died, but I have heard of users getting away with that.
The background light has nothing to do with the display.