My Ender 3 LCD display was working ok, I went to turn it on recently but is not showing any signal of life anymore...
I have tried unplugging and plugging again, is there a way to test if the screen still works?
What is the issue? Or should I just buy and install a new LCD?
This is hard to answer, it depends on your skills if you can can repair it or not. As you haven't changed the firmware, it is unlikely that this is a software issue. If the display doesn't light up, the power to the module may be broken.
If you have an Arduino Uno or similar you can try to upload a sketch and connect the display to see if it works, there are plenty of sites explaining how you should do that (software sketch and hardware connections) based on the pins exposed on the EXP port. Note that you can forget the EXP port that controls the SD card.
Personally, I would just buy a new controller, they are cheap (found on those typical Chinese vendor or auction sites).
What you can do is check whether the printer board still works, if you connect a USB cable directly to the board and connect it to a PC, you could see if the printer responds using a printer application such as Pronterface (part of the PrintRun suite).
Can you tell if the fans are turning on for your Ender 3? If not then the problem may be with your power supply or main board. If you can hear your power supply is on (listen for the fan near where you plug in the 120/230 V power plug), then the issue may be with either your main board or LCD screen.
If this post on reddit is accurate, the Ender 3 uses a standard Reprap 12864 LCD module. If you have a breadboard and a 5 volt power source, you can try connecting pin 1 to the power supply and pin 2 to the ground. If the LCD turns on then the issue is most likely with the main board.
Alternatively, @0scar♦ suggestion is good too, a cheap LCD screen can potentially save a bunch of diagnostic time.
