
My first advice will be, check your computer with another Monitor and then check it is working or not. If the monitor is working fine that mean the motherboard and the VGA is working fine. The problem is with the computer monitor. And also it will confirm that the connection between the Graphic Processing Unit and motherboard is working fine.
Now if the External monitor is not working then the problem is with the GPU. You need to check that. Open the back panel of the laptop or if you are having a desktop then open the CPU and check the GPU. You can replace that. Hopefully, the problem will get resolved.
Another important key is the inverter which provides voltage to the LCD. Now if that has gone bad in that case you need to take the PC to the computer repair center and change the inverter. If you get a faint image then the problem is with the back light of the computer. You need to replace that as well. And it is easy fix.