Hi @someonealone ,
Turn on the laptop and then shine a torch at an angle close to the laptop screen and check if you can detect an image at all.
It will be very faint so try it in a darkened room to help you see it if it is there.
If there is no image then you have a motherboard problem.
If there is an image there then you have a screen backlight problem.
This could be either a faulty backlight power supply from the motherboard, a faulty LVDS cable or cable connection at either end or a faulty display panel.
Here’s a link to the Lenovo G700 hardware maintenance manual which may be of some help if you want to check the LVDS cable, cable connections or to replace the LCD display panel if it is determined that the problem is with the LCD display panel.