Often a flickering screen can mean buying ballast or a bulb or perhaps a whole new screen. But if the computer was ever worked on by another technician there is a chance it was reassembled improperly. Or the manufacturer of the computer assembled the screen improperly.
This was the case on a Gateway MX7340 that I repaired for the customer. Gateway had assembled the laptop and the screen wires were being pinched by the hinges. There is not alot of room to work with when it comes to the screen wires as they make their way to the motherboard. This Gateway screen would flicker when you opened or moved the screen even the tiniest bit.
After cracking the laptop open and disassembling the cover I saw a pinched wire. After several attempts I was able to move the wire bundle out of the way of the hinge. Reassemble the laptop and wala it worked as advertised. So next time you have a flickering screen, double check the wire bundle before buying parts.