Laptop/how to repair display IC on mother board

Hello house, pls iam in Abuja Nigeria.I have two laptops with the same problem....i met a pro who asked me to try fix the display IC but iam not sure its the way to go(not that i can do that yet!).
The problem
Both systems will turn on but wont display nothing.I took both systems (e systems and a Toshiba) apart and discovered when i power on,the fans would spin for 2-3secs and then stop while the system stays on without any display of anything (including POST).
I have swapped RAMs and even removed pci cards(mainly wireless modem cards) yet the same issue...i tested the boards without the RAM and the system beeps to shw that it still works and not ded.
What do i do?