CPU starting but not displaying information or not sending signal to monitor

I have this Linux box that i have not used for almost a year and i just want to use it now. The problem is that when i start the CPU, it does not send signals to the monitor.
What could be the problem(s)? And any troubleshooting solutions.

Thanks…

hope you need to give a blow to your system board and reinsert RAM then try to power ON .

Okay let me try cleaning it…