As I said, to get a beep or something on screen, you need good mb, cpu, ram, and powersupply. If it doesn't display anything nor beep, any of these 4 can be defective.
Assuming everything is properly connected and excluding the powersupply, the most probable defective one is ram, then MB, then cpu.
You can just try swapping them with known good one to find out which is the culprit