Monitor stays black when i turn on the computer

Hello,
i am having trouble like many ppl with a black screen when I boot up. I have tried everything possible, but no luck. I have an onboard vga port and one on a pci card. I switched from the onboard one to the pci but still the same problem. I hooked up the desktop monitor to my laptop and the monitor works fine. I also plugged the monitor into another computer, and the monitor worked just fine. I finally went out and bought a new motherboard, cpu, and ram hoping that my problem was solved. So basically I wasted money for nothing because the problem still exists. Please help.
my system is:

motherboard: Gigabyte Z270-HD3
CPU: INTEL CORE I5-7600K LGA 1151
RAM: BALLISTIX SPORT 16GB (2X8GB)