Monitor light blinks. I have not checked the voltage and not sure how but I have tried 4 power

Question

I have not checked the voltage and not sure how but I have tried 4 power supplies 3 motherboards at least 5 video cards. when i plug my monitor in to the power and turn it on you see where it is searching for conection. then you hook up a video card not hooked up to the motherboard and turn on the monitor you see the green light then you hear a click the green light starts to flash and nothing on the screen not even the searching logo. i've tried 4 monitors with the same results.