power boot problem monitor wont turn on

I have a clone amd 850, 512 ram, 2 hdd, 2 cdroms, 4 pci cards used and agp slot used for video
when i turn on the computer most of the time the light on the monitor wont switch over from amber to green. sometimes it does turn green but only for 10seconds then it switches back to amber tried unplugging everything except video card, ram, cpu and mouse… still no go … changed video cards with new one does the same thing. plugged in different monitor and does the same thing. Help please