No signal from computer

Fix key

Reputable
Feb 23, 2014
1
0
4,510
Motherboard gigabyte GA-990FXA-UD5
Cpu AMD sempron 145
Gpu Giabyte Radeon 280x
Ram kingston 1GB 1333Mhz KTW149-ELD
Psu lepa 1000W
Fans are working, but there isn't any beep from speaker or there isn't any signal to monitor(I tried both hdmi and vga)
It's first start of this computer. Any help, please?