No Display inig boot up then sige ra blink ang 3 keyboard leds.

I've tried:
1. switched mem slots
2. swap memory
3. swap monitor, psu, vga card, keyboard and mouse
4. backbone mobo (w/out vga card, hdd and memory)
5. naay beeps pero wala gihapon display
6. reset to deafults ang cmos.bios
7. pero wala gihapon ni display

Is it the mobo?