My screen going off after 10 seconds of booting

[Sukhbat]

I dunno why i think its because of my gpu. my screen goes off but my gpu fan is still working my keyboard mouse's led light are still on when i connect my vga to my board using a4 apu it works with no problem im using hd 6770 and chinese 500w psu with no gpu pins so i used converter to support my gpu

 

[Sukhbat]

Wait sometimes my mouse and keyboard lights go off