no video is No Post assuming good video cable connection and good monitor. first try clear cmos by reset jumper on motherboard, and also replace cmos battery with new one.
Hi i have a old dell optiplex that was just working fine and when i turn it on today it has no video signal i am running windows 7 enterprise n on it
Dell optiplex 380 not video output and turns off when i hit the power button 
once without hold