why does my led screen shut off

i used LED IVANA 32" tv monitor, why does my led tv monitor shut off for a second when i on or off my fan, tube, speakers. i used my monitor as a tv with set top box its shut off but as a vga mode its giving me above problem, i called electrician for checking electrical fitting & TV technician but both said the problem is in ur system, when i used my friend's cpu with my monitor my screen not shut off