My laptop identifies my tv via hdmi but does not send a pic

[71167]

My laptop (Acer Travelmate 5730) identifies my TV's (Sony Bravia and Toshiba) via HDMI cable but does not send any picture or sound. I have tried adjusting the screen setting and resolution but this has not helped at all.

 

[Peettreedish]

Do u have an external screen Fn button that needs to be pressed. Also I had a laptop once that would not use external monitors without the bios being set to do so.