Q: HDMI output not working MACBOOK Pro (Oct 2014)

I am trying to get another screen connected to my MBP, I have tried numerous screens and cables to achieve this, but I can not get it to work.

Is there a on/off or disable HDMI output on the MBP?

I have used various screen, which i know work. And a HDMI to DVI and HDMI to HDMI cables to screens . I know the cable and screens work as I use them at work on a daily basis.

All I get is "No signal connected".

Is there any diagnostics or tests I can do?

Regards,

Rowland