Hardware No Monitor Signal

[Sop]

Hi, I recently upgraded my PC and now there is no monitor signal. I put in a new CPU, ram and mobo. The GPU fan is on and connected and the PC isn't overheating.

It was working fine, then it just shut off and now I get no signal.

 

[Originality]

Unplug the graphics card and video cable and plug them back in. That's the first thing to try.

 

[Count Duckula]

-Monitor isn't just set to another input or not quite plugged in at one end (sorry, got to start at the most simple)?
-Do you get a signal prior to windows booting (BIOS splash screen or POST info)?
-Any beeps from the motherboard when first powered on?
-Does the motherboard have any other kind of status indicator (mine has a 2 digit display that shows status codes)?
-Does the HDD activity indicator flash as though windows is booting despite the lack of display?
-Does the motherboard have an onboard video output you can test to see if that displays anything at all?

As you've just built it, it'd be worth ensuring everything is seated well before looking into other possible causes.