av1 not working for gaming after trying hdmi

[#1]

My son has happily been playing in the PS3 network for the past 6 months. Everything worked fine - the tv, ps3, cables etc. Last week he bought a gioteck headset and that too worked fine. He got a HDMI cable with it so today we thought we'd try it to see if it improved the picture. It didn't make much of a difference so he decided to go back to using av1 - but now it won't work!  The screen is just blank!  Does anyone know what's wrong and how to fix it please?

[#2]

Make sure you remove the hdmi cable or it will default to that

[#3]

When you turn on the PS3, press and hold the on button for a few seconds until it beeps twice (I think it's twice anyhow), this will reset the settings.  Basically the PS3 is still sending the signal through HDMI as that it what it is set up for so you need to reset the setting.