Is it the HDMI cable?
The PS3 or the TV.
erm when i first got my ps3 i coudnt get sound or picture then i got the picture then finally sound came....
only thing i know is put your ps3 into standby (red light is on) hold the power button you should hear 1 beep when it turns on and if you keep it held down you should here a second beep take your finger off.
this means the ps3 will look for a new video and sound source and should find your hdmi!!!!