there may be 2 problems
1.your tv has forgotten the ps3 settings so will not show picture
if this is the case Simply reset your PLAYSTATION 3 to restore the default SD setting in the following way: turn off the PLAYSTATION 3 system then press and hold the power button for approximately 5 seconds until you hear a beep. You can then use the Settings category in the XMB to configure your Display settings manually.
2.Hdmi cable broken
if this is the case see if you have gotten nything else in your house that works with hdmi cable if it does work you know its a faulty cable