But since you are into repairs did you check the switch that is in that jack with an ohm meter?
I have a 42" plasma hp-t4254, that is only getting audio through the headphone jack. No audio is coming from the main speakers. I replaced the power supply board to fix the bad capacitor/diode/mosfet issues which the new board took care of but I still only get audio through the headphone jack on the side AV panel. Anybody with any ideas would be greatly appreciated.