No Audio from earphone jack or 30 pin dock

iPod works fine controlled by car unit or docked to Mac or connected to speaker with dock all controls and interfaces are fine but I cannot get any audio out of either the earphone jack or dock. This has worked nearly every day since I purchased it and has only had a hard drive swop. The earphone plays neither music or clicks on scroll wheel. Is this the logic board can it be replaced and where would I get reliable replacement parts.