What was found
AFTER TAKEOFF, AT APPROXIMATELY 18,000 FT, FELT A LOUD BANG UNDER FOOT, FOLLOWED BY A VIBRATION. THE VIBRATION NEVER WENT AWAY FOLLOWED BY AN ELECTRICAL ODOR. FAS FELT THE VIBRATION IN THE FIRST CLASS GALLEY. ACCOMPLISHED W/C 05-96-70, AND FOUND THE FWD E/E EXTRACTION FAN HAD FAILED AND THE CIRCUIT BREAKER TRIPPED. REMOVED AND REPLACED THE FAN IAW MM 21-26-51. OPS AND LEAK CHECKED GOOD.