What was found
HEARD A LOUD THUMP UNDER THE FLIGHT DECK FLOOR, BEHIND AND IN THE MIDDLE OF THE FLIGHT DECK. THE CREW THEN SMELLED ELECTONIC BURNING ODOR WHICH DISSAPATED AFTER APPROXIMATELY A MINUTE AFTER THE NOISE. IT ALL HAPPENED ON THE APPROACH. PERFORMED TSM 24-00-00-810-823-A. NO EVIDENCE OF ARCING OR CHAFING OF ELECTRICAL CIRCUITS OR MECHANICAL COMPONENTS. ACCOMPLISHED A VISUAL INSPECTION OF THE AVIONICS SYS COMPONENTS. NO DEFECTS NOTED. DURING THE OPERATION, HEARD A LOUD VIBRATION COMING FROM THE AVIONICS FAN. R & R AVIONICS FAN IAW 21-26-51. SYSTEM OPS CHECK GOOD.