What was found
SJU FLT 1568 CLT TO SJU. WHEN THRUST LEVERS WERE REDUCED TO IDLE FOR INITIAL DESCENT, A VERY STRONG ODOR SMELLING LIKE WET SOCKS AND/OR DIRTY FEET CIRCULATED THROUGH THE PASSENGER CABIN AND FLIGHT DECK. THE FLIGHT LANDED WITHOUT FURTHER INCIDENT. INSPECTED THE ENGINES FOR LEAKS, PACK BAYS, WHEEL WELLS, APU, HYD SYSTEM. NO LEAKS FOUND. PERFORMED ENGINE RUN ISOLATING PACKS AND GENERATING WITH DIFFERENT AIR SOURCES. REMOVED AND REPLACED RECIRCULATION FILTERS. NO SMELLS PRESENT. THE AIRCRAFT WAS MAINTENANCE FERRIED BACK TO CLT. APU CHANGE DUE TO CABIN ODOR. REMOVED AND REPLACED APU.