What was found
UPON APPROACH THE PILOTS REPORTED THAT THE LANDING GEAR DID NOT EXTEND AND THE CIRCUIT BREAKER POPPED. THEY THEN PERFORMED A MANUAL EXTENSION. MAINTENANCE INSPECTED THE LANDING GEAR AND FOUND THE HYDRAULIC POWER PACK WOULD NOT SHUT OFF CAUSING THE CIRCUIT BREAKER TO POP. MAINTENANCE REMOVED AND REPLACED THE LANDING GEAR RELAY UNDER THE LT AFT NACELLE REF. GMM 9.3.0. MAINTENANCE PERFORMED NUMEROUS EXTENSION & RETRACTION CHECKS. OPERATIONAL CHECKS WERE GOOD.