What was found
FLT 5011 (LAX/CLD), PILOT REPORTED AFTER TAKEOFF THAT THE GEAR WOULD NOT RETRACT, AND RECEIVED THREE RED INTRANSIT LIGHTS. PILOT RECYCLED TWICE WITH SAME RESULTS. MAINTENANCE DETERMINED EMERGENCY EXTENSION LANDING GEAR RELEASE VALVE POPPED. MAINTENANCE RESET VALVE, SERVICED HYDRAULIC ACCUMULATOR RESERVOIR AND PERFORMED REQUIRED GEAR SWINGS. FUNCTION CHECKS WERE GOOD IAW JS 3201 MM CHAPTER 29-00 AND 32-00. THE AIRCRAFT WAS RELEASED BACK TO SERVICE.