What was found
ON TAKEOFF, COULD NOT RETRACT MAIN LANDING GEAR. FOLLOWED COCKPIT OPERATING MANUAL (COM), TAKEOFF WARNING HORN CAME ON, NO AUTO PRESSURIZATION. PULLED GROUND SHIFT CIRCUIT BREAKER'S GEAR CHECKS NORMAL. FLIGHT RETURNED TO MSP AND LANDED WITHOUT INCIDENT. MAINTENANCE SERVICED NOSE STRUT, LUBED NOSE GEAR AND GROUND SHIFT MECHANISM, OPERATION CHECKS GOOD.