What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO DFW TO ELECTRIC STAB TRIM NOSE DOWN INOPERATIVE IMMEDIATELY AFTER TAKEOFF. AUTOTHROTTLE DID NOT RESPOND. NO CAUTIONS OR WARNINGS. AIRCRAFT LANDED SAFELY AT DFW WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED HORIZONTAL STABILIZER TRIM CONTROL SYSTEM RELAY R850 (AALA202308044969). REPLACED AUTOTHROTTLE COMPUTER PER AMM 22-31-10. ACCOMPLISHED SATISFACTORY OPERATIONAL TESTS. (AALA202308046573)