What was found
FLT 4529 - DURING CLIMB-OUT FROM ATL-MGM, THE CREW RECEIVED A LEFT THRUST REVERSER UNLOCK AMBER CAUTION MESSAGE. QRH PROCEDURES WERE COMPLIED WITH AND THE LEFT ENGINE WAS REDUCED TO FLIGHT IDEL FOR A SINGLE ENGINE LANDING. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ATL, LANDING SAFELY. MAINTENANCE REMOVED AND REPLACED TERMINAL DIODE MODULE 207-7 AND ZENER DIODE 1CR1KE. OPS CHECK OF THE SYSTEM GOOD. AIRCRAFT OK FOR SERVICE. (M)