What was found
LAX - INFLIGHT SFO-DFW. CAPTAIN HEARD A POPPING SOUND AND NUMBER 1 AUTO CONTROLLER STOPPED WORKING. CAPTAIN INITIATED EMERGENCY DESCENT TO 16000 FT. EMERGENCY DECLARED FLIGHT DIVERTED LAX. THE CREW TRIED THE NUMBER 2 AUTO CONTROLLER AND IT WORKED AND THEN TRIED THE NUMBER 1 CONTROLLER AGAIN AND IT STARTED TO WORK FINE. THE MECHANIC THEN DID A SYSTEM CHECK OF THE NUMBER 1 CONTROLLER AND FOUND NO FAULTS. BOTH CONTROLLERS WERE REPLACED AT DFW ON 02/26/2010 DUE TO REPEAT OF ISSUE. SYSTEM GROUND CHECK NORMAL OPERATION.