What was found
DURING SLAT EXTENSION ON APPROACH INTO MSP, SLAT EXTEND LIGHT BEGAN FLICKERING, THEN EXTINGUISHED AND SLAT DISAGREEMENT LIGHT ILLUMINATED. PERFORMED MISSED APPROACH AND CAPTAIN DECLARED AN EMERGENCY. SUCCESSFUL LANDING WAS ACCOMPLISHED ON SECOND ATTEMPT WITH FLAPS AT 40 DEGREES AND NO SLATS. CYCLED SLATS AND FLAPS SEVERAL TIMES AND DISCREPANCY COULD NOT BE DUPLICATED. AIRCRAFT RETURNED TO SERVICE.