What was found
BOS - FLT 1507 - ON DESCENT INTO BOS, CAPTAIN ADVISED THAT THE FLAPS WOULD NOT COME DOWN WHEN SELECTED. CREW WAS ADVISED BY MAINTENANCE IN BOS TO CHECK CIRCUIT BREAKER FOR FLAP INDICATOR AND RESET. SLATS BEGAN TO DEPLOY ASYMMETRICALLY AND WERE THEN RETRACTED. AN EMERGENCY WAS DECLARED WITH ATC AND THE ALTERNATE ELECTRIC FLAP EXTENSION WAS USED. FLIGHT LANDED WITHOUT FURTHER INCIDENT AND TAXIED TO THE GATE WITH EMERGENCY TRUCK ESCORT. MAINTENANCE REMOVED AND REPLACED THE FLAP POSITION INDICATOR. RAN FLAPS UP AND DOWN SEVERAL TIMES. OPERATIONAL CHECK NORMAL. (M)