What was found
(CAN) WHILE IN FLIGHT, NR1 ALTERNATOR FAILED, NR1 ALT AMBER LIGHT CAME ON, ON THE GROUND, INSP REVEALED THAT THE DRIVE PULLEY HAD SEPARATED FROM ALTERNATOR, PULLEY FOUND DAMAGED WITH OTHER BROKEN PULLEY PIECES ON THE BUTTOM OF COWLING. RETAINING NUT HAD GONE AWAY. END SHAFT (ARMATURE) WAS NOT SEIZED. SUSPECT A QC PROBLEM IN THIS CASE. ALTERNATOR REPLACED WITH O/H UNIT. (TC NR 20080229004)