What was found
BRIEF ELECTRICAL BURNING SMELL NOTED BY FLT ATTENDANT AND PASSENGERS APPROX ROWS 28-32. DURING FLIGHT SMELL DISSIPATED THEN RETURNED ON DESCENT. MTC IN SJO OPENED AND CHECKED ALL PSU FROM ROW 20-39, FOUND NORMAL CONDITIONS. OPERATED BOTH A/C PACKS AND RECIRCULATION FANS WITH DOORS CLOSED FOR ONE HOUR, NO SMELL DETECTED. RAN BOTH ENGINES AND OPERATED ALL CABIN ELECTRICAL SYSTEMS COULD NOT DUPLICATE SMELL.