What was found
FLT 690 - SAL/MST/SFO - DESCENDING AT MAZATLAN, NR 1 GEN OFF BUS, BUSS OFF, AND HIGH OIL TEMP LIGHTS CAME ON. AT THIS TIME, THE APU WAS DEFERRED AS PER MEL 49-1. DURING GROUND INSPECTION, CHIP DETECTOR METAL IN THE CSD AND THE CSD OIL COOLER WERE FOUND CONTAMINATED. AS CORRECTIVE ACTION, CSD NR 1 WAS REPLACED AS PER MM 24-21-11. AFTER THIS, THE AIRPLANE WAS RETURNED TO OPERATION.