What was found
CABIN SMOKE WARNING, TWO TIMES. FIRST TIME IN CLIMB PASSING FL310. BRIEF FLASH OF MASTER WARNING THEN WENT AWAY. 4-5 MIN LATER LEVEL AT FL330 GOT 2ND MASTER WARNING AND CABIN SMOKE FOR ABOUT 10 SECS. LANDED AT KPDX. FIRE DEPARTMENT INSPECTION NO INDICATION OF HEAT. PER MX TURNOVER CREW REPORTED AREA 2 OF UPPER DECK WAS AREA CAUSING INPUT DURING FLIGHT. REMOVED AND REPLACED ALL NR 2 AREA DETECTOR UNITS PER MM 26-15-00. REMOVED AND REPLACED MSC PER MM 26-15-00. ALL OPS CKS C/W SYSTEM CKS NORMAL. ALSO CHECKED EACH VIA IN COMMAND MODE PER MM 26-15-01, OPS CK NORMAL.