What was found
AIRCRAFT WOULD NOT HOLD SCHEDULED CABIN PRESSURE WITH SINGLE PACK OPS AT FL 210. CABIN WAS 8000 FT, CLIMBING 500-700 FEET PER MIN. DESCENDED TO 15,000 TO HOLD LEVEL AT 8000 FEET CABIN PRESSURE. PRESSURIZED ACFT. FOUND AIR LEAKS AT L-1 AND R-1 DOOR SCUFF PLATES. REPAIRED PLATES AND SEALS ON BOTH DOORS. REPLACED RIGHT PNEUMATIC HIGH PRESSURE REGULATOR AS PRECAUTION.