What was found
AT FL330 LOST CABIN PRESS, WARNING HORN SOUNDED AND GAUGE READ 10,000 FT. ATTEMPTED TO RECOVER ALT WITH STANDBY, BUT MANUAL AC WORKED. ALT 3500 FT AFTER EMER DESCENT TO FL240. PACKS HAD TO REMAIN ON HIGH TO KEEP PRESS. SUSPECTED FWD SERVICE DOOR SEAL. FOUND LOWER GATE COVER AND SEAL BENT L-1 DOOR. REMOVED AND REPLACED LOWER HINGE COVER PER M/M. ACFT PRESSURIZED NORMALLY PER M/M, LEAK CHECK GOOD.