What was found
CREW DECLARED AN EMERGENCY AFTER A MOMENTARY, CABIN ALTITUDE, WARNING HORN SOUNDED ON DESCENT. MAINTENANCE FOUND THE SUPPLY PRESSURE SENSE LINE BETWEEN THE PCCV AND BAR BROKEN AND REPLACED IT. PERFORMED PNEUMATIC HEALTH CHECK IAW W/C 3610-7956 AND THE OPS CHECK WAS GOOD. PERFORMED BITE CHECK CPC-1 AND FOUND RATE HI, LO INFL, HI LEAKAGE. BITE OF CPC-2 SHOWED NO FAULTS. PERFORMED PHASE 1 SINGLE PACK CHECK IAW AMM 21-00 CHECKS OK. PERFORMED PHASE 3 SINGLE PACK CONFIDENCE CHECK LEAK RATE OUT OF LIMITS. FOUND APU BLEED DUCT CLAMP AT P-DOME NOT SECURE. RESECURED SAME. TIGHTENED KEEL BEAM DUCT CLAMPS. PERFORMED AMM 21-00-05-780-801, PHASE 1, 2, 3 TESTS. ALL NORMAL. SINGLE PACK AND LEAKAGE RATE WITHIN LIMITS. ACFT RETURNED TO SERVICE.