As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PASSING FL 220 PILOTS BOTH HEARD A LOUD BANG UNDERNEATH OUR SEATS. PRESSURIZATION WENT ERRATIC FOR ABOUT 10 SECONDS, SHORTLY FOLLOWED BY A LEVEL 2 AIR SYS 1-2 OFF LIGHT. FOLLOWED QRH, ISOLATED NR 1 MANIFOLD WHICH SUSPECT WAS THE PROBLEM. DIVERTED TO ATL. FOUND NR 1 PNEUMATIC SUPPLY DUCT BLOWN. INSTALLED NR 1 PNEUMATIC SUPPLY AT STA 655. DUCT AND LEAK CHECKED PER MM 36-14-02. OPS CHECKED GOOD.