B767-200
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Other / Unknown
Aircraft Equipment Problem Dissipated; Flight Crew Overcame Equipment Problem
Aircraft
Flight Leveling From ZZZ1 to ZZZ at Flight Level 340 on Aircraft X with the right pack deferred. As we approached the TOD (Top of Descent) for the ZZZZZ arrival about an hour and a half into the flight we received a Master warning and EICAS (Engine Indication and Crew Alerting System) warning 'Cabin Altitude'. We donned our oxygen masks and accomplished the QRH (Quick Reference Handbook) procedures. We requested a lower altitude from ATC. They turned us 10 degrees right and we descended to Flight Level 280. The cabin altitude indicated 10;200 ft. As we approached Flight Level 280; master warning and EICAS extinguished. The Flight Level was continued and landed normallyThe right pack was deferred for a temperature problem. Taking off out of a high altitude airport in this configuration may have contributed to the aircraft not being able to maintain pressurization at altitude. I deadheaded to ZZZ1 on the flight prior from ZZZ2 to ZZZ1 and there was no problem on that leg with this aircraft. Maintenance in ZZZ replaced the temperature valve; serviced the O2 and finished the paperwork to have the right pack working for our trip back to ZZZ1. It may have been better to repair the aircraft in ZZZ2 before sending it to a high altitude airport like ZZZ1. The maintenance team in ZZZ did an outstanding job repairing the aircraft during a scheduled turn in ZZZ. We departed on time to ZZZ1.
B767 Flight Crew reported pressurization problem inflight.