Narrative:

We departed normally from ZZZ on the ZZZZZ5.ZZZZZ1 RNAV departure; runway xxl. All checklists were completed prior to takeoff and systems were normal. Climbout was as planned with systems operating normally. In the right (course) turn as published we were cleared direct to ZZZZZ2. After passing ZZZZZ3 we were approaching the assigned intermediate altitude of FL340 for crossing traffic.while at FL340 and before ZZZZZ4; approximately 20 mins into the flight the crew experienced a pressurization control loss and numerous cass messages; lights and alarms. We noted a marked cabin climb rate. Both crew donned oxygen masks and began a descent--commencing a right turn off the published departure procedure course. During the descent got priority handing by center. We asked for a diversion airport and noted ZZZ1 in front of our course and within a safe and expeditious distance.once safely established at a lower altitude; I noted and confirmed with the captain an emergency bus fail on the EICAS as a red message; with numerous other cass cautionary failures and lights. I pulled the QRH and referenced the EICAS messages index which prompts the crew for related chapters to identify the appropriate actions. We continued with the checklists as directed by the QRH. I executed the directives of the emergency bus fail checklist in cooperation with the captain. The emergency bus failure cleared upon the first directed action to return power to the bus. Systems came back on-line and returned to (ab)normal operation. We proceeded to configure the aircraft for landing and confirmed landing performance in the FMS. ATC soon after asked if we had the airport in sight; we confirmed and received the notification that radar services were terminated. We announced position and intentions on CTAF (tower services unavailable) and commenced a normal landing. Upon safely leaving the runway; we came to a stop to ascertain the status of the aircraft before commencing taxi. We agreed that the aircraft was safe to taxi to the ramp and FBO. Upon arriving at the FBO ramp; we continued with the shutdown checklist; completed the shutdown and safely secured the aircraft for disembarking. The sic walked the aircraft interior; as is protocol; for remaining personal items and other notable items; if left behind. Upon returning to the cockpit with all ships power off; I noticed a 60-amp emerg buss feeders 'bat' circuit breaker had tripped. I communicated this to the captain.manufacturers service team arrived to identify the failed system and components. The manufacturers technicians noted thermal damage to the 60-amp emerg buss feeders 'bat' circuit breaker and wire. Technicians agree this would cause the fault we experienced. The team continues to troubleshoot the aircraft for potential root cause or systematic factors that may have contributed to this kind of thermal damage.the aircraft had just received an emergency battery replacement the prior week due to EICAS thermal reading abnormalities of the previous battery--which were remedied with the replacement battery by company maintenance. The aircraft then subsequently had an annual avionics inspection by a contracted party immediately before this trip sequence (failure occurred on the 4th leg; second day). Crew is interested in what factors any of these maintenance actions/inspections may have had; if any; or when the last overhead circuit breaker panel inspection would have occurred. More information needed/forthcoming from the service team.

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Original NASA ASRS Text

Title: Gulfstream 200 reported a pressurization control loss and landed at a diversion airport.

Narrative: We departed normally from ZZZ on the ZZZZZ5.ZZZZZ1 RNAV departure; RWY XXL. All checklists were completed prior to takeoff and systems were normal. Climbout was as planned with systems operating normally. In the right (course) turn as published we were cleared direct to ZZZZZ2. After passing ZZZZZ3 we were approaching the assigned intermediate altitude of FL340 for crossing traffic.While at FL340 and before ZZZZZ4; approximately 20 mins into the flight the crew experienced a pressurization control loss and numerous CASS messages; Lights and Alarms. We noted a marked cabin climb rate. Both crew donned oxygen masks and began a descent--commencing a right turn off the published departure procedure course. During the descent got priority handing by Center. We asked for a diversion airport and noted ZZZ1 in front of our course and within a safe and expeditious distance.Once safely established at a lower altitude; I noted and confirmed with the Captain an EMER BUS FAIL on the EICAS as a RED MESSAGE; with numerous other CASS cautionary failures and lights. I pulled the QRH and referenced the EICAS Messages Index which prompts the crew for related chapters to identify the appropriate actions. We continued with the checklists as directed by the QRH. I executed the directives of the EMER BUS Fail checklist in cooperation with the captain. The emergency bus failure cleared upon the first directed action to return power to the bus. Systems came back on-line and returned to (ab)normal operation. We proceeded to configure the aircraft for landing and confirmed landing performance in the FMS. ATC soon after asked if we had the airport in sight; we confirmed and received the notification that radar services were terminated. We announced position and intentions on CTAF (tower services unavailable) and commenced a normal landing. Upon safely leaving the runway; we came to a stop to ascertain the status of the aircraft before commencing taxi. We agreed that the aircraft was safe to taxi to the ramp and FBO. Upon arriving at the FBO ramp; we continued with the shutdown checklist; completed the shutdown and safely secured the aircraft for disembarking. The SIC walked the aircraft interior; as is protocol; for remaining personal items and other notable items; if left behind. Upon returning to the cockpit with all ships power off; I noticed a 60-amp EMERG BUSS FEEDERS 'BAT' CB had tripped. I communicated this to the Captain.Manufacturers service team arrived to identify the failed system and components. The Manufacturers technicians noted thermal damage to the 60-amp EMERG BUSS FEEDERS 'BAT' CB and wire. Technicians agree this would cause the fault we experienced. The team continues to troubleshoot the aircraft for potential root cause or systematic factors that may have contributed to this kind of thermal damage.The aircraft had just received an emergency battery replacement the prior week due to EICAS thermal reading abnormalities of the previous battery--which were remedied with the replacement battery by company Maintenance. The aircraft then subsequently had an annual avionics inspection by a contracted party immediately before this trip sequence (failure occurred on the 4th leg; second day). Crew is interested in what factors any of these Maintenance actions/inspections may have had; if any; or when the last overhead CB panel inspection would have occurred. More information needed/forthcoming from the service team.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.