AN ACR B757 CREW HAD A DIVERSION TO ALTERNATE AFTER AN ACFT EQUIP PROB LOSS OF PRESSURIZATION. EMER DECLARED.

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THE EVENT WAS AN UNCTLABLE CABIN ALT WHICH REQUIRED A RAPID DSCNT TO PRESERVE CABIN PRESSURE. THE ACFT WAS DISPATCHED WITH AN INOP APU AND SUBSEQUENTLY; DURING TAXI OUT; AN INOP L AIR CONDITIONING PACK. THIS RESULTED IN ONLY 1 AIR SOURCE FOR CABIN PRESSURE. A MALFUNCTION OF THE REMAINING AIR SOURCE SYS RESULTED IN AN UNSCHEDULED DSCNT AND LNDG. I FELT THE DECISION TO LAND AT RNO WAS SOUND. HOWEVER; THE DECISION I MADE TO ACCEPT THE ACFT INITIALLY; WHILE LEGAL; COULD BE QUESTIONED. I ALSO THINK; IN RETROSPECT; THE MAINT LOG WRITE-UP I MADE DID NOT PROVIDE ENOUGH INFO TO OUR MAINT PERSONNEL AND FUTURE CREW MEMBERS. SUPPLEMENTAL INFO FROM ACN 355017: HAD A PACK PROB ON TAXI OUT. L PACK WAS NOT WORKING. ON TKOF; THE L BLEED OFF LIGHT CAME ON. IT WAS TURNED OFF. THE BLEED OFF SWITCH TURNED OFF AS PER CHKLIST. WE NOW HAD L PACK OFF AND L BLEED OFF. R PACK ON AND BLEED ON. IN CRUISE; WE GOT THE CABIN ALT WARNING LIGHT AND THEN THE WARNING HORN. WE STARTED AN EMER DSCNT. WE ALSO TURNED OFF TRACK. THE CAPT DECLARED AN EMER. AS WE WERE GOING DOWN; HE TURNED THE L BLEED AND L PACK BACK ON. WE THEN GOT CTL OF THE CABIN BACK. WE DIVERTED TO RNO. AFTER TALKING TO ACR MAINT AND DOING ALL THE MAINT CHKS; WE DID NOT PUT AN ENTRY INTO THE BOOK. WE JUST FORGOT.