As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GUM - FLT 0862 - L/P 7957135 - A-SYSTEM HYDRAULIC PRESSURE IS ZERO. CREW COMPLETED A-SYSTEM CHECK LIST/PROCEDURES. MAINTENANCE TROUBLESHOT SYSTEM AND FOUND AIR PRESSURE REGULATOR AT FAULT. REMOVED AND REPLACED A-SYSTEM AIR REGULATOR PER MM 29-11-12. OPS CHECK NORMAL AND RELEASED AIRCRAFT FOR SERVICE. (X)