As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BRAKE PSI DROPPED TO 2000 PSI IMMEDIATELY AFTER SETTING BRAKE. APPLIED MEL, PARK BRAKE VALVE CB 'F4' PULLED & COLLARED, ANTI-SKID AND AUTO BRAKES INOP PER MEL 3244E. -INF- :NO FURTHER BRAKE ACCUMULATOR PRESSURE DECAY WITH PARK BRAKE VALVE IN POSITION '2'. PARTS: (643-9272 MR29240 VALVE). REPLACED PARKING BRAKE VALVE. PERFORMED PARKING BRAKE SYSTEM TEST.