What was found
STARTED ENGS TO DEPART & ACFT BEGAN ROLLING WITH PARKING BRAKE SET & GOOD PRESSURE IN EM BRK ACCUMULATOR. REGULAR BRAKES WORKED, BUT EM BRAKE DID NOT. RESET EM BRAKE- NO CHANGE. NO BRAKE FAIL OR ANY OTHER CAS MESSAGES. VERIFIED SQUAWK NOT GETTING ANY BREAK PRESSURE OR INDICATION WHEN BREAK HANDLE IS PULLED. REMOVED INOP EMERG BRAKE VALVE. INSTALLED A REPAIRED EMERG BRAKE VALVE. REMOVED BRAKE PRESSURE SWITCH. INSTALLED A NEW BRAKE PRESSURE SWITCH. OPS AND LEAK CHECK GOOD. IAW AMM 32-43-02-400-801-A AND 32-43-0S-400-801-A.