What was found
DURING PERFORMANCE A STATIC TAKE OFF, THE LT SEAT BRAKES WOULD NOT HOLD THE AIRPLANE. PERFORMED ENGINE RUNS AND VERIFIED DISCREPANCY. CHECKED FOR CORRECT BRAKE PRESSURE WITH BRAKES APPLIED, NO DEFECTS NOTED. CHECKED LEFT AND RIGHT SEAT BRAKE CABLE TENSIONS, NO DEFECTS NOTED. REMOVED AND REPLACED THE PARKING BRAKE VALVE. BLED BOTH BRAKES, SERVICED RESERVOIR AND ACCUMULATOR. BRAKES NOW HOLD AIRCRAFT FROM EITHER SEAT WITH BOTH ENGINES AT TO POWER. IAW AMM 32-42-03, 32-44-00 AND 32-44-10.