TM  55-1520-240-T 7-6.11 7-6.11  UNABLE  TO  APPLY  BRAKES  THREE  TIMES  ON  BRAKE ACCUMULATOR   PRESSURE FAULT  ISOLATION  PROCEDURE INITIAL   SETUP Personnel Required: Medium   Helicopter   Repairer   (2) References: TM   55-1520-240-23 Applicable Configurations: All START APU. DOES UTILITY HYD PRESS  INDICATOR  REACH 3000  PSI? REPLACE AIR VALVE ON ACCU- MULATOR. Equipment Condition: TM   55-1520-240-23 Battery   Connected Electrical  Power  On Hydraulic  Power  On Aircraft   Jacks   Removed Tools: Aircraft   Mechanic’s   Tool   Kit, NSN   5180-00-323-4692 REFER TO TROUBLE SYMPTOM TASK  7-8.4. M a t e r i a l s: None PERFORM LEAK CHECK WITH SOAP  AND  WATER  ON  ACCU- MULATOR GAGE. IS GAGE LEAKING?      CHECK ACCUMULATOR AIR SHUT DOWN APU. DOES BRAKE ACCUMULATOR (25 CU. IN) HOLD 1400 PSI? PRECHARGE. DOES PRE- CHARGE HOLD AT 600 TO 800 PSI? REFER TO TROUBLE SYMPTOM TASK 7.6.12. REPLACE GAGE ON ACCUMU- LATOR. BLEED OFF PRESSURE AT A MASTER BRAKE CYLINDER. DISCONNECT AND CAP OFF PRESSURE LINE TO ALL FOUR MASTER BRAKE CYLINDERS. PRESSURIZE  SYSTEM.  THEN SHUT DOWN APU DOES BRAKE  ACCUMULATOR  HOLD 1400  PSI? ISOLATE FAULT TO A MASTER BRAKE CYLINDER. CONNECT CYLINDERS ONE AT A TIME TO SYSTEM.  PRESSURIZE  SYSTEM, THEN  SHUT  DOWN  APU.  RE- PLACE CYLINDER THAT CAUSES   ACCUMULATOR PRESSURE  TO  DROP. REPLACE CHECK VALVE BETWEEN  ACCUMULATOR AND  POWER  CONTROL MODULE. 45 x 54 D145-9658-SPA END  OF  TASK 7-194 Change 1