A CRJ-200 WAS DISPATCHED FROM THE GATE THREE TIMES FOR 'DCU 1 AURAL INOP' STATUS MESSAGES AND DCU CIRCUIT BREAKER TRIPPED. FOURTH DISPATCH 25 MINS INTO FLT CIRCUIT BREAKER TRIPPED. CREW NOTED 5% N1 SPLIT.

Narrative

DURING THE FIRST TAXI OUT; ABOUT 20 MINS AFTER ENG START; THE 'DCU 1 AURAL INOP' STATUS MESSAGE AND DCU 1 CB POPPED. WE RETURNED TO THE GATE AND AN ACFT MECHANIC CAME ON BOARD AND CLEARED THE MESSAGE BY RESETTING THE SYSTEM. THE ACFT WAS SIGNED OFF. WE LEFT THE GATE. ON THE SECOND TAXI OUT; THE CB POPPED AND THE MESSAGE RETURNED ABOUT 15 MINS AFTER ENG START. WE RETURNED TO THE GATE A SECOND TIME AND THE PAX WERE DEPLANED. MAINT REPLACED THE #1 DCU AND CLEANED ALL ASSOCIATED SWITCHES. THE MESSAGE CLEARED AND THE ACFT WAS SIGNED OFF. THEN THE ENGINES WERE RUN AT THE GATE TO DUPLICATE THE PROB. NO MESSAGES APPEARED. NOW THE FLT WAS OPERATED AS A REPOSITION FLT TO ZZZ1. ON THE THIRD TAXI OUT; THE MESSAGE CAME ON AND THE CB POPPED 5 MINS AFTER ENG START. WE TAXIED BACK TO THE GATE AND MAINT CLEARED THE MESSAGE FOR THE THIRD TIME. THE ENGINES WERE RUN AT THE GATE AND NO MESSAGE APPEARED AND THE ACFT WAS SIGNED OFF. AT THIS POINT; I REFUSED TO FLY THE ACFT. THEN ZZZ1 MAINT CTL HAD ACFT MAINT REPLACE THE AUDIO CTL COMPUTER. THIS WAS COMPLETED AND THE ACFT WAS SIGNED OFF. I HAD A CONFERENCE CALL WITH MAINT CTL AND THE CHIEF PLT. MAINT EXPLAINED THE TROUBLESHOOTING PROCESS AND THE DECISION WAS MADE TO COMPLETE THE FLT. THIS IS NOW THE FOURTH ATTEMPT TO COMPLETE THE FLT. THIS TIME; ABOUT 25 MINS AFTER DEP; THE MESSAGE REAPPEARED AND THE CB POPPED. THE CREW DISCUSSED THE PROB AND DECIDED THE BEST THING TO DO IS CONTINUE TO ZZZ1 OPERATING ON THE LAST DCU. WE WERE AT 22000 FT AND ZZZ1 WAS GOOD VFR. DURING THE DSCNT TO ZZZ1 WITH THE THRUST LEVERS MATCHED; THE N1 SPLIT WAS DIFFERING BY 5%. THE LNDG WAS COMPLETED NORMALLY AND THE 'DCU 1 AURAL INOP' MESSAGE AND THE N1 SPLIT WAS ENTERED IN THE ACFT MAINT LOG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT MAINT RPTED THE AUDIO COMPONENT OF THE DATA CONCENTRATOR UNIT (DCU) HAD FAILED. THE RPTR SAID THE UNIT WAS CALLED THE AUDIO ELECTRONICS CTL UNIT (AECU).