What was found
SUSPECTED BURNING SMELL. MX C/A: PERFORM A GENERAL VISUAL INSPECTION OF THE #2 CDU AND ALL FOUR ADF’S FOR VISIBLE DAMAGE AND SECURITY. PROVIDED PROTECTION TO #1 PDU GROUND TERMINAL. RAN ENG FOR 10 MINUTES. RAN APU AND HAD COCKPIT AVIONIC UNITS POWER UP FOR 1 HOUR NO SIGNS OF ELECTRICAL SMELL AT THIS TIME ON GROUND. PERFORM AN OPERATIONAL CHECK OF THE #1 CDU PER AMM 34-61-05-710-801. COMPLIED WITH AQRD ENGINEERING ERO-989061 PROCEDURES. OPEN AND INSTALL A CIRCUIT BREAKER COLLAR ON C/B A4 CDU #2 (DISABLING THE SYS, R&R CDU W/IN 20 DAYS).