A B727-200 UNDERGOING HVY MAINT HAD A JOB CARD TO REPLACE THE FEEL COMPUTER AND ELEVATOR FEEL CTL UNIT. THE ELEVATOR FEEL CTL UNIT WAS NOT REPLACED.

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WHILE WORKING AS A MECH; FOR ABC; DOING MAINT ON DDD; I WAS ASSIGNED THE TASK OF REPLACING THE ELEVATOR FEEL COMPUTER UNIT AND ELEVATOR FEEL CTL UNIT. I WAS GIVEN DDD JOB CARD NUMBER XXXX TO CHANGE ELEVATOR FEEL CTL UNITS. UPON RECEIVING ELEVATOR FEEL COMPUTER UNIT; WE ASSUMED THE FEEL CTL UNIT WAS MOUNTED PIGGYBACK ON ELEVATOR FEEL COMPUTER UNIT. THERE WAS NO SERIAL NUMBER VERIFICATION ON ANY DDD PAPERWORK AND WE SIGNED OFF COMPLETE CARD; ASSUMING WE HAD CHANGED BOTH UNITS. WHEN DDD DID THEIR WORK PACKAGE AUDIT; THEY ASKED WHY THEY HAD RECEIVED THE SAME SERIAL NUMBER BACK FROM ELEVATOR FEEL CTL UNIT. THAT'S WHEN THEY QUESTIONED WHETHER ELEVATOR FEEL CTL UNIT HAD BEEN CHANGED. UPON FURTHER INVESTIGATION; ON OUR PART; AFTER BEING QUESTIONED ABOUT SERIAL NUMBERS BEING THE SAME; WE DETERMINED THE UNIT I CHANGED WAS NOT 2 UNITS PIGGYBACK; BUT IN FACT 1 UNIT; AND ELEVATOR FEEL CTL UNIT WAS IN ANOTHER LOCATION; AND INADVERTENTLY DID NOT GET CHANGED. HAD SERIAL NUMBER VERIFICATION BEEN REQUIRED ON PARTS CHANGES; I FEEL THIS PROB WOULD NEVER NAVE OCCURRED.