A B727-200 HAD THE NACELLE ATTACH FASTENER HOLES INSPECTED WITH AN EDDY CURRENT INST THAT MAY NOT HAVE BEEN ACCURATE.

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ON THE EVENING OF JAN/XA/98 I PERFORMED A HIGH FREQ EDDY CURRENT INSPECTION FOR XYZ IN ZZZ; AT ZZZ ARPT ON AN ACR B727 (YYY) PER BOEING SVC BULLETIN. THE FASTENER HOLES HAVE YET TO BE MODIFIED ON THIS ACFT; SO I ACCOMPLISHED PREMODIFICATION INSPECTION PART 1; PARAGRAPH C. THE INSPECTION WAS DONE PER B727 NON DESTRUCTIVE TESTING MANUAL. NO CRACKS WERE DETECTED. THE EDDY CURRENT INST USED IS PROPERTY OF XYZ (MAGNAFLUX ED520 S/NGFE301). PRIOR TO ACCOMPLISHING THE INSPECTION; I CHKED TO MAKE SURE THE INST HAD NOT EXCEEDED ITS CALIBRATION INTERVAL. IT HAD A CALIBRATION STICKER AFFIXED TO THE FRONT OF THE INST WHICH INDICATED IT WAS LAST CALIBRATED ON DEC/XX/97 BY ABC TEST EQUIP CERTIFICATION FACILITY IN XXX. I NOTED THAT THE STICKER CALLED FOR A RECERTIFICATION ON THE SAME DATE AND BROUGHT IT TO THE ATTN OF XYZ DIRECTOR OF QUALITY ASSURANCE. HE THEN SHOWED ME A CALIBRATION RPT FOR THE INST THAT CALLED FOR RECERTIFICATION BY DEC/XX/98; WHICH WAS THE DATE YOU WOULD EXPECT TO SEE ON THE STICKER. IT SEEMED REASONABLE TO ME THAT THE TEST LAB SIMPLY ACCIDENTALLY PUT 1997 INSTEAD OF 1998 ON THE STICKER; AND HE HAD THE RPT TO SUBSTANTIATE SUCH AN ERROR. I PROCEEDED TO CHK THE OP OF THE INST AND NOTED THE BATTERY WAS NEARLY COMPLETELY DEAD. THIS SEEMED ODD; SINCE THE INST WAS JUST IN FOR CALIBRATION; HOWEVER; AFTER CHARGING THE UNIT FOR APPROX 1 HR; THE CHARGE LEVEL WAS UP TO APPROX 1/2 SCALE ON THE METER; INDICATING THAT THE INST WAS ACCEPTING A CHARGE. BY NOW; THE ACFT WAS OPEN FOR INSPECTION SO I PROCEEDED TO ACCOMPLISH THE INSPECTION WITH THE INST PLUGGED INTO EXTERNAL AC PWR. I WAS ABLE TO OBTAIN AN ACCEPTABLE RESPONSE FROM THE REF STANDARD AND PROCEEDED TO ACCOMPLISH THE INSPECTION. AFTER FINISHING; I VERIFIED THE RESPONSE (POST CALIBRATION) AND STILL HAD AN ACCEPTABLE RESPONSE (ALTHOUGH ONLY WHEN PLUGGED INTO EXTERNAL PWR). I SUGGESTED XYZ LEAVE THE INST CHARGING OVERNIGHT AND CHK THE BATTERY CONDITION THE NEXT DAY. I SIGNED OFF THE PAPERWORK AND WENT HOME. NORMALLY; THIS WOULD BE THE END OF THE STORY WITH NO DISCREPANCIES TO RPT; HOWEVER; I HAVE SINCE THEN LEARNED SOME INFO ABOUT THE EDDY CURRENT INST THAT I FELT OBLIGATED TO RPT. ON JAN/ZZ/98; I WENT TO YYX ELECTRONICS IN XZX FOR AN UNRELATED ASSIGNMENT AND NOTICED SOME OF XYZ EQUIP WAS THERE FOR SVC. I WAS SURPRISED TO SEE THE ABOVE NOTED ED520 EDDY CURRENT INST SINCE IT HAD THE DEC/XX/97 CALIBRATION PERFORMED ELSEWHERE; SO I CAN ONLY GUESS THAT THE BATTERY WOULD NOT CHARGE SO THEY SENT IT IN TO SEE WHAT WAS WRONG. THE TECHNICIAN WORKING ON THE INST TOLD ME THAT THE INSTALLED BATTERIES WERE THE WRONG TYPE; AND THE INST WAS NOT WORKING PROPERLY. THIS LEADS ME TO BELIEVE THE CALIBRATION DONE BY ABC WAS INVALID AND THE MACHINE SHOULD NOT HAVE BEEN RETURNED TO XYZ WITH A CALIBRATION RPT UNDER THESE CONDITIONS.