AN INTL WDB CREW HAD A COMPASS PROB RIGHT AFTER TKOF.

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NORMAL TKOF RWY 13R JFK; CLRED TO CLB AND MAINTAIN 5000 FT AND HDG OF 155 DEGS. AFTER CALLING GEAR UP AND HDG SELECT; I SCANNED GEAR LIGHTS; ENG INST; TFC WATCH AND COMMAND STEER BAR. FOLLOWED COMMAND BAR TO 155 DEG HDG ON HSI. FO CALLED 'CHK HDG' AND FE POINTED TO MAGNETIC COMPASS AND READING 100 DEGS. I BEGAN R TURN USING MAGNETIC COMPASS AND FO SIMULTANEOUSLY INITIATED FAST SLAVE ON BOTH SIDES (BECAUSE HIS CARD WAS PRECESSING WITH WINGS LEVEL); AND HE NOTIFIED DEP 'WE HAVE A HDG PROB.' THEY RESPONDED 'I CAN HELP' AND GAVE R TURN FOR VECTOR WHICH I FLEW ON MAGNETIC COMPASS. FO THEN COMPLETED SECOND FAST SLAVE CYCLE. ALL COMPASS SYS OPERATED NORMALLY FOR REMAINDER OF FLT. LATER CHK WITH FLT ATTENDANT REVEALED FIRST CLASS PAX WAS USING LAP TOP COMPUTER ON GND AND INFLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS ACFT WAS ON ITS WAY FROM JFK TO PARIS AND NEEDED A COMPASS. THE SLAVED/FREE DIRECTIONAL GYROSCOPE SWITCHES WERE CHKED IN SLAVED ON THE PREFLT AND COMPASS CHKS WERE MADE IN THE CHOCKS AND ON TAXI OUT. A TWR SUPVR NOTIFIED THE AIRLINE AND THERE HAVE BEEN SEVERAL MEETINGS BTWN THE RPTING CAPT AND HIS CHIEF PLT ON THIS SITUATION. THE GENERAL AGREEMENT IS THAT 'IT'S A WDB;' MEANING THIS SORT OF THING HAPPENS ON THIS ACFT AND THEN IT FIXES ITSELF. EVERYONE SEEMS TO AGREE THAT ELECTRONIC DEVICES CAN AFFECT NAV SYS; BUT NO ONE WANTS TO BELIEVE THAT THESE DEVICES CAN AFFECT THE COMPASS SYS.