AN L1011 WAS DISPATCHED IN NON COMPLIANCE WITH #1 IDG DEFERRED PER THE MEL IN CONFLICT WITH A PREVIOUS DEFERRED ITEM.

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PREFLT FOUND ACFT HAD MULTIPLE DEFERRALS (10). WENT OVER EACH ONE WITH MAINT PERSONNEL PRESENT; HAVING THEM REPLACE MISSING DEFERRAL STICKERS. 2 DEFERRALS WERE INTERRELATED -- ELECTRICAL SYS LIGHT ON PLT'S CAUTION WARNING ANNUNCIATOR PANEL INOP AND #1 IDG. THE ELECTRICAL SYS LIGHT REQUIRED MAINT TO PERFORM A LIGHT TEST ON FE'S ELECTRICAL SYS PANEL; FOR THE FE TO SCAN ELECTRICAL PANEL DURING TKOF FOR ABNORMAL INDICATIONS; AND CRUISE TO SCAN ELECTRICAL SYS PANEL MORE FREQUENTLY. THE MEL ALSO STATED 3 IDG SYS ARE OPERATIVE AND REFERRED TO THE IDG SYS MEL. UPON READING IDG MEL; IT STATED 3 WERE INSTALLED; 2 WERE REQUIRED FOR DISPATCH AND LISTED APU OPERATING PROCS BELOW 10000 FT AND SELECTING ESSENTIAL PWR TO OPERATING GENERATORS. UNFORTUNATELY; IN GOING OVER THE PROCS TO OPERATE THE ACFT WITH MULTIPLE MEL'S; I MISSED THE POINT WITH ELECTRICAL SYS LIGHT INOP ON ANNUNCIATOR PANEL INOP; 3 IDG'S WERE REQUIRED -- NOT 2 IDG'S AND AN APU GENERATOR. NOT ONLY DID I MISS THIS; MAINT CTL WHO ISSUED THE MELS; THE DISPATCHER; THE MECH WHO SIGNED THE MAINT RELEASE; AND THE MECHS I DISCUSSED THE MEL'S MISSED IT. DURING QUIET TIME DURING CRUISE; DISCOVERED MISTAKE. NOTIFIED MAINT AND OUTBOUND CREW OF MISTAKE. MAINT REPAIRED #1 IDG.