A B767 LOSES IT'S #1 ENG DRIVEN GENERATOR DURING DSCNT INTO CVG. THE APU WAS PLACED ON LINE AND; AFTER 10 MINUTES; THE CAPT BEGAN TO LOSE HIS FLT INSTRUMENT DISPLAY ON AN ON-AND-OFF-AGAIN BASIS. THE FLUCTUATING PWR ALSO AFFECTED THE RADIOS BUT THE CREW WAS ABLE TO DECLARE AN EMER AND LANDED STRAIGHT IN.

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DURING OUR DSCNT FOR APCH AND LANDING IN CVG WE HAD A L GENERATOR FAIL. WE ACCOMPLISHED THE ABNORMAL PROC CHECKLIST WHICH INCLUDES STARTING THE APU AND USING ITS GENERATOR TO PWR THE ITEMS NORMALLY PWRED BY THE L ENG GENERATOR. HAVING DONE THIS; THE ELECTRICAL SYSTEM WAS NOW FULLY PWRED AGAIN AND EVERYTHING WORKED OK FOR ABOUT 10 MINUTES. ABOUT THE TIME WE TURNED ONTO A LONG FINAL APCH; THE CAPT'S INSTRUMENTS WENT BLANK THEN PWRED UP AGAIN; THEN WENT BLANK AGAIN; THEN PWRED-UP AGAIN; ETC. THIS SURGING AND CYCLING ON AND OFF CAUSED THE L SIDE INSTRUMENTS TO FLASH ON AND OFF LIKE A 'PINBALL MACHINE.' OUR RADIOS BEGAN TO CUT IN AND OUT; AND EVEN THE FO'S (R SIDE) INSTRUMENTS SHOWED A FEW STRANGE FLUCTUATIONS (PROBABLY DUE TO ALL THE ELECTRICAL PWR SURGES). THE ACFT WAS ALMOST IMPOSSIBLE TO FLY FROM THE L SIDE (DUE TO THE FLASHING INSTRUMENTS); SO I TURNED ACFT CTL OVER TO THE FO. BECAUSE WE DIDN'T KNOW HOW LONG OUR RADIOS OR R SIDE INSTRUMENTS WOULD LAST; WE DECLARED AN EMER AND REQUESTED AN IMMEDIATE LNDG CLRNC. WE BROKE OUT OF THE CLOUDS AND LANDED OK. NOTE: WE WERE ABLE TO RADIO OUR EMER AND GET LNDG CLRNC (IN SPITE OF OUR RADIOS CUTTING IN AND OUT WITH THE ELECTRICAL SURGES). WE NEEDED TO LAND. IF THE PWR SURGES TOTALLY KNOCKED OUT OUR RADIOS; I COULD HAVE GRABBED MY CELL PHONE OUT OF MY BRIEFCASE AND CALLED THE TWR IF I KNEW THE TELEPHONE NUMBER. SUGGESTION: PUT THE TWR TELEPHONE NUMBER ON THE COMMERCIAL CHART PAGES (FOR EMER SITS LIKE OURS; OR A HIGHJACKING; OR OTHER SERIOUS EMERGENCIES). CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT THE POST FLT INSPECTION REVEALED THAT THE L GENERATOR CTL UNIT HAD MALFUNCTIONED; CAUSING A L BUS TIE FAULT. THIS WAS SHORTING THE CAPT'S INSTRUMENTS AND INTERFERING WITH THE RADIO CIRCUITS. THE L GENERATOR CTL UNIT WAS REPLACED. THE CAPT COULD NOT UNDERSTAND WHY THIS OCCURRED SINCE THE GENERATOR HAD BEEN DISCONNECTED DURING THE APCH AND PRIOR TO THE APU BEING PLACED ON LINE.