A B757 EXPERIENCED ELECTRICAL PROBLEMS ON TAKEOFF ROLL. THE FLT CREW CONFERRED WITH MAINTENANCE AND DISPATCH; EVENTUALLY RETURNING THE ELECTRICAL SYSTEM TO NORMAL AND CONTINUING THE FLIGHT.

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DEPARTING ZZZ DURING THE HIGH SPD PHASE OF THE TKOF ROLL; BOTH FMC CDU'S; THE FMC CAUTION LIGHT AND THE LOWER EICAS SCREEN AND THE R LNDG LIGHT STARTED FLICKERING OFF AND ON. AT ROTATION; VERY MANY EICAS MESSAGES STARTING APPEARING ON THE UPPER EICAS CRT. ON LIFT-OFF WE HAD AN ELECTRICAL FAILURE. AFTER ENSURING THE FLT'S SAFETY; WE SAW THAT THE R BUS OFF LIGHT; THE R GENERATOR CTL OFF LIGHT AND THE R BUS TIE ISOL LIGHT WERE ON AND ASSOCIATED SYS FAILURE CAUTION LIGHTS. THE APU HAD BEEN LEFT RUNNING FOR TKOF; BUT; OF COURSE; DIDN'T PICK UP THE BUS DUE TO THE BUS TIE ISOL. THE FO LOST MUCH OF HER FLT INFO; SO ACFT CTL WAS HANDED OFF TO ME WHILE SHE ACCOMPLISHED IRREGULAR PROCS. THE R BUS TIE ISOL WAS STILL ILLUMINATED AND A CALL TO DISPATCH/MAINT INITIATED. MAINT ADVISED TO CYCLE THE BUS TIE SWITCH (NOT COVERED PER FLT MANUAL PROC) THUS REGAINING THE BUS TIE; WITHOUT WHICH; ONLY THE ASSOCIATED GENERATOR COULD PWR. THE R YAW DAMPER INOP LIGHT WAS STILL ON AFTER ACCOMPLISHING ALL CHKLISTS AND MAINT ADVISED TO CYCLE ITS CIRCUIT BREAKER GIVING US BACK THE R YAW DAMPER.