A B757 AT CRUISE LOST BOTH L AND R AC BUSSES. ISOLATED PROB TO THE R GENERATOR SYS AND PWRED R BUS WITH APU.

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WE WERE IN CRUISE AT FL350. WE HEARD A CLICKING (THUMP) NOISE AND LOOKED DOWN AT EFIS AND REALIZED ALL BLANK. CAPT CALLED 'I GOT IT' AND I REPLIED 'OK; GETTING THE BOOK' (ACFT MANUAL FO'S CARRY). WE REALIZED A DOUBLE GENERATOR (OR SIMILAR) FAULT AND I LOOKED UP ELECTRICAL ABNORMAL. I ADVISED ATC WE WERE EXPERIENCING AN ELECTRICAL PROB AND WOULD KEEP THEM INFORMED. THEY ACKNOWLEDGED. THE CAPT AND I DECIDED TO FIRST GET THE APU STARTED. I INITIATED THAT; THEN WENT BACK TO THE HANDBOOK. WE PROCEEDED WITH THE ALL ELECTRICAL PWR LOST CHKLIST. AFTER SEVERAL ATTEMPTS WITH TURNING EACH GENERATOR RELAY OFF/ON/OFF AND GETTING THE APU ON LINE; WE REALIZED THE R GENERATOR WAS KNOCKING ALL PWR OFF LINE. I SECURED THE R GENERATOR RELAY OFF; ESTABLISHED L GENERATOR AND APU GENERATOR ON LINE; AND CONTINUED CHKLIST TO LOAD FMC WITH PERFORMANCE AND RTE DATA. ALSO; START TO ESTABLISH CONTACT WITH COMPANY DISPATCH. WE ADVISED ATC WE HAD RETURNED SYS ELECTRICAL PWR AND REQUESTED DIRECT TO CAP VOR. THEY HANDED US OFF TO THE NEXT FREQ WHO PROMPTLY GAVE US DIRECT CAP VOR AND AS FILED. AS FAR AS I KNOW (SINCE I WAS ENGROSSED IN THE CHKLIST) IS THAT WE WERE CLOSE TO ON COURSE AND ALT THROUGHOUT THE PWR OUTAGE. WE CONTINUED TO LAX WITHOUT FURTHER PROBS AND ENTERED PROB IN MAINT LOGBOOK.