AN AIRBUS 319 IN CRUISE AT FL350 DECLARED AN EMER AND DIVERTED DUE TO LOSS OF #1 BUS AND ESSENTIAL BUS #1. CAUSED BY WELDED CONTACTS ON #1 GENERATOR CONTACTOR.

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AT CRUISE FL350; I (CAPT) WAS TALKING TO 'B' FA ON INTERPHONE WHEN IT CUT OFF. SIMULTANEOUSLY; I NOTICED ALL 6 CRTS WERE BLANK. FO FLYING ON STANDBY INSTRUMENTS. SCREENS EVENTUALLY CAME BACK ON; ONE AT A TIME (COMPLETELY BLANK APPROX 30 SECS). MULTIPLE ELECTRICAL FAILURES: GEN 1; AC ESS BUS 1; AC BUS 1; VENT EXTRACT; NW STEERING. MULTIPLE SECONDARY FAILURES. NUMEROUS SYSTEM ITEMS INOP. FA'S RPTED AN ELECTRICAL SMELL. DECLARED EMER; DIVERTED TO ZZZ. STOPPED ON RWY AND TOWED TO GATE. APU AND EXTERNAL POWER WOULD NOT SUPPLY LEFT SIDE OF ELECTRICAL SYSTEM. MAINT REPLACED SEVERAL COMPONENTS OF THE ELECTRICAL SYSTEMS; SUSPECTING A LOOSE BUS TIE CONTACTOR. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE SIX CRT INSTRUMENTS WERE BLANK FOR ABOUT 30 SECS AND THEN RECOVERED. THE RPTR SAID THE ENTIRE #1 AC BUS WAS LOST INCLUDING ESSENTIAL AC WHICH DID NOT SWITCH IN NORMALLY THROUGH THE ESSENTIAL AUTO FEED. THE RPTR STATED THE APU WOULD NOT POWER #1 BUS. THE RPTR SAID THE #1 GENERATOR CONTACTOR WAS FOUND FAILED WITH WELDED CONTACTS.