What was found
RIGHT GEN CONT OFF LIGHT ILUMINATED. RESET, LIGHT EXTINGUISHED SOON AFTER RH BUS TIE ANUNCIATOR LIGHT CAME ON. CREW DID NOT ATTEMPT RESETOF RH BUS TIE.SDR DUE TO DECLARED IN-FLIGHT EMERGENCY CREW PHOTOS PART 1 BPCU BITE SHOWS : RIGHT GCU MONITOR "NO R GCU DATA (24-34002). BPCU MONITOR 2 FAULTS : NO APU GCU DATA ON DATA BUS CH A AND NO R GCU DATA ON ANY DATA BUS. RIGHT GEN TRIPPED OFF, RESET 1 TIME AND CAME BACK ONLINE THEN DROPPED OFF. R BUS OFF LIGHT CAME ON. STARTED APU BUT DID NOT PICK UP R BUS. RESET R BUS TIE, DID NOT HELP. FLEW REMAINING OF FLIGHT WITH R BUS OFF. PERFORMED BPCU BITE PER FIM 24-20 T 810, BITE PASSED, PREVIOU FLIGHT GOT R GCU FAULT WITH MSG 24-30102. RAN BOTH ENGINES WITH ELECT LOAD AND NO EXISTING FAULTS ON EICAS, ENGINES RAN FOR 20 MINUTES WHILE DISCONNECTING RT ENG GEN APU AND BUS TIE; STILL NO FAULTS. SWAPPED APU AND RT ENG GCU PER AMM 24-22-02-004-001-001 AND TRIED CONNECTING APU GEN, APU GEN WOULD NOT CONNECT. NO VOLTS OR FREQS DISPLAYED. LOG CONTINUED, PICS ADDED. LOG CONTINUED... RAN BPCU BITE AGAIN ON APU SWAPPED GCU AND RECIEVED APU MSG 24-30103 AND GOT APU GCU FAULT. SWAPPED ORIGINAL GCU'S BACK TO ORIGINAL. RAN APU AND APU GEN CONNECTED, VOLTS AND FREQ