What was found
FLT#506, BNA-BOS. (AIRCRAFT DIVERTED TO BWI AND DECLARED AN EMERGENCY) 'AT 35000 FT ELECTRICAL FAILURE (AC POWER LOST "KIND OF"). RAT FAIL. APU START BELOW 30000 NO HELP. QRH AC BUS 1 OFF NO CHANGE; REF LOG 3989640-1 (REMOVED AND REPLACED GLC #1 FOR ASSURANCE AND ACCOMPLISHED SATISFACTORY CHECK OUT ALL WORK AMM 24-21-21 900CA01 6179 900CA01 4615), 3989640-2 (REMOVED AND REPLACED BTC FOR ASSURANCE AND ACCOMPLISHED SATISFACTORY CHECK OUT ALL WORK AMM 24-51-07 900CA01 6180 900CA01 2711), 3989636-2 (R/R GCU # 1 IAW 24-21-19 OPS CHECK GOOD 1701321F 1191 1701321F 1487), 3989637-1 (REMOVED AND REPLACED GCU #2 IAW AMM 24-21-19 OPS CHECK GOOD ) REPLACED GCU 1, GCU 2, GLC 1 AND BTC. ACCOMPLISHED SATISFACTORY GROUND RUN ENGINES 1 AND 2 NO FAULTS NOTED OK FOR CONT SERVICE.'