During the generator ops check, the book tells you to sequentially turn on/off the generators to tell you if the generator can handle the load of the aircraft. When generator 2,3,4 are off generator #1 shows high voltage on phase B only (121 volts). Along with that, we are getting ECBU's 6,7,8 input failures. We have changed GCU, engine generator and swapped BIU's. We still are getting the same problem. Any input will help. Thanks in advance