The standby light is on, indicating CPU is now working.
but receiver doesn't power up -- either by switch on front or by remote. There is no display & no operational mode is functioning. This means the power on relay RL901 isn't ON, perhaps. Follow these steps:
(1)download TX DS555 service manual
(2)Unplug the amp
(3)open the amp cover(4)check the AC inlet board, PS6303
(5)see P.31 B(vert.)D(horizon.)(6)Check R922, R923 ,Q921 ,C922, RL901 and a T-fuse,thermal fuse, located at the primary side of the large transformer, ETC-6304.