Four things I can think of off the top of my head on the Hoshizakis. First is the bin switch. Second is the 10 amp safety fuse Third is the high pressure safety switch, Fourth is the power switch in ice mode. Any one of these will prevent the transformer from making control power. You can test for it at plug K2 on the bottom left of the control board. Pins 1 and 2. Also you mentioned that you had power coming in the back of the machine, Do you have a good neutral. The power supply transformer on this machine requires it.