Did the technician check the power supply already?
The first thing the technician should do is to check the power supply voltages: +Vcc, -Vcc, +15V, -15v, +5V and +3,3V. These voltages can be checked on the FAJ pcb, refer to the servicemanual FAJ 2/2 circuit diagram. It looks like the +5V is o.k. because the blue light and the FDD light do lit and these are powered directly by +5V.
If one or more voltages are not correct it can be caused by a defective component in the power supply itself or by a too heavy load and thus activating the overload protection. This can be checked by disconnecting the connectors that distribute the voltages to the other boards.
Good luck!
Bert