Colchester 3000 L Fanuc OT

I press and hold two buttons to start up the machine and clear the set z and x axis so I can move the carriage to the end of the machine with out over travel alarms , it seems that I press the wrong buttons , the screen become black , no more display. After checking the power unit found that the fuses burned , I replaced the 4 fuses with new ones same problem again got burned , replaced the power unit the fuses stay ok mean not burn, but screen still off, I follow the wire from the power unit to the screen should give 24Volt to screen but read low .
Could any one help?