I got this printer with scanner problem - it does strange things including moving here and there, blinking etc. during initialization, than the formatter gives up and writes "scanner error".
But I've noticed the main power supply makes noise which corresponds to the scanner action. Quite loud noise actually. It hums even with light load (that's even worse). I've removed the board and tested without anythign connected, the noise is better but still there, comes from main transformer area. Besides the HV area for motors and fixing unit, It has one main 24V output, +3,3 V is derived from it. The A2719 MOSFET was quite overloaded, darkening PCB around. There is also +5 V, not sure where it comes from.
Voltages check fine with multimeter but I've found quite high low-frequency ripple in there, see attachement. All caps are good quality and check fine. Not sure where the problem may be, feedback?
But I've noticed the main power supply makes noise which corresponds to the scanner action. Quite loud noise actually. It hums even with light load (that's even worse). I've removed the board and tested without anythign connected, the noise is better but still there, comes from main transformer area. Besides the HV area for motors and fixing unit, It has one main 24V output, +3,3 V is derived from it. The A2719 MOSFET was quite overloaded, darkening PCB around. There is also +5 V, not sure where it comes from.
Voltages check fine with multimeter but I've found quite high low-frequency ripple in there, see attachement. All caps are good quality and check fine. Not sure where the problem may be, feedback?
Attached Files
Half of the computer problems is caused by bad contacts 
