Rack rotation failure
- The rack positioning sensor is in the blocked state when the rack motor remains deenergized. 
- The rack positioning sensor is not blocked a second time even after the lapse of a predetermined period of time after it has been blocked once while the rack motor remains energized.
- The rack positioning sensor is unable to detect the deceleration control position after the lapse of a given period of time after the rack motor has started while the rack motor is turning. 
- The count value of the edge of ON signal of the rack positioning sensor during each developing positions are not a predetermined value while the rack motor is turning.