Xerox ColorQube 9303 Series Service Manual page 1716

Print Engine Self Test (PEST)
The ColorQube Print Engine Self Test (PEST), which runs automatically as part of the image
marking engine (IME) boot-up sequence, detects basic electrical wiring or electro-mechanical
faults in the IME. The PEST raises error codes to identify the IME component where the fault
has occurred.
The PEST activates each of the primary components in the IME and monitors the power con-
sumed during the test along with any associated sensor or feedback signals. The test induces
only limited component motion, does not feed any media through the IME and cannot test sen-
sors activated by media or door and cover interlocks. Media sensor and door interlock errors or
more advanced calibrations and mechanical defects are detected by the IME's run-time firm-
ware. An advantage of the PEST over run-time error detection is the PEST's ability to test indi-
vidual components in isolation, allowing more accurate pin-pointing of the fault location. PEST
can also detect partially damaged components that might pass run-time component control
tests.
Both 'hard' and 'soft' faults can be detected by the PEST:
• Hard errors indicate that a fault has occurred in a component critical to marking function-
ality and/or damage could occur to the machine if it continues to operate with the fault
present. Hard errors prevent the IME from booting and are viewable via the user interface
(UI) fault list or by entering dC123 PEST Fault History.
• Soft errors indicate that a fault has occurred in a non-critical component of the IME or that
the component may still retain some level of functionality. Soft errors do not prevent the
machine from booting, allowing the machine to continue being used at a reduced level of
functionality instead of keeping the IME shutdown until attended by the CSE. Soft PEST
fault codes are only viewable by entering
Principles of Operation
dC123 PEST Fault History.
Sensor Types and Function
The system contains sensors of various types that perform a variety of functions. One group of
sensors track the progress of the media along the media path, and detects if a jam occurs.
Other sensors detect the presence of the Ink Sticks, stop system activity if a door is open
(interlock), detect the presence and size of media, and monitor system temperatures.
Sensor Types
The types of sensors used vary with function. In general, there are several types in use:
• Photo Sensors
• Microswitches
• Hall Effect Sensors
• Temperature Sensors
• Scan Bars
Two types of photo sensors are used, photo-reflective and photo-receptive. Photo-reflective
sensors use light reflected back from an object to detect its presence. Photo-receptive sensors
use an actuator or the object itself to block the light path to detect an object or condition. Photo-
reflective sensors have the light emitter and light receiver aligned on a single surface. Output
of the photo-receptor is High when light is being reflected back and Low when it isn't. Photo-
receptive sensors consist of a LED in one arm of a U-shaped holder, and a photo-transistor in
the other arm. When the sensing area is vacant, nothing is between the arms of the sensor,
light falls on the photo-receptor sending a high signal. If the light is interrupted, the photo-tran-
sistor goes low.
Microswitches are used primarily as paper size sensors and cover interlocks. They are in a
normally open state, and close when actuated. A bank of microswitches is used to detect paper
size in the universal trays. Microswitches also employ hooks or catches for retention in the
bracket or frame.
Hall effect sensors are used to detect the presence of the waste tray, the status of the ink
loader door and to detect the drum motor position.
Temperature sensors (thermistors) have a known value of resistance whose value varies with
temperature. Used primarily in the preheater, drum, ink melt heaters, ink reservoir, and print-
heads for temperature sensing.
The IOD sensor and registration / preheat assembly scan bar outputs are digitized with a high
speed ADC. The ADC is implemented with a 10-bit CCD image digitizer. The IOD scan bar
connects to the drum driver circuit board with a 28-pin connector. The registration / preheat
assembly scan bar connects to the drum driver circuit board with an 11-pin connector.
IME Sensors
Refer to Table 1.
Sensor Function
IOD Scanbar Scan images on the Drum
Registration Scan Bar Detect media edge
(#10)
February 2013
8-22
Table 1 IME Sensor Functions
ColorQube® 9303 Family
Type Output
Optical Analog
Optical Analog