Lexmark C 746 Service Manual

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Photoconductor unit/toner cartridge drive
The photoconductor units (four) and toner cartridges (four) receive drive power from the EP drive assembly 
motors. The top cartridge motor 1 on the EP drive assembly provides drive to the top two photoconductor units 
and toner cartridges (yellow and cyan). Likewise, the bottom cartridge motor 2 drives the two bottom 
photoconductor units and toner cartridges. When the printers top access door is open, the couplers...

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Transfer belt drive
The transfer belt unit receives drive from a motor located on the EP drive assembly. When the top access door 
is open, the coupler for the transfer belt disengages.
Fuser drive
The fuser drive (motor) is built into the fuser assembly and drives the fuser rollers to turn.
Inside
Coupler
Transfer belt motor
Outside 

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Duplex drive
The duplex drive is driven by the MPF/duplex motor through the MPF/duplex gear. Drive is provided to three 
drive shafts in the duplex unit by a belt that is driven by the MPF/duplex motor. The drive shafts move the print 
media through the duplex unit during printing.
Paper sensing
Sensors are strategically placed in the printer to ensure that the print media is making it to specific points within 
a given time in the electrophotographic...

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Paper exit/duplex entry sensor and bin full flag
The paper exit/duplex sensor flag detects movement in two directions: as the paper exits the fuser and as it is 
retracted from the exit tray back into the duplex path. Each sheet must be driven past the fuser exit flag and 
allowed to fall before being turned around and starting the duplex path. If the print media activates the paper exit 
flag for too long, or the print media doesnt reach the paper exit flag...

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Electrophotographic (EP) process
Main components
System board
The system board is the brain of the printer. During the print process, an image is sent from a computer to the 
system board. The raster image processor (RIP) portion of the system card converts the data into a raster image 
and feeds this data along with control information to the printhead.
Fuser
Printhead High voltage
power supply
Developer (toner)
cartridge
Transfer belt
Photoconductor...

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High voltage power supply (HVPS)
Provides a high voltage charge to:
•The charge roll located in the photoconductor unit
•The photoconductor drum located in the photoconductor unit
•The toner adder roller (TAR) located in the toner cartridge
•The developer roll located in the toner cartridge
•The doctor blade located in the toner cartridge
•The four transfer rolls located in the transfer belt
Printhead assembly
The printhead receives control and image data...

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Charging
The primary component of the charging process is the high voltage power supply. The following provides 
information that covers the mechanical transfer of the high voltage through a set of springs to each 
subcomponent of the charging process.
Photoconductor unit (charge roll)
The following illustration shows the circuit path that allows high voltage current to flow from the HVPS to the 
charge roll contact on the photoconductor unit. It is...

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Toner cartridge
The following illustration shows the circuit path that allows high voltage current to flow from the HVPS to the 
toner cartridge. The toner cartridge contains three parts that are provided high voltage from the HVPS. These 
three parts are: the doctor blade, the developer roll, and the toner adder roll (TAR). It is essential that the contact 
springs are properly touching to provide a good flow. If not, print quality problems will occur....

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Transfer belt
The transfer belt houses four transfer rollers that provide image transfer from the photoconductor drum to the 
print media. The transfer belt receives its high voltage charge through spring contacts located on the transfer 
contact assembly as shown in the following illustration. For the sake of simplicity, only one of the rollers high 
voltage paths is shown. This path is typical for the other three rollers as well.
Transfer belt high...

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Exposing
The main components in the exposure process are the system card, the printhead and the photoconductor unit. 
The following illustration depicts a typical data path for a single color exposure.
Data is received from a computer into a port on the system card. The system cards RIP function converts this 
data into raster information which is fed to the printhead along with other control data. The data is converted by 
the printhead laser into light...