Lexmark C 746 Service Manual
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Diagnostic aids3-59 5026 Go Back Previous Next 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 for the toner cartridges and photoconductor units disengage. Toner cartridge couplers Inside Photoconductor couplers Fuser motor Cartridge motor 1 Cartridge motor 2 (upper) Cartridge motor 2 (lower) Outside
3-60Service Manual 5026 Go Back Previous Next 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
Diagnostic aids3-61 5026 Go Back Previous Next 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 process. There are two paper flags: one at the bottom of the machine (paper pick) to detect input paper, including duplex second side, from all sources and one at the top (paper exit) to detect paper movement beyond the fuser. The flags are similar in design, in that a mechanical arm is moved by the media to interrupt an optical sensor; both are normally blocked when no media is present. There is also a multifunction transparency sensor that detects if: 1) tray 1 is present, 2) narrow media is being used, and 3) the media is a transparency. The sensor works for tray 1, tray 2 (500-sheet option), and the MPF. Paper pick sensor Paper pick mechanism Narrow media sensor Input sensor
3-62Service Manual 5026 Go Back Previous Next 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 within a given time, a paper jam error will be posted. Paper exit/duplex entry flag Paper exit/duplex entry sensor
Diagnostic aids3-63 5026 Go Back Previous Next 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 beltSystem board
3-64Service Manual 5026 Go Back Previous Next 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 from the system card (RIP). Through the use of a laser unit, the printhead irradiates the photoconductor drum with light and creates an invisible image called a latent or electrostatic image. Photoconductor unit The photoconductor unit consists primarily of a charge roll and the photoconductor drum. The charge roll charges the surface of the photoconductor drum to prepare it for the latent image “drawn” by the laser. Once the photoconductor drum has been written to by the laser, it is responsible for picking up toner from the cartridge developer roller and then transferring the image to the print media. Toner cartridge This unit consists primarily of the developer roll and the toner adder roll. The primary function of this unit is to supply charge toner to the photoconductor unit for transfer onto the print media. The toner adheres to the electrostatic image on the surface of the photoconductor drum which is then transferred to the print media. Fuser The fuser assembly uses heat and pressure to fuse the toner image onto the print media.
Diagnostic aids3-65 5026 Go Back Previous Next 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 essential that the contact springs are properly touching to provide a good flow. If not, print quality problems will occur. Photoconductor unit (photoconductor drum) The following illustration shows the circuit path that allows high voltage current to flow from the HVPS to the photoconductor drum contact on the photoconductor unit. It is essential that the contact springs are properly touching to provide a good flow. If not, print quality problems will occur. High voltage contact pathHigh voltage power supply High voltage contact pathHigh voltage power supply
3-66Service Manual 5026 Go Back Previous Next 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. Toner add roll high voltage contact pathDeveloper roll high voltage contact path High voltage power supplyCleaner blade high voltage contact path
Diagnostic aids3-67 5026 Go Back Previous Next 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 voltage path
3-68Service Manual 5026 Go Back Previous Next 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 energy data that is directed to the light sensitive photoconductor unit. System card Printhead Photoconductor unit