Lexmark C 746 Service Manual
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Diagnostic aids3-69 5026 Go Back Previous Next Developing The two primary components of the developing process are the photoconductor unit and the toner cartridge. The toner cartridge contains a toner adder roll, developer roll and toner. Toner is advanced toward the toner adder roll by three paddle assemblies. The advanced toner clings to the electrically charged toner adder roll. The toner on the toner adder roll is then electrically attracted to the developer roll because of the difference in electrical charge between the toner adder roll and the developer roll. The toner uniformly coats the developer roll with help from the doctor blade and is introduced to the electrostatic image on the photoconductor drum. The toner then transfers to the photoconductor drum. Photoconductor unit Developer cartridge Paddles Toner add roll (TAR) Developer roll Photoconductor drum
3-70Service Manual 5026 Go Back Previous Next Transferring After the toner is attracted to the photoconductor drum, the image is ready for transfer onto the print media. The print media is advanced in the paper path onto the transfer belt and is carried along the belt underneath each photoconductor unit. The charged transfer roll(s) located inside the transfer belt pulls the image from the photoconductor drum to the print media. This is a direct transfer method. The main function of the transfer belt is to provide transport for the print media. Toner is not transferred directly to the belt during the print process. Photoconductor unit Photoconductor drum Transfer roll
Diagnostic aids3-71 5026 Go Back Previous Next Fusing After the image has been transferred onto the print media, it is ready for fusing. The print media is transported into the fuser where the hot roll and backup roll use a combination of high heat and pressure to melt and press the toner to the media. Backup roll Hot roll
3-72Service Manual 5026 Go Back Previous Next Cleaning The transfer belt and photoconductor drum are cleaned at the end of the electrophotographic process cycle. The transfer belt surface is cleaned as it rotates past a cleaning blade and shaft located inside the transfer belt assembly. Any waste toner that is scraped off of the belt is collected in the waste toner container located next to the belt inside the transfer belt unit. The photoconductor drum is cleaned by the cleaning blade. Transfer belt cleaning bladePhotoconductor drum cleaning blade Transfer belt cleaning shaft Transfer belt waste toner container
Diagnostic aids3-73 5026 Go Back Previous Next Electrical interlock 5 V interlock switch An interlock switch (A) triggered by the front access door disables the +5 V output to the printhead which turns off the laser. 24 V interlock switch The 24 V interlock switch is located at the front-right side of the machine when you open the front door. Opening the front door disengages the 24 V interlock switch and cuts the 24 V supply to the system board, HVPS, motors, and fuser. Closing the front door triggers a switch that initializes the motor. When the 24 V switch opens, the normally open side of the switch is activated which signals the system board to disable a +24 V power supply output, turning off all high voltage supplies, the bump/align motor, the duplex motor and the fuser motor for safety considerations. Warning:Never poke or force cover the switch while fixing the machine. This can harm the person and machine. Gearbox shield removed 24V interlock switch
Repair information4-1 5026 Go Back Previous Next 4. Repair information Safety information •The safety of this product is based on testing and approvals of the original design and specific components. The manufacturer is not responsible for safety in the event of use of unauthorized replacement parts. •The maintenance information for this product has been prepared for use by a professional service person and is not intended to be used by others. •CAUTION: When you see this symbol, there is a danger from hazardous voltage in the area of the product where you are working. Unplug the product before you begin, or use caution if the product must receive power in order to perform the task. Data Security Notice This printer contains various types of memory that are capable of storing device and network settings, information from embedded solutions, and user data. The types of memory-along with the types of data stored by each-are described below. •Volatile memory—This device utilizes standard Random Access Memory (RAM) to temporarily buffer user data during simple print and copy jobs. •Non-volatile memory—This device may utilize two forms of non-volatile memory: EEPROM and NAND (flash memory). Both types are used to store the operating system, device settings, network information, scanner and bookmark settings, and embedded solutions. •Hard disk memory—Some devices have a hard disk drive installed. The printer hard disk is designed for device-specific functionality and cannot be used for long term storage for data that is not print-related. The hard disk does not provide the capability for users to extract information, create folders, create disk or network file shares, or FTP information directly from a client device. The hard disk can retain buffered user data from complex scan, print, copy, and fax jobs, as well as form data, and font data. To erase volatile memory, turn off the printer. To erase non volatile memory see “Configuration menu (CONFIG MENU)” on page 3-27 item pertaining to this. To erase the printer hard disk see “Configuration menu (CONFIG MENU)” on page 3-27 item pertaining to this. The printer operator panel and RIP/controller board contain NVRAM. After removing the old part the part must be returned to your second level support. CAUTION—POTENTIAL INJURY: The printer weight is greater than 54 lbs (24.5kg), and requires two or more trained personnel to lift safety.
4-2Service Manual 5026 Go Back Previous Next Handling ESD-sensitive parts Warning: Read the following before handling electronic parts. Many electronic products use parts that are known to be sensitive to electrostatic discharge (ESD). To prevent damage to ESD-sensitive parts, follow the instructions below in addition to all the usual precautions, such as turning off power before removing electronic cards: •Keep the ESD-sensitive part in its original shipping container (a special “ESD bag”) until you are ready to install the part in the printer. •Make the fewest possible movements with your body to prevent an increase of static electricity from clothing fibers, carpets, and furniture. •Put the ESD wrist strap on your wrist. Connect the wrist band to the system ground point. This discharges any static electricity in your body to the printer. •Hold the ESD-sensitive part by its edge connector shroud (cover); do not touch its pins. •If you need to put down the ESD-sensitive part for any reason, first put it into its special bag. •Printer covers and metal tables are electrical grounds. They increase the risk of damage, because they make a discharge path from your body through the ESD-sensitive part. (Large metal objects can be discharge paths without being grounded.) •Prevent ESD-sensitive parts from being accidentally touched by other personnel. Install printer covers when you are not working on the printer, and do not put unprotected ESD-sensitive parts on a table. •If possible, keep all ESD-sensitive parts in a grounded metal cabinet (case). •Be extra careful in working with ESD-sensitive parts when cold-weather heating is used, because low humidity increases static electricity. Handing the photoconductor unit The following precautions must be observed when handling the photoconductor unit. The photoconductor unit is a supply item you will have to remove during some of the repair procedures: Transportation/storage Use the specified carton whenever moving or storing the photoconductor unit. Handling •The optical photoconductor roller in the photoconductor unit exhibits the greatest light fatigue after being exposed to strong light over an extended period of time. Never expose it to direct sunlight. Cover the photoconductor unit when you remove it from the printer. •Use care not to contaminate the surface of the optical photoconductor roller with an oil-based solvent, fingerprints, and other foreign matter. •Do not scratch the surface of the optical photoconductor roller. Parts not to be touched Any part where the mounting screws are used to meet a printer alignment set at the factory must not be removed, disassembled, or adjusted.
Repair information4-3 5026 Go Back Previous Next Screw and retainer identification table The following table contains screw types and retainers, locations, and quantities necessary to service the printer. Pay careful attention to each screw type location when doing removals. You must install the correct screw type in each location during reassembly. Sizes are as close to actual as possible, as long as the printout is not scaled or resized. Screw identification table P/N Screw type Location Qty 10B1580 #6 panhead Cartridge cooling fan to top cover 2 Cooling fan to top cover 2 1126828 E-clip M3 LR overcenter bell crank to side frame 1 1126829 E-ring M4 MP feeder gears to right side frame studs 2 18B0832 Taptite M3 L6 panhead5 V interlock switch to right frame 1 Card support plate to upper plate 2 Card support plate to lower plate 3 Card support plate (and printhead ground) to left frame 5 Card support plate to right frame 4 Cartridge left guide assembly to left plate (interior side of plate assembly) 4 COD (color-on-demand) drive assembly to upper plate 3 COD shaft assembly to upper plate 2 Contacts assembly to left frame next to auger worm gear 2 Contacts assembly to left frame near duct 2 EP drive to right plate (exterior side) 8 Front door ground wire to right frame bracket 1 HVPS to left frame plate 1
4-4Service Manual 5026 Go Back Previous Next 18B0832 (Cont.)Taptite M3 L6 panheadLaser support plate to lower plate 2 Left camshaft lock assembly to printer frame 2 Left frame assembly to laser support plate 2 Left frame assembly to lower plate 4 Lower plate to left frame assembly 2 LVPS support plate to right plate 4 LVPS to right frame plate and support bracket 5 Motor driver card to EP drive assembly 2 MPF driver cover to right frame 3 Right camshaft lock assembly to printer frame 2 Right frame assembly to laser support plate 2 Right frame assembly to lower plate 3 System board to RIP plate 9 Top cover assembly to printer frame 5 Upper plate to right frame assembly 3 Upper plate to left frame assembly 3 Upper plate to laser support plate 3 18B0939 Plastite M3x6 flatheadGearbox plate assembly to frame 4 18B2302 Machine M2.6 L3-3.5MP feeder/duplex drive motor to rightside plate 2 18B2315 Machine M3 panhead L35Printhead 1 27S2836 Taptite M3 L6 panhead, blackLeft cover to printer frame (next to system board) 1 Rear cover frame to frame 8 Rear left cover to printer frame 1 Rear right cover to printer frame 1 Right cover to printer frame 4 Screw identification table (continued) P/N Screw type Location Qty