Lexmark X 850 Owners Manual
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General information1-9 7500-XXX Media transport path layout The following is a cross section of the laser printer, showing main components directly associated with the media path and transport. Main components associated with transport of media Duplex media transport roll ASM MPF MPF Transport pinch roll MPF Transport roll ASM Transport roll ASM Media transport pinch roll Separation rollFeed roll Duplex media center transport roll ASM Duplex media transport pinch roll Duplex media transport roll ASM MPF pick rollRegistration roll ASM Pick rollRegistration pinch roll Drum Transfer roll ASM Heat Roll Exit 1 media exit pinch rolls Exit 1 media exit roll ASM Exit 2 media transport roll ASM Exit 2 media exit pinch rolls Exit 2 media exit roll ASM Pressure roll Exit 2 Duplex TR AY 4 TR AY 3 (TTM) Tandem tray Tray 4 transport roll ASM
1-10MFP Service Manual 7500-XXX Functions of main components •Media tray assembly •Media feed unit assembly •MPF •Xerographics •Fuser •Drive •Electrical components and rolls Media tray assembly It is necessary to adjust the front media tray guide assembly, rear media tray guide and media tray end guide of the media tray assembly to match the media size. Front media tray guide assembly and rear media guide The front media tray guide assembly can be adjusted to different media sizes by moving the guides to the front or rear. These guides come into contact with the media and hold it in position. The rear media tray guide moves together with the front media tray guide assembly. Media tray end guide The media tray assembly is designed so it can adapt to the media length in the media feed direction by moving the media tray end guide to the left or right. Bottom plate The force pushing up the bottom plate is transmitted by the driving force of the motor on the media feed unit assembly to the lift up shaft through the gear (13/60 tooth) and sector gear (12 tooth). The bottom plate is pushed up by the rotation of the lift up shaft, which causes the supplied media to come in contact with the pick roll.
General information1-11 7500-XXX Media tray assembly Detection of media size The media size set for the media tray assembly is transmitted to the switch (media size) by moving these guides. The media size is detected by the on/off information of these switches. Media feed unit assembly Since tray 1 and tray 2 are functionally equivalent in terms of the switch (media size), sensor (media out), sensor (media level) and sensor (pre-feed), only the components of one tray are described here. The media feed unit assembly is a mechanical unit supplying media from the media tray assembly to the printer. The driving force, from the media feed lift motor on the media feed unit assembly, is transmitted to the three media feed rolls to feed media. When the pick roll picks up media, the remaining media decreases, and the actuator of the sensor (media level) lowers accordingly. When the sensor (media level) detects the lowering, the media feed lift motor is activated to lift the lift up shaft and the bottom plate accordingly. Thus, the remaining media is ready to be fed. Media feed lift motor This motor is activated to feed media and to lift the bottom plate. When feeding media, it rotates forward to drive the pick roll. When lifting the bottom plate, it rotates reversely to drive the tray module gears to lift the lift up shaft. Switch (media size) This switch (media size) sets the size of media supplied from each media tray assembly. A signal indicating the media size is transmitted as a voltage to the printer engine card assembly. Sensor (media out) If media runs out in a media tray assembly, the actuator lowers and the actuator flag, unlocks the sensing area of the sensor (media out). The sensor light is transmitted. When the sensing area is blocked (media is present), the signal is off. Rear media tray guide Bottom plate Front media tray guide assemblyMedia end guide
1-12MFP Service Manual 7500-XXX Sensor (media level) This sensor detects by the actuator position whether media in the media tray assembly is lifted. When the flag of the actuator unblocks the sensing area of the sensor (media level), the sensor detects that the media has been lifted. Sensor (pre-feed) This sensor detects a media jam in the media tray assembly by the media position and sensor on/off time. The sensor on/off states can be monitored by media passing through the sensor (pre-feed) sensing area. Media feed lift motor Sensor (pre feed) Sensor (media level) Sensor (media out) Media feed unit asm Front Tray asmSwitch (media size)
General information1-13 7500-XXX Multi-purpose feeder (MPF) The MPF is a mechanical unit suppling media to the printer. The driving force from the transport motor of the dual drive motor assembly is transmitted to the MPF feed roll to feed media. MPF pick roll The MPF pick roll feeds media set on the MPF and into the feeder. MPF pick solenoid The MPF pick solenoid transmits the driving force from the main motor to the MPF pick roll. Sensor (MPF media out) The sensor (MPF media out) detects whether media is present on the MPF. Sensor (MPF media width) The MPF side guides detects the width (length in the main scanning direction) of media on the MPF. MPF media transport roll ASM Sensor (MPF media out) MPF pick roll MPF pick solenoid Sensor (MPF media width)
1-14MFP Service Manual 7500-XXX Detecting media size The size of media on the MPF is transmitted by moving the MPF side guide, and is determined by the printer engine card assembly. Media sizes that can be automatically detected are as follows: Media size Width (mm) Feed length (mm) Side-guide stopper (min.) 84 - Media detection area (min.) 88.2 - 3.5” x 8.5”SEF 88.9 215.9 Postcard SEF 101.6 152.4 5.5” x 8.5” SEF 139.7 215.9 Postcard LEF 148 100 A6 LEF 148 105 A5 SEF 148 210 Postcard LEF 152.4 101.6 B6 LEF 182 128.5 B5 SEF 182 257 Monarch LEF 190.5 98.4 A5 LEF 210 148 A4 SEF 210 297 5.5” x 8.5” LEF 215.9 139.7 5.5” x 11” SEF(Letter) 215.9 279.4 5.5” x 13” SEF(Legal) 215.9 330.2 5.5” x 14” SEF(Legal) 215.9 355.6 DL LEF 220 110 C5 LEF 229 162 C4 SEF 229 324 Rectangular LEF 235 120 Com10 LEF 241.3 104.8 B5 LEF 257 182 B4 SEF 257 364 Executive LEF 266.7 184.2 16K LEF TFX(PRC) 267(270) 194(195) 8K SEF TFX(PRC) 267(270) 389(390) 8.5” x 11” SEF(Letter) 279.4 215.9 11” x 17” LEF 279.4 431.8 A4 LEF 297 210 A3 SEF 297 420 Stopper (max.) 303 -
General information1-15 7500-XXX Registration Sensor (registration) The sensor (registration) must be installed before the registration roll assembly can detect whether media exists in the registration path. Registration clutch The registration clutch transmits the drive force of the main motor to the registration roll assembly. Transport roll assembly The transport roll assembly feeds paper from the tray 2, TTM, and optional tray to the PC cartridge and fuser. Registration roll assembly The registration roll assembly feeds paper from the tray 2, TTM, and optional tray or MPF to the PC cartridge and the fuser. Transfer roll assembly The transfer roll assembly is driven by direct contact with the drum of the PC cartridge. The transfer roll assembly applies positive charges to the rear surface of the media when the media passes between the transfer roll assembly and the drum. The negatively charged toner image is attracted by positive Registration clutch Registration roll assembly Sensor (registration) Transport roll assembly Front
1-16MFP Service Manual 7500-XXX charges on the rear surface of the media. Thus, the toner image is transferred from the drum surface to the media surface. Printhead assembly The printhead scans the drum surface with a laser beam. It consists of four components: laser diode (LD) card assembly, printhead motor, polygon mirror, and start of scan card assembly. 1.LD card assembly – generates a laser beam with the two LDs of LD1 and LD2. The beam is turned on or off according to a print data signal. 2.Printhead motor/polygon mirror – the polygon mirror is mounted to the shaft of the printhead motor, and is rotated at a high speed by the printhead motor. The mirror rotation shifts the incidence and reflection angles of a laser beam to scan the laser beam in the drum axial direction. The laser beam reaches the polygon mirror as it passes through the lens (L1), lens (L2), and window. The laser beam then arrives at the drum surface. 3.SOS card assembly – when a laser beam hits the SOS sensor on the SOS card assembly, the beam is converted to an electrical signal (SOS signal), and detects the initial position where a scan starts on each line. When a laser beam is scanned across the drum surface from one end to the other while turning on and off the beam, one line of latent image is created. If the scanning by the laser beam is repeated while rotating the drum, a two-dimensional image is created. The resolution in the scanning direction (from right to left) is determined by the rotational speed of the printhead motor, depending on how quickly the laser is adjusted. The resolution in the process direction (from top to bottom) is determined by the rotational speed of the printhead motor. (The higher the scanning speed becomes, the sooner the scanning of the next row can be started.) PC cartridge Transfer roll assembly
General information1-17 7500-XXX Conceptual diagram of an image created by scanning SOS card ASM LD card ASM Polygon mirror Printhead motor
1-18MFP Service Manual 7500-XXX Fuser Heat roll The heat roll is a hollow metal tube with a coated surface. This tube is heated by the inner heater lamp. The heat is applied to the media passing between the heat roll and pressure roll, fusing the toner on the media. Pressure roll The pressure roll is a metal shaft coated with sponge rubber. Pressure is applied to the media between the pressure roll and heat roll, pressing the melted toner against the media. Heater lamp The heater rod of the lamp is compressed of a quartz glass tube containing a heater coil. A terminal is mounted to the end of the heater rod via a harness. Three heater lamps are provided: the main heater rod to heat entire heat roll, and the sub heater lamp 1 and 2 to heat the central portion of the heat roll. Thermostat If the heat roll temperature exceeds the preset temperature, the thermostat cuts off the circuits of the main heater rod and sub heater rods 1 and 2. Center thermistor The center thermistor monitors the surface temperature of the media-feed portion of the heat roll to control on/off of the main heater lamp and sub heater lamps 1 and 2. Rear thermistor The rear thermistor monitors the surface temperature at the rear side of the heat roll to switch the heater lamp to on. Pressure roll thermistor The pressure roll thermistor monitors the temperature of the pressure roll to control the idling time for fuser warm-up before printing.