HP 2500 L Service Manual
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EN 4 Theory of operation59 4Theory of operation Chapter contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 Engine control system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 Basic sequence of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Power-on sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Motors and fans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Laser/scanner system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 Pickup and feed system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Paper trays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67 Jam detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 Photosensors and switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Solenoid and clutches. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 Printed circuit assemblies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Image formation system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Image formation process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Latent image formation stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Developing stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Transfer stage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76 Fusing stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Print cartridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Imaging-drum E-label . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
60Theory of operation C9706-90926 Introduction This chapter presents an overview of the relationships between major components in the HP Color LaserJet 2500 series printer, and includes a detailed discussion of the image-formation system. The following systems are discussed: engine control system laser/scanner system pickup and feed system image-formation system Figure 10. Cross-section of the printer 12345 6 7 8 9 10 11 12 13 1415161718192021 22 23 1 Laser/scanner 9 Transfer belt cleaning roller 17 Feed belt 2 Developing cylinder 10 Registration shutter18 Carousel 3 Photosensitive drum 11 Pickup roller 19 Print cartridge 4 Primary charging roller 12 Tray 1 20 Fusing film 5 Imaging drum 13 Separation pad21 Pressure roller 6 Transfer belt 14 Registration roller22 Fuser delivery roller 7 Density sensor 15 Secondary transfer roller 23 Top output bin delivery roller 8 Primary transfer roller 16 Auxiliary transfer-belt cleaning roller
EN 4 Theory of operation61 Engine control system The engine control system coordinates all printer functions. It drives the laser/scanner system, the image formation system, and the pickup and feed system. The engine control system contains the following components: dc controller high-voltage power-supply PCB low-voltage power unit: fuser-control circuit low-voltage power-supply PCB Figure 11. Engine control system (includes the basic configuration of the printer)
62Theory of operation C9706-90926 Basic sequence of operation Operation sequences are controlled by the CPU in the dc controller in the engine control system. Table describes engine operations for each period of a print operation. Table 15. Basic sequence of operation Period Duration Purpose Remarks WAIT (wait) From the time the power switch is turned on until transfer-belt cleaning is complete. Clears potential from the drum surface and cleans the transfer belt. See figure 12 for a complete description of the WAIT (power-on) period. Also see the general timing charts beginning on page 212 for detailed information about timing. STBY (standby) From the end of the WAIT or LSTR period until either a print command is sent from the formatter or the power is turned off. Allows the printer to be ready for print commands. INTR (initial rotation) From the time of the print command until detection of the HP1 (transfer-belt home- position detection) signal for the first color. Prepares the photosensitive drum for printing. PRINT (print) From the end of the INTR period until detection of the transfer-belt home-position signal for the secondary transfer. Forms the image on the photosensitive drum and transfers the toner image to the transfer belt. LSTR (last rotation) From the end of the PRINT period until the main motor stops rotating. Transfers the toner image on the transfer belt to the media and delivers the printed media.After LSTR, the printer returns to STBY.
EN 4 Theory of operation63 Power-on sequence The power-on sequence is represented by the flowchart in figure 12. Figure 12. Power-on sequence
64Theory of operation C9706-90926 Motors and fans Figure 13.Motors and fans 1 23 4 5 6 Table 16. Motors and fans Reference Description 1 Engaging motor 2 Developing-rotary motor 3 Toner-cartridge motor 4 Fuser motor 5 Main motor 6 Cooling fan
EN 4 Theory of operation65 Laser/scanner system The laser/scanner system receives video signals from the dc controller, and then it converts the signals into latent images on the photosensitive drum. The dc controller controls the laser/ scanner. Figure 14. Laser/scanner system
66Theory of operation C9706-90926 Pickup and feed system The pickup and feed system consists of several types of feed rollers and sensors. The dc controller drives the paper and feed system by controlling two motors, two clutches, and the solenoid. Two photo-interrupters (PS1 and PS711) detect media as it passes. If media does not reach or pass each sensor within the specified time period, the dc controller determines that a jam has occurred and alerts the video controller circuit. The following components are identified in figure 15: PS1 fusing-delivery paper sensor PS711 registration paper sensor PS718 tray 1 (multipurpose tray) paper sensor DCM701 main motor PM702 fuser motor SL92 tray 1 pickup solenoid CL1 registration clutch CL2 roller-engaging clutch Figure 15. Pickup and feed system
EN 4 Theory of operation67 Paper trays The dc controller drives the operation sequence of the paper trays. It signals the driver PCB in tray 2 (250-sheet paper tray) and in tray 3 (250-sheet paper tray), and then each driver PCB controls the motors and solenoids in its paper tray. The following components are identified in figure 16: DCM701 gear-train motor (printer) SL9 pickup solenoid (optional tray 2) PS716 paper sensor (optional tray 2) PS717 paper-feed sensor Note Only tray 2 (250-sheet tray) is shown; tray 3 (500-sheet tray) is similar. Figure 16. Optional tray 2 (250-sheet paper tray)
68Theory of operation C9706-90926 Jam detection The registration sensor (PS711) and the fusing paper sensor (PS1) detect media moving through the printer. If a jam is detected, the dc controller immediately stops the printing process and sends a message to the video controller circuit. A jam can be detected under any of the following conditions: Pickup delay jam. The leading edge of the paper does not reach the registration sensor (PS711) within 1.1 seconds (tray 1), 1.7 seconds (optional tray 2), or 2.8 seconds (optional tray 3). Pickup stationary jam. The registration clutch is on, and the registration sensor (PS711) does not detect the trailing edge of the paper within 3.4 seconds after the start of a re-pickup operation. Delivery delay jam. The registration clutch is on, and the fusing-delivery paper sensor (PS1) does not detect the leading edge of the paper within 2.3 seconds after the start of a re- pickup operation. Delivery stationary jam. The leading edge of paper does not pass the fusing-delivery paper sensor (PS1) within 2.4 seconds after it has passed the registration sensor (PS711). Door open jam. The main CPU detects that the top cover is open during a print operation. Residual paper jam. The main CPU detects one or more of the following conditions: Powe r is t ur n ed o n. The printer is returning from sleep mode. The printer door is closed after a jam occurrence. The registration sensor (PS711) and fusing-delivery sensor (PS1) detect paper.