HP Laserjet 5 Service Manual
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EconoMode The EconoMode setting uses approximately 50% less toner than standard mode printing by reducing the dot density. However, EconoMode does not extend toner cartridge component life. EconoMode, which can also be thought of as “draft mode,” is user-selectable through some software applications. The default setting is Off. EconoMode vs Normal Mode NoteEconoMode does not affect print speed or memory usage. Memory Enhancement technology (MEt) The Hewlett-Packard Memory Enhancement technology (Met) effectively doubles the standard memory through a variety of font and data compression methods. MEt is only available in PCL mode and is not customer selectable. When using the host-based driver, your PC handles memory management. Figure 5-3 5 - 10 Functional Overview
Enhanced I/O The Enhanced I/O feature allows printer memory to be used for storing data received from the host computer. When Enhanced I/O is enabled, you can send more data to your printer in shorter amounts of time, which allows you to return to your application sooner. Enhanced I/O has the following options: ·Auto—allows the printer to use Enhanced I/O memory allocation to increase the speed of data transfer from the host computer to the printer, if necessary. ·Off—uses the minimum amount of printer memory for storing data sent from the host computer. Enhanced I/O is only available in PCL mode. When using the host-based driver, your PC handles memory management. Page Protect Page complexity (rules, complex graphics, or dense text) may exceed the printer’s ability to create the page image fast enough to keep pace with the Image Formation process. If Page Protect is disabled and a page is too complex, the page may print in parts (for example, the top half on one page and the bottom half on the next page). Some print data loss is likely in these instances, and the printer will display an error message. Page Protect allows the Formatter to create the entire page image in page buffer memory before physically moving the paper through the printer. This process ensures that the entire page will be printed. Page Protect applies only to PCL printing. The default setting is Auto. PJL Overview Printer Job Language (PJL) is an integral part of configuration, in addition to the standard Printer Command Language (PCL). With standard Centronics cabling, PJL allows the printer to perform functions such as: ·Two-way communicationwith the host computer through a Bi-directional Parallel connection. The printer can tell the host such things as the control panel status. ·Isolation of print environment settingsfrom one print job to the next. For example, if a print job is sent to the printer in landscape mode, the subsequent print jobs print in landscape only if they are formatted for landscape printing. 5 Functional Overview Functional Overview 5 - 11
Image Formation System Laser printing requires the interaction of several different technologies (such as electronics, optics, and electrophotographics) to provide a printed page. Each process functions independently and must be coordinated with the other printer processes. Image formation consists of six processes: ·Step 1. Drum Cleaning ·Step 2. Drum Conditioning ·Step 3. Image Writing ·Step 4. Image Developing ·Step 5. Image Transferring ·Step 6. Image Fusing Image Formation Block Diagram 2. Scanning Exposure 1. Primary Charging 7. Drum Cleaning3. Developing 5. Separation 4. TransferRegistration 6. Fusing Paper Delivery Manual Feeding Slot Multi-Purpose Tray Drum Cleaning Block Fuser Block Transfer Block Electrostatic Latent Image Formation Block Developing Block Flow Of Paper Direction Of Drum Rotation Figure 5-4 5 - 12 Functional Overview
Toner Cartridge As the “heart” of the Image Formation System, the toner cartridge houses the cleaning, conditioning, and developing steps of the process. The toner cartridge contains the photosensitive drum, primary charging roller, developing station, toner cavity, and cleaning station. Including these components, which wear, degrade, or are consumed in the replaceable toner cartridge, eliminates the need for a service call when replacement is required. The special photosensitive properties of the drum allow an image to be formed on the drum surface and then transferred to paper. CAUTIONThe printer’s toner cartridge does not include a light-blocking shutter. Be careful to avoid exposing the drum to light, which can permanently damage the drum. Protect the cartridge whenever removing it from the printer. Step 1: Drum Cleaning The cleaning blade is in contact with the surface of the drum at all times. As the drum rotates during printing, excess toner wiped off and stored in the waste toner receptacle. Step 2: Drum Conditioning After the drum is physically cleaned, it must be conditioned. This process consists of applying a uniform negative charge on the surface of the drum with the primary charging roller, located in the toner cartridge. The primary charging roller is coated with conductive rubber. An AC bias is applied to the roller to erase any residual charges from any previous image. In addition, a negative DC bias is applied by the charging roller to create a uniform negative potential on the drum surface. The amount of DC voltage is modified by the print density setting. Step 3: Image Writing During the writing process, a modulated laser diode projects the beam onto a rotating scanning mirror. As the mirror rotates, the beam reflects off the mirror, first through a set of focusing lenses, off a mirror, and finally through a slot in the top of the toner cartridge, and onto the photosensitive drum. The beam sweeps the drum from left to right, discharging the negative potential wherever the beam strikes the surface. This creates a latent electrostatic image, which later is developed into a visible image. Because the beam is sweeping the entire length of the drum and the drum is rotating, the entire surface area of the drum can be covered. At the end of each sweep, the beam strikes the beam detect lens, generating the Beam Detect Signal (BD). The BD signal is sent to the DC Controller, where it is converted to an electrical signal used to synchronize the output of the next scan line of data. 5 Functional Overview Functional Overview 5 - 13
Step 4: Image Developing At this stage of the process, the latent electrostatic image is present on the drum. The toner particles obtain a negative surface charge by rubbing against the developing cylinder which is connected to a negative DC supply. The negatively charged toner is attracted to the discharged (exposed, grounded) areas of the drum, and repelled from the negatively charged (non-exposed) areas. Step 5: Image Transferring During the transferring process, the toner image on the drum surface is transferred to the paper. A positive charge applied to the back of the paper by the transfer roller causes the negatively charged toner on the drum surface to be attracted to the paper. After separation, the drum is cleaned and conditioned for the next image. Step 6: Image Fusing During the fusing process, the toner is fused into the paper by heat and pressure to produce a permanent image. The paper passes between a heated fusing element and a soft pressure roller. This melts the toner and presses it into the paper. 5 - 14 Functional Overview
Paper Feed System Both the Paper Input Bin and the Single Sheet Input Slot merge into one, main input area. Paper placed in either of these areas enables the Paper Out Sensor (sensor 202), which informs the DC Controller that paper is present. When the printer receives a print job and is ready to print, the DC Controller enables the Laser/Scanner Assembly and the Motor. Paper motion begins when the DC Controller energizes solenoid SL1. This causes the paper pick up roller to rotate once. Two actions occur as a result of this rotation. First, the paper kick plate pushes the paper against the pick-up roller. Second, the pick-up roller grabs the top sheet and advances it to the Feed Assembly drive rollers. To ensure that only one sheet is fed, a main separation pad, along with two subpads, hold the remainder of the stack in place. The feed assembly drive rollers advance the paper to the Paper Registration photosensor (PS203). This sensor informs the DC Controller of the exact location of the paper’s leading edge, so that the image being written on the photosensitive drum can be precisely positioned on the page. The feed assembly drive rollers then advance the paper to the transfer area where the toner image on the photosensitive drum is transferred to paper. After the image is transferred, the paper enters the fusing assembly where heat from the fuser and pressure from the Pressure Roller permanently bond the toner image to paper. The Paper Exit Sensor (PS201) determines that paper has successfully moved out of the fusing area. The fusing assembly exit rollers deliver paper to either the Output Paper Bin or the Front Output slot, depending upon the position of the Face-up/Face-down lever. 5 Functional Overview Functional Overview 5 - 15
Figure 5-5 shows a simplified paper path and the locations of the photosensors and rollers. Simplified Paper Path Figure 5-5 5 - 16 Functional Overview
Figure 5-6 shows the locations of the photosensors, switches, solenoid, and other important printer elements. Table 5-1 describes the function of each photosensor and the solenoid. Solenoid and Sensors Figure 5-6 No. Name Description SL1 Paper Pick-up Solenoid Enables the Paper Pickup Roller. PS201 Paper Exit Sensor Senses when paper has successfully moved out of the fusing area and the next sheet of paper can be fed. PS202 Paper Out Sensor Senses no paper in either the Paper Input Bin or Manual Input Slot. If this sensor does not sense paper in the Input Paper Bin or the Single-Sheet Input Slot, the formatter displays the paper-out indication on the front panel. Paper must be reloaded before printing can resume. PS203 Paper Registration Sensor Detects the leading and trailing edges of the paper. Synchronizes the photosensitive drum and the top of the paper. PS204 Door Open/Cartridge Sensor (HP LaserJet 5L only) In the HP LaserJet 6L, SW101 performs the functions of 5L’s PS204.Detects whether printer door is open and cartridge is in place. If the door is open or the cartridge is not in place, the control panel LEDs will display an error message. Printing cannot continue until the door is closed and the cartridge is in proper position. Table 5-1Solenoid and Photosensors 5 Functional Overview Functional Overview 5 - 17
Paper Jam Detection The Paper Out Sensor (PS202), Paper Registration Sensor (PS203), and the Paper Exit Sensor (PS201) detect when paper is moving through the printer. (See Figure 5-5 for roller and sensor locations.) If a paper jam is detected, the DC Controller immediately stops the printing process and causes a paper jam indication on the front panel. A paper jam can be detected under any of the following conditions: ·Power-On Jams.Paper is present under either PS201 or PS203 at power-on. ·Pickup Jams. Paper does not reach and clear photosensor PS203 within a specified period of time. The time period begins when the Paper Pickup Solenoid (SL1) is energized. ·Delay Jams. Paper does not reach or clear a specific photosensor within a specified period of time. 5 - 18 Functional Overview
Basic Sequence of Operation The Formatter PCA and the DC Controller PCA share information during printer operation. The DC Controller-to-Formatter Connector (J201) forms a link which operates as a serial data bus. This allows printer status, command information, and dot-image data to be passed between the two PCAs. Figure 5-7 shows the general timing of the printer events. The following events take place during normal printer operation: Period Timing Purpose WAIT From when the paper is inserted to the end of Main Motor initial rotation.Clear the drum surface potential and clean the Transfer Roller. STBY (standby) From the end of the WAIT or the LSTR period until the input of the PRNT signal from the Formatter. Or from the end of the LSTR period until power OFF.Maintain the printer in ready state. INTR (initial rotation)From the input of the PRNT signal from the Formatter until the laser diode intensity has been stabilized.Stabilize the photosensitive drum sensitivity in preparation for printing. Also clean the Transfer Roller. PRNT From the end of initial rotation until the Scanner Motor stops.Form images on the photosensitive drum based on the /VDO signal from the Formatter and transfer the image to paper. LSTR (last rotation)From the primary voltage (DC) OFF until the Main Motor stops. If another PRNT signal is sent from the Formatter, the printer returns to the INTR period. If not, it returns to the STBY period.Deliver the last sheet of paper. Also clean the Transfer Roller. Refer to Timing Diagram on the next page Table 5-2 Printer Timing 5 Functional Overview Functional Overview 5 - 19