Lexmark C 950 Service Manual
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Diagnostic aids 3-59 5058-030 Go Back Previous Next of the paper. The toner image is now on the paper and the paper is now stuck to the transfer belt due to the relative electrical differences. Service tips •If the transfer roller has nicks, pits, or flat spots on it, the surface doesn’t come into contact with the media and transfer unit properly. This will cause voids or light spots on the page or repeating voids/light areas, because the toner can’t be fully transferred due to the charge difference in the areas of damage. •If the transfer roller does not engage the transfer unit, or does not have voltage coming from the high-voltage power supply, the toner will not fully transfer from the transfer unit. As a result, the entire page will be very light or blank. Any toner that does transfer will be due to a contact transfer instead of a charge transfer. Check the high-voltage power supply contacts to the transfer roller. Step 7: Electric Discharge A detack saw evenly neutralizes the charge on the paper in order to separate the paper from the belt. Step 8: Cleaning (Transfer belt/2nd transfer roll) Some of the unwanted toner will remain on the 2nd transfer roll. To remove these, a positive voltage from the HVPS is applied to transfer the unwanted toner to the transfer belt. A cleaning blade comes into contact with the transfer belt and scrapes off the remaining toner on the belt surface. The scraped toner is then transported to the waste toner cartridge. Step 9: Fusing The paper with the toner image has to go through fusing in order to bond the toner particles to the paper surface. The paper passes to a heat belt, which is heated by the inner heater to melt the toner particles on the paper surface. At the same time, pressure is also applied to permanently fuse the toner onto the media. The fuser then moves the printed media to the redrive rolls, which transport the media to the output bin. The fuser is equipped with a pressure roll retract mechanism that retracts the fuser pressure roll from the fuser heat belt when printing is not taking place or when the fuser is removed from the machine. This feature reduces HVPS Transfer belt2nd transfer roll assembly
3-60 Service Manual 5058-030 Go Back Previous Next the possibility of the fuser pressure roll receiving flat spots that can result in abnormal thumping noises and possible print quality issues. Service tips •If the fuser belt or rollers are damaged, they can cause toner to be pulled off the page or cause paper jams. •Toner that does not properly adhere to a printed page can be a sign of a malfunctioning fuser or an improper media setting. Always check the paper type setting before replacing the fuser. A common mistake is to print on heavier media (such as cardstock) with the paper type set to plain paper. Paper path theory SFP paper path For an image to be printed, the media has to be moved from an input source (such as a tray) into the printer and eventually exit into an output source. The most important component in this process is the media. Old, damaged, or out-of-specification media can and will cause feed and transport problems. If problems are encountered, then the media should always be checked first. See “Media input size specifications” on page 1-7 and “Media input type specifications” on page 1-9. In addition, it is always a good practice to check the printer and driver settings to see if the media being used matches the user’s settings. It is not uncommon to find a user printing on cardstock with the printer programmed to print on a plain paper setting. The printer’s feed and transport components can fail and cause paper jams or other feed and transport problems. These components should be examined for damage or wear, and replaced if necessary. SFP paper path rolls TRAY 1 TRAY 2 TRAY 3 TRAY 4 Duplex media transport roll assembly MPF transport roll MPF feed roll MPF pick roll MPF separation roll Tray module transport roll assembly Separation roll Feed rollFeed roll Feed rollFeed roll Separation rollSeparation roll Separation roll Pick roll Pick roll Pick roll Pick roll Tray1transport roll assembly Registration roll assembly 2nd transfer roll assembly fuser Redrive roll
Diagnostic aids 3-61 5058-030 Go Back Previous Next SFP Sensors TRAY 1 TRAY 2 TRAY 3 TRAY 4 Sensor (tray1media level) Sensor (tray1media out) Sensor (tray2media level Sensor (tray2media out) Sensor (tray3media level) Sensor (tray3media out) Sensor (tray4 media level) Sensor (tray4 media out) Sensor (media level) Sensor (MPF media present) Sensor (MPF feed out) Sensor (tray2feed out) Sensor (tray3feed out) Sensor (tray 4 feed out) Sensor (registration) Sensor (paper on belt) Sensor (fuser exit) Sensor (upper redrive exit) Sensor (duplex wait) Sensor (tray1media size) Sensor (tray2media size) Sensor (tray3media size) Sensor (tray 4 media size) Sensor (MPF media width)Sensor (transparency detect)
3-62 Service Manual 5058-030 Go Back Previous Next Paper feed process Media tray paper feed When the media tray is inserted into the printer, the media feed lift motor causes the bottom plate of the tray to elevate, in order to press the media against the feed roll. At the same time, the pick roll is also lowered and pressed against the media, in preparation for feeding. As the paper feed is starting, the pick roll rotates to insert the media between the feed roll and the separation roll. The separation roll separates the media to make sure that only one sheet at a time is fed. Bottom plate Media feed lift motor Pick roll Feed roll Separation rollpick roll feed roll separation roll
Diagnostic aids 3-63 5058-030 Go Back Previous Next MPF paper feed In an MPF paper feed, the MPF pick roll lowers to make contact with the media. The MPF pick roll rotates to insert the media between the feed roll and the separation roll. The separation roll separates the media to make sure that only one sheet at a time is fed. Registration Paper that was fed from the media tray or MPF is picked up by their corresponding transport rolls, feeding the sheet to the registration roll assembly. The media is pushed against the registration roll, putting pressure on the media until its lead edge is properly aligned. MPF registration path MPF pick roll motor Feed roll Separation roll MPF pick roll Registration roll Media tray transport roll MPF transport roll
3-64 Service Manual 5058-030 Go Back Previous Next Media tray registration path Transfer After the edge of the media is aligned, the registration roll feeds the media between the 2nd transfer roll and the transfer belt in preparation for toner transfer. At this point, a toner image is already embedded on the transfer belt. As the media passes between the transfer belt and the 2nd transfer roll, the toner image is also transferred to the media. Fusing/exit The media with the embedded toner image needs to go through the fuser assembly to permanently bond the toner image to the sheet. When the sheet passes between the heat belt and the pressure roll, the combination of Registration roll Media tray transport roll MPF transport roll HVPS Transfer belt2nd transfer roll assembly
Diagnostic aids 3-65 5058-030 Go Back Previous Next applied heat and pressure fuses the toner image to the media. At the same time, the fuser assembly rolls also move the media to the redrive rolls, which transport the media to the output bin. Redrive rolls Fuser assembly Heat belt Pressure roll
3-66 Service Manual 5058-030 Go Back Previous Next Duplexing After one side of the media has finished printing, the exit rolls push the printed sheet towards the output bin (1). Then the upper redrive motor reverses direction, pulling the sheet with its trailing edge first, towards the opposite direction (2) into the duplexing area. DUPLEX Exit rolls Upper redrive motor 2 1 Upper redrive motor
Diagnostic aids 3-67 5058-030 Go Back Previous Next The exit rolls feed the sheet to the duplex rolls, which transport the media again to the registration rolls. The printing cycle is performed again, this time on the other side of the same sheet. Color theory What is RGB color? Red, green, and blue light can be added together in various amounts to produce a large range of colors observed in nature. For example, red and green can be combined to create yellow. Televisions and computer monitors create colors in this manner. RGB color is a method of describing colors by indicating the amount of red, green, or blue needed to produce a certain color. What is CMYK color? Cyan, magenta, yellow, and black inks or toners can be printed in various amounts to produce a large range of colors observed in nature. For example, cyan and yellow can be combined to create green. Printing presses, inkjet printers, and color printhead LED printers create colors in this manner. CMYK color is a method of describing colors by indicating the amount of cyan, magenta, yellow, and black needed to reproduce a particular color. How is color specified in a document to be printed? Software programs typically specify document color using RGB or CMYK color combinations. Additionally, they allow users to modify the color of each object in a document. For more information, see the software program Help topics. How does the printer know what color to print? Duplex rolls
3-68 Service Manual 5058-030 Go Back Previous Next When a user prints a document, information describing the type and color of each object is sent to the printer. The color information is passed through color conversion tables that translate the color into the appropriate amounts of cyan, magenta, yellow, and black toner needed to produce the desired color. The object information determines the application of color conversion tables. For example, it is possible to apply one type of color conversion table to text while applying a different color conversion table to photographic images. Why doesnt the printed color match the color I see on the computer screen? The color conversion tables used in Auto Color Correction mode generally approximate the colors of a standard computer monitor. However, because of technology differences that exist between printers and monitors, there are many colors that can also be affected by monitor variations and lighting conditions. For recommendations on how the printer color sample pages may be useful in solving certain color-matching problems, see the question, “How can I match a particular color (such as a corporate logo)?” The printed page appears tinted. Can I adjust the color? Sometimes a printed page may appear tinted (for example, everything printed seems to be too red). This can be caused by environmental conditions, paper type, lighting conditions, or user preference. In these instances, adjust the Color Balance setting to create a more preferable color. Color Balance provides the user with the ability to make subtle adjustments to the amount of toner being used in each color plane. Selecting positive or negative values for cyan, magenta, yellow, and black (from the Color Balance menu) will slightly increase or decrease the amount of toner used for the chosen color. For example, if a printed page has a red tint, then decreasing both magenta and yellow could potentially improve the color balance. My color transparencies seem dark when they are projected. Is there anything I can do to improve the color? This problem most commonly occurs when projecting transparencies with reflective overhead projectors. To obtain the highest projected color quality, transmissive overhead projectors are recommended. If a reflective projector must be used, then adjusting the Toner Darkness setting to 1, 2, or 3 will lighten the transparency. Make sure to print on the recommended type of color transparencies. What is manual color correction? When manual color correction is enabled, the printer employs user-selected color conversion tables to process objects. However, Color Correction must be set to Manual, or no user-defined color conversion will be implemented. Manual color correction settings are specific to the type of object being printed (text, graphics, or images), and how the color of the object is specified in the software program (RGB or CMYK combinations). Notes: •Manual color correction is not useful if the software program does not specify colors with RGB or CMYK combinations. It is also not effective in situations in which the software program or the computer operating system controls the adjustment of colors. •The color conversion tables—applied to each object when Color Correction is set to Auto—generate preferred colors for the majority of documents.