Lexmark C 950 Service Manual

Diagnostic aids 3-59
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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...

3-60  Service Manual 5058-030  
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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...

Diagnostic aids 3-61
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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...

3-62  Service Manual 5058-030  
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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...

Diagnostic aids 3-63
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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...

3-64  Service Manual 5058-030  
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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...

Diagnostic aids 3-65
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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 

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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
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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...

3-68  Service Manual 5058-030  
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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...