Lexmark C792 Family, Service Manual

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Service Manual
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Transport components
The paper is fed from the tray into the printer by a pick roll and sent to two sets of feed rollers which time the
paper to enter the Electrophotographic Process (EP Process) at just the right moment. The feed rollers push the
paper to the transfer roll (ITU) where the image is transferred to the page.
The transfer roller moves the paper to the fuser where heat and pressure are applied to the page. The fuser
rollers push the paper toward the exit bin and past the exit sensor. The exit rollers guide the paper into the
output bin.
Note: If the printer posts a paper jam message but no paper is found, paper dust or paper particles may have
fallen into one of the sensor eyes. Use a can of compressed air to gently clean the sensor.
Bubble sensors
The printer uses two bubble sensors to adjust the speed of the fuser motor to better avoid image smearing and
paper jams.
The fuser bubble sensor, located before the fuser in the paper path, senses the bubble, or amount of curve in
the paper, when it hits the fuser rollers. If the curve is too great, the fuser motor speeds up to avoid causing a
paper jam. If the curve is too small, the motor slows to avoid smearing the image.
The redrive bubble sensor, located after the fuser exit rollers in the paper path, senses the bubble in the paper
as it exits the fuser. It then adjusts the fuser motor speed as necessary to avoid jams and smearing on the
trailing edge of the paper.
Duplexing (models with duplex support only)
Printers with duplex support use a secondary paper path to print on the second side of a sheet of paper. The
following steps summarize the duplexing process:
After the first side of the paper is printed and the trailing edge of the paper clears the fuser exit sensor, the
redrive motor engages to reverse the paper direction and feed it into the duplex unit.
Note: While the sheet is being transported through the duplex unit, it is the only piece of paper being processed
by the print engine. A user should not attempt to insert a piece of paper into the manual paper feed while a
duplex job is being processed. This would cause a paper jam error.
After the D1 sensor in the duplex unit is triggered by the leading edge of the paper, the speed of the paper is
adjusted on its way to the D2 sensor to accommodate the speed of the transfer belt, ensuring the proper
registration of the image on the paper. The paper then re-enters the primary paper path to travel to the ITU, and
the second image is transferred to the reverse side of the paper.
Once the imaged is transferred, the paper returns to the fuser, the fuser exit rolls, and the output bin.