Lexmark MS312, Service Manual, Page: 315 / 343

Theory of operation
POR sequence
As the printer turns on, the engine code goes through a series of tests to verify hardware integrity. If a hardware
failure is detected, then it is reported to the printer. If the POR sequence cannot be completed successfully,
then the printer may post an error message. The message states that service may be needed.
Printer control
The printer uses a single processor for both RIP and engine functions. The raster image processor (RIP) code
performs system responsibilities such as PC connection, LAN, ISP attachments, and bitmap generation. The
engine code performs tasks related to the operation of the electrical and mechanical device systems such as
motors, lasers, power supplies, and fusers. The NVRAMs are located on the controller board and control panel,
replacement of either the controller board or control panel will pull or mirror NVRAM data from each other.
Paper path information
Input tray
When feeding media, the ACM lowers to come into contact with the media. The pick rollers on the ACM rotate
to push the media to the wear strips at the front of the tray. The wear strips provide a fixed resistance to ensure
that sheets are fed one at a time. The media is then fed to the secondary input roller and then to the first input
roller.
First input roller
Secondary input
roller
Wear strips
Pick rollers
Option tray
Multipurpose feeder (MPF)
The driving force from the main drive motor is transmitted through the MPF gearbox. When the MPF solenoid
activates, it allows the MPF sector gear linked to the MPF gearbox to rotate. The MPF pick roll shaft is connected
to the MPF sector gear.
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Theory of operation
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