Power And Control - Lexmark W820 Service Manual

4025-XXX

Power and Control

The printer power cord plugs into an AC wall outlet. The other end of the power cord
plugs into the Noise Filter PWB, where the Filter removes fluctuations from the AC line
voltage. A Ground Fault Interrupter in the AC line protects the printer from electrical
shorts. With the Main Power Switch on, AC line voltage flows from the Noise Filter, and
into the Low Voltage Power Supply (LVPS) and into the AC Driver PWB. The LVPS
converts and distributes +5VDC and +24VDC voltages to the MCU PWB and I/O PWB.
The MCU PWB distributes +5VDC and +24VDC to the Printhead and various printer
components. The I/O PWB distributes +5VDC and +24VDC to various printer
components and distributes +24VDC to the High Voltage Power Supply (HVPS) and to
the PSHV-R2 power supply. The HVPS converts the +24VDC supplied to it by the MCU
PWB into the high voltages that are used by the xerographic components of the printer.
The PSHV-R2 provides the Fuser Bias voltage. The AC Drive PWB distributes 110VAC
filtered line voltage to the two Fuser Heat Lamps.
The host computer, loaded with the correct printer driver software, connects to the printer
through the ESS (Controller) PWB. The ESS PWB is connected to the MCU PWB. The
ESS PWB sends image data and process information to the MCU PWB. The MCU PWB
is the brain of the printer - housing printer parameters and timing tables, monitoring
printer operations, and controlling all printer functions. The MCU PWB monitors sensors
along the paper path, signaling the I/O PWB to switch components on and off, and
generates error codes whenever sensor statuses indicate a problem.
Drive Generation and Distribution
The printer base engine contains five motors. The MCU PWB controls all motor functions.
The Main Motor supplies mechanical drive to the Main Drive Assembly. The Main Drive
Assembly and a series of individual gear clusters transfer drive throughout the printer.
The Drum Motor also supplies mechanical drive to the Main Drive Assembly. Electric
clutches control drive to specific components. Lift Motor 1 and 2 supply drive to Trays 1
and 2. The Offset Motor supplies drive to the Offset Rollers.
Xerographics
Xerographics consists of the Printhead which houses the laser, the EP Cartridge, and
the Bias Transfer Roll (BTR). Image data sent from the host computer to the MCU PWB
rapidly switches the laser on and off, shining onto the Drum and creating an invisible
electrical image on the surface of the electrically charged Drum. Dry ink, or toner,
transfers to the Drum surface, creating a visible toner image. The Drum, the Bias Charge
Roll (BCR), and the toner are all housed in the replaceable EP Cartridge. When the
sheet of paper travels between the Drum and the electrically charged Bias Transfer Roll
(BTR), the toner image on the Drum transfers to the sheet of paper. The Detack Saw
helps remove the paper from the Drum.
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Service Manual