Lexmark X 850 Owners Manual

General information1-59
7500-XXX
Media transport path
The following is a cross section of the printer and the tandem tray module, showing the main components 
directly associated with the media path and transport.
Functions of main components
When the tandem tray module is installed under the printer, additional trays are available.
Duplex media
transport roll
ASM
MPF
MPF Transport
pinch roll
MPF Transport
roll ASM
Transport
roll ASM Media transport
pinch roll
Separation rollFeed roll Duplex media
center...

1-60MFP Service Manual 7500-XXX
Media tray assembly
Media feed unit assembly
It is necessary to adjust the front and rear side guides in the media tray assembly to match the media size.
Front media guide / rear media guide
The front media guide can be adjusted to different media sizes by moving it to the front or rear. These guides 
come into contact with the front and rear edges of the media and hold it in position.
The rear side guide moves together with the front side guide.
Bottom plate
The force...

General information1-61
7500-XXX
Tray 4 media tray assembly  
Media feed unit assembly
Since the tray 3 and tray 4 are functionally equivalent in terms of the switch (TTM media size), sensor (media 
out), sensor (media level) and sensor (pre-feed), only the components of one tray are described here.
The media feed unit assembly is a mechanical unit supplying media from the media tray assembly to the printer. 
The driving force from the media feed lift motor on the media feed unit assembly is transmitted...

1-62MFP Service Manual 7500-XXX
Sensor (media level)
This sensor detects by the actuator position whether media in the media tray assembly is lifted. When the flag of 
the actuator leaves the sensor (media level) sensing area, the sensor detects that the media has been lifted.
Sensor (pre-feed)
This sensor detects a media jam in the media tray assembly by the media position and sensor on/off time.
The sensor on/off states can be monitored by media passing through the sensor (pre-feed) sensing area....

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Main components
Switch (2TM/TTM left door interlock) 
The left door interlock switch detects open/close of the left door assembly.
Sensor (tray 3 feed-out)
The sensor (tray 3 feed-out) detects media fed from the tray 3 or tray 4.
Sensor (tray 4 feed-out)
The sensor (tray 4 feed-out) detects media fed from the tray 4.
2TM/TTM media transport roll assembly 
The 2TM/TTM transport roll assembly feeds media from the tray 3 or tray 4 to the printer.
2TM/TTM controller card...

1-64MFP Service Manual 7500-XXX
Switch (tandem tray media size)
The following table gives on/off states of the switches on the switch (TTM media size), corresponding to the 
media sizes of the media tray assembly.
Note:  The switches (TTM media size) are denoted by “S/W1” and “S/W3” respectively from the left side.
Media SizeAnalog switch
S/W1 S/W3
No Tray Off Off
B5L/7.25” x 10.5”L Off On
8.5” x 11”L On Off
A4L On On 

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Duplex
Duplex drive motor
The rotating force of the drive motor is transmitted through the gears to components that need mechanical 
driving force as shown below.
The transmitted driving force drives the two duplex media transport roll assemblies, and the (duplex media 
center transport roll assembly) through the gears.
Duplex drive motor
Duplex drive gear 33/74T
Duplex drive gear 28T
Duplex drive gear 33T
Duplex drive gear 42T
Duplex drive gear 33T
Duplex drive gear 28T...

1-66MFP Service Manual 7500-XXX
Media transport
Media transport path
With the duplex installed, media is supplied from the MPF, tray 1 or tray 2, and is transported to the printer along 
the media transport path shown below.
MPF
MPF pick roll
MPF Transport Roll ASM
MPF ASMMedia feed
unit ASMMedia feed
unit ASM Pick roll Pick roll
Separation roll Separation roll
Feed roll
Media transport roll ASM
Registration roll ASM
Transfer roll ASM
PC cartridge Drum
Heat roll
Pressure roll
Fuser unit ASM
Exit 1 media...

General information1-67
7500-XXX
Layout of media transport path
The main components associated with the media path and transport with the duplex installed.
Functions of main components
When the duplex is installed to the left of the printer, duplex (double-sided) printing is available with the printer.
The following outlines the functions of the main components of the duplex.
Switch (duplex left door interlock)
The switch (left door interlock) detects open/close of the left door.
Sensor (duplex wait)
The...

1-68MFP Service Manual 7500-XXX
Duplex media transport roll assembly 
The two duplex media transport roll assemblies and the duplex media center transport roll assembly re-feeds 
the media printed on the front side through the duplex to print on the rear side.
Duplex controller card assembly
The duplex controller card assembly that contains a CPU controls media feed in the duplex upon receiving a 
command from the printer engine card assembly and sensor/switch information.
Duplex drive motor
The duplex...