Lexmark X 850 Owners Manual

General information1-39
7500-XXX
Duplex document
The ADF scans the image on Side 1 (side facing up when set on the tray), inverts the document sheet, scans 
the image on Side 2 (side facing down when set on the tray), and then ejects the document sheet while inverting 
it.
Therefore, the duplex document sheet is ejected with Side 2 up as with the simplex document sheet.
For two simplex documents, feed is performed in the following sequence.
1.The first document sheet (Side 1) is fed to the ADF transport...

1-40MFP Service Manual 7500-XXX
11.When the sensor (ADF pre-registration) detects the lead edge of document sheet (Side 1), the inverter 
solenoid assembly is turned on to release the nipped ADF exit roll assembly and exit pinch roll and the 
ADF registration motor decelerates and stops.
12.After the predetermined time, the ADF registration motor starts rotating in the reverse direction (CCW 
direction) to drive the ADF registration roll assembly and ADF feed-out roll assembly in the exit direction in...

General information1-41
7500-XXX
Image data flow
The image date from the document set on the scanner unit assembly or ADF goes through the following 
components before it is printed at the Engine section.
Lens
CCD image sensor
Scanner controller card assembly
Scanner
Engine
RIP card assembly
Printhead assembly
PC cartridge assembly (drum)Document 

1-42MFP Service Manual 7500-XXX
Drive torque transfer scheme
ADF feed motor assembly
The rotational force of the ADF feed motor assembly is transferred to each document feeding roll as shown 
below.
ADF feed motor assembly
ADF drive belt
Feed drive rear pulley 14/32/37
Transport roll drive beltFeed/pick drive gear 20T
Transport roll drive
gear/pulley 20/50TFeed/pick drive
shaft assembly
Transport roll drive gear 20TFeed roll drive gear 26T
Transport roll assembly
Feed roll Pick roll idler gear 36T
Pick...

General information1-43
7500-XXX
ADF registration motor
The rotational force of the ADF registration motor is transferred to each document feeding roll as shown below.
Gear layout
ADF registration motor
Registration roll drive belt
Registration drive
gear/pulley 21/54T
Registration drive belt
Exit/feed-out drive
pulley 25/28Registration roll
drive gear 28T
Exit roll drive belt
Feed-out roll assemblyRegistration roll assembly
Exit roll drive pulley 20T
Exit roll assembly 

1-44MFP Service Manual 7500-XXX
Feed roll Exit roll assembly Pick rollPick roll drive gear 34TExit roll drive pulley 20T Pick roll idler gear 36T Feed roll drive gear 26T ADF feed motor assembly Feed/pick drive gear 20T
Feed drive gear/pulley14/32/37T
Transport roll drive
gear pulley 20/50T
ADF registration motor
Registration main drive
pulley 21/54T
Transport roll drive gear 20T
Registration roll drive pulley 28T
Exit/feed-out drive pulley 25/28
Transport roll assembly
Registration roll assembly...

General information1-45
7500-XXX
Names and functions of components
The sections below describe the functions of main components of the scanner.
Scanner unit assembly
Sensor (platen length APS 1)
Sensor (platen length APS 2)
The document length in the slow scanning direction is detected by a combination of the two reflector sensors.
Switch (platen interlock)
A switch that detects whether the ADF is open and determines the timing of platen document size detection.
Sensor (ADF angle)
A sensor that detects...

1-46MFP Service Manual 7500-XXX
Scanner cooling fan
A fan that prevents overheating of the scanner controller card assembly and exposure lamp.
ADF
Sensor (ADF tray length 1)
Sensor (ADF tray length 2)
The document length in the slow scanning direction is detected by a combination of these two sensors.
Sensor (document tray width 1)
Sensor (document tray width 2)
Sensor (document tray width 3)
The document length in the fast scanning direction is detected by the combination of these three sensors...

General information1-47
7500-XXX
Sensor (pick roll position HP)
A sensor that detects the home position of the pick roll.
ADF Document Set LED
An LED that illuminates when a document is set on the ADF Document Tray.
Switch (ADF left cover interlock)
A switch that detects whether the ADF left cover assembly is open.
ADF controller card assembly
A card that controls the ADF unit assembly. The ADF controller card assembly is connected to and controlled by 
the Scanner controller card assembly.
Sensor (ADF...

1-48MFP Service Manual 7500-XXX
Sensor (ADF pre-registration)
The ADF sensor (ADF pre-registration) is installed immediately upstream from the ADF transport roll assembly 
to detect that the preceding document sheet has left the ADF transport roll assembly, triggering the pre-feed of 
the next document sheet.
Sensor (ADF registration)
The sensor (ADF registration) is installed upstream from the ADF registration roll assembly to detect that the 
preceding document sheet has left the ADF registration roll...