Lexmark X 850 Owners Manual

General information1-49
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Sensor (ADF pre-registration)
ADF feed motor assembly
Sensor (sheet through)
ADF registration
motor
Sensor (ADF registration)
Sensor (ADF inverter)
Sensor (ADF APS 1)Sensor (ADF APS 2)Sensor (ADF APS 3)Inverter solenoid assembly 

1-50MFP Service Manual 7500-XXX
Control
Document size detection at scanner unit assembly
The width (fast-scan-directional size) of the document sheet on the Platen Grass is detected with the CCD 
image sensor, and the length (slow-scanning-directional size) is detected with the sensor (platen length APS 1) 
and the sensor (platen length APS 2).
Document size detection timing
The size of the document sheet on the platen glass is detected at the following timings:
•When the Platen Cover (ADF) is closed...

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Shown below are the combinations of document size, detection range in the fast scanning direction, and 
sensors. 
Document SizeWidth (Fast scanning 
direction: mm)Length (Slow scanning direction) Area
Fast 
scanning 
WidthDetection 
RangeSensor (platen 
length APS 1)Sensor (platen 
length APS 2)012
Japanese Post 
Card SEF100.0 90–115 Off Off X X N
Post Card SEF 101.6 N O X
A6 SEF 105.0 O N O
5 X 7 SEF 127.0 115–138 Off Off N O N
B6 SEF 128.0 O N O
5.5 X 8.5 SEF 139.7...

1-52MFP Service Manual 7500-XXX
O: Detectable by default.
N: Detectable by replacing the document size marked as O with the system data having the same detection 
information.
X: Not detectable.
*1: Changeable from 5.5 X 8.5 LEF to A5 LEF, or from 8.5 X 11 SEF to A4 SEF by the system data.
*2: Changeable from B5 LEF or 8.5 X 11 LEF to 8 X 10.5 LEF by the system data.
*3: Detectable by setting the system data.
*4: Changeable from Executive LEF to 8 X10 LEF.
*5: Changeable from A4 LEF to 8.5 X 11 LEF, or...

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The standard document sizes to be identified by the same given detection information are defined on an 
area-by-area basis. Each area is to be set in the system data.
Sensor (document tray width 2)
Sensor (document tray width 3)Sensor (document tray width 1) Document tray media size actuator 

1-54MFP Service Manual 7500-XXX
The table below shows the combinations of document sizes and sensors. 
O: Detectable
X: Not Detectable
While the document is traveling, document size detection is performed as follows.
When the document goes through the sensor (ADF APS 1), sensor (ADF APS 2) and the sensor (ADF APS 3), 
the document width in the fast scanning direction is detected according to the combination of shielded/
unshielded status of each sensor.
The document length in the slow scanning direction...

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Document scanning steps
The CCD image sensor is used to read image data from the document. To stabilize the read image data, the 
CCD image sensor output is adjusted and the read image data is compensated.
The CCD image sensor output is adjusted with the gain/offset voltage of the amplifier in the analog circuit. This 
adjustment includes AGC and AOC.
In addition, the reference data is collected and compensation values are calculated to compensate for the read 
image...

1-56MFP Service Manual 7500-XXX
Tandem tray theory 

General information1-57
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Driving force transmission path
2 tray / tandem tray drive motor assembly
The rotating force of the 2 tray / tandem tray motor is transmitted through the gears to components that require 
mechanical driving force as shown below.
The driving force transmitted to the gear 22/40T drives the transport roll assembly through the clutch and gears.
TTM drive gear (60T)
TTM drive gear (37T)
TTM drive gear (32T)
TTM drive gear (37T)
2TM/TTM media transport
roll ASMTTM drive gear...

1-58MFP Service Manual 7500-XXX
Media transport 
Media transport path
Media is supplied from tray 3 or tray 4, and is transported to the printer along the media transport path shown 
below.
Pick roll Pick roll
Separation roll Separation roll
Feed roll
Transfer roll ASM
PC cartridge Drum
Heat roll
Pressure roll
Fuser unit ASM
Exit 1 media exit roll ASM
Duplex media transport roll ASM
Duplex mediaCenter transport
roll ASM Exit 2 media transport roll ASM
Exit 2 media exit roll ASMTray 3Tray 4
Upper pinch...