Lexmark C 746 Service Manual

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4.Look at the coarse and fine adjustments on the top left of the page, and enter the best number for the top 
adjustment in the T space. Transfer this number over to the computation area for Z.
5.On the operator panel, use   and   to locate Top Margin. Press  , and then use   or  to enter the 
setting computed for T. Press   to save.
6.Repeat this process for skew (Z). Add the T value and the current Z value to obtain the new skew (Z) 
value.
7.Reprint the Quick Test page, and observe the results. Make additional adjustments if necessary before 
proceeding on to Quick Test step two page.
8.Obtain left (L), right (R), and Bow (P) value using the same method as obtaining T from Quick Test Step 1. 
Reprint the Quick Test to ensure the settings are correct. Make additional adjustments as required.
9.Press   to return to ALIGNMENT MENU. 
Alignment (C748x)
To perform alignment:
1.Touch ALIGNMENT MENU from the Diagnostics Menu. Scroll until you reach the color that you desire to 
align. Go to each submenu, and use   and   to zero out all settings.
Note:  It is important to zero out all settings to make the adjustment easier.
2.Scroll and touch Quick Test in the same color menu. Two pages print.
3.On the pages, make sure all the Current Values are set to zero. If not, go back two steps and repeat.
4.Look at the coarse and fine adjustments on the top left of the page, and enter the best number for the top 
adjustment in the T space. Transfer this number over to the computation area for Z.
5.On the operator panel, touch Top Margin, and then use   or   to enter the setting computed for T. 
Touch  to save.
6.Repeat this process for skew (Z). Add the T value and the current Z value to obtain the new skew (Z) 
value.
7.Reprint the Quick Test page, and observe the results. Make additional adjustments if necessary before 
proceeding on to Quick Test step two page.
8.Obtain left (L), right (R), and Bow (P) value using the same method as obtaining T from Quick Test Step 1. 
Reprint the Quick Test to ensure the settings are correct. Make additional adjustments as required.
9.Touch Back to return to ALIGNMENT MENU.
See “Printhead mechanical alignment (C746)” on page 4-8 for printout samples and additional information. 
						

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Motor tests
The motor tests are run to locate noises in the printer and isolate failures between the motors, cables, and 
system board. 
General motor tests procedures
In some instances, when you enter a particular test, you will be given the choice to run the motor in forward or 
reverse. Other times, there will only be the option to run the motor in forward direction.
In general, the test should work as follows:
1.Select MOTOR TESTS from the Diagnostics Menu.
2.Select the motor that you need to test.
3.Check the table below for setup requirements, if any.
4.Select the direction if a choice is offered (Forward or Reverse) or other setting for that test. 
Press   or   to stop the motor and end the test.
The following tests have special setup before running the test:
Motor diagnostic setup
MotorSetup requirements
Notes
Top cover 
positionFront door 
position
Tray 1 N/A Closed • Ok
• Picks paper – use empty or remove tray
Open Ok
Align N/A Closed Ok
Open
defeat +25 V switch•Ok
• View align mechanism
Duplex N/A Closed Ok
Closed
split front door•Ok
• View duplex mechanism (pull tray to isolate gears)
Open
defeat +25 V switch•Ok
• Duplex mechanism disconnected from motor
Belt stepper N/A Closed • No motion
• No error reported
Open • Ok
• Belt disconnected from motor
Cartridge K – 3 N/A Closed • No motion 
• No error reported
Open • Ok
• Cartridge disconnected from motor
Cart MCY – 2 N/A Closed • No motion 
• No error reported
Open • Ok
• Cartridge disconnected from motor 
						

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Motor diagnostics
PCU CY – 1 N/A Closed • No motion 
• No error reported
Open • Ok
• Cartridge disconnected from motor
Fuser Closed Closed Ok
Open Possible under-temp 120.04 error
Open N/A Not recommended, fuser errors possible
Cam N/A Closed • Ok
• Front door locks & unlocks
Open • Ok
• Door disconnected from motor
• View gearbox
COD N/A Closed • Ok
• Engages and disengages cartridges
Open • No motion
• No error reported (open while test is running)
Motor Direction Action Notes
Tray 1 Forward Pick from Main Tray • Will pick continuously
• View with tray removed or empty
Reverse N/A Function not supported
Align Forward Push media toward belt • Nip is closed
• Fails with waste box missing
Reverse Align leading edge Function not supported
Duplex Forward Push media down toward 
input• Will run continuously
• View with front cover split
Reverse Pick from MPF (MPF test) • Will pick continuously
• View empty or pull tray
Belt stepper Forward only Gear turns counter clockwise View with front cover open (No forward 
menu)
Reverse N/A Only used to clear cleaner nip
Cartridge K – 3 Forward only Gear turns counter clockwise View with front cover open (runs PCU KM 
also)
Reverse N/A Only used to clear blade nip
Cart MCY – 2 Forward only Gear turns counter clockwise View with front cover open
Reverse N/A Not used
PCU CY – 1 Forward only Gear turns counter clockwise View with front cover open
Reverse N/A Only used to clear blade nip
Fuser Forward Push media toward output 
binBackup roll turns
Top cover should be closed
Reverse Push media toward output 
binBackup roll is disengaged MotorSetup requirements
Notes
Top cover 
positionFront door 
position 
						

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Print Tests
Input source tests
The purpose of the diagnostic Print Tests is to verify that the printer can print on media from each of the installed 
input options. The contents of the Print Test Page varies depending on the media installed in the selected input 
source.
Check each Test Page from each source to assist in print quality and paper feed problems.
To run the Print Test Page:
1.Select PRINT TESTS from the Diagnostics Menu.
2.Select the media source.
Tray 1
Tray 2 (if installed)
Tray 3 (if installed)
Tray 4 (if installed)
Tray 5 (if installed)
Multi-Purpose Feeder (if installed)
3.Select Single or Continuous. 
•If Single is selected, a single page is printed.
•If Continuous is selected, printing continues until   is pressed to cancel the test. Cam Forward Engage motor couplings • Runs to stall position
• Locks door
• Enables print operations
Reverse NOP Disengage motor couplings • Runs to stall position
• Unlocks door
• Disables printing
COD Forward Engage color cartridges • Runs to stall position
• Disables color print operations
Reverse NOP Disengage color cartridges • Runs to stall position
• Enables color printing Motor Direction Action Notes 
						

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If a source is selected that contains envelopes, an envelope test pattern is printed. If Continuous is 
selected, the test pattern is printed only on the first envelope.
Note:  The Print Test Page always prints on one side of the paper, regardless of the duplex setting.
4.Press  or touch Back to return to PRINT TESTS. 
Print quality test pages (Print Quality Pages)
The print quality test consists of five pages. Pages one and two contain a mixture of graphics and text. The 
remainder of the pages only contain graphics. The test prints on the media in the default tray.
This test may be printed from either Configuration Menu or the Diagnostics mode. To run the print quality pages 
from the Diagnostics mode, select PRINT TESTS and Print Quality Pages from the menu. Once the test is 
started, it cannot be canceled. When the test pages print, the printer returns to the original screen.
To run the Print Quality Test Pages, select Print Quality Pages from PRINT TESTS. The message Printing 
Quality Test Pages is displayed, and the test prints.  
						

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Hardware Tests
Panel Test
This test verifies the operator panel LCD function.
To run the Panel Test:
1.Select HARDWARE TESTS from the Diagnostics Menu.
2.Select Panel Test.
Note:  For C748x, the panel test continually executes. Each pixel is activated at the darkest level to the 
lightest level, and then the backlight illuminates and turns off. This is repeated continuously.
Note:  For C746x, the operator panel display cycles through red, green, blue, white, and black.
3.Press   to cancel the test at any point.
Button Test
This test verifies the operator panel button function.
To run the Button Test:
1.Navigate to Diagnostics Menu > HARDWARE TESTS > Button Test.
2.C746x and C748x models have different button tests.
•For C746x, follow the instruction on the operator panel display on which button to press.
•For C748x, a keypad displays on the operator panel. Press each physical button one at a time and 
observe if its corresponding button on the display lights up.
3.Press   or touch Back to end the test.
DRAM Test
This test checks the validity of DRAM, both standard and optional. The test writes patterns of data to DRAM to 
verify that each bit in memory can be set and read correctly.
To run the DRAM Test, navigate to Diagnostics Menu> HATDWARE TEST > DRAM Test. The power indicator 
blinks indicating the test is in progress.
Note:  If you need to exit the test before it is complete, turn off the printer.
P:###### represents the number of times the memory test has passed and finished successfully. Initially, 
000000 displays with the maximum pass count being 99,999.
F:##### represents the number of times the memory test has failed and finished with errors. Initially, 00000 
displays with the maximum fail count being 99,999.
Once the maximum pass count or fail count is reached, the test is stopped, the power indicator turns on solid, 
and the final results appear. If the test fails, SDRAM Error appears for approximately three seconds and the 
failure count increases by 1.
Serial 1 Wrap
The Serial 1 Wrap Test is used to check the operation of the serial port hardware using a wrap plug. Each serial 
signal is tested.DRAM Test 128M P:######  F:##### 
						

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To perform the Serial 1 Wrap Test:
1.Disconnect the serial interface cable, and install the serial wrap plug.
2.Select HARDWARE TESTS from the Diagnostics Menu.
3.Select Serial 1 Wrap.
The power indicator blinks indicating the test is in progress. The following screens appear
Upon completion of the POR, the following screen is displayed:
P:###### represents the number of times the serial port hardware has passed.
Initially, 000000 is displayed. The maximum pass count is 999,999.
F:###### represents the number of times the serial port hardware has failed.
Initially, 0000 is displayed. The maximum fall count is 999,999.
Any of the following explanations for failure may display:
•Receive Status Interrupt Error
•Status Error
•Receive Data Interrupt Error
•Transmit Data Interrupt Error
•Transmit Empty Error
•Threshold Error
•Receive Data Ready Error
•Break Interrupt Error
•Framing Error
•Parity Error
•Overrun Error
•Data Error
•Data 232 Error
•Data 422 Error
•FIFO Error
•DSR Error
•DSR PIO Error
•DSR Interrupt Error
•CTS Error
•CTS PIO Error
•CTS Interrupt Error Serial Wrap [x] Testing…
Resetting the 
Printer
Serial Wrap
P:###### F:#### 
						

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USB HS Test Mode
1.
Select HARDWARE TESTS from the Diagnostics Menu.
2.Select USB HS Test Mode.
3.Select the port (Port 0, Port 1, Port 2, Port 3).
4.Select the test for that port from the following list:
Test J
Test K
Test SE0 NAK
Test Packet
Test Force Enable
5.While the test executes, USB High Speed Testing… displays.
To exit the test, restart the printer.
Duplex Tests
Quick Test (duplex)
Note:  Before you set the duplex top margin, be sure to set the skew and alignment. See “Printhead 
alignment” on page 4-8.
This test prints a duplex version of the Quick Test that can be used to verify the correct placement of the top 
margin on the back side of a duplex page. 
You can run one duplexed page (Single), or continue printing duplexed pages (Continuous) until   is 
pressed. For information about changing the margin, see “Top Margin (duplex)” on page 3-18.
The paper you choose to print the page on should be either Letter or A4. 
						

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To run the Quick Test (duplex):
1.Select Quick Test from DUPLEX TESTS.
2.Select Single or Continuous. 
•The single Duplex Quick test cannot be canceled.
•The printer attempts to print the Quick Test Page from the default paper source. 
•Check the Quick Test Page for the correct offset between the placement of the first scan line on the 
front and back side of a duplexed sheet.
The single test stops automatically when a single duplex sheet is printed, and the continuous test continues until 
you press  .
Print Test (duplex)
This test provides service personnel with a way to verify the function of the printer’s duplex hardware. After the 
user selects this test, the device automatically executes a continuous print test that generates a duplexed, color 
output page. To stop the test, the user must press  . While this test executes, the power indicator light blinks 
green and the panel displays “DUPLEX TESTS Printing...”.
The paper you choose to print the page on should be either Letter or A4.
To run the Print Test (duplex):
1.Select DUPLEX TEST in the Diagnostics Menu.
2.Select Print Test.
The printer executes a continuous print test that generates a duplexed, color output page.
3.To stop the test, press  .  
						

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Skew (duplex)
This setting adjusts the duplex motor speed when it feeds through the aligning roll. It controls the skew between 
the first scan line and the top of the page. Adjustments are made to the image that is facedown in the output 
tray.
To set the Skew (duplex):
1.Select DUPLEX TESTS from the Diagnostics Menu.
2.Select Quick Test.
3.Select Single.
The test page prints.
4.Look at the dotted arrows at the top of the page. If the page is skewed on the page, select Skew.
5.For C746x, use   or   to select the skew setting you need to change, and press  . For C748x, use   
or   to select the skew setting you need to change, and touch  .
•Each increment shifts the skew by about 6 pixels at 600 dpi.
•The Skew (duplex) range is -50 to +50, and the default value is 0.
•An increase moves the image at the top right down the page. A decrease moves the image at the top 
right up the page.
6.Perform Quick Test again to verify the adjustment. Check the page to see if the image on the page is still 
skewed. If it is, repeat the adjustment. 
Top Margin (duplex)
This setting controls the offset between the first scan line on the front of the duplex page and the first scan line 
on the back of the page. The duplex adjustments are made to the image that is face down in the output tray. 
Therefore, be sure to set the top margin in REGISTRATION before setting the duplex top margin. See 
“Registration” on page 3-5.
To set the Top Margin (duplex):
1.Select DUPLEX TESTS from the Diagnostics Menu.
2.Select Quick Test.
3.Select Single.
The test page prints.
4.Hold the page to the light to see whether the top margin of the back aligns with the top margin of the front.
5.If they do not match, select Top Margin.
6.For C746x use   or   to select the margin setting you need to change, and press  . For C748x, use   
or   to select the margin setting you need to change, and touch  .
•Each increment shifts the duplex top margin by 1/100 of an inch. 
•The Top Margin (duplex) range is -25 to +25, and the default value is 0.
•An increase moves the top margin down and widens the top margin. A decrease moves the top 
margin upward and narrows the top margin.
7.Print the Quick Test again to verify the adjustment. Repeat until the front and back top scan lines match.
Left Margin (duplex)
By modifying this setting you can shift the image on the back side of a duplex page to the right or to the left.
To set the Left Margin (duplex):
1.Select DUPLEX TESTS in the Diagnostics Menu.
2.Select Quick Test.
3.Select Single.
The test page prints.
4.Hold the page to the light to see whether the left margin of the back aligns with the left margin of the front.
5.If they do not match, select Left Margin.