Lexmark C760 Service Manual

							
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3.  Diagnostic aids
This chapter explains the tests and procedures to identify printer failures and verify repairs have corrected the 
problem.
There are different test menus that can be accessed to identify problems with the printer.
Diagnostic aids
Printhead diagnostics
See “Printheads” on page 7-13  for the part number.
If you get a printhead error, follow this diagnostic to find the specific failure. 
1.Verify all the printhead cables are properly seated.
If the printhead cables are properly seated and the error remains, record the error code. Continue to the 
next step.
2.Determine how to setup the printhead diagnostic tool.
a.Verify the printhead diagnostic tool is configured as in the illustration below. Reconfigure if necessary. 
b.Select which pair of printheads to use based on the error code. 
If the printer displays the codes that indicate yellow or cyan, use the tool to switch the yellow and cyan 
signals. If the error codes indicated a magenta or black error, use the tool to switch the magenta and 
black signals.
Magenta/black
Connect tool here for:
 
Yellow/cyan 
						

							
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3.Install the printhead diagnostic tool and determine the problem.
The following procedure shows the yellow and cyan switch as an example.
a.Turn off the printer.
b.Unplug the printhead cables from the system board in the printer and connect them to the printhead 
diagnostic tool.
c.Connect the printhead diagnostic tool cables to the connectors on the system board in the printer. 
This reverses the printhead color signals for the selected pair of colors. 
						

							
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d.Turn on the printer and note the new error codes.
 If an automatic calibration begins,  36 Printer Service Required may appear. The printhead and 
system board are working correctly and the printhead cable connections should be checked. 
Press  Go to clear the error.
 If the error code remains the same, replace the system board. If that solves the problem, you  are finished.
 If the printer displays a different printhead error code, which indicates another color, the  printhead or the printhead cables are defective. See the table below for the printhead codes.
For example, the printer originally displays the printhead error code  108 (yellow). After switching the 
signals using the diagnostic tool, the printer displays the printhead error code  106 (cyan).
4.Remove the printhead diagnostic tool.
5.The problem is in either the printhead cables or the printhead. Replace the printhead cables. If the problem 
persists, replace the printhead. See  “Printhead removal and adjustments” on page 4-60 .
Note:   Replace and adjust only one printhead at a time. Printhead error codes Printhead error codes
Yellow Cyan Magenta Black (K)
For 10x errors 108 106 107 109
For 11x errors 117 115 116 114
For errors 169–175 175 171  173 169
Not commonly seen 176 172 174  170 
						

							
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Print quality defect locator chart
The print quality locator chart is copied below, but the tool is a transparent sheet available with this printed book. 
Use the tables and rulers to determine the source of repeating defects.
Using the chart
Measure repeating horizontal lines from the reference lines at the top to determine what may have caused the 
lines to form in that pattern. Be sure to use portrait orientation for the test file.
Rollers
Component 
descriptionComponentPlanes 
affected Defect period
mm inches
Charge roll
CartridgeOne 38.7 1.5
PC drum One 96.8 3.8
PC cleaner One 96.8 3.8
Developer roll One 47.9 1.9
TAR One 46.4 1.8
Toner meter One 1092.2 43
Cart auger One 349.9 13.8
First transfer roll ITU One 53.2 2.09
Second transfer roll Second  transfer rollAll 59.4 2.34
ITM drive roll ITU All 101.0 3.98
ITM reverse roll ITU All 50.5 1.99
Fuser hot roll FuserAll 147.0 5.79
Fuser BUR All 147.0 5.79
Metering rolls Reference Edge All 47.0 1.85
Color charge roll short C, M, or Y cart C, M and Y 101.0 3.98
NIP shock
NIP distances Defect period
mm Inches
Y-C-M-K cartridge spacing 101.0 3.98
K to second transfer roll 144.6 5.69
M to second transfer roll 245.6 9.67
C to second transfer roll 346.6 13.65
Y to second transfer roll 447.6 17.62
Meter 1 to second transfer 164.8 6.49
Meter 2 to second transfer 126.4 4.98
Meter 3 to second transfer 86.4 3.40
Meter 4 to second transfer 51.4 2.02
Second transfer to fuser 319.4 12.57
Fuser nip to first redrive 50.0 1.97
Fuser nip to exit sensor 58.2 2.29
Fuser nip to exit tray nip 420.3 16.55 
						

							
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Printing the chart
The printer has an internal copy of the defect locator chart under the Help Menu. Verify the proper image size by 
measuring any of the marks on the chart and comparing them to the corresponding measurement in the chart. 
Use Step 2 if adjustments are needed.
Copying the chart
Use the provided transparent sheet if at all possible. If you need to make a copy, be aware that fax machines, 
digital scanners, and xerographic copiers can distort images. Charts should be printed using the transparent 
copy provided in the service manual. In order to maintain the accuracy of the edge rulers, the following steps 
should be heeded when printing a copy of the Defect Location Chart.
1.When printing this document, make sure “Fit to page” is not selected.
2.Measure the distance between the  Reference line and the 110 mm  Calibration Mark to verify that it is 
correct. If the distance is inaccurate, the bottom registration margin setting can be adjusted to correct the 
discrepancy. Increasing the bottom margin value stretches the image, reducing it shrinks the image. 
Original margin settings should be noted in the case that these changes adversely effect the print quality or 
registration when printing normal documents.
Print quality
For a transparency of the defect locator chart, go to the back of the hard copy service manual.
Note:   If you want to copy the chart, then the following should be observed.
Since fax machines, digital scanners, and xerographic copiers can distort images, charts should be printed using 
the transparent copy provided in the service manual. In order to maintain the accuracy of the edge rulers, the 
following steps should be heeded when printing a copy of the Defect Location Chart.
1.When printing this document, make sure “Fit the page” is NOT selected.
2.Measure the distance between the reference line and the 110 mm calibration mark to verify that it is 
correct. If the distance is inaccurate, the bottom registration margin setting can be adjusted to correct the 
discrepancy. Increasing the bottom margin value stretches the image, reducing the bottom margin value 
shrinks the image. Original margin settings should be noted in case these changes adversely effect the 
print quality or registration when printing normal documents. 
						

							
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Partial Print Test
Diagnostic procedure for missing or faded planes
1.
Turn the printer off.
2.Remove all cartridges and the ITU.
3.Inspect the bellcranks.
4.Enter the Configuration Menu. See  “Configuration Menu” on page 3-8 .
5.Select Prt Quality Pgs  and press Select.
6.Open the vacuum transport belt (VTB) jam access door and watch the test pages pass from left to right 
over the VTB. 
There is a delay between the first and second page. 
7.Once the pages are printed, examine the pages for to confirm the color plane is not printing. 
Note:   The third page is particularly important since it is the image on the belt when the test printed.
8.Select Prt Quality Pgs  and press Select.
Open the VTB through the access door and, once again, watch the test pages pass over the VTB. 
9.When the top half of the second page passes over the VTB, quickly open the front cover. The printing 
stops.
10.Remove all four toner cartridges and set them face down.
Look at the surface of each toner cartridge and check for a developed image.
Approximate
final stopping
place 
						

							
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Interpreting the results
If the developed images are not visible on one of the PC drums, the following components should be checked:
Toner cartridge - Switch cartridges to determine if the problem stays with the slot or cartridge.
Cartridge contact block pins - Verify that pins are spring loaded and properly positioned. See  “Cartridge 
contact assembly pin locations (cyan, magenta and yellow)” on page 5-4
Developer HVPS cable - Make sure that there is no damage to the cable running from the system board.
Developer HVPS board.
System board.
If the image is well developed on the PC drum, but the same plane is missing or faded on the ITU belt, the 
following components should be checked:
Bell cranks - Check the condition of the bell cranks.
Continuity on the bell crank circuit - Turn the printer off. Using a multimeter, check the continuity between 
the rear bell crank contact for the failing color and the respective cable on the transfer HVPS board. See 
“Transfer high voltage power supply (HVPS)” on page 5-20 .
Transfer HVPS cable - Make sure that there is no damage to the cable running from the system board to 
the transfer HVPS board. Verify the connection at both ends.
Transfer HVPS board.
Engine board. 
						

							
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Configuration Menu
The Configuration Menu contains a set of menus, settings and operations which are infrequently used by a user. 
Generally, the options made available in this menu are used to configure a printer for operation.
Note:  An asterisk(*) in the value list in the following menus indicates the default value.
The following are available from the Configuration Menu: ITU Cnt Value
Fuser Cnt Value
Reset Fuser Cnt
Prt Quality Pgs  (This is not displayed if in Demo mode.)
Color Trapping
Tray Inser t Msg
SIZE SENSING
Panel Menus
PPDS Emulation (This only displays if the PPDS interpreter is available.)
Demo Mode
Factory Defaults
Energy Conser ve
Auto Color Adjust
ERROR LOG
Font Sharpening
Paper Prompts
Env Prompts
Exit Config Menu (Press  Select to exit CONFIG MENU and reboot.)
Entering Config Menu
To enter the Configuration Menu:
1.Turn the printer off.
2.Press and hold the  Select and Return  buttons.
3.Turn the printer on.
4.Release the buttons when  Performing Self Test  is displayed.
Exiting the Config Menu
Select EXIT Config Menu  to exit the Configuration Menu and return to normal mode. 
						

							
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ITU Count Value
This is the page count of the current ITU. It cannot be reset unless a new ITU is installed. 
Press Select  to view the count value.
Fuser Cnt Value
Enter the Configuration Menu and select  Fuser Cnt Value. 
The value can be reset in Reset Fuser Cnt.
This only displays if the Maintenance Warning and Intervention function is enabled in the printer Configuration 
ID. The fuser maintenance page counter is incremented when a page is printed and incremented by two when a 
duplex sheet is printed. The counter can be used to track printer usage. When the counter reaches 200,000, the 
printer posts a fuser maintenance message on the operator panel.
Reset Fuser Cnt
This only displays if the Maintenance Warning and Intervention function is enabled in the printer Configuration 
ID. The fuser maintenance page counter is incremented when a page is printed and incremented by two when a 
duplex sheet is printed. The counter can be used to track printer usage. When the counter reaches 200,000, the 
printer posts a fuser maintenance message on the operator panel.
1.Select  Reset Fuser Cnt  in the Config Menu to view the page count.
2.Press Return  to retur n to the previous menu or press  Select to reset the maintenance page counter back 
to zero.
Prt Quality Pgs
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. Use this test to identify print quality problems. The Test Pages 
must be printed on A4, Legal or Letter paper.
1.Select  Prt Quality Pgs  from the Config Menu. 
2.Press Select .
Go to  “Print tests” on appendix page B-3  for representative samples of the pages.
Color Trapping
Color trapping is an aid to graphic and text. When a text or graphics appear over other colors, a misalignment 
may allow white paper to show through at the borders of the colors. Color trapping reduces the cutout area 
under the upper image so a slight misalignment does not show.This only affects PostScript printing. 
1.Select Color Trapping  from the Config Menu 
2.Select the value or  Off. The range is 1 to 5 and the default value is 2.
Use  Menu  to increase the value.
Tray Insert Msg
This setting controls how long, in seconds, the tray insert message displays when a tray is inserted.
The values are  Disabled and 1 to 90. The default value is 5. 
						

							
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SIZE SENSING
Automatic size sensing can be disabled or enabled in this menu. Only paper sources that support Auto Size 
Sensing are displayed.
1.Select SIZE SENSING  from the Config Menu.
2.Select a tray. Only those trays with size sensing display. One of the following is displayed:
Tray 1 Sensing
Tray 2 Sensing
Tray 3 Sensing
Tray 4 Sensing
3.Select  Auto to turn size sensing on for that tray, or select  Off to disable size sensing.
4.Select  Return  to exit.
Panel Menus
Disabling Panel Menus prohibits users from modifying any setting or executing any operation available in the 
Ready Menu group. 
1.Select Panel Menus  from the Config Menu.
2.Select Disable  or Enable .
Enable is the default.
PPDS Emulation
This only displays if the PPDS inter preter is available.
1.Select  PPDS Emulation  from the Config Menu.
2.Select Activate  or Deactivate .
Demo Mode
This printer supports a demo mode that is usually used in retail environments to illustrate the features of the 
printer. The printer features are illustrated by demonstration files stored in the RIP firmware, flash option, or disk 
option.
1.Select Demo Mode  from the Config Menu.
2.Select Activate  or Deactivate .
Deactivate is the default value.
Factory Defaults
The customer can restore either the network settings or the base printer settings to their factory default values. 
When Restore Base is selected, non-critical base printer NVRAM settings are restored. When Restore Network 
is selected, all network NVRAM settings are restored to their factory default settings. This option is only available 
on models with an integrated network adapter. In either case, Restoring Factory Defaults is displayed after the 
operation is selected.
1.Select  Factory Defaults  from the Config Menu.
2.Select Restore Base  or Restore Network .
Note:   Restore Network is only listed on models that have integrated network support.