Lexmark C 746 Service Manual

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Speaker removal
See “Speaker” on page 7-5 for the part number.
1.Remove the rear upper cover. See “Rear upper cover removal” on page 4-50.
2.Remove the right cover. See “Right cover removal” on page 4-51.
3.Disconnect the speaker connector (A).
4.Loosen the three screws (B), then remove the speaker.
System board removal
Warning:  See the system board part number for the model you need on page 7-11. This part might contain 
customer confidential information. See “Data Security Notice” on page 4-1 for more details. After 
removing this part, return it to your next level of support so any data can be removed. If the customer 
requests to keep the part, they must sign a confirmation of memory device retention form.
Warning:  When replacing any one of the following components:
•Operator panel assembly
•System board
•Top access cover assembly
Only replace one component at a time. Replace the required component, and perform a POR before 
replacing a second component listed above. If this procedure is not followed, the printer will be 
rendered inoperable. 
BA
CAUTION
This product contains a lithium battery. THERE IS A RISK OF EXPLOSION IF THE BATTERY 
IS REPLACED BY AN INCORRECT TYPE. Discard used batteries according to the battery 
manufacturer’s instructions and local regulations. 
						

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Warning:  Be careful not to damage the printhead cable when removing the system board.
1.Remove the left cover and the rear left cover. See “Left cover removal” on page 4-31. 
2.Remove the rear frame cover. See “Rear frame cover removal” on page 4-47.
3.Remove the hard disk if one is installed. See “Hard drive assembly removal” on page 4-114.
4.Remove all the screws (A) from the left side of the printer so you can remove the system board, including:
•USB port connector (1 screw)
•Ethernet port connector (1 screws)
•Modem shield (1 screws)
•Hard disk shield (2 screws)
•Ground screw (1 screw) 
						

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5.Disconnect all the cables from the system board.
Warning:  Do not use tools to remove the printhead ribbon cable (B). A flat ribbon cable can be damaged 
and should be removed gently by hand. 
6.Remove the nine screws (C) from the system board.
7.Remove the system board. 
						

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Installation notes:
1.Place the system board in position.
Note:  Check that the mirror motor cable and the printhead cable do not rub against the edges of the 
frame.
2.Replace the nine screws (A) in the system board in the following order:
•Loosely attach the four corners (A1) in a clockwise order, beginning with the left top corner.
•Replace the USB connector screw (A2).
•Replace the top center, right center side, and left center side (A3).
•Tighten the top left corner and top right corner.
•Replace the two screws on the center bottom (A4).
•Tighten the bottom right and bottom left corners (A1).
3.Route the cables through the access holes on the right side of the printer.
A2
A1 A3 A4A1A3A1
A1 A3 
						

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4.Replace all the screws (B) from the left side of the printer, including:
•Ethernet port connector (1 screws)
•Modem shield (1 screws)
•Hard disk shield (2 screws)
•Ground screw (1 screw)
Note:  Be sure to attach the ground wire (C) to the ground screw.
5.Reconnect all the cables to the system board. Use the diagram below as a guideline.
Warning:  Be careful reconnecting the printhead ribbon cable (D). It can be damaged and should be 
handled carefully. A flat ribbon cable can easily be damaged and should be connected gently by hand.
6.Install the hard disk if appropriate.
7.Replace the rear frame cover and the left cover.
D 
						

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System board support shield removal
See “System board support shield” on page 7-11 for the part number.
1.Remove the system board. See “System board removal” on page 4-155.
2.Remove the right cover. See “Right cover removal” on page 4-51.
3.Pull the cables through the access holes on the right side of the printer.
4.Remove the five mounting screws (A) from the outer left side of the printer. 
Note:  Make a note of the attachment of the printhead ground cable (B) to the fourth screw from the top for 
later installation.
5.Remove the four screws (C) from the inner right side of the support shield. 
						

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6.Remove the five mounting screws (D) from the top and bottom of the support shield.
Note:  Only the ribbon and mirror motor cables come through the access holes in the system board 
support shield.
7.Lower and remove the support shield. Be careful not to damage the ribbon cable that routes through the 
bottom frame of the printer.
Installation notes:
1.Loosely attach the two mounting screws (A).
2.Set the system board support shield in place.
Note:  Check that the ribbon mirror motor cable (white) and the printhead cable (bottom) do not rub against 
the edges of the frame. 
						

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3.Replace the remaining system board support shield screws in the following order:
•Replace the four screws (B) from the inner right side of the support shield.
•Tighten the two mounting screws (A) to the top of the support shield.
•Replace the three screws (C) from the bottom of the support shield, and two screws from the top.
•Replace the five mounting screws (D) to the outer left side of the printer. 
Note:  Be sure to connect the printhead ground cable (E) to the fourth screw from the top. 
						

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Toner level sensor removal
See “Toner level sensor” on page 7-13 for the part number.
Note the locations of the toner sensors.
1.Remove the HVPS. See “High-voltage power supply (HVPS) removal” on page 4-115.
2.For the upper two sensors: These sensors are more difficult to reach because the toner is difficult to 
reach: 
						

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It is difficult to press both locking tabs at the same time. Using a spring hook, press the locking tab (A), and 
disengage the sensor on that side. Press the other locking tab (B), and remove the sensor.
Note:  Use a slight pressure on the cable to keep the first locking tab from relatching, while you disconnect 
the second locking tab.
For the lower two sensors:
Using a spring hook, press the locking tab (C), and disengage the sensor on that side. Press the other 
locking tab (D), and remove the sensor.