Lexmark C 746 Service Manual

							Repair information4-145
 5026
Go Back Previous
Next
Printhead removal, installation, and adjustment
See “Printhead assembly” on page 7-11 for the part number.
Service tip—Testing the new printhead
See “Printhead verification” on page 3-39 for quick way to verify that the existing printhead is failing 
before installing the new printhead. If the new printhead also fails, the existing printhead is probably 
working properly, so the system board is probably the failing component.
Printhead removal
1.
Turn the printer off.
2.Disconnect the power cord from the electrical outlet and from the printer.
3.Remove the paper tray.
4.Open the front access door.
5.Open the top access door.
6.Remove the fuser.
7.Remove the transfer module and photoconductor units.
a.Disconnect the transfer module cable (A). 
b.Press the two tabs (B) to release the front access cover assembly.
c.Press the two tabs (C) on either side of the transfer module, and lift out the transfer module.
Note:  Leave the photoconductor units on the transport belt when removing.  
						

							4-146Service Manual 5026 
Go Back Previous
Next
Warning:  To avoid damaging the photoconductor drum, place the transfer module with the 
photoconductor units on a clean surface. Never expose the photoconductor units to light for a prolonged 
period of time. Place a clean, dry cloth over the transfer module and photoconductor units until they are 
required.
8.Remove all of the toner cartridges.
9.Remove the right cover and the right side cover (attached). See “Right cover removal” on page 4-51. 
10.Remove the LVPS. See “Low-voltage power supply (LVPS) removal” on page 4-119. 
11.Remove the system board support shield. See “System board support shield removal” on page 4-160. 
12.Push the top access cover down until it clicks into place.
BC
A 
						

							Repair information4-147
 5026
Go Back Previous
Next
13.Remove the three printhead mounting screws (D). 
						

							4-148Service Manual 5026 
Go Back Previous
Next
14.Remove the printhead alignment screw cover (E).
15.While still holding the printhead in place, loosen the printhead alignment screw (F) until the printhead 
comes out.
Warning:  Secure the printhead when loosening the printhead alignment screw. Failure to do this allows 
the printhead to fall out of the printer, potentially damaging the printhead. 
Install the printhead and replace parts
Warning:  
•When reinstalling the printhead, it is important to keep in mind that the printhead mounting screws should 
be initially tightened just enough to hold the printhead in the printer. The printer parts are installed 
with the printhead mounting screws loose so you can print the pages that will be used to align the black 
plane to the printer frame. This also allows the black skew adjustment to be adjusted with the printhead 
alignment screw. 
•Once the black skew is aligned, the mounting screws will be fully tightened, and the next steps of 
alignment can be completed.
1.When installing the printhead, visually center the printhead and center the hole in the frame (A). 
						

							Repair information4-149
 5026
Go Back Previous
Next
2.Loosely attach the three printhead mounting screws (B).
Warning:  Do not fully tighten the printhead mounting screws until skew has been adjusted. 
3.Lightly tighten the alignment screw (C). 
4.Feed the ground cable through the hole in bottom leftside frame. 
						

							4-150Service Manual 5026 
Go Back Previous
Next
5.Replace the system board support shield screws (E): 
a.Loosely attach the two mounting screws (E2)
b.Set the system board support shield in place.
Check that the ribbon mirror motor cable (white) and the printhead cable (bottom) do not rub against 
the edges of the frame.
c.Replace the remaining system board support shield screws in the following order:
•Replace the four screws (E1) from the inner right side of the support shield.
•Tighten the two mounting screws (E2) to the top of the support shield.
•Replace the three screws (E3) from the bottom of the support shield, and two screws from the 
top.
•Replace the five mounting screws (E4, E5) to the outer left side of the printer. 
•Reattach the printhead ground cable (E6) to the fourth screw from the top. 
						

							Repair information4-151
 5026
Go Back Previous
Next
6.Replace the system board. 
a.Place the system board in position.
Check that the mirror motor cable and the printhead cable do not rub against the edges of the frame.
b.Replace the nine screws (F) in the system board in the following order:
•Loosely attach the four corners (F1) in a clockwise order, beginning with the left top corner.
•Replace the USB connector screw (F2).
•Loosely attach the left center side, top center, and right center side (F3).
•Tighten the top left corner and top right corner.
•Replace the two screws on the center bottom (F4).
•Tighten the bottom left and bottom right corners (F1).
c.Route the cables through the access holes on the right side of the printer.
F2
F1 F3 F4F1F3F1
F1 F3 
						

							4-152Service Manual 5026 
Go Back Previous
Next
d.Replace all the screws (G) 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 (H) to the ground screw.
e.Reconnect all the cables to the system board. Use the diagram below as a guideline.
Warning:  Be careful in reconnecting the printhead ribbon cable (J). It can be damaged and should be 
handled carefully. A flat ribbon cable can easily be damaged and should be connected gently by hand.
f.Install the hard disk if appropriate.
7.Replace the LVPS.
a.Install the LVPS, and make sure the cable is in the cable guides, and not behind the LVPS.
b.Reconnect the cable to the LVPS.
c.Replace the five LVPS mounting screws. 
						

							Repair information4-153
 5026
Go Back Previous
Next
d.Reconnect the cable in connector JLVPS1 on the system board.
8.Replace the right cover.
a.Slide the right cover up until it locks into position.
Be sure the tab in the top access cover engages the slot in the right cover. 
b.Replace the screw at the bottom of the rear frame cover.
c.Replace the two screws securing the right cover at the bottom.
d.Replace the metal screw at the bottom on the inside front cover
e.Replace the plastic screw at the top on the inside of the front cover.
9.Replace the left cover, the rear left cover, and the paper tray dust cover.
a.Place the paper tray dust cover into position.
b.Slide the cover down until it locks into place. 
Be sure the post in the top access cover engages the hole in the left cover, and that the post in the 
paper tray dust cover engages the hole in the left cover properly.
c.Replace the taptite screw on the rear frame cover.
d.Replace the three screws on the left cover.
10.Replace the rear frame cover.
a.Replace the rear frame cover.
b.Tighten the eight screws. 
11.Replace the rear upper cover (two screws).
12.Reinstall the transfer module with the photoconductor units still attached.
13.Reconnect the transfer module cable. 
14.Replace the toner cartridges. 
15.Reinstall the fuser.
16.Close the top access door. 
17.Close the front access door.
18.Replace the paper tray.
Align the printhead
Note:  The printhead mounting screws should be initially tightened just enough to hold the printhead in the 
printer. 
There is one printhead that houses the four color planes. The black plane is aligned to the printer, and the color 
planes are internally aligned to black. Electrical alignment is done to fine tune the alignment of the color planes 
to the black plane after the printhead is installed, and black skew is adjusted using the alignment screw.
1.Plug the electrical cord into the printer.
2.Plug the electrical cord into the outlet.
3.Align the printhead skew for black. Go through steps 13 to 18 on page 4-10 for printhead alignment skew 
for black on the C746 model, or go through steps 13 to 18 on page 4-19 for printhead alignment skew for 
black on the C748 model
4.Perform top margin alignment for black. Go to page 4-13 for top margin alignment for black on the C746 
model, or go to page 4-23 for top margin alignment for black on the C748 model.
5.Perform bottom margin alignment for black. Go to page 4-13 for bottom margin alignment for black on the 
C746 model, or go to page 4-23 for bottom margin alignment for black on the C748 model.
6.Perform left margin alignment for black. Go to page 4-14 for left margin alignment for black on the C746 
model, or go to page 4-24 for left margin alignment for black on the C748 model.
7.Perform right margin alignment for black. Go to page 4-14 for right margin alignment for black on the C746 
model, or go to page 4-24 for right margin alignment for black on the C748 model.
8.Perform alignment for cyan, yellow, and magenta. Go to page 4-14 for cyan, yellow, and magenta 
alignment on the C746 model, or go to page 4-24 for cyan, yellow, and magenta alignment on the C748 
model. 
						

							4-154Service Manual 5026 
Go Back Previous
Next
Right bell crank assembly removal
See “Right bellcrank assembly, with spring” on page 7-7 for the part number.
1.Remove the right cover. See “Right cover removal” on page 4-51.
2.Remove the C-clip (A).
3.Remove the right bell crank assembly.
A