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Service Guide ML320/ML321
Chapter 3 Maintenance & Disassembly
3.3.01 Printhead Gap Adjustment
Before performing this adjustment, always verify that the printhead is properly installed.
The printhead gap should measure:
Rev A, B, and C:
0.016 inch, + / - 0.002 inch
Rev D:
0.018 inch, + / - 0.002 inch
The printhead gap adjustment procedure should be performed when the following occur.
- Print quality is darker on either side of the document.
- Parts /Assemblies are replaced.
- Space Motor Assembly
(3.2.15
)
- Carriage Shaft ........... (3.2.16
)
- Guide Rail ................ (3.2.18
)
- Platen Assembly ........ (3.2.19
)
This adjustment has four phases.
Phase 1: Setup Phase (Steps 1-6)
The cover is removed and the printhead is placed at a known reference point.
Phase 2: Printhead Gap Modification Phase (Steps 7-9)
The distance between the printhead and the platen at the left (line feed motor) side of
the platen is modified by turning the adjust screw. Turning the adjust screw varies the
vertical position of the space motor.
Phase 3: Parallel Adjustment Phase (Steps 10 - 12)
The adjust cam lever is moved to ensure that the printhead moves parallel to the platen.
Phase 4: Check Phase (Steps 13 - 14)
This phase verifies that the Parallel Adjustment Phase did not affect the Printhead
Gap Modification Phase.
To adjust the printhead gap, follow this procedure.
1) Remove the upper cover.
2) Move the change lever to the rear paper feed position.
