Quick Triage & Baseline
The Symptom: Horizontal or vertical lines appear at regular intervals across the page. This is a rhythmic mechanical failure.
Immediate Branch Logic:
Do not start buying parts. You must run a diagnostic test page first to determine if this is isolated to one colour channel or affects the entire carriage movement.
⚠ STOP LINE: Do not run more than 3 consecutive printhead cleaning cycles without printing a test page. You will flood the waste ink pad and lock the printer permanently.
Fast Resolution Checklist
Perform these immediate actions (30-60 seconds) before escalating to a hardware repair.
- Step 1: Determine if lines are Horizontal (spray gap) or Vertical (roller defect)
- Step 2: Run a CMYK Test to isolate the colour
- Step 3: Inkjet: Run Printhead Clean
- Step 4: Laser: Measure the distance between repeating lines
- Step 5: Match distance to internal roller circumference
Likely Causes
1. Printhead nozzles partially blocked (Horizontal). 2. Laser drum roller scratched (Vertical). 3. Dirty encoder strip (Vertical/Jagged).
The Physical Mechanism
As the carriage sweeps left-to-right (Horizontal banding), a blocked nozzle leaves a gap in spray. As the rollers turn (Vertical banding), damage on a cylinder transfers a line every exact circumference.
Decision Rule (If X, Then Y)
If the lines are horizontal on an inkjet, clean the printheads. If the lines run vertically down the page on a laser, replace the drum showing the matching interval.
Common Wrong Assumptions
Running endless cleaning cycles for vertical lines on a laser printer. Cleaning cycles do not fix scratched metal rollers.
Limits & Escalation
Stop attempting DIY repair if the defect persists after fresh consumables, 3 cleaning cycles, and a driver reset. You are now looking at a failed Logic Board, Fuser, or permanent Printhead block. Consult your brand’s support path.
Prevention & Early Warning
Avoid using paper with staples. Do not touch laser drums with bare hands (oils degrade the coating).