Konica Minolta C308/C368 Platen Glass Scanning Black Line Issue: Comprehensive Technical Guide (Scan Area Adjustment)

Applicable Models: bizhub C308 / C368 / C458

The [Scan Area] parameters in Service Mode are intended to correct overall image-position errors that result in uniform black borders or image shifts. They are generally not effective for a thin black line that remains at a fixed position or for intermittent black bands caused by contamination, scratches, or scanner hardware problems. Hardware inspection and cleaning should therefore be performed before making any Service Mode adjustments.

I. Scan Area Menu Parameter Definitions (Axis definitions are fixed and do not change with the original document orientation)

Parameter Item Control Dimension Target
Image Position: Lead Edge FD (Longitudinal/Feed Direction) Top/Bottom black borders / Vertical image shift
Scanner Image Side Edge CD (Lateral/Scan Lamp Track) Left/Right black borders / Horizontal image shift
CD / FD Direction Scaling Fine-scale correction (0.990–1.010) For image stretching/compression only; do not use to eliminate black lines; keep at 1.000 unless under special circumstances

Golden Rule: Perform hardware cleaning and inspection before making software adjustments in Service Mode. Do not reverse this order.

Adjustable via software: Overall image shift resulting in uniform black borders at the top/bottom or left/right (consistent width; classified as “pseudo-black lines”).

Not adjustable via software: Single fine black lines or intermittent black bands at fixed coordinates/thickness (caused by dirty/scratched glass or CCD failure; classified as “true black lines”).

II. Symptom Classification

A. Uniform Black Border or Overall Image Shift

  • The entire copied image is uniformly shifted up, down, left, or right.
  • A uniform black band with a consistent width appears along the edge of the paper.
  • When the position of the original document is changed, the black band moves with the image rather than remaining at a fixed position on the paper.
  • The black band remains after cleaning the platen glass and white reference strip, indicating that the image-position shift has not been corrected.

B. Fixed Fine Black Line or Intermittent Black Band

  • The black line has a consistent thickness and appears at the same position on the paper regardless of the original document’s position.
  • It may appear as a vertical black line extending along the page or, in some cases, as a horizontal black band.
  • If the line appears when copying from the platen glass but not through the ADF, the fault is more likely related to the platen scanning path.
  • If the same line appears in both platen and ADF copies, the fault may involve the CCD, mirror assembly, or white reference area.

Note: If the black line appears only when scanning through the ADF while platen copying is normal, inspect and clean the ADF’s narrow scanning glass strip first. This type of issue is separate from the main platen scanner bed and the [Scan Area] parameters.

III. Standardized Repair Procedure (Proceeding from simple to complex, verifying at each step)

1. Clean the platen glass: Use a lint-free cloth and anhydrous alcohol to thoroughly remove toner, adhesive residue, correction fluid, etc.; inspect the glass surface for physical scratches (scratches are irreversible and require glass replacement).

2. Clean the white reference strip (the long white strip on the underside of the document cover): Dust or stains can directly cause a fixed black band.

3. Disassemble the scanner unit and clean dust from the four mirror sets and the lens surface; inspect the scanner optical path and CCD area for dust, contamination, or other visible abnormalities.

4. Check the scanner carriage rails to ensure smooth movement without sticking or excessive friction. Mechanical resistance or abnormal carriage movement may contribute to intermittent scanning artifacts.

Note: The available adjustment range and baseline values may vary by model, firmware, or service documentation. Verify the applicable values for the specific machine before making adjustments.

  • If the black line disappears → The fault is resolved; do not enter service mode to alter scanning area parameters; retain the factory default values.
  • If a uniform black border (pseudo-black line) persists along the entire edge → Enter Service Mode → [Machine] → [Adjustment] → [Scan Area] and perform fine-tuning.
  • If a fixed, thin black line persists → Abandon software adjustments; identify hardware damage (e.g., scratched mirror, CCD degradation) and replace the scanner assembly.
  • Before modification: Capture and save all original parameters via screenshot. If adjustment fails, use the one-click [Restore] function to revert to factory defaults and prevent batch alignment errors.
  • Uniform top/bottom black border → Fine-tune [Image Position: Lead Edge]; adjust in increments of ±0.5 mm (max. total adjustment ±3.0 mm); do not apply the full adjustment in a single step.
  • Uniform left/right black border → Fine-tune [Scanner Image Side Edge] (current baseline: 2.4 mm); adjust in increments of ±0.5 mm (max. total ±5.7 mm).
  • CD/FD Scaling: Default is X1.000; do not alter (unless addressing image stretching/compression issues) to avoid font distortion or image/text misalignment.
  • After each adjustment, print a configuration page for comparison testing until the black border is eliminated.
  • Once parameters are correct, perform continuous copying of 5 A4 sheets to verify stability.
  • Record the final modified parameters and archive them for future reference in similar repairs.

IV. Long-term Prevention Plan (Reduce recurrence, extend equipment lifespan)

Aspect Specific Measures
Daily Maintenance Regularly clean the platen glass and white reference plate monthly; prohibit customers from using correction fluid or glue to affix originals to the platen.
Consumables Control Use genuine or reliable, properly tested compatible toner. Poor toner quality or toner leakage may increase internal contamination and potentially contribute to optical contamination.
Equipment Environment Place in a dust-free, dry area to prevent dust accumulation and mirror fogging due to moisture.
Repair Standards Do not alter factory [Scan Area] parameters unless necessary; after replacing the scanner assembly or glass, verify image alignment and apply minor corrections as needed.
Customer Training Advise users to clean the platen glass and check the scanning surface first when a black line appears. Users should not enter Service Mode or change machine parameters without proper technical guidance, as incorrect adjustments may introduce image-position or scaling problems.

V. Common Maintenance Misconceptions (Pitfall Avoidance Guide)

Misconception 1: Immediately entering maintenance mode to adjust the scan area upon seeing a black line → Correct Approach: Black lines caused by hardware contamination cannot be fixed by parameter adjustments; doing so only wastes time.

Misconception 2: Believing that changing the document orientation (landscape vs. portrait) swaps the parameters for the leading edge and side edge → Correct Approach: FD (Feed Direction) and CD (Cross-feed Direction) are defined by the scanner’s movement path; menu assignments are fixed and unaffected by document orientation.

Misconception 3: Drastically adjusting scaling parameters to “eliminate” black borders → Correct Approach: Scaling adjustments should be minimal; drastic changes distort the proportions of copies (such as blueprints or contracts), rendering them unusable.

Quick Summary (Maintenance Notes)

Clean the glass first to verify the issue; adjust scan settings for uniform black borders (top/bottom for leading edge, left/right for side edge); replace hardware for persistent fine lines; do not alter machine parameters unless there is a genuine fault; perform regular dust cleaning for prevention.