Fixing Colored Stripe Defects on Solid Fill Areas in Konica Minolta Bizhub Color Prints

Colored stripe defects on solid fill areas are one of the most diagnostically demanding image quality complaints on Konica Minolta bizhub color multifunctional systems. Unlike vertical black lines, which typically trace to a single physical scratch or contamination point, colored stripes on solid fills arise from a wider range of interacting electrophotographic, mechanical, and electronic root causes. The defect presents as one or more bands of incorrect color—typically a lighter or darker band, a hue-shifted band, or a sharply contrasting stripe in a wrong color—appearing within an area that should print as a uniform flat tint or solid coverage.

Solid fill areas (also called area fills or flood fills) are the most demanding test of color engine consistency because any variation in toner density, charge uniformity, developer output, transfer efficiency, or laser exposure across the width or length of the page is immediately visible against the surrounding uniform color field. Defects that would be undetectable in text or halftone content become clearly visible in solid fills.

This article covers the complete diagnostic and repair pathway for colored stripe defects in solid fill output on bizhub color machines, spanning the charge, exposure, development, transfer, and calibration subsystems. Each root cause is mapped to its specific corrective action, replacement part, and required post-repair calibration sequence.

NOTICE: Always power off the machine and disconnect the AC power cord before accessing internal components unless a specific step explicitly requires the machine to be energized. Allow the fusing unit at least 30 minutes to cool before handling. OPC drum surfaces must not be exposed to room light for more than 60 seconds at any time during service procedures.

2. Affected Model Reference Table

Model Family	Representative Models	Engine Type	Drum Unit Designation	Developer Unit Designation	Laser Unit Designation	ITB Unit	Main Control Board(s)	High-Voltage Power Supply
C360 / C280 / C220 Series	bizhub C360, C280, C220	4-drum tandem color	DR-311 (C, M, Y, K)	DV-311 (C, M, Y, K)	LU-301 / LU-302	Integrated belt unit	PRCB / MFPB	HVPS-1 / HVPS-2
C458 / C368 / C308 Series	bizhub C458, C368, C308	4-drum tandem color	DR-512 (C, M, Y, K)	DV-512 (C, M, Y, K)	LU-302	Integrated belt unit	PRCB / MFPB	HVPS-1 / HVPS-2
C554 / C454 / C364 / C284 / C224 Series	bizhub C554, C454, C364, C284, C224	4-drum tandem color	DR-512 (C, M, Y, K)	DV-512 (C, M, Y, K)	LU-302	Integrated belt unit	PRCB / MFPB / EXCB	HVPS-1 / HVPS-2
C759 / C659 Series	bizhub C759, C659	4-drum tandem color	DR-612 (C, M, Y, K)	DV-612 (C, M, Y, K)	LU-302	Integrated belt unit	PRCB / BASEB / CPUB	HVPS-1 / HVPS-2 / HVPS-3
C3350 / C3850 Series	bizhub C3350, C3850	4-drum tandem color	DR-C3JK / DR-C3YMC	DV-C3JK / DV-C3YMC	Integrated laser unit	Integrated belt unit	PRCB / MFPB	HVPS
C3300i / C3800i / C4000i Series	bizhub C3300i, C3800i, C4000i	4-drum tandem color	DR-C4 Series (C, M, Y, K)	DV-C4 Series (C, M, Y, K)	Integrated laser unit	Integrated belt unit	PRCB / MFPB	HVPS
C250i / C300i / C360i Series	bizhub C250i, C300i, C360i	4-drum tandem color	DR-C4 Series (C, M, Y, K)	DV-C4 Series (C, M, Y, K)	Integrated laser unit	Integrated belt unit	PRCB / MFPB	HVPS
C650i / C750i / C850i Series	bizhub C650i, C750i, C850i	4-drum tandem color	DR-C5 Series (C, M, Y, K)	DV-C5 Series (C, M, Y, K)	LU-302 / Integrated	Integrated belt unit	PRCB / BASEB / CPUB	HVPS-1 / HVPS-2

Note: Always verify part numbers against the specific machine serial number and service manual before ordering. Regional variants and firmware revisions may affect part compatibility.

3. Symptom Description and Classification

Before beginning component-level diagnosis, precisely characterize the stripe defect. The color, width, orientation, periodicity, affected mode, and location of the stripe within the page all serve as diagnostic indicators that point toward specific subsystem failures. Record all observable characteristics before touching any component.

3.1 Key Observation Points

Stripe color: Does the stripe match one of the CMYK process colors, or is it a mixed/shifted hue? A pure cyan stripe in a solid magenta fill isolates the defect to the C color station. A stripe that is a lighter or darker version of the background fill color indicates a density or charge variation within a single channel.
Stripe orientation: Is the stripe horizontal (perpendicular to paper travel, across the width of the page) or vertical (parallel to paper travel, along the length of the page)? Horizontal banding in solid fills almost always points to periodic mechanical causes (drum rotation, developer paddle rotation, ITB seam). Vertical stripes in solid fills point to laser exposure variation, developer roller streaking, or charge roller non-uniformity.
Periodicity: Does the stripe repeat? Measure the distance between repeating stripes in millimeters and compare against the circumferences of rotating components (see Section 3.2). Matching a repeat interval to a known rotating component is one of the most reliable diagnostic tools available.
Mode dependency: Does the stripe appear in copy mode, print mode, or both? Defects present in copy mode only implicate the scanner; defects present in print mode (and optionally copy mode) implicate the image formation path.
Paper size / orientation dependency: Does the stripe appear at the same position on the page regardless of paper size, or does it shift with paper size? A stripe that appears at a fixed distance from the paper edge in both A4 and A3 is more likely caused by a component positional fault than a rotating-component periodic fault.
Color station isolation: On the machine’s color separation test (Service Mode → Test Print → Color Separation), identify which channel(s) carry the stripe. A stripe visible only in the C channel output but absent in M, Y, and K channels isolates the defect to the C color station components exclusively.

3.2 Rotating Component Circumference Reference Table

Component	Typical Diameter (mm)	Typical Circumference (mm)	Defect Periodicity Pattern
OPC Drum (DR-311 / DR-512 family)	30	~94	Horizontal stripe repeats every ~94 mm along page length
OPC Drum (DR-612 / DR-C5 family)	35–40	~110–125	Horizontal stripe repeats every ~110–125 mm along page length
Developer Roller (inside DV unit)	16–20	~50–63	Horizontal stripe repeats every ~50–63 mm along page length
Primary Charge Roller (PCR, inside DR unit)	10–14	~31–44	Horizontal stripe repeats every ~31–44 mm along page length
ITB Drive Roller	varies by model	~180–220 (belt seam interval)	Wide stripe or density shift repeating at full belt revolution interval
Primary Transfer Roller (PTR)	16–20	~50–63	Horizontal stripe repeats every ~50–63 mm; may be subtle
Secondary Transfer Roller (2nd BTR)	18–24	~56–75	Horizontal stripe repeats at secondary transfer roller circumference interval
Fusing Roller (upper heat roller)	varies by model (60–80 mm typical)	~188–251	Stripe with smear or gloss variation repeating at fuser roller circumference

Note: Measure the actual circumference on the specific machine if the service manual lists a different drum or roller diameter than shown above. These figures are representative ranges across the model families covered by this article.

3.3 Symptom-to-Cause Quick Reference Table

Stripe Symptom Detail	Orientation	Affected Mode	Most Likely Root Cause(s)	Primary Suspect Component
Lighter or darker horizontal band in solid fill, one color station only, repeats at drum circumference interval	Horizontal	Copy + Print	OPC drum surface wear, coating delamination, or physical damage creating a zone of inconsistent charge retention	Drum unit (DR-xxx) for affected color
Horizontal band repeating at shorter interval (~50–63 mm), one color station only	Horizontal	Copy + Print	Developer roller contamination, developer roller surface damage, or doctor blade irregularity creating periodic toner density variation	Developer unit (DV-xxx) for affected color
Horizontal band repeating at short interval (~31–44 mm), one color station only, with possible background fogging around the band	Horizontal	Copy + Print	Primary Charge Roller (PCR) contamination or wear; localized charge deficit producing density variation	PCR (inside DR-xxx drum unit) for affected color
Vertical stripe (along page length) in solid fill, one color station only, constant position regardless of paper size	Vertical	Copy + Print	Laser exposure non-uniformity: dirty laser window, f-theta lens contamination, or failing laser diode in one beam channel	Laser unit (LU-xxx), laser window
Vertical stripe in solid fill, one color station only, with abrupt edge	Vertical	Copy + Print	Developer roller sleeve damage (longitudinal scratch or carrier bead deposit) creating a streak of excess or deficit toner	Developer unit (DV-xxx) for affected color
Horizontal band or density shift affecting ALL four color channels simultaneously, repeating at ITB belt seam or drive roller interval	Horizontal	Copy + Print	ITB surface damage, ITB seam area, or ITB drive roller speed irregularity; secondary transfer roller contamination	ITB unit, 2nd BTR (Secondary Transfer Roller)
Wide horizontal band of wrong color in solid fill area, all channels, at consistent position on every page	Horizontal	Copy + Print	ITB primary transfer voltage irregularity (HVPS output fault); color registration phase error causing misaligned color plane overlay	HVPS-1 / HVPS-2, PRCB; ITB registration sensor (PS38 or equivalent)
Colored stripe that appears faint or shifts slightly between consecutive prints	Horizontal or Vertical	Copy + Print	Toner supply irregularity: toner low condition, toner supply motor (M11 / M29) intermittent fault, toner hopper agitator failure	Toner supply motor M11 (K) / M29 (color), toner hopper assembly
Horizontal band with gloss or texture difference (not a density stripe), repeating at fuser roller circumference	Horizontal	Copy + Print	Fusing roller surface contamination, coating damage, or separation claw mark on fuser roller	Fusing unit (fuser roller, separation claws)
Stripe present in copy mode only, not in print mode	Horizontal or Vertical	Copy only	Scanner CCD / CIS element defect; scanner illumination lamp uneven output (fluorescent or LED array)	Scanner CCD board, scanner lamp / LED illumination array
Intermittent stripe that appears after extended runs and clears on cool-down	Horizontal	Copy + Print	Thermal expansion causing developer unit paddle interference or ITB tension variation; thermistor (TH1 / TH2) drift causing fusing temperature excursion	Developer unit (DV-xxx), fusing unit thermistors TH1 / TH2
Wide stripe (5–20 mm) of completely wrong hue across entire page width, consistent position, all prints	Horizontal	Copy + Print	Auto Color Registration (ACR) failure or miscalibration causing one color plane to be shifted relative to others; ITB registration sensor (PS59 or equivalent) contaminated or failed	ACR calibration, ITB registration sensor PS59, PRCB

4. Required Tools and Materials

Lint-free dry cloths (IPA-compatible)
Isopropyl alcohol (IPA), 99% purity
Cotton swabs (ESD-safe)
Flashlight or pen light
Millimeter ruler or caliper (for measuring stripe repeat intervals)
Printed color separation test pages (one per color channel: C, M, Y, K) for visual diagnosis
Printed solid fill test pages (full-page flat tints at 100%, 75%, 50% density for each color)
Service manual for the specific machine model
Replacement drum unit DR-xxx (appropriate to model and affected color station)
Replacement developer unit DV-xxx (appropriate to model and affected color station)
Replacement ITB unit (if ITB is indicated as the cause)
Replacement 2nd BTR (Secondary Transfer Roller) kit, if indicated
Replacement laser unit LU-xxx, if indicated
ESD wrist strap and ESD mat

WARNING: The OPC drum surface is extremely sensitive to light, fingerprints, and abrasion. Never expose the drum to ambient room light for more than 60 seconds. Always handle drum units by the end flanges only. Do not touch, wipe with solvents, or attempt to repair the green or blue OPC drum surface. Any direct contact or solvent exposure will permanently damage the photoconductive layer, causing permanent image defects, and is not covered under component warranty or exchange programs.

5. Preliminary Verification Procedure

These steps must be completed before any component is removed or replaced. They establish a precise defect profile that directs all subsequent diagnostic effort. Skipping or shortcutting these steps leads to unnecessary part replacement and unresolved callbacks.

Generate a machine-internal solid fill test print.
Access Service Mode → Machine → Test Print. Select or create a test page that includes solid fill blocks at 100% density for each of the four CMYK process colors plus a full-coverage composite black block. Print this page from the machine’s internal controller (not from a host PC or network driver). This eliminates any possibility that the stripe originates in the host RIP, driver, or document data.
Generate a color separation test print.
Access Service Mode → Machine → Test Print → Color Separation (terminology varies by model; refer to service manual). This prints each color plane (C, M, Y, K) as an isolated solid fill page. Examine each page individually under good lighting. Note precisely which channel(s) show the stripe defect. If only the C page shows a stripe, the defect is isolated to the C color station. If all four pages show a stripe at the same position, the defect is in the shared transfer, fusing, or paper transport path.
Measure the stripe repeat interval.
Using a millimeter ruler, measure the distance from the leading edge of one stripe to the leading edge of the next repeating stripe along the page length (process direction). Compare this measurement against the circumference values in Section 3.2. Match the measurement to the closest rotating component circumference to identify the likely defect source. Record this measurement for documentation.
Run a flatbed copy of a plain solid-color printed test sheet.
If the stripe appears on the copy but not on the machine-internal test print, the scanner imaging system (CCD, illumination lamp / LED array, or scanner board) is at fault. Proceed to Section 6.7. If the stripe appears on both the copy and the internal test print, the defect is in the image formation path.
Check the Auto Color Registration (ACR) status.
Access Service Mode → Adjust → Image Quality → Auto Color Registration → Result (or Last Result, model-dependent). If the ACR result shows a registration error exceeding ±0.3 mm on any color plane, ACR miscalibration may be contributing to a color plane misalignment that presents as a hue-shifted stripe in composite color solid fills. Proceed to Section 6.6 before replacing physical components.
Record the page count and developer/drum counter values.
Access Service Mode → Counter → Life Counter (or equivalent). Record the drum counter (per color) and developer counter (per color) values. These values indicate whether consumable components are at or near end-of-life, which affects diagnostic probability weighting. A drum unit at 85,000 impressions on a 100,000-impression rated unit is a strong candidate for replacement even before visible surface damage is confirmed.

6. Diagnostic and Repair Procedures

6.1 Developer Unit (DV-xxx) Toner Density and Roller Defect

Applies when: Stripe repeats at developer roller circumference interval (~50–63 mm); stripe is present in one color station only; stripe appears as a slightly lighter or darker band within the solid fill; or a vertical streak is present at a consistent lateral position.

The developer unit (DV-xxx) contains the developer roller (magnet roller sleeve), doctor blade, toner-carrier mixture, and agitation paddles. The developer roller delivers a metered layer of toner to the OPC drum surface. Any periodic variation in the toner layer thickness—caused by developer roller surface damage, a bent or contaminated doctor blade, agitation paddle imbalance, or carrier bead contamination on the sleeve—creates a repeating stripe in solid fill areas at the developer roller rotation interval.

Power off the machine. Open the front door and slide out the drum unit (DR-xxx) for the affected color station, placing it on a covered surface away from direct light.
With the drum unit removed, release the developer unit (DV-xxx) lock lever for the same color station. Slide the developer unit straight outward horizontally from the machine. Keep the unit level throughout removal to prevent carrier bead spillage.
Using oblique flashlight illumination, inspect the developer roller sleeve surface along its full length for:
- Longitudinal scratches or scoring on the sleeve surface
- Embedded carrier beads (appear as bright metallic specks on the sleeve)
- Toner clumping or packed deposits in any zone along the sleeve length
- Visible damage to the doctor blade: bending, separation from the blade holder, or packed toner at the blade-to-sleeve gap
Slowly rotate the developer roller by hand using the drive gear. Observe whether the developer layer is applied uniformly across the full sleeve width during rotation, or whether a thin zone (indicating a doctor blade gap irregularity) or a thick zone (indicating carrier bead buildup) is visible.
If developer roller damage, doctor blade damage, heavy carrier bead contamination, or toner clumping is confirmed:
Replace the developer unit (DV-xxx) for the affected color. Do not attempt field repair of the developer roller sleeve or doctor blade. After installing the replacement developer unit, perform Developer Unit Initialization: Service Mode → Machine → Developer → Initialize → Select affected color → Execute. Allow the initialization cycle to complete fully before printing (approximately 2–5 minutes per station).
If no physical damage is found on the developer unit but the developer counter shows high usage (at or beyond rated interval):
The developer (toner-carrier mixture) itself may be aged. Carrier beads lose their charge-retention capacity over time, producing inconsistent toner triboelectric charging and resulting in density variation in solid fills. Replace the developer unit proactively. Perform Developer Unit Initialization after replacement.
Reinstall the drum unit and run a fresh solid fill test print. If the stripe is resolved, proceed to Section 7 (Post-Repair Calibration). If the stripe persists, proceed to Section 6.2.

NOTICE: Always keep developer units horizontal during removal, transport, and installation. If carrier beads spill into the machine interior, power off the machine immediately and vacuum all spilled carrier from the paper path, drum station slots, and ITB surface using an ESD-safe toner vacuum before any further operation. Carrier beads on the OPC drum surface cause severe immediate damage to the drum coating.

6.2 OPC Drum Unit (DR-xxx) Coating Wear or Damage

Applies when: Stripe repeats at drum circumference interval (~94–125 mm depending on model); stripe is present in one color station only; stripe may appear as a lighter band (reduced charge retention) or a darker band (physical recess or coating damage holding excess toner).

The OPC drum surface degrades with use. The photoconductive coating thins gradually, and in areas of high-density print coverage the coating may wear unevenly, creating zones of different charge retention. This produces a repeating horizontal band of lower or higher density in solid fills at the drum rotation interval. Physical damage—from a foreign object, a cleaning blade chip, or an improper handling incident—produces a sharper, more defined stripe.

Power off the machine. Remove the drum unit (DR-xxx) for the affected color station. Shield the drum from room light immediately.
Using a flashlight at a very low (oblique) angle, slowly rotate the drum by the end flanges through at least two full revolutions. Inspect the entire drum circumference for:
- Zones of dulled or matted finish compared to the surrounding shiny drum surface (indicating coating wear)
- Toner filming (a thin, uniform toner deposit that does not wipe off with a dry cloth pass)
- Scratches, pits, or abrasion marks
- Residual cleaning blade marks (lateral drag marks across the drum surface)
- Bright reflective spots or depressions (physical damage to the drum substrate)
If coating wear, toning filming, physical damage, or cleaning blade marks are found:
Replace the drum unit (DR-xxx) for the affected color. Drum coating defects cannot be field-repaired.
Before installing the replacement drum unit, inspect the drum station slot interior for:
- Toner contamination on the drum unit guide rails
- Any sharp burr or metal edge on the guide rails that could contact and damage the new drum surface during insertion
- The condition of the drum grounding contact spring (a small leaf spring or contact pin at the rear of the drum station slot); a bent or broken grounding contact will cause immediate charge uniformity problems on the new drum
Clean guide rails with a dry lint-free cloth. Straighten or replace any damaged grounding contact spring before inserting the new drum unit.
After installing the replacement drum unit, run a solid fill test print. If the stripe is resolved, proceed to Section 7. If the stripe persists at the same position with the new drum, the cause is upstream of the drum (charge or exposure system) or downstream in the transfer path. Proceed to Section 6.3.

6.3 Primary Charge Roller (PCR) Contamination or Wear

Applies when: Horizontal stripe repeats at PCR circumference interval (~31–44 mm); stripe may be accompanied by background fogging in the solid fill area surrounding the stripe; stripe is present in one color station only; drum unit replacement did not resolve the defect.

The Primary Charge Roller (PCR) is an electrically biased rubber roller that applies a uniform electrostatic charge to the OPC drum surface immediately before laser exposure. The PCR rotates in contact with (or in very close proximity to) the drum surface. Contamination on the PCR surface—from toner particles, paper dust, or environmental debris—creates a periodic charge non-uniformity at the PCR rotation interval. This charge non-uniformity is reproduced faithfully on the drum as a zone of different potential, which attracts a different quantity of toner and appears as a stripe in solid fills.

On most current bizhub color models, the PCR is integrated into the drum unit (DR-xxx) assembly and is not a field-replaceable standalone component. The PCR is replaced as part of the drum unit.
If the drum unit has already been replaced in Step 6.2 and the stripe persists at the PCR circumference repeat interval, consider whether the new drum unit was properly stored and handled (exposure to contamination during unboxing or installation can contaminate the PCR surface of a new drum unit).
On models where the PCR is accessible as a separate component within the drum unit housing (model-dependent; consult the service manual): remove the PCR from its holder by sliding it out of the end bearings. Wipe the PCR surface gently with a dry, clean lint-free cloth in a longitudinal direction only. Do not use IPA or any solvent on the PCR surface; solvent contact will swell or crack the PCR rubber coating.
Inspect the PCR surface for: embedded toner particles that do not wipe off, surface cracking or crazing, flat spots on the rubber from prolonged stationary contact, or permanent contamination. If any of these conditions are present, the PCR must be replaced (either as a standalone part where available, or as part of a drum unit replacement).
Also inspect the PCR bias contact (the electrical contact spring or pin that supplies the charge bias voltage to the PCR from the HVPS). A bent, corroded, or disconnected PCR bias contact will cause a complete charge failure (entire page black or heavily fogged) rather than a periodic stripe; however, an intermittent contact can cause periodic charge variation. Clean the contact surfaces with a dry lint-free cloth or IPA-dampened swab and allow to dry before reconnecting.
After PCR cleaning or replacement, reinstall the drum unit and run a solid fill test print. If the stripe is resolved, proceed to Section 7. If the stripe persists, proceed to Section 6.4.

6.4 Laser Exposure Unit (LU-xxx) Non-Uniformity

Applies when: Stripe is vertical (along the process direction) rather than horizontal; stripe is present in print mode; stripe does not repeat periodically; stripe position is constant regardless of paper size; drum and developer unit replacement did not resolve the defect.

The laser unit (LU-xxx) exposes the charged drum surface to create the latent electrostatic image. On multi-beam laser units (common on production-speed bizhub models), each beam covers a specific lateral zone across the drum width. A failing or degraded laser diode in one beam channel, contamination on the laser window, or debris on the f-theta lens creates a zone of under-exposure or over-exposure that appears as a vertical stripe of different density in solid fill output.

Power off the machine. Open the front or top cover to access the laser unit area.
Locate the laser window(s) for the affected color station. On the LU-302 used in mid-range to high-speed color bizhub models, there are separate laser windows for each color plane, oriented as narrow transparent strips (glass or acrylic, approximately 5–10 mm wide and 200–350 mm long) at the bottom of the laser unit housing.
Using oblique flashlight illumination, inspect each laser window along its full length for: toner dust deposits, paper fiber strands, smears, or scratches. Pay particular attention to the zone of the laser window that corresponds laterally to the position of the vertical stripe on the printed page.
If contamination is found on the laser window:
Wipe the laser window gently with a lint-free cloth lightly moistened with IPA. Use a single longitudinal stroke along the window length. Follow with a dry lint-free cloth pass. Do not press on the laser window; on some models it is bonded with adhesive and can crack or shift under pressure.
If a scratch or physical damage is found on the laser window:
Replace the laser window sub-assembly (if available as a separate service part for the model) or replace the full laser unit (LU-xxx). Consult the parts list for the specific model.
If the laser window is clean and undamaged:
Suspect f-theta lens contamination or a laser diode degradation within the LU-xxx. Check Service Mode for any laser aging counter or laser power correction flags. On models that log laser power correction values per beam channel, compare the correction value for the beam channel covering the stripe zone against the values for adjacent channels. A correction value significantly higher (indicating the PRCB is compensating for a weak diode) confirms laser diode degradation. Replace the laser unit (LU-xxx).
After laser window cleaning or LU-xxx replacement, run: (a) Auto Color Registration (ACR), (b) Auto Gradation Adjustment (AGA) in sequence before test printing. Run a solid fill test print and verify the stripe is resolved before proceeding to Section 7.

WARNING: Never operate the machine with laser unit covers removed, the front door open, or any interlock defeated while the machine is energized. The LU-xxx emits near-infrared laser radiation that is invisible to the human eye and capable of causing permanent retinal injury without any visible warning. The door interlock switch (door sensor connected to the PRCB) disables laser output when the front door is open; never bypass this interlock under any circumstances.

6.5 Intermediate Transfer Belt (ITB) and Secondary Transfer System Defect

Applies when: Stripe or density shift appears across all four color channels simultaneously; stripe repeats at ITB belt drive roller interval or ITB belt seam interval; stripe may shift slightly in position between consecutive prints; 2nd BTR (Secondary Transfer Roller) shows visible contamination or damage.

The ITB receives the four individual CMYK toner images from the drum stations and combines them into a composite color image before transferring the complete image to paper at the secondary transfer nip. Any variation in ITB surface condition, ITB belt tension, ITB drive roller speed, or secondary transfer roller condition introduces a density or color uniformity defect that spans all four color channels and therefore appears as a stripe in all solid fill colors simultaneously.

Power off the machine. Open the ITB access panel as described in the model service manual to expose the ITB unit.
Slowly rotate the ITB belt by hand (using the belt edge seam as a handle, never touching the flat belt surface) through at least one full revolution. Using oblique flashlight illumination, inspect the full belt surface for:
- Scratches, scoring, or abrasion marks on the belt surface
- Toner filming or carrier bead deposits on the belt surface
- Visible damage at or near the belt seam (a reinforced splice across the belt width)
- Edge damage, cracking, or delamination along the belt edge guidance ribs
Inspect the ITB cleaning blade (at the belt cleaning station): check for a turned or cracked blade edge, toner bypass deposits on the belt surface downstream of the blade, or a blade that has separated from its holder.
Inspect the four Primary Transfer Rollers (PTR-C, PTR-M, PTR-Y, PTR-K): these foam or rubber rollers press against the inside of the ITB to create the electrostatic field that transfers toner from each drum to the belt surface. Check for: toner contamination on the PTR surface, deformation (flat spots or permanent compression), or loose PTR bearings. Wipe PTR surfaces with a dry lint-free cloth if lightly contaminated. Replace the PTR set if surface contamination is embedded in the foam or if physical deformation is present.
Inspect the 2nd BTR (Secondary Transfer Roller): this roller presses the ITB-carried toner image onto the paper at the secondary transfer nip. Contamination, surface damage, or electrical connection failure on the 2nd BTR causes transfer inconsistency that presents as a periodic stripe across all color channels.
- Check the 2nd BTR surface for toner buildup, embedded paper fibers, or surface crazing.
- Check the 2nd BTR bias contact connector for corrosion or poor seating.
- Wipe the 2nd BTR surface with a dry lint-free cloth if lightly contaminated. If contamination is embedded or surface damage is present, replace the 2nd BTR.
If ITB belt surface damage is confirmed:
Replace the ITB unit. After ITB replacement, perform: (a) ITB Phase / Belt Phase Adjustment if required by the model (Service Mode → Adjust → Machine → Belt Phase Adjustment), (b) Auto Color Registration (ACR), (c) Auto Gradation Adjustment (AGA).
Run a solid fill test print across all four color channels after any ITB or 2nd BTR service. Confirm that the stripe is resolved on all channels before returning to service.

6.6 Auto Color Registration (ACR) Miscalibration and Registration Sensor Defect

Applies when: Stripe in a solid fill area consists of a clearly wrong hue rather than a lighter/darker version of the fill color; stripe appears at the same position on every print; stripe is wide (5–20 mm or more); stripe may appear as a secondary color (e.g., a green band in a solid red fill, indicating misregistered cyan and yellow planes).

Color plane misregistration causes one or more of the four CMYK color images to be offset from the correct position on the ITB. In solid fill areas that are composed of two or more overlaid color planes (for example, a solid red fill composed of 100% M + 100% Y), a misregistration of even 0.5–1.0 mm causes a visible stripe of the wrong color at the leading or trailing edge of the fill block where the planes are misaligned. This is fundamentally a calibration problem, not a hardware failure, and is corrected by executing ACR before replacing any physical components.

Access Service Mode → Adjust → Image Quality → Auto Color Registration → Execute. Allow the ACR cycle to complete fully. The machine will print a registration target pattern, scan it with the ITB registration sensor (PS59 or equivalent, model-dependent), and automatically compute and apply correction offsets for each color plane.
After ACR completion, check the result values: Service Mode → Adjust → Image Quality → Auto Color Registration → Result. Each color plane (C, M, Y) should show a correction value within ±0.3 mm of zero in both the main scan (lateral) and sub-scan (process) directions. Values significantly outside this range after ACR execution indicate a sensor or mechanical problem.
If ACR produces large residual errors after execution:
Inspect the ITB registration sensor (PS59 or model-equivalent). This sensor reads the registration target marks printed on the ITB surface by each color station. A contaminated sensor lens or a sensor that has shifted from its mount will cause ACR to compute incorrect offset values.
- Locate the ITB registration sensor (PS59) inside the ITB access area. The sensor is a reflective optical sensor positioned close to the ITB belt surface.
- Clean the sensor lens with a dry lint-free cloth or a dry cotton swab. Do not use IPA on the sensor lens.
- Verify the sensor mounting bracket is secure and the sensor is positioned at the correct distance from the ITB belt surface (see the model service manual for the specified sensor-to-belt gap; typically 3–6 mm).
- If the sensor is damaged or the output voltage is outside specification when checked with a voltmeter at the sensor connector, replace the ITB registration sensor (PS59 or equivalent). The sensor is typically available as a standalone service part.
If ACR succeeds and result values are within specification but the stripe persists in solid fill areas:
The stripe is not caused by color plane misregistration. Return to the symptom classification in Section 3.3 and proceed with the appropriate hardware diagnostic path.
After successful ACR, always run Auto Gradation Adjustment (AGA) before final test printing. Run a solid fill test print across all color channels and verify that the hue-shifted stripe is resolved.

6.7 Scanner Illumination or CCD / CIS Defect (Copy Mode Only)

Applies when: Stripe in solid fill appears only in copy mode output; machine-internal test prints (print mode) do not show the stripe; the stripe position may shift slightly with scanning speed or lamp warm-up state.

When the stripe defect is isolated to copy mode, the imaging path upstream of the OPC drum—specifically the scanner illumination system and the image sensor array—is the cause. On current bizhub color models, the scanner uses either a CCD (Charge-Coupled Device) array with a cold-cathode fluorescent or LED illumination bar, or a CIS (Contact Image Sensor) array. Uneven illumination or a failing sensor element creates a density variation in scanned image data that reproduces as a stripe in solid fill areas of the copy output.

Open the scanner lid and inspect the scanner illumination assembly (visible through the platen glass when the lid is open): look for a dark zone or dim section along the lamp / LED bar. On fluorescent-lamp models, a failing lamp may show a dark or brownish discoloration at one end of the tube.
Clean the underside of the scanner lid white reference plate (the white strip on the underside of the ADF or scanner cover) with a dry lint-free cloth. A contaminated white reference plate causes the scanner to apply incorrect shading correction, which can produce a banding artifact in solid fill copies.
Run the Scanner Auto Shading / Auto Calibration function: Service Mode → Adjust → Scanner → Auto Shading (terminology varies by model). This resets the scanner’s shading correction profile against the white reference plate. After completion, run a test copy of a solid-color original and observe whether the stripe is resolved.
If the stripe persists after scanner calibration:
Suspect a failing CCD/CIS element or scanner lamp / LED array. Check whether the stripe position corresponds to a specific pixel column in the CCD array by observing whether it is fixed relative to the scanned image width regardless of the document’s lateral position on the platen. A fixed-position stripe that does not move with document placement confirms a CCD element or lamp zone defect. Replace the scanner lamp / LED bar (if available as a standalone service part) or the CCD / CIS scanner unit as indicated by the model service manual.

6.8 Toner Supply System Irregularity

Applies when: Stripe is intermittent and varies in intensity between consecutive prints; stripe may appear faint and inconsistent; toner low indicator may be present for the affected color; stripe clears temporarily after shaking the toner bottle.

An irregular toner supply to the developer unit causes temporary toner density fluctuations within the developer that present as intermittent stripes of lighter density in solid fill areas. Root causes include a near-empty toner bottle, a failed toner supply motor (M11 for K; M29 or model-equivalent for color stations), or a jammed or worn toner supply auger.

Check the toner level indicator for the affected color in the machine’s user interface and in Service Mode → Counter → Toner Level. If the toner level is critically low, replace the toner bottle for the affected color and run 10–20 test prints to allow the developer unit toner concentration to stabilize before evaluating the defect.
If the toner bottle is not empty but the stripe persists, access Service Mode → Machine → Motor / Drive → Toner Supply Motor (M11 for K or M29 for color, model-dependent) and execute a manual drive test. Confirm that the toner supply motor energizes and runs at the expected speed. Listen for abnormal noise (grinding, intermittent running) that may indicate a motor or auger failure.
If the toner supply motor runs normally but toner delivery appears insufficient, inspect the toner supply auger (the helical screw conveyor inside the toner supply path between the toner bottle receiver and the developer unit inlet). A worn or broken auger tooth will reduce toner throughput and cause intermittent density variation. Replace the toner supply auger or the toner supply assembly as indicated in the model service manual.
After toner bottle replacement or toner supply motor / auger repair, run Developer Unit Initialization for the affected color: Service Mode → Machine → Developer → Initialize → Select color → Execute. Follow with Auto Gradation Adjustment before returning to service.

7. High-Voltage Power Supply (HVPS) Verification

If all component-level diagnostics in Sections 6.1 through 6.8 fail to resolve the stripe defect, the High-Voltage Power Supply (HVPS) may be delivering an incorrect or unstable bias voltage to one of the following circuits: the Primary Charge Roller (PCR) bias, the developer roller bias, or the Primary Transfer Roller (PTR) bias. An unstable HVPS output causes the same type of periodic or positional density variation in solid fills as a contaminated roller, but it cannot be resolved by replacing drums or developer units.

Access Service Mode → Machine → Input Check / Output Check → HVPS (model-dependent menu path). Review any HVPS fault flags or abnormal voltage reporting.
Using a DC voltmeter and the appropriate service manual test point specifications, measure the HVPS output voltages at the PCR bias connector, developer bias connector, and PTR bias connector for the affected color station. Compare measured values against the specified nominal voltages and allowable tolerances listed in the service manual. A voltage reading outside the specified tolerance at a specific output indicates an HVPS circuit fault.
Inspect the bias contact connectors between the HVPS harness and the drum unit / developer unit contact springs. Corrosion, bending, or poor seating of any of these contacts produces the same symptom as an HVPS output fault. Clean all contact surfaces with a dry lint-free cloth or IPA-dampened swab and verify firm seating before condemning the HVPS board.
If the HVPS output voltage is confirmed out of specification after cleaning and reseating all contacts:
Replace the HVPS board (HVPS-1, HVPS-2, or HVPS-3 as applicable for the model). Note that on some bizhub models the HVPS is integrated into the PRCB (Process Control Board); consult the service manual to confirm the board architecture before ordering a replacement part.

WARNING: High-voltage bias circuits in the HVPS produce voltages in the range of −500 V to −1200 V DC on charging outputs and −200 V to −600 V DC on developer and transfer outputs. Never probe HVPS test points with bare hands or non-insulated probes. Use only insulated test probes rated for the voltage levels specified in the service manual. Do not short HVPS output contacts together or to machine frame ground.

8. Post-Repair Calibration Sequence

After any component replacement or adjustment in the imaging path, perform the following calibrations in the exact order listed. Solid fill stripe defects are especially sensitive to calibration errors; incomplete or out-of-order calibration will produce residual density variation that may be misattributed to an unresolved hardware defect.

Developer Unit Initialization (required if developer unit DV-xxx was replaced or reinstalled):
Service Mode → Machine → Developer → Initialize → Select affected color(s) → Execute.
Allow the full initialization cycle to complete (approximately 2–5 minutes per color station). Do not interrupt. This cycle sets the toner concentration sensor (TCS) baseline for the new developer mixture.
Auto Color Registration (ACR) (required if any drum unit, ITB unit, laser unit, or belt phase was changed):
Service Mode → Adjust → Image Quality → Auto Color Registration → Execute.
Verify result values are within ±0.3 mm for all color planes in both scan directions. If values are outside this range, repeat ACR execution once. If large errors persist after a second execution, inspect the ITB registration sensor (PS59) as described in Section 6.6.
Auto Gradation Adjustment — Full Adjustment (required after any imaging path component change):
Service Mode → Adjust → Image Quality → Auto Gradation Adjustment → Full Adjustment → Execute.
This is the most critical calibration step for solid fill quality. The machine prints and scans a multi-step gradation target for each color channel and recalculates the tone reproduction curves. Ensure A4 or Letter paper (whichever is the default for the machine region) is loaded in the designated calibration tray before executing. Do not interrupt this cycle.
Image Density Fine Adjustment (if residual density variation remains after AGA):
Service Mode → Adjust → Image Quality → Density → Adjust individually for C, M, Y, K as needed.
Make small adjustments only (one or two steps at a time) and print a test page after each adjustment to assess the effect before making further changes.
Final verification print:
Print a full-page solid fill test page for each of the four CMYK process colors plus a composite secondary color page (solid red, solid green, solid blue fills) and a full-page composite black. Examine each output carefully under good, consistent lighting (ideally a daylight-equivalent lamp) for any remaining stripe, banding, density variation, or color shift. All solid fills should appear smooth and uniform with no visible banding.

9. Escalation Criteria

Escalate to Level 2 support or escalate to unit replacement discussion if any of the following conditions apply after completing all procedures in this article:

The stripe defect persists after replacement of the drum unit (DR-xxx), developer unit (DV-xxx), and laser unit (LU-xxx) for the affected color station, combined with a confirmed clean ITB and 2nd BTR.
HVPS output voltage is confirmed out of specification on multiple output channels after board replacement, suggesting a PRCB fault driving the HVPS circuits.
ACR continues to produce large residual errors after ITB registration sensor (PS59) cleaning and replacement, combined with a verified-good ITB surface, suggesting a PRCB or CPUB processing defect in the ACR computation.
The stripe defect is intermittent in a pattern that correlates with specific environmental conditions (high humidity, low temperature) and cannot be reproduced consistently for diagnosis, indicating a potential high-voltage insulation breakdown that requires depot-level inspection.
Physical damage to the drum station guide rails, laser unit mounting rail, or ITB belt tension mechanism prevents proper component seating and correct geometric alignment of the image formation components.
The PRCB, MFPB, BASEB, or CPUB (main control and process control boards) is suspected based on abnormal behavior in multiple unrelated subsystems simultaneously.

10. Technician Summary

Colored stripe defects on solid fill areas are diagnostically demanding because solid fills amplify any inconsistency in the electrophotographic process chain into a clearly visible defect. The key to efficient diagnosis is precise characterization of the defect before touching any component: determine the stripe orientation (horizontal versus vertical), measure the repeat interval, isolate the affected color station(s) using color separation test prints, and confirm whether the defect appears in copy mode, print mode, or both.

The most common root causes, in approximate order of field frequency, are: developer unit aging or damage (DV-xxx), OPC drum coating wear (DR-xxx), PCR contamination (inside DR-xxx), laser window contamination (LU-xxx), ITB surface damage or 2nd BTR contamination, and ACR miscalibration. HVPS faults and scanner CCD/illumination defects are less frequent but should be considered when component replacement and calibration do not resolve the defect.

Never replace multiple components simultaneously without test printing between each replacement. Replacing drum, developer, and ITB together in a single visit makes it impossible to identify which component was actually defective, prevents accurate documentation, and introduces unnecessary cost and risk of handling damage to serviceable parts.

Auto Color Registration and Auto Gradation Adjustment are mandatory after any imaging path component replacement. A solid fill stripe that appears to be a hardware defect is frequently a calibration artifact. Always run ACR and AGA and print a verification solid fill test page before concluding that a hardware defect remains unresolved.