Konica Minolta bizhub — Error Code P-27: Secondary Transfer ATVC Failure

Error Code P-27 on the Konica Minolta Bizhub series is defined as Secondary Transfer ATVC Failure. It is a process control alert that belongs to the P-series fault category — process control errors that relate to the machine’s ability to automatically manage imaging quality, transfer voltages, and calibration.

P-27 specifically targets the 2nd image transfer section of the machine, which is the critical zone where the complete color toner image assembled on the intermediate transfer belt (ITB) is transferred onto the paper (media) passing through the machine. When the machine’s automatic voltage regulation system for this transfer zone — known as ATVC (Auto Transfer Voltage Control) — detects an abnormal value during its adjustment cycle, P-27 is generated and printing halts.

Understanding this error requires a solid grasp of what ATVC is, what the 2nd transfer assembly does, and how the electrical circuit flows through the transfer belt and roller components. This article explains all of these elements in depth and provides a verified, step-by-step diagnostic and repair procedure based on official Konica Minolta service manual data and real-world field experience.

2. What Is ATVC? — Auto Transfer Voltage Control Explained

ATVC (Auto Transfer Voltage Control) is one of the most sophisticated process control systems in the Konica Minolta Bizhub color engine. Its purpose is to automatically calculate and apply the optimal electrical voltage to the image transfer rollers based on the actual measured resistance of the transfer belt at any given moment.

2.1 Why Voltage Control Is Necessary

Toner transfer in a laser electrophotographic system is driven by electrical charge. The toner particles, which carry a specific electrostatic charge, must be attracted off the intermediate transfer belt (ITB) surface and deposited onto the paper as it passes through the 2nd transfer nip. This requires an electrical potential difference applied across the transfer zone.

The challenge is that the resistance of the transfer belt changes constantly due to:

Temperature — belt resistance drops as temperature rises
Humidity — moisture in the belt material changes its conductivity
Belt age and wear — as the belt ages, its bulk resistance increases
Paper type — different paper thicknesses and coatings require different transfer voltages
Toner coverage — the amount of toner on the belt affects the effective electrical load

If a fixed transfer voltage were applied regardless of these variables, the result would be inconsistent transfer quality — too little voltage means light, washed-out prints; too much voltage means toner scattering, hollow characters, or back-transfer of toner. ATVC eliminates this problem by dynamically adjusting the voltage every time the machine runs.

2.2 How ATVC Works — The Measurement Circuit

According to the official Konica Minolta Bizhub C450 Theory of Operation documentation, ATVC operates as follows:

The machine uses a constant current injection method:

For 2nd Transfer ATVC: A known, constant current is output by the DC power supply (High Voltage Unit / HV) and fed into the 2nd Image Transfer Roller.
This current flows through the transfer roller, across the intermediate transfer belt, and returns via the Transfer Belt Drive Roller to complete the circuit back to the DC power supply.
By measuring the voltage that develops across this known current, the machine’s controller calculates the actual resistance of the transfer belt at that moment using Ohm’s Law (V = I × R).
The controller then uses this resistance measurement to calculate the optimum transfer voltage required to achieve consistent toner transfer for the current operating conditions.
This calculated voltage is then applied during the actual printing process, ensuring optimal toner transfer regardless of environmental conditions or belt age.

The ATVC measurement cycle is carried out immediately before each image stabilization control sequence — meaning it runs at every machine initialization, after power-on, after the front door is opened and closed, and at regular intervals during high-volume print jobs.

2.3 1st Transfer vs. 2nd Transfer ATVC

There are two ATVC systems in a Bizhub color machine. It is important to understand the difference:

1st Transfer ATVC: Controls the voltage applied to the 1st Transfer Rollers that transfer toner from each drum unit (Y, M, C, K) onto the intermediate transfer belt. A common ATVC value is calculated and shared for the Y, M, and C channels; K may be separate. Failures in 1st transfer ATVC produce different error codes (not P-27).
2nd Transfer ATVC (P-27 domain): Controls the voltage applied to the 2nd Image Transfer Roller that transfers the complete assembled color image from the belt onto the paper. This is what P-27 monitors. An abnormal ATVC value measured here is what triggers the P-27 error.

3. Official Error Code Definition

The following definition is confirmed from Konica Minolta official service manuals across models C227, C258, C308, C368, C458, C558, C658, C450, and C200:

P-27 — Secondary Transfer ATVC Failure:
An abnormal average value is detected during an adjustment of the second transfer ATVC value.

In practical terms: when the machine runs its 2nd transfer ATVC measurement routine, the calculated average ATVC value falls outside the acceptable range. This means the resistance measurement circuit is returning values that are either impossibly high or impossibly low — indicating an electrical fault, a broken circuit, poor contact, or a failed component somewhere in the 2nd transfer circuit.

Key symptom associated with P-27: The most visible symptom before the machine halts is very light (washed-out) print output. This occurs because the ATVC system, unable to determine the correct transfer voltage, either applies too little voltage or no voltage to the 2nd transfer roller — resulting in toner remaining on the belt instead of transferring to paper. Field technicians on Copytechnet have confirmed this relationship directly: P-27 causes very light images because 2nd image transfer ATVC is failing to regulate the transfer voltage properly.

Service mode confirmation: Under State Confirmation → Level History 2 in service mode, the ATVC 2nd value can be read directly. On a healthy machine, this value typically reads between approximately 300 and 5000 (units are volts DC on most models), with most machines in the field sitting around 1500–1700V DC depending on belt age and temperature. A machine with P-27 may show the ATVC 2nd value stuck at the minimum of 300 or pegged at an abnormal extreme, indicating the measurement circuit is not functioning.

4. The 2nd Transfer Assembly — Component Overview

To diagnose P-27 correctly, a technician must understand all the components that form the 2nd transfer circuit and assembly:

4.1 2nd Image Transfer Roller (2nd Transfer Assy)

The 2nd image transfer roller is a conductive rubber roller that presses against the intermediate transfer belt from the outside (non-image side) at the 2nd transfer nip point. The positive high voltage (or controlled current) is applied to this roller by the High Voltage Unit (HV). This electrical bias, combined with the grounded back-up roller on the opposite side of the belt, creates the electric field that pulls toner from the belt onto the paper passing through the nip.

The 2nd transfer roller is typically mounted in its own assembly (2nd Transfer Assy) that pivots on a spring-loaded mechanism. This mechanism allows the roller to apply consistent pressure against the belt and then retract when no paper is present. The spring mechanism is critical to ATVC operation because the roller must make firm, consistent electrical contact with the belt to complete the measurement circuit.

4.2 Roller Opposed to the 2nd Transfer Roller (Back-Up Roller / Drive Roller)

On the opposite side of the transfer belt from the 2nd transfer roller sits the transfer belt drive roller (also called the back-up roller or counter roller). This roller is electrically grounded and serves as the return path for the ATVC measurement current. The circuit flows: HV → 2nd Transfer Roller → Transfer Belt → Drive Roller → Ground → HV.

This grounding contact is one of the most critical and most frequently faulty elements in P-27 diagnosis. If the grounding contact between the drive roller shaft and the machine frame is contaminated with toner, oxidized, or broken, the ATVC measurement circuit is incomplete and P-27 results.

4.3 Image Transfer Entrance Guide

The image transfer entrance guide is a plastic or metal guide plate positioned at the entry of the 2nd transfer nip. It ensures paper is correctly directed into the nip and also plays a role in the electrical isolation of the transfer zone. If this guide is improperly installed, warped, or displaced, it can physically interfere with the 2nd transfer roller’s contact pressure against the belt, disrupting the ATVC circuit integrity.

4.4 Transfer Belt Unit (Intermediate Transfer Belt — ITB)

The intermediate transfer belt is the medium through which the ATVC measurement current flows between the 2nd transfer roller and the drive roller. The belt’s bulk electrical resistance is the key variable being measured. A belt with extremely high resistance (aged, cold, or dry) or extremely low resistance (electrically damaged, contaminated with conductive materials) will cause the ATVC calculated value to fall outside the acceptable range, triggering P-27.

4.5 High Voltage Unit (HV)

The High Voltage Unit generates and delivers all the high-voltage outputs required for the imaging process, including the 2nd transfer ATVC voltage and current. On newer models, there may be two high voltage units (HV1 and HV2) dividing the responsibilities between primary and secondary transfer sections and other charging functions. A faulty HV board that cannot regulate its output voltage/current correctly, or cannot read the feedback signal from the circuit, will produce abnormal ATVC values and trigger P-27.

4.6 MFP Board (MFPB) / Printer Control Board (PRCB)

The main controller board orchestrates the entire ATVC measurement cycle. It commands the HV unit to output the test current, reads the resulting voltage feedback, performs the resistance calculation, determines the optimum transfer voltage, and monitors whether the measured values fall within specification. A fault in the MFPB or PRCB’s ATVC processing circuit, ADC (analog-to-digital converter) input, or HV drive circuitry will produce P-27 even if all external hardware is functioning correctly.

On certain models, the MFPB contains protection fuses (designated F3E, F12E, F13E on some variants, or ICP-type polyfuses on others) in the high voltage drive lines. A blown fuse breaks the HV circuit to the 2nd transfer section and will cause P-27. These fuses must be checked before condemning the entire board.

5. Official Causes of Error Code P-27

The following are the officially listed causes across all documented Bizhub models, confirmed from the Konica Minolta service manuals:

5.1 High Voltage Unit (HV) Fault

The HV board is the primary candidate when all mechanical contacts are confirmed good. Failure modes include:

Failed output driver for the 2nd transfer high voltage channel
Degraded or failed feedback sensing circuit — cannot read the ATVC measurement voltage
Internal arc or breakdown of HV insulation due to toner or moisture contamination inside the unit
Connector or harness fault between HV and the 2nd transfer roller contact point
Worn or corroded HV output contact terminal that connects to the 2nd transfer assy

5.2 Poor Grounding of the Back-Up Roller (Roller Opposed to 2nd Transfer Roller)

This is consistently the first check item in every model’s official service manual remedy. The grounding contact between the back-up (drive) roller shaft and the machine frame must be electrically clean and firm. Common failure modes:

Toner contamination on the grounding contact — the most common field cause. Toner, being an insulating material, accumulates on metal contact surfaces and breaks electrical continuity.
Oxidation on the contact terminal — especially in machines in humid environments or machines that have been idle for long periods.
Bent, displaced, or missing grounding spring — the grounding contact is often made via a leaf spring or contact pin that must press firmly against the roller shaft or a grounding plate.
Worn grounding contact — contact surfaces that have worn down over time and no longer make reliable electrical connection.

5.3 2nd Transfer Assembly (2nd Transfer Assy) Fault

Issues with the 2nd transfer roller assembly itself:

Roller spring dislodged or broken — the spring that maintains pressure of the 2nd transfer roller against the belt has come off its seat, reducing or eliminating roller contact pressure. This disrupts both the mechanical transfer nip and the electrical ATVC circuit.
Contaminated contact between 2nd transfer assy and HV terminal — the electrical connection point where the HV board delivers voltage to the 2nd transfer roller shaft is dirty, corroded, or physically damaged.
Worn or glazed 2nd transfer roller surface — an aged roller with changed bulk resistance can shift the ATVC measurement outside tolerance.
Physically damaged roller — cracks, deformation, or chunks missing from the roller surface disrupt both transfer quality and electrical contact.

5.4 Image Transfer Entrance Guide Fault

The image transfer entrance guide is often overlooked but is specifically listed in official service manuals as a cause of P-27. Problems include:

Guide not installed in the correct position (may have been displaced during other service work)
Guide warped or deformed from heat, causing it to push against the 2nd transfer roller and prevent full pressure contact with the belt
Guide contaminated with paper dust or toner causing it to bind
Guide missing entirely (may have been removed and not reinstalled during a service call)

5.5 Transfer Belt Unit (ITB) Fault

The ITB is part of the ATVC measurement circuit. Belt-related causes of P-27 include:

Belt resistance out of specification — a very old belt with greatly increased resistance, or a belt that has been electrically damaged, shifts the ATVC measurement outside acceptable limits.
Belt surface delamination or internal damage — physical damage to the belt body can change its bulk electrical properties.
Conductive contamination on the belt — metallic particles, moisture, or other conductive contamination on the inner belt surface can cause abnormally low resistance readings in the ATVC circuit.

5.6 MFP Board / PRCB Fault

Board-level causes of P-27:

Blown protection fuse on the HV drive line (check before replacing the board)
Failed ADC input that reads the ATVC feedback voltage
Failed HV drive output driver on the board
Corrupt ATVC calibration data in EEPROM (see field note in Section 6.3)

6. Affected Models and Component Naming Variations

P-27 appears across a wide range of Bizhub color models. Component naming varies by generation. The following table provides model-specific reference:

Model Group	Control Board	HV Board Designation	Belt Drive Roller Grounding	Notes
C200, C203, C253, C300, C350	PRCB	HV / DC power supply	Check grounding terminal on belt unit door roller	Older model; PRCB replaced for board fault; check ICP fuses
C220, C280, C360	PRCB	HV (single board)	Grounding terminal at belt drive roller	Check PRCB ICP fuse for conduction; 2nd transfer spring check critical
C227, C287	MFPB	HV (single board)	Grounding terminal at back-up roller	No FRB in cause list; MFPB replaces PRCB in newer architecture
C258, C308, C368	MFPB	HV (single board)	Grounding terminal at back-up roller	FRB not listed for P-27; standard 5-step remedy
C458, C558	MFPB	HV (single board)	Grounding terminal at back-up roller	Standard remedy; check HV contact to 2nd transfer assy
C450, C550, C650, C452, C552, C652	PRCB	HVT board	Grounding terminal on belt unit / door roller	Special EEPROM PWB-EE board failure documented; see Section 6.3
C658, C754, C759	MFPB	HV1, HV2 (dual boards)	Grounding terminal at back-up roller	Dual HV architecture; check HV1 CN1/CN2 and HV2 CN1 connectors specifically
Bizhub 223, 283, 363, 423 (mono)	PRCB	HV (single board)	Transfer roller unit grounding terminal	Monochrome variant — described as “Transfer ATVC failure” not “Secondary”

6.3 Special Field Note: EEPROM Board Failure on C450/C550/C650 Series

A documented Technical Service Bulletin (TSB) for the Bizhub C450/C550/C650 series identifies a specific failure mode that causes extremely low ATVC 2nd values and very light output. The root cause in these cases was a failed Service EEPROM board (PWB-EE).

The distinguishing symptom: the image on the transfer belt looks correct (adequate density), but the final printed output is washed out or grainy. In service mode under State Confirmation → Level History 2, the ATVC 2nd value does not rise above 300V DC after printing, where it should normally be between 300 and 5000V DC (healthy machines typically read 1500–1700V DC).

Important: If the EEPROM board has failed on C450/C550/C650 models, the repair requires replacing not just the EEPROM board but also performing a comprehensive reset of all related consumables and calibration. A full re-initialization and calibration sequence is mandatory after EEPROM board replacement on these models. Contact Konica Minolta technical support for the specific TSB procedure applicable to your machine serial number range.

7. Relationship Between P-27 and Other Fault Codes

P-27 can appear in combination with other P-codes or C-codes. Understanding these relationships helps identify the true root cause quickly:

Code Combination	Likely Root Cause	Priority Action
P-27 alone, light output	2nd transfer grounding contact failure or HV contact contamination	Check and clean back-up roller grounding terminal; check HV-to-roller contact
P-27 + P-21 or P-22	Broad transfer system failure; transfer belt unit suspect	Inspect and replace ITB; check all transfer contacts
P-27 + P-28 (IDC sensor Rr failure)	Combined transfer belt and IDC sensor system failure	Replace ITB; clean IDC sensors; check HV board
P-27, ATVC 2nd stuck at 300V in service mode	EEPROM board failure (C450/C550/C650) or MFPB/PRCB fault	Check EEPROM board; apply TSB procedure if applicable; check MFPB fuses
P-27 + C-series code (e.g., C4101, C2414)	Combined HV board failure affecting multiple circuits	Replace HV board; check all wiring from HV to transfer assemblies
P-27 recurring after belt replacement	Grounding contact or HV contact still dirty/faulty; spring still dislodged	Re-inspect all electrical contacts; check 2nd transfer spring seating

8. Step-by-Step Official Remedy Procedure

The following procedure combines the official Konica Minolta service manual remedy (confirmed across C227, C258, C308, C368, C558, C200, and C360 documentation) with field-verified best practices. Follow steps in order, testing after each before proceeding.

Step 1 — Check and Clean the Back-Up Roller Grounding Contact

This is the first and most important step and is listed first in the official remedy for all documented models.

The back-up roller (the roller inside the transfer belt unit that opposes the 2nd transfer roller) must be solidly grounded to the machine frame for the ATVC measurement circuit to function.

Open the machine and remove or partially slide out the transfer belt unit to access the grounding terminal area.
Locate the grounding contact between the back-up roller shaft and the machine frame (this is typically a metal spring contact, pin contact, or leaf spring).
Inspect for toner contamination, oxidation, or damage.
Clean the contact surfaces thoroughly with a clean, dry, lint-free cloth. If oxidation is present, use a cotton swab with IPA to clean the metal surfaces and allow to dry completely.
Ensure the contact spring or pin makes firm, positive contact against the roller shaft or grounding plate when the unit is reinstalled.
Reinstall the belt unit, run Initialize + Image Stabilization, and check if P-27 clears.

Special note for C250 / older models: On the machine’s front door there is a roller with a gear on the left-hand side. This roller has a grounding contact on the door itself. When the door is closed, this contact must make electrical connection with the machine frame. Inspect this contact area specifically on door-mounted transfer assemblies.

Step 2 — Check the Image Transfer Entrance Guide

Locate the image transfer entrance guide — the guide plate at the paper entry point of the 2nd transfer nip.
Verify it is correctly installed in its designed position. Consult the service manual diagram for your specific model to confirm the correct orientation.
Check for warping, deformation, or displacement. The guide must not press against the 2nd transfer roller in a way that lifts it away from the belt surface.
If the guide is damaged or warped, replace it.
If it was not correctly installed (common after service work in the transfer belt area), reseat it correctly and test.

Step 3 — Check the 2nd Transfer Roller Pressure Spring

The spring mechanism that maintains the 2nd transfer roller in contact with the belt is critical to both transfer quality and ATVC circuit integrity.

Visually inspect the spring on the 2nd transfer assembly.
Verify the spring is correctly seated on both ends — it must not have come off its post or pivot point.
Check that the spring provides positive pressure pushing the roller against the belt surface.
If the spring is dislodged: reattach it to its correct seating position. This is a common cause of P-27 following any service work that involved moving the 2nd transfer assembly.
If the spring is broken or has lost its tension: replace the 2nd transfer assembly.
After correction, test the roller movement by hand to confirm smooth pressure engagement and retraction.

Step 4 — Check and Clean the HV-to-2nd Transfer Assembly Contact

The electrical connection from the High Voltage Unit to the 2nd transfer roller shaft must be clean and making firm contact.

Locate the HV output contact terminal that connects to the 2nd transfer assy (refer to the service manual wiring diagram for your model).
Inspect the contact terminal on both the HV unit side and the 2nd transfer assy side for toner contamination, oxidation, corrosion, or physical damage.
Clean both contact surfaces with a dry lint-free cloth. If heavily oxidized, use a cotton swab with IPA and allow to dry completely.
Ensure the connector is firmly seated and the contact makes positive electrical connection when the 2nd transfer assy is in its operating position.
Check the wiring harness between the HV unit and the 2nd transfer assy for damage, pinching, or loose connectors at both ends.
Test after cleaning. If P-27 persists, continue to Step 5.

Step 5 — Read ATVC 2nd Value in Service Mode

Before replacing expensive components, use the service mode diagnostic to confirm the ATVC circuit status:

Enter Service Mode using the technician access code for your model.
Navigate to: Service Mode → State Confirmation → Level History 2
Perform a print or copy job (or run an Initialize + Stabilization sequence).
Observe the ATVC 2nd value displayed.

Interpreting the reading:

Value between approximately 300–5000 (varies by model): ATVC circuit is functional; the measurement produced a result within range. P-27 may have been a transient error. Run Initialize + Stabilization and retest.
Value stuck at minimum (e.g., 300V DC) regardless of conditions: Circuit is open or HV is not delivering current. Check grounding contacts and HV output. On C450/C550/C650, check EEPROM board per TSB.
Value at maximum or abnormally high: Circuit resistance is extremely high; possible belt failure, open circuit in grounding path, or HV feedback failure.
Value erratic or fluctuating wildly: Intermittent contact fault in the grounding terminal or HV connector. Re-clean and re-secure all contacts.

Step 6 — Replace the Transfer Belt Unit (ITB)

If all contact checks are clean and correct, and the ATVC 2nd value is abnormal, the transfer belt’s bulk resistance may be out of specification.

Replace the intermediate transfer belt unit with a genuine Konica Minolta OEM belt.
After installation, run Initialize + Image Stabilization immediately.
Check the ATVC 2nd value in Level History 2 — it should now read in the normal range.
Run Gradation Adjustment for all modes, then Image Stabilizer.
Perform test prints and verify output quality and absence of P-27.

Step 7 — Replace the High Voltage Unit (HV)

If all mechanical contacts are verified clean and correct, and the ITB has been replaced without resolving P-27, the HV board is the next replacement candidate.

Before replacing, re-verify all HV connector harnesses are firmly seated and undamaged.
On dual-HV models (C658, C754, C759): check which HV handles the 2nd transfer output (typically HV1 on these models — verify in service manual). Replace only the relevant board first.
Replace the HV unit with a genuine Konica Minolta part.
After replacement, run Initialize + Image Stabilization and check ATVC 2nd value.
Run Gradation Adjustment and Stabilizer sequence.

Step 8 — Check MFPB / PRCB Fuses and Replace Board

If HV replacement did not resolve the issue:

Check for protection fuses on the MFPB or PRCB in the HV drive circuit. On applicable models, fuse designations include F3E, F12E, F13E (C759) or ICP-type polyfuses. Test each for continuity.
If a fuse is open, replace it (or the board if fuses are not separately serviceable). Investigate the root cause of the fuse blow before powering on.
If no fuses are blown and all other steps are exhausted, replace the MFPB (newer models) or PRCB (older models). This is a specialist repair requiring firmware flashing or board initialization on some models — consult Konica Minolta Level 2 support.

9. Service Mode Diagnostic Reference

The following service mode functions are directly relevant to P-27 diagnosis and should be used during the diagnostic process:

9.1 Level History 2 — ATVC 2nd Value

Path: Service Mode → State Confirmation → Level History 2
Function: Displays the ATVC 2nd transfer voltage value calculated by the machine after the last ATVC measurement cycle.
Expected Range: Approximately 300–5000 (model dependent); typical field readings on healthy machines are 1500–1700V DC. Values outside this range confirm P-27 is caused by an electrical fault in the 2nd transfer circuit.

9.2 Transfer Power — Secondary Transfer Adjustment

Path (example — varies by model): Service Mode → Adjustment → Transfer Power / Secondary Transfer Adj.
Function: Adjusts the 2nd image transfer ATVC output on the 1st page and the 2nd page (duplex) for each paper type. This is a fine-tuning tool used after P-27 has been resolved to optimize transfer quality for specific media types. It can also be used as a diagnostic tool — if adjustments in either direction make no difference to output density, the ATVC circuit is not communicating with the transfer assembly.
Note: After making adjustments, a full machine restart is required to force a stabilize sequence on the new adjustment values. Changes do not take immediate effect without restart.

9.3 I/O Check — HV Output Monitoring

On models with I/O check capability in service mode, the HV output to the 2nd transfer roller can be monitored during a test sequence. Absence of expected HV output confirms a failed HV board or a broken circuit to the roller.

10. Parts Replacement Reference Table

Component	Fault Condition Leading to Replacement	Diagnosis Method	Post-Replacement Actions Required
Transfer Belt Unit (ITB)	Belt resistance out of spec; all contacts clean but ATVC abnormal	ATVC 2nd value check; visual belt inspection	Initialize + Stabilization; Gradation Adj. all modes; Stabilizer
2nd Transfer Assembly	Broken spring; worn roller; damaged HV contact on assembly	Visual spring check; roller surface inspection; contact cleaning and retest	Initialize + Stabilization; 2nd Transfer Fine Adjustment if needed
Image Transfer Entrance Guide	Warped, displaced, or damaged guide interfering with roller contact	Visual check against service manual diagram	Initialize + Stabilization
High Voltage Unit (HV)	All contacts clean; ITB replaced; ATVC 2nd still abnormal	ATVC 2nd value reading; HV connector checks; I/O test if available	Initialize + Stabilization; Gradation Adj.; Stabilizer
EEPROM Board PWB-EE (C450/C550/C650)	ATVC 2nd stuck at 300V; good image on belt but light on paper; TSB confirmed	ATVC 2nd Level History 2 reading; comparison with TSB description	Full re-initialization per TSB; all consumables reset and calibration sequence
MFPB / PRCB	All hardware good; HV replaced; fuses intact; P-27 persists	Fuse continuity check; all I/O tests normal; error persists	Firmware verification; full calibration sequence; KM L2 support

11. Post-Repair Calibration Sequence

After resolving P-27, the following calibration sequence must be performed in this exact order:

Initialize + Image Stabilization — This re-runs the ATVC measurement cycle (confirming the circuit is now working), calibrates the IDC sensors, and sets toner density baselines. This step is mandatory first.
Check ATVC 2nd value in Level History 2 — Confirm the reading is now in the normal range (1500–1700V DC typical). If still abnormal, the root cause has not been fully resolved.
Gradation Adjustment (Copier, Printer, and Fax modes separately) — Restores correct tone reproduction curves for all color channels after the transfer voltage change.
Image Stabilizer — Final imaging process fine-tuning.
2nd Transfer Fine Adjustment (if output trailing edge transfer is still an issue) — Service Mode → Transfer Power → Secondary Transfer Adj. Adjust for each paper type if needed. Restart machine after changes.
Trouble Reset — Clear P-27 from the fault history in service mode.
Full Cold Power Cycle — Power off completely for 30 seconds, then power on. Confirm P-27 does not return on the next initialization cycle.
Test Prints — Run a minimum of 30–50 pages on standard paper and the media types used by the customer. Verify consistent density, absence of light output, and no P-27 recurrence.

12. Quick Diagnostic Decision Tree

Is print output very light or blank?
- Yes, but image looks good on the belt → 2nd transfer circuit failure confirmed. Begin with Step 1 (grounding contact check).
- Yes, and image is also light on the belt → Problem may be in 1st transfer or imaging process, not exclusively P-27 related. Check drum/developer units and IDC sensors as well.
Was any recent service work performed in the transfer belt area?
- Yes → Check the 2nd transfer roller spring seating and the entrance guide position immediately — these are the most commonly disturbed items during belt area service.
What does the ATVC 2nd value read in Level History 2?
- Stuck at 300V DC → Open circuit; grounding contact or EEPROM board (C450/C550/C650). Check grounding first, then EEPROM TSB.
- Abnormally high (near or above 5000V) → Very high resistance; suspect aged/damaged ITB or open grounding circuit.
- Normal range (1500–1700V typical) → ATVC circuit is working; P-27 may have been transient. Run full stabilization and retest.
Are P-21 or P-28 also active?
- Yes → Transfer belt unit is highly suspect. Prioritize ITB replacement and IDC sensor cleaning alongside grounding contact checks.
Has ITB been replaced without resolving P-27?
- Yes → The fault is electrical, not belt-related. Work through HV board diagnosis and MFPB/PRCB fuse checks.
Is this a C450/C550/C650 machine with ATVC 2nd stuck at 300V but good image on belt?
- Yes → Apply the EEPROM board TSB procedure. Do not replace HV or MFPB first.

13. Preventive Maintenance to Avoid P-27 Recurrence

13.1 Clean All Transfer Electrical Contacts at Every PM Visit

At every scheduled PM visit, clean the grounding contact terminal of the back-up roller, the HV-to-2nd transfer assy contact, and all related electrical contact points in the transfer zone. This is the single most effective preventive action against P-27. Use a dry lint-free cloth; use IPA on cotton swabs for stubborn oxidation.

13.2 Inspect the 2nd Transfer Spring

At every PM visit, visually verify the 2nd transfer roller spring is correctly seated. This takes seconds and prevents P-27 caused by a dislodged spring — one of the most easily avoided field failures.

13.3 Transfer Belt Life Management

Replace the transfer belt unit before it reaches end-of-life. An aged belt with increasing resistance will gradually push ATVC values toward the tolerance limit. Proactive replacement avoids P-27 triggered by out-of-specification belt resistance.

13.4 High Voltage Unit Inspection

During PM visits, visually inspect the HV board for signs of arcing (burn marks, carbon traces), toner contamination on the HV output contacts, and damage to the HV output wiring. Clean HV contacts and replace the board if arcing evidence is found.

13.5 Firmware Maintenance

Keep machine firmware current. Some firmware updates include improvements to ATVC tolerance windows and measurement algorithms that reduce the frequency of P-27 in marginal conditions.

13.6 Correct Paper Type Selection

Advise users to always select the correct paper type setting for the media being used. Running thick or coated paper on standard paper settings forces the ATVC system to apply incorrect transfer voltages, accelerating belt wear and stressing the HV circuit. Always select “Thick 4” or the appropriate coated stock setting when using heavy or coated media through the bypass tray.

14. Summary

Error Code P-27 — Secondary Transfer ATVC Failure — is a process control error that indicates the machine’s Automatic Transfer Voltage Control system for the 2nd image transfer section has measured an abnormal resistance value from the transfer circuit. This system dynamically calculates the optimal voltage to apply to the 2nd transfer roller to ensure consistent, high-quality toner transfer from the intermediate transfer belt onto the paper under all operating conditions.

When P-27 fires, the most visible symptom is very light or blank print output, because the machine cannot determine the correct transfer voltage and defaults to an insufficient level — leaving toner on the belt rather than transferring it to paper.

The diagnosis follows a logical electrical circuit path: starting from the most accessible and most frequently faulty point — the grounding contact of the back-up roller — through the 2nd transfer roller spring and pressure mechanism, to the HV-to-transfer contact, the transfer belt unit, the High Voltage Unit, and finally the main control board.

In the majority of field cases, the fault is found at the first or second diagnostic step: a dirty or oxidized grounding contact, or a dislodged 2nd transfer roller spring. These are quick, inexpensive fixes. Only in a minority of cases is board-level replacement required.

Always follow the official service manual remedy sequence for your specific model, clean all electrical contacts meticulously, and perform the mandatory post-repair calibration sequence (Initialize + Stabilization, Gradation Adjustment, Stabilizer) after any repair to restore correct machine operation.