Introduction
Paper jams are an inevitable reality in any high-volume document processing environment. When a sheet of paper fails to traverse the paper path within the expected time window, the machine must detect the fault, halt operations to prevent damage, and guide the user—or the service technician—to the exact location of the problem. The Konica Minolta bizhub paper jam detection system is a sophisticated network of sensors, timing logic, and diagnostic codes designed to accomplish precisely that.
This article provides a comprehensive guide to the jam detection system, covering the key sensors and their locations, the timing logic that governs detection, the structure and meaning of jam codes, and systematic troubleshooting procedures.
1. The Philosophy of Jam Detection
1.1 The Fundamental Principle
At its core, the jam detection system operates on a simple principle: paper is expected to pass each sensor within a specific, predetermined time window. If a sensor does not detect the leading edge of the paper when expected, or if a sensor remains blocked longer than expected, the machine declares a jam.
1.2 Sensor States
Each paper path sensor is a photosensor—typically a transmission-type (photo-interrupter) sensor paired with a mechanical actuator flag. The sensor outputs one of two states:
| State | Meaning |
|---|---|
| Unblocked (0) | No paper is present; the actuator is in its resting position |
| Blocked (1) | Paper is present and has pushed the actuator |
The machine’s CPU continuously monitors these sensors at millisecond intervals, comparing actual sensor states against the expected states based on the machine’s internal timing model.
1.3 Two Types of Jam Detection
The jam detection system identifies two primary categories of paper jams:
| Jam Type | Description |
|---|---|
| Timing Jams | Paper does not reach or clear a sensor within the expected time window |
| Residual Paper Jams | Paper is detected at a sensor when it should not be present—typically at power-on, after door closure, or after a jam reset |
2. Key Sensors — The Eyes of the Machine
Every bizhub model has a specific sensor layout, but the fundamental sensor types are consistent across the product line. The most critical sensors in the paper path are:
2.1 Registration Sensor (PS1)
The registration sensor is the most important sensor in the paper path. It is positioned immediately before the registration roller and detects the leading edge of the paper as it arrives for image synchronization.
Role in jam detection: If the registration sensor does not detect paper within the specified time after the feed operation begins, the machine declares a misfeed at the source tray.
Common jam codes involving PS1:
- 10-01 — Paper from the manual bypass tray does not reach PS1
- 11-01 — Paper from tray 1 does not reach PS1
- 20-01 — Paper from tray 2 does not reach PS1
2.2 Fusing Loop Sensor (PS2)
The fusing loop sensor monitors paper as it enters the fusing section, detecting the loop formed before the fusing roller to prevent skew.
Role in jam detection: If paper does not reach or clear this sensor within the expected time, the machine declares a jam in the fusing section.
2.3 Paper Exit Sensor (PS3)
The paper exit sensor is located at the exit of the fusing section, just before the paper exits to the output tray.
Role in jam detection: This sensor confirms that paper has successfully passed through the fusing section and is exiting the machine. If paper does not reach PS3, or if PS3 remains blocked too long, a jam is declared.
Common jam codes involving PS3:
- 32-05 — PS3 is not turned ON after paper has turned ON PS2, or PS3 is not turned OFF within the expected time
2.4 Tray Feed Sensors and Vertical Transport Sensors
Each paper tray and each section of the vertical transport path has dedicated sensors:
| Sensor | Typical Designation | Location |
|---|---|---|
| Tray 1 feed sensor | PS1 or PS101 | At the tray 1 feed section |
| Tray 2 vertical transport sensor | PS19 | In the vertical transport path from tray 2 |
| Tray 3 vertical transport sensor | PS113 | In the vertical transport path from tray 3 |
| Tray 4 vertical transport sensor | PS123 | In the vertical transport path from tray 4 |
2.5 ADU Sensors
For duplex printing, additional sensors monitor paper through the Automatic Duplex Unit:
| Sensor | Typical Designation | Location |
|---|---|---|
| ADU paper passage sensor/1 | PS40 | In the ADU transport path |
2.6 Finisher and Optional Unit Sensors
When optional finishers, punch units, or folding units are installed, additional sensors monitor paper through these modules:
- PS201 — Paper feed sensor in finisher
- PS202 — Punch motor sensor
- PS2 — Punch position sensor
- PS11 — Saddle path sensor
- PS9 — Lower path sensor
3. How the Machine Pinpoints Jam Locations
3.1 The Timing Model
The machine’s MFP board (MFPB) maintains an internal timing model for every possible paper path. This model specifies:
- The expected time for paper to travel from each tray to each downstream sensor
- The expected time for paper to clear each sensor
- The maximum allowable deviation before a jam is declared
These timings are calibrated for each paper type and paper size, as different media have different transport characteristics.
3.2 The Detection Sequence
The jam detection sequence follows this logical flow:
- Paper feed begins — A clutch or motor is energized to start paper movement from a tray or the bypass tray.
- Timer starts — The MFPB starts an internal timer for the first sensor in the path.
- Sensor monitoring — The MFPB continuously monitors the relevant sensor(s).
- Expected sensor change — The paper is expected to trip the sensor actuator within the specified time window.
- Jam declaration — If the sensor does not change state within the expected time, the MFPB declares a jam and halts all paper feed and imaging operations.
3.3 Residual Paper Detection
The machine also detects paper that was left in the paper path from a previous jam or malfunction. This is accomplished by checking all paper path sensors at critical moments:
- When the main power switch is turned ON
- When a door or cover is opened and closed
- When a misfeed or malfunction is reset
If any sensor is blocked at these moments, the machine declares a residual paper jam and displays the appropriate jam code and location.
3.4 Jam Display and Location Indication
When a jam occurs, the control panel displays:
- A message indicating that a jam has occurred
- The jam location — The position where the jam occurred blinks, while the position of remaining paper lights up
- The jam code — A numeric code that identifies the specific jam type and location
Note: The jam code is displayed on the jam warning screen only when the following setting is enabled: [Service Mode] → [System 2] → [JAM Code Display Setting]. This setting is typically enabled for service technicians.
3.5 Misfeed Processing Location
Each jam code in the service manual includes a “Misfeed processing location” that tells the technician exactly which door or cover to open to clear the jam:
| Processing Location | Typical Use |
|---|---|
| Right door | Access to feed and transport sections |
| Front door | Access to registration and image transfer sections |
| Horizontal conveyance cover | Access to the horizontal transport section |
| Bypass tray | Access to the manual feed section |
4. Common Jam Codes and Their Meanings
Jam codes follow a consistent numbering scheme across the bizhub product line. The first two digits typically indicate the section, and the last two digits indicate the specific condition.
4.1 Tray Feed Section Jams
| Jam Code | Meaning | Typical Cause |
|---|---|---|
| 10-01 | Paper from bypass tray does not reach registration sensor (PS1) | Worn feed roller, improper loading, paper misfeed |
| 10-02 | Loop forming not complete for bypass-fed paper | Timing issue, worn rollers, sensor fault |
| 11-01 | Paper from tray 1 does not reach registration sensor (PS1) | Worn pick-up roller, tray lift issue |
| 12-01 | Paper from tray 2 does not reach vertical transport sensor (PS19) | Worn feed roller, tray 2 feed issue |
| 20-01 | Paper from tray 2 does not reach registration sensor (PS1) | Worn feed roller, vertical transport issue |
4.2 Fusing and Exit Section Jams
| Jam Code | Meaning | Typical Cause |
|---|---|---|
| 30-03 | Paper does not reach paper exit sensor (PS3) | Fusing roller wear, paper curl, transport issue |
| 32-01 | ADU paper passage sensor (PS40) not turned ON | ADU transport issue, duplex feed failure |
| 32-05 | Paper exit sensor (PS3) not turned ON or OFF | Fusing section jam, exit roller issue |
4.3 Finisher and Optional Unit Jams
| Jam Code | Meaning | Typical Cause |
|---|---|---|
| 72-14 | Lower path sensor (PS9) or saddle path sensor (PS11) issue | Finisher transport issue |
| 72-16 | Job separator transport section jam | Job separator roller issue |
| 72-43 | Finisher punch section jam | Punch unit jam, misfeed in punch section |
| 72-70 | Finisher staple section jam | Staple unit issue, staple jam |
4.4 ADF (Document Feeder) Jams
| Jam Code | Meaning | Typical Cause |
|---|---|---|
| 66-05 | Document exit sensor (PS5) not turned OFF | ADF exit roller issue |
| 66-06 | Reading roller sensor (PS4) not turned OFF | ADF reading section jam |
| 66-07 | Sensor detects paper at unexpected timing | Residual paper in ADF |
5. Troubleshooting Jam Issues
5.1 Initial Check Items
Before diving into complex diagnostics, always perform these initial checks:
- Does the paper meet product specifications? Verify that the paper type, weight, and size are within the machine’s supported range.
- Is the paper curled, wavy, or damp? Improperly stored paper is a leading cause of jams.
- Is there a foreign object along the paper path? Check for debris, torn paper fragments, or obstructions.
- Are the rollers dirty, deformed, or worn? Inspect feed rollers, transport rollers, and fusing rollers.
- Do the paper size and the detected paper size match? Verify that the edge guides are correctly adjusted.
- Are the actuators operating correctly? Ensure that sensor flags move freely and are not stuck.
5.2 Using the Service Mode Sensor Check
The most powerful diagnostic tool for jam issues is the Sensor Check function in Service Mode:
- Enter Service Mode on the machine.
- Navigate to the appropriate sensor check screen (e.g., [ADF] → [Sensor Check]).
- Operate the suspect sensor manually using paper or an actuator.
- Verify that the screen display changes correctly (Paper detected: 1, No paper detected: 0).
5.3 I/O Check for Clutches and Motors
When a sensor is confirmed to be working correctly, the next step is to verify that the associated drive components are functioning:
- In Service Mode, navigate to the Load Check or I/O Check screen.
- Activate the suspect clutch or motor manually.
- Observe whether the component operates correctly (e.g., does the clutch engage? Does the motor rotate?).
5.4 Electrical Checks
If mechanical and sensor checks pass, perform electrical checks:
- Verify connector seating on the relevant boards (MFPB, FRB, PCCB, FSCB).
- Check for continuity on wiring between sensors and boards.
- Verify proper voltage supply to sensors and loads.
6. Model-Specific Variations
While the principles described in this article apply broadly across the bizhub product line, specific sensor designations and jam code formats vary by model:
| Model Series | Key Sensors | Notes |
|---|---|---|
| bizhub C658/C558/C458 | PS1, PS2, PS3, PS19, PS113, PS123 | Registration, fusing loop, exit sensors |
| bizhub 367/287/227 | PS1, PS19, PS113, PS123 | Similar sensor layout to C658 series |
| bizhub 751/600 | PS44, PS1, PS6, PS5, PS7 | Registration sensor designated PS44 |
| bizhub 423 | PS1, PS2, PS3 | Simple sensor layout |
| bizhub C360/C280/C220 | PS1, PS2, PS3 | Similar to 423 series |
Always consult the appropriate service manual for model-specific details.
7. Preventive Measures
7.1 Regular Cleaning
Clean all paper path sensors and actuators at every preventive maintenance visit. Paper dust accumulation on sensor optics can cause false readings.
7.2 Roller Maintenance
Worn or glazed feed rollers are the most common cause of timing jams. Replace feed rollers according to the published maintenance cycles—typically every 100,000 to 300,000 feeds, depending on the model.
7.3 Customer Education
Educate customers on proper paper storage and loading techniques. Many jams originate from:
- Overfilled trays
- Improperly adjusted paper guides
- Damp or curled paper
- Mixed paper types in the same tray
Conclusion
The Konica Minolta bizhub jam detection system is a sophisticated network of sensors and timing logic designed to detect paper transport failures with precision. By understanding the sensor locations, timing principles, and jam code structure, the field technician can quickly diagnose and resolve jam issues.
Key takeaways:
- The system operates on timing logic — Paper must reach and clear each sensor within a specified time window.
- The registration sensor (PS1) is the most critical sensor — Most feed section jams are detected when paper fails to reach PS1.
- Jam codes are diagnostic tools — The two-digit section code and two-digit condition code guide the technician to the exact failure point.
- Residual paper detection occurs at power-on, door closure, and jam reset.
- Initial checks — Paper quality, roller condition, and sensor actuator operation should always be verified first.
- Service Mode tools — Sensor Check and Load Check are essential for isolating faults.
By mastering the jam detection system, the technician can minimize machine downtime, reduce unnecessary parts replacements, and provide faster, more reliable service to customers.