Archive December 27, 2025 by rawaha

Troubleshooting Konica Minolta bizhub C451 Jam or Misfeed at Tray 4 Feed Section

A consistent jam from Tray 4 on the Konica Minolta bizhub C451 indicates a breakdown in the specialized horizontal feed mechanism serving this high-capacity tray. These jams disrupt high-volume printing and require a focused diagnostic strategy. Success hinges on understanding the unique sensor logic for this tray and methodically testing the electromechanical components responsible for its operation.

Understanding the Jam Detection

The machine identifies a Tray 4 jam based on one of three specific conditions. The phrasing around sensor PS26 is critical: it is designed to be blocked at rest and unblocked when paper passes.

  1. Standard Misfeed: The leading edge of the paper fails to unblock the Tray 4 Paper Feed Sensor (PS26) within the expected timeframe. This means the paper never reaches the sensor to move its actuator, indicating a complete failure in pickup or initial transport.
  2. Paper Left in Path: Sensor PS26 is found in the unblocked (ON) state during system initialization. This is the opposite logic of some other trays. It signals that paper is either physically holding the sensor actuator in the unblocked position, or the sensor mechanism is stuck.
  3. TOD Permit Waiting Jam: The “Top Of Document” synchronization signal is not enabled in time. This points to a high-level timing or communication fault between the tray’s feed system and the main printer controller.

Relevant Components (Key Parts)

Diagnosis should center on these tray-specific and shared components:

  • Transport Motor (M25): Drives the horizontal transport rollers for upper trays (shared with Tray 3).
  • Tray 4 Paper Feed Clutch (CL7): Engages the Tray 4-specific pickup mechanism.
  • Tray 4 Paper Feed Sensor (PS26): The critical optical or mechanical sensor that detects paper passage by changing from a blocked to an unblocked state.
  • Paper Feed/Transport Drive Board (PFTDB): The intermediary controller that powers M25 and CL7, and reads the signal from PS26.
  • Printer Control Board (PRCB): The main system processor.

Systematic Troubleshooting Procedure

Follow these steps in order to isolate the root cause.

Step 1: Initial Mechanical Checks

  • Remove Tray 4. Thoroughly inspect the pickup roller and separation pad/roller assembly for significant wear, flat spots, or contamination. Clean or replace these consumable parts first.
  • Examine the entire horizontal paper path from the tray exit to the merge point. Look for and remove any obstructions like torn paper, sticker labels, or debris.
  • Ensure the paper in the tray is correctly loaded, not exceeding the fill line, and that the side and end guides are properly adjusted to prevent skew.

Step 2: Check Tray 4 Paper Feed Sensor (PS26)

  • Action: Perform an I/O check for PS26 in the printer’s service mode. Verify the state toggles correctly when you manually move the sensor actuator. Note: The expected signal at the board is ON (PFTDB CN9-3) when the sensor is unblocked (paper present).
  • Physical Check: Locate PS26 along the feed path. Ensure its actuator lever moves freely and returns to its default (“blocked”) position. Clean any dust or debris from the optical sensor slot or mechanical switch.
  • Signal Verification: Use a multimeter if necessary to confirm the voltage change at the PFTDB connector when the actuator is toggled.

Step 3: Check Tray 4 Paper Feed Clutch (CL7) Operation

  • Action: Utilize the service mode’s actuator test function to energize CL7. Listen and feel for a definitive click, indicating electromagnetic engagement.
  • Check: A silent test points to a failed clutch, a broken wire, or a bad drive signal. Inspect the mechanical linkage from the clutch to the pickup roller for wear or disconnection.
  • Control Signal: The clutch is activated by a signal from PFTDB connector CN24-2.

Step 4: Check Transport Motor (M25) Operation

  • Action: Use the service mode to run the Transport Motor (M25). Since it is shared with Tray 3, a failure here would affect both trays.
  • Observation: Listen for smooth, consistent operation. A faulty motor may stall, run unevenly, or not start at all. Visually confirm that the associated transport rollers for Tray 4 are rotating.
  • Control Signal: Motor control is managed via the PFTDB at connector CN12-6 (LOCK signal).

Step 5: Replace the Paper Feed/Transport Drive Board (PFTDB)

  • If sensor PS26, clutch CL7, and motor M25 all test within specifications, the local controller (PFTDB) that manages them is likely faulty. Replacing the PFTDB is the next logical step.

Step 6: Replace the Printer Control Board (PRCB)

  • If the jam persists after installing a new PFTDB, the final step is to replace the main controller (PRCB). This addresses potential communication or processing faults at the highest level.

Conclusion

Effectively resolving Tray 4 feed jams requires careful attention to its specific sensor logic. Begin with physical inspections and sensor verification, proceed to testing the dedicated clutch (CL7) and shared transport motor (M25), and finish with the control boards if needed. This structured approach—emphasizing the correct “unblocked” state of PS26—ensures an accurate diagnosis and restores reliable high-capacity feeding from Tray 4 on the bizhub C451.