A paper jam originating from Tray 1 on a Konica Minolta bizhub C451 is a common service issue that halts productivity. Unlike misfeeds at other locations, a jam here can stem from several specific failure points in the initial pickup and feed path. This guide provides a systematic method to diagnose and resolve these jams by understanding their detection timing and checking the relevant components.
Understanding the Jam Detection (Why It Happens)
The machine reports a Tray 1 feed jam based on one of these specific conditions:
- Standard Misfeed: The leading edge of the paper does not activate the Tray 1 Vertical Transport Sensor (PS4) within a set time after the feed cycle begins. This indicates a failure in pickup or initial transport.
- Paper Left in Path: Sensor PS4 is already blocked (ON) when the machine powers up, a door is closed, or after a jam is cleared. This signals leftover paper or a faulty sensor.
- Loop Registration Jam: Paper from Tray 1 arrives too slowly at the timing rollers. The “loop” of paper needed for proper registration isn’t formed before the registration motor starts. This often points to a drive or transport issue after PS4.
- TOD Permit Waiting Jam: The “Top Of Document” permit signal stays disabled too long after it should activate. This is a more complex timing/control issue related to the main board synchronization.
Relevant Components (Key Parts)
Focus your investigation on these electrical and mechanical parts:
- Take-up Motor (M22): Drives the vertical transport rollers that move the paper upward from the tray.
- Tray 1 Paper Feed Clutch (CL1): Engages the pickup mechanism to start feeding paper from the tray.
- Tray 1 Vertical Transport Sensor (PS4): The critical sensor that detects the paper has successfully left the tray area.
- Paper Feed/Transport Drive Board (PFTDB): Controls M22 and CL1, and receives the signal from PS4.
- Printer Control Board (PRCB): The main system controller.
Systematic Troubleshooting Procedure
Follow these steps in order to isolate the cause.
Step 1: Initial Checks
- Remove Tray 1 and inspect the pickup and separation rollers for severe wear, smoothness, or contamination. Clean or replace them.
- Check for and remove any torn pieces of paper, debris, or obstructions in the entire paper path from the tray to the registration area.
- Ensure the paper in the tray is within specifications, not curled, damp, or overloaded, and that the side and end guides are set correctly.
Step 2: Check Tray 1 Vertical Transport Sensor (PS4)
- Action: Perform an I/O check for PS4 in the service mode to verify the machine correctly reads its status.
- Physical Check: Locate the sensor (often near the top rear of the tray cavity). Manually check its actuator arm for free movement and clean any dust.
- Signal Verification: Confirm the signal at PFTDB connector CN4-8 toggles between ON (actuator blocked) and OFF (actuator free).
Step 3: Check Tray 1 Paper Feed Clutch (CL1) Operation
- Action: Use the service mode to energize the Tray 1 feed clutch (CL1) and listen for its engagement (a distinct click).
- Check: If it does not engage, it may be faulty. Also, inspect the mechanical linkage and gears from the clutch to the pickup roller for damage or wear.
- Control Signal: The clutch is controlled via PFTDB connector CN4-14.
Step 4: Check Take-up Motor (M22) Operation
- Action: Use the service mode to activate the take-up motor (M22) independently.
- Observation: Listen and observe if it runs. A failing motor may be noisy, slow, or stall. Ensure the associated drive rollers are turning.
- Control: The motor is driven by signals from the PFTDB at connector CN5, pins 5 through 8.
Step 5: Replace the Paper Feed/Transport Drive Board (PFTDB)
- If sensors, the clutch, and the motor all test correctly but the jam persists, the local controller (PFTDB) that drives them may have failed. Replacement is the next step.
Step 6: Replace the Printer Control Board (PRCB)
- If the problem remains after replacing the PFTDB, the issue may lie with the main system board (PRCB). This is a final step when all other components are confirmed operational.
Conclusion
Effectively troubleshooting a Tray 1 feed jam on the bizhub C451 requires understanding the precise jam condition and then methodically testing the involved components. Start with the essential mechanical checks and sensor verification (PS4), then proceed to the actuators (CL1 and M22), and finally the control boards. This logical progression from simple to complex will reliably restore proper paper feed from Tray 1.