Other Problems May 14, 2026 by zakaria

Konica Minolta Bizhub Restarts Spontaneously – Complete Troubleshooting Guide

A Konica Minolta Bizhub that restarts spontaneously can be just as alarming as a machine that won’t power on at all. Instead of a completely dead machine, you observe a continuous cycle where the unit attempts to boot, only to shut down and restart again — sometimes during or after warm‑up, sometimes as soon as the splash screen appears. In the worst cases the machine enters a loop with no way to enter Service Mode.

This guide will walk you through every possible cause — from an overloaded wall outlet to a faulty SSD or control board — and provide step‑by‑step diagnostic procedures to isolate the fault and restore normal operation.

Possible Causes

  • Incoming power issues (unstable voltage, overloaded circuit, faulty UPS/power strip)
  • Corrupt or incomplete firmware update
  • Bad or failing SSD / eMMC storage board
  • Defective NVRAM (non‑volatile RAM) causing boot‑time data errors
  • Faulty MFP board (Main Control Board) or Baseboard (BASEB)
  • Power Supply Unit (LVPS / DCPU) delivering unstable voltages
  • Fuser unit short circuit or temperature protection triggering
  • Short circuit in an option board (dual scan card, fax kit, Fiery controller)
  • Corrupt print job in the network queue causing repeated crashes
  • Overheating due to clogged fan or poor ventilation

Step‑by‑Step Troubleshooting

Important: Before beginning, check that you have a stable power source. Plug the machine directly into a wall outlet (bypass any UPS or power strip) and ensure the line voltage matches your model’s specification (110–120V / 220–240V). Many intermittent reboot issues disappear when the copier is no longer sharing a circuit with high‑draw equipment like space heaters.

Step 1 – Isolate the Reboot Pattern

Observe exactly when the restart happens:

  • Immediately after pressing the sub power switch → The MFP board or BASEB fails to complete the POST (Power On Self Test).
  • During warm‑up (about 30‑60 seconds after power‑on) → Fuser unit or power supply likely at fault.
  • When a network print job is sent → Corrupt job in the queue or network interface problem.
  • Intermittently in standby → Power fluctuations, overheating, or failing SSD/eMMC.

Identifying the pattern will help you skip irrelevant steps.

Step 2 – Eliminate External Factors

  1. Disconnect the network cable (including Wi‑Fi if equipped). A corrupt print job or malformed network packet can cause the MFP board to crash and reboot. If the machine now starts normally, clear all print queues and check your print server.
  2. Remove all optional devices (fax kit, extra trays, ADF, finisher, etc.). A shorted optional board — such as a dual scan card — has been known to cause a continuous reboot loop. Reconnect options one by one to find the culprit.
  3. Disconnect any USB devices (authentication units, flash drives, etc.).
  4. If the machine now powers up correctly, you have identified the external cause. If the reboot persists, proceed to Step 3.

Step 3 – Reset the Machine and Perform a Firmware Check

  1. Turn OFF the main power switch (the physical switch, not the soft button). Wait at least 10 seconds, then turn it back ON.
  2. Attempt a Trouble Reset: On many models, a small “warm reset” button is located near the CompactFlash slot or beside the CF card cover. Press it with a paperclip while powering on to bypass certain boot errors. On other machines, holding the Utility/Counter key while powering on may bring up a Trouble Reset screen.
  3. Check the firmware version. If the machine sometimes boots but then reboots, enter Service Mode (Stop → 0 → 0 → Stop → 0 → 1) and navigate to Firmware Version. If the displayed version is unusually old or missing, the firmware may be corrupt. Reload the latest official firmware using a USB drive and the standard procedure (see Konica Minolta service manual for your model). Corrupt firmware is a known cause of spontaneous reboots.

Step 4 – Inspect the SSD / eMMC Storage Board

In many Bizhub models — especially the 8‑series and 4‑series (e.g., C224e, C284e, C364e) — a failing or corrupt SSD is the number one cause of a reboot loop at the logo screen. The machine tries to load the operating system from a corrupted storage partition and fails repeatedly.

  1. Power OFF the machine and remove the SSD or eMMC board (refer to your service manual for its exact location — it is usually a small module near the MFP board).
  2. Try booting the machine without the storage board installed. If the machine now boots to a “No HDD / No SSD” error screen (or enters Service Mode), the storage board is the problem.
  3. If you have a known‑good replacement SSD, install it and reload the firmware. On some models, the SSD controller itself may need a firmware update; refer to the service manual for the procedure.
  4. If the machine still reboots, the problem is elsewhere — proceed to Step 5.

Step 5 – Test the Power Supply Unit (LVPS / DCPU)

Unstable DC output from the Low Voltage Power Supply (LVPS) can cause the control boards to reset at random times. This often manifests as reboots that occur after the machine has been running for a few minutes.

  1. Access the LVPS (location varies by model — consult your service manual).
  2. With the machine powered on (and running if possible), use a multimeter to measure the output voltages on the main LVPS connectors (usually +5V, +12V, +24V).
  3. If any output is missing, fluctuating by more than 5%, or dropping out when a load is applied (e.g., when the fuser turns on), the LVPS must be replaced.
  4. On older models, the DC Power Supply (DCPU) may be separate; test it the same way.

Step 6 – Check the NVRAM and RAM Modules

Corrupted NVRAM (non‑volatile RAM) can store invalid boot parameters that trigger a restart during the initialisation sequence. NVRAM errors often appear as C‑D3xx codes, but not always.

  1. If you can reach Service Mode, perform a Data Clear (Tech Rep Mode → System 1 → Initialization → Clear All Data). Warning: This erases all settings and addresses.
  2. If the machine is in a reboot loop and you cannot access Service Mode, you may need to replace the NVRAM module (usually a black plastic‑encased component with a small battery on the MFP board). For some models, removing and re‑seating the NVRAM can temporarily restore operation.
  3. Also reseat the SODIMM memory modules. A faulty RAM stick can cause spontaneous reboots. If you have spare modules, swap them to test.

Step 7 – Inspect the MFP Board (Main Control Board) and Baseboard

When all other components have been eliminated, a defective MFP board (or Baseboard on i‑series models) is the likely cause. The symptom is often a reboot that happens immediately after pressing the power button, with no display or logo appearing at all.

  1. Check all connectors on the MFP board for loose pins, corrosion, or burn marks.
  2. Reseat all flat cables and power jumpers.
  3. If you have a known‑good MFP board of the same part number, replace the board and test. Keep your original NVRAM module if it is removable — it contains machine‑specific data (counters, serial number).
  4. On the Bizhub 287 and similar models, a reboot loop that cannot be interrupted even with a firmware update often points to a faulty MFP board.

Step 8 – Investigate the Fuser Unit (Thermal Protection)

If the reboot occurs 30‑60 seconds after power‑on (during warm‑up), the fuser unit is a prime suspect. A shorted heater lamp, a faulty thermostat, or a failed thermistor can cause the AC relay to trip, effectively cutting power and forcing a restart.

  1. Inspect the fuser unit for visible damage, burned connectors, or a smell of overheated plastic.
  2. Test the fuser heater lamps for continuity (with the machine unplugged).
  3. Replace the entire fuser unit with a known‑good unit and test. If the reboot stops, the original fuser is defective.

On machines equipped with IH (induction heating) fusers, a defective IH power supply can also cause similar symptoms.

Step 9 – Check for Overheating (Cooling Fans)

Intermittent reboots in standby can be caused by thermal shutdown. The machine reboots when an internal component reaches a critical temperature.

  1. Listen for all cooling fans (power supply fan, MFP board fan) when the machine is on. A stuck or failing fan will cause the board to overheat.
  2. Clean any dust obstructing the fan grilles or heat sinks.
  3. If a fan does not spin, check its connector and replace the fan if necessary. A fan failure may also generate an error code (e.g., 004E on some models).

Summary Diagnostic Table

Symptom Most Likely Cause Action
Reboots instantly after power button pressed, no boot logo MFP board / Baseboard faulty, or corrupt firmware Disconnect options → reload firmware → replace MFP board
Reboots at the logo / hourglass Corrupt SSD / eMMC storage Remove SSD → if machine starts, replace SSD
Reboots during warm‑up (30‑60 sec) Fuser unit or LVPS failing Test with known‑good fuser → measure LVPS outputs
Intermittent reboots in standby Overheating, unstable LVPS, or NVRAM corruption Clean fans → check LVPS → run Data Clear
Reboots only when receiving a network print job Corrupt job in queue or network controller issue Disconnect network → clear print queues on server
C‑D3xx error displayed before reboot NVRAM data error Perform NVRAM Data Clear or replace NVRAM module

When to Call a Certified Technician

The steps in this guide that involve opening the machine, measuring live voltages, replacing storage boards, or performing a Data Clear should only be carried out by a trained technician. If you are not comfortable with any of the following, please call your Konica Minolta service provider:

  • Removing the SSD, eMMC, or MFP board
  • Measuring power supply voltages on a live machine
  • Reloading firmware in recovery mode
  • Performing a Data Clear or NVRAM replacement
  • Disassembling the fuser unit

Replacing boards without proper diagnostics can be expensive and may not solve the problem. A good technician will have a set of known‑good spare boards and the official service software to isolate the fault quickly.

Conclusion

A Konica Minolta Bizhub that restarts spontaneously can be frustrating, but in most cases the root cause is one of a few known failure points: a corrupt SSD, a failing power supply, a misbehaving option board, or a bad NVRAM. By following the step‑by‑step diagnostic approach above, you can systematically eliminate possibilities and restore your machine to full operation.