• Code: C510
• Description: Main charger problem
  • MC ALM signal is detected continuously for 800 ms when MC REM signal is turned on.
• Causes: Defective LSU. Defective main PCB. Poor contact of the high-voltage transformer PCB connector terminals. Defective high-voltage transformer PCB. Leakage during main charging. Deformed high-voltage transformer PCB terminal spring.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, repair or replace the cable. Replace the high-voltage transformer PCB. Check and clean the main charger assembly. Replace the spring.

• Code: C610
• Description: Broken fixing heater wire
  • Warm-up does not end within 90 s.
  • The secondary stabilization fixing temperature drops to 100°C/212°F or below.
  • The fixing temperature remains below 40˚C/104˚F for 7 s or longer after the fixing heaters have been turned on.
• Causes: Fixing heater installed incorrectly. Broken fixing heater wire. Poor contact in the fixing unit thermistor connector terminals. Broken fixing unit thermistor wire. Fixing unit thermistor installed incorrectly. Fixing unit thermostat triggered.
• Remedy: Check and reinstall if necessary. Check for continuity. If none, replace fixing heater. Check the connection of connector CN12 on the main PCB and the continuity across the connector terminals. Remedy or replace if necessary. Measure the resistance. If it is ∞Ω, replace the fixing unit thermistor. Check and reinstall if necessary. Check for continuity. If none, replace the fixing unit thermostat. Check the operation of the cooling fan and repair if necessary.

• Code: C620
• Description: Abnormally low fixing unit thermistor temperature
  • The fixing temperature remains below 100˚C/212˚F for 10 s during copying.
• Causes: Fixing heater installed incorrectly. Broken fixing heater wire. Poor contact in the fixing unit thermistor connector terminals. Broken fixing unit thermistor wire. Fixing unit thermistor installed incorrectly. Fixing unit thermostat triggered.
• Remedy: Check and reinstall if necessary. Check for continuity. If none, replace fixing heater. Check the connection of connector CN12 on the main PCB and the continuity across the connector terminals. Remedy or replace if necessary. Measure the resistance. If it is ∞Ω, replace the fixing unit thermistor. Check and reinstall if necessary. Check for continuity. If none, replace the fixing unit thermostat. Check the operation of the cooling fan and repair if necessary.

• Code: C630
• Description: Abnormally high fixing unit thermistor temperature
  • The fixing temperature exceeds 240˚C/464˚F for 10 s.
• Causes: Shorted fixing unit thermistor. Broken fixing heater control circuit on the power source PCB.
• Remedy: Measure the resistance. If it is 0 Ω, replace the fixing unit thermistor. Replace the power source PCB.

• Code: C710
• Description: Toner sensor problem
  • The sensor output voltage is outside the range of 0.5 to 4.5 V during toner control.
  • The toner sensor control voltage cannot be set within the setting range when maintenance item U130 is run.
• Causes: Defective toner sensor. Poor contact of the toner sensor connector terminals. Developer problem.
• Remedy: Replace the toner sensor. Reinsert the connector. Also check for continuity within the connector cable. If none, repair or replace the cable. Replace the developer.

• Code: C730
• Description: Broken external temperature thermistor wire
  • The input voltage is above 4.5 V.
• Causes: Poor contact of the humidity sensor PCB connector terminals. Defective external temperature thermistor.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, repair or replace the cable. Replace the humidity sensor PCB.

• Code: C731
• Description: Short-circuited external temperature thermistor
  • The input voltage is below 0.5 V.
• Causes: Poor contact of the humidity sensor PCB connector terminals. Defective external temperature thermistor.
• Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, repair or replace the cable. Replace the humidity sensor PCB.

• Code: C740
• Description: Image formation unit connector insertion problem
  • Absence of the image formation unit is detected continuously for 1500 ms while there is no error on the copier.
• Causes: Image formation unit connector inserted incorrectly. Defective image formation unit connector.
• Remedy: Reinsert the image formation unit connector if necessary. Replace the image formation unit.