Description: Abnormally low fixing unit thermistor temperature • The fixing temperature remains below 120C/248F for 10 s.
Causes: Poor contact in the fixing unit thermistor connector terminals. Broken fixing unit thermistor wire. Fixing unit thermistor installed incorrectly. Fixing unit thermostat triggered. Fixing heater M and S installed incorrectly. Broken fixing heater M and S wire.
Remedy: Check the connection of connector CN25 on the engine PCB and the continuity across the connector terminals. Repair 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 and reinstall if necessary. Check for continuity. If none, replace the fixing heater M and S.
Code: C6400
Description: Zero-crossing signal problem • The main PCB does not detect the zero-crossing signal (Z CROSS SIG) for the time specified below. At power-on: 3 s Others: 5 s
Causes: Poor contact in the connector terminals. Defective power source PCB. Defective main PCB.
Remedy: Check the connection of connectors CN17 on the main PCB and CN2 on the power source PCB, and the continuity across the connector terminals. Repair or replace if necessary. Check if the zero-crossing signal is output from CN2-7 on the power source PCB. If not, replace the power source PCB. Replace the main PCB if C6400 is detected while CN2-7 on the power source PCB outputs the zero-crossing signal.
Code: C7100
Description: Toner sensor problem • The toner sensor output voltage is outside the range of 0.5 to 4.5 V during copying or in maintenance item U130. • The toner sensor control voltage cannot be set within the range in maintenance item U130
Causes: Defective toner sensor. Poor contact in the toner sensor connector terminals. Defective developer.
Remedy: Replace the toner sensor. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the developer.
Code: C7300
Description: Toner hopper problem • Toner level is not detected when toner empty is detected.
Causes: Defective toner level detection sensor. Poor contact in the toner level detection sensor connector terminals.
Remedy: Replace the toner level detection sensor. Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable.
Code: C7800
Description: Broken external temperature thermistor • The input voltage is 4.5 V or more.
Causes: Poor contact in the humidity sensor PCB connector terminals. Defective external temperature thermistor.
Remedy: Reinsert the connector. Also check for continuity within the connector cable. If none, remedy or replace the cable. Replace the humidity sensor PCB and check for correct operation.
Code: C7810
Description: Short-circuited external temperature thermistor • The input voltage is 0.5 V or less.
Causes: Defective external temperature thermistor. Defective humidity sensor PCB.
Remedy: Replace the humidity sensor PCB and check for correct operation. Replace the humidity sensor PCB and check for correct operation.