Fusing unit error (ERROR 71) (ERROR 72) (ERROR 73) � Turn the power off, then back on. � Does the fusing unit error occur immediately? � Yes Is the thermistor open or shorted? Measure the resistance between thermistor contacts (about 220k� at room temperature) (see Fig. 6-2 or see 7.3).
Heater contacts Themistor contacts
� Yes Replace the fusing unit.
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Figure 6-2
� No
Do the thermistor contacts touch the contact assembly properly when the fusing unit is mounted in the printer (see Fig. 6-4 contact F )? � No Adjust the contact.
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� Yes
Replace the Main Control PCB or power supply board.
� No � No
Does the fusing unit error occur about 60 seconds after the power is turned on? Check the thermistor for poor contact or replace the Main Control PCB. Turn the power off, then back on.
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� Yes
� Is the heater of the fusing unit turned on (when the heater is turned on, light is emitted)? � Yes
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Check thermistor contacts or replace the Main Control PCB or the fuser unit.
� No
Is the heater or the thermostat open? Measure the resistance between the heater contacts (normal resistance: about 0�) (see Fig. 6-2 or see 7.3). � Yes Replace the fusing unit.
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� No
Is the AC voltage being supplied to the contacts for the heater of the contact assembly? (Refer Fig. 6-2) � No Replace the Main Control PCB or the power supply board.
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� Yes
Check the heat contact of the fusing unit and the contact assembly for poor contact (see Fig. 6-4 contact G ).
