4069-XXX
Fuser Operation
Hot Roll Fuser
The hot roll fuser in the Optra T printer is made up of two primary assemblies. The first assembly is the top fuser cover which contains the thermistor/cable, thermal fuse, cable assembly, left and right lamp brackets and cover. This is a complete assembly and the parts cannot be individually replaced as in previous Lexmark laser printers.
The thermal fuse (two fuses in series) protects the fuser assembly and surrounding parts from ignition in the event of a failure in the fuser control circuitry by opening the AC circuit to the lamp. The thermistor assembly is designed to keep the temperature of the fuser hot roll within a predetermined temperature by being in contact with the fuser hot roll and changes resistance as the temperature of the hot roll increases. The thermistor resistance changes from approximately 150K ohms to approximately 260K ohms as the temperature of the fuser hot roll increases. The thermistor is connected to the fuser control board connector
The voltage drop across the thermistor is proportional to the fuser temperature and varies from approximately 2.0 V dc (cold) to 2.3 V dc (warm during idle) to approximately 2.7 V dc during continuous printing. These voltages are assuming the fuser temperature is set to normal. The HEATON signal from
Diagnostic Aids
