Ricoh P C300W Field Service Manual page 289

7.Detailed Descriptions
The heat from the fusing lamp [A] is reflected by the reflector [B] and heats the fusing sleeve belt [C].
The nip pad [D] at the sleeve belt side is pushed against the pressure roller [E] and keeps the nip width
on the sleeve belt.
The pressure roller is operated by a gear train driven by the fusing motor. The fusing sleeve belts turns
with the rotation of the pressure roller (there is no drive mechanism for fusing sleeve belt itself).
The fusing entrance sensor in the fusing unit is provided to detect paper jams in the fusing unit.
Overheat Protection
The fusing thermopile [A] on the machine side monitors the surface temperature of the fusing sleeve
belt [B] and turns off the power supply to the fusing lamp [C] if it detects a temperature above 240°C.
The pressure roller thermistor (center) [D] and pressure roller thermistor (end) [E] monitor the surface
temperature of the pressure roller [F] and turn off the power supply to the fusing lamp if either thermistor
detects a temperature higher than 248°C.
If a high temperature is detected, the machine will issue a high temperature (software) alert, SC543,
SC563, or SC573, and then shut down machine operation. After the SC code has been issued, you
must enter the SP mode to reset the error with SP menu.
The fusing NC sensor [G], which also monitors the surface temperature of the fusing sleeve belt, cuts
the power supply to the fusing lamp if it detects a high temperature. If this occurs the machine will issue
SC554-00, the high temperature (hardware) alert, and shut down machine operation.
After the machine issues SC554-00 there is a strong possibility that the fusing unit has been damaged,
so the fusing unit must be replaced with a new unit, followed by the execution of SC reset in the SP
mode.
The fusing thermostat [H] provides protection against overheating if either the fusing thermopile or
pressure roller thermistors fail. If the temperature reaches 185°C the bimetal strip in the thermostat will
cut the power supply to the machine and shut it down. After the bimetal of the thermostat triggers a
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