3-4
Service Manual
Y101700-5
(3) Thermal control
1. The heater lamp, thermistor, main PWB, DC power
supply PWB, and triac within the power supply unit are
used to control the temperature in the fuser unit.
To prevent against abnormally high temperature in the
fuser unit, a thermal breaker and thermal fuse are used for
safety purposes.
2. The surface temperature of the upper heat roller is set
to 165°C ~ 190°C. The surface temperature during the
power save mode is set to 100°C.
3. The self-check function comes active when one of the
following malfunctions occurs, and an “H” is displayed on
the multicopy window.
a. When the heat roller surface temperature rises above
240°C.
b. When the heat roller surface temperature drops below
100°C during the copy cycle.
c. Open thermistor
d. Open thermal fuse
e. When the heat roller temperature does not reach
190°C within 27 second after supplying the power.
(4) Fusing resistor
Fusing resistor
This model is provided with a fusing resistor in the fusing
section to improve transfer efficiency.
General descriptions are made in the following.
General descriptions
Since the upper heat roller is conductive when copy paper is
highly moist and the distance between the transfer unit and
the fusing unit is short, the transfer current leaks through the
copy paper, the upper heat roller and the discharging brush.
3.4
Fuser section
3.4.1 General description
General block diagram (cross section)
(
1) Heat roller
A Teflon roller is used for the heat roller and a silicone
rubber roller is used for the lower heat roller for better toner
fusing performance and paper separation.
(2) Separator pawl
Three separator pawls are used on the upper heat roller. The
separator pawls are teflon coated to reduce friction with the
roller and prevent a smear on the paper caused by the
separator pawl.
Safety device (thermal
breaker, thermal fuse)
Triac (in the power
supply unit)
Heated by the heater
lamp (950 W)
The surface temperature
of the upper heat roller is
sensed by the termistor.
Level of the thermistor
is controlled by the
main PWB
With the signal from the
main PWB, the triac is
controlled on and off
(power supply PWB)
