Controlling The Fixing Temperature - Canon SmartBase 1270D Service Manual

6.2 Controlling the Fixing Operation

6.2.1 Controlling the Fixing Temperature

The fixing film unit has a plate-shaped fixing heater built into it for heating the fixing
film.
The fixing heater is equipped with 2 thermistor: a main thermistor in the middle and a sub
thermistor at the end. The main thermistor is used to control the temperature of the fixing
heater and to detect its overheating, while the sub thermistor is used to detect an error tem-
perature on the end of the fixing heater.
The CPU on the DC controller PCB monitors the main thermistor signal (FSRTH) and the
sub thermistor signal (SUBTH) from the thermistors for control of the fixing heater drive
signal (FSRD0) and the relay drive signal (RLYD), thus varying the supply of power to the
heater and, ultimately, controlling the temperature of the fixing heater.
Fixing
heater
COPYRIGHT © 2002 CANON INC.
Image processor PCB
Fixing assembly
Sub
thermistor
Main
thermistor
Power supply PCB
+24V
2000 2000 2000 2000 CANON SmartBase PC1210D/1230D/1270D REV. 1 MAR. 2002
DC controller PCB
Fixing heater high tempe-
rature error detection
F04-602-01
CHAPTER 4 OPERATION
SUBTH
FSRTH
CPU
+3.3V
FSRDO
RLYD
4-27