Temperature - Canon PC920 Service Manual

B. Controlling the Fixing Temperature
1. Outline
The fixing lower roller of the fixing assembly is driven by the main motor (M1). When the
fixing lower roller rotates, the film of the fixing upper unit starts to rotate in conjunction.
The fixing film is heated by the fixing heater (H1), which is a flat heater mounted in contact
with the inner side of the film. The fixing heater is equipped with a thermistor (TH1), which sends
the fixing thermistor signal (TH1) to the microprocessor (Q101) on the DC controller PCB; in
response, the microprocessor controls the fixing heater duty signal (HEAT_PWM) to vary the
power supplied to the heater by way of controlling the temperature of the fixing heater.
Relay
RL601
Thermal
fuse 2
FU2
COPYRIGHT © 1999 CANON INC.
+5V
Auxiliary
power supply
Fixing
thermistor
TH1
Fixing heater
H1
Composite power
supply PCB
Figure 6-103
CANON PC800s/900s REV.0 AUG. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
CHAPTER 6 FIXING SYSTEM
RLOFF*
Relay
+5V
drive signal
Timer
circuit
Fixing heater high

temperature

error detection circuit
HEAT_TRG
Fixing heater
drive signal
+
E0 detection signal
(Q101)
HEAT_ERR*
Fixing heater
error signal
Micro-
HEAT_OFF
processor
Fixing heater
OFF signal
HEAT_PWM
Fixing heater
duty signal
E0_DT
DC controller PCB
6-3