Fixing Control Circuit; Controlling The Fixing Temperature - Canon CP660 Service Manual

CHAPTER 6 FIXING SYSTEM
II. FIXING CONTROL CIRCUIT
A.

Controlling the Fixing Temperature

Fixing assembly
Upper thermistor
(THU)
Upper
fixing roller
Upper thermal
switch
Lower
thermal switch
Lower
fixing roller
Lower thermistor
(THL)
The fixing temperature is monitored by the upper thermistor (THU) mounted on the
upper fixing roller and the lower thermistor (THL) mounted on the lower fixing roller.
When the surface temperature of the upper fixing roller and the lower fixing roller
increases, the resistance of THU and THL will decrease, gradually lowering the voltage
of the fixing temperature detection signal (FXTHU, FXTHL) sent to the M-CPU (IC202)
on the DC controller PCB.
The M-CPU on the DC controller PCB controls the fixing heater drive signal (FXUON,
FXLON) according to the voltage of the FXTHU and FXTHL signals and through the
expansion I/O (IC203) so that the fixing temperature remains a specific value.
6-2
COPYRIGHT © 1999 CANON INC.
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Power supply assembly
RL101
Fixing heater
drive circuit
+5V
Sub drive circuit
+5V
+5V
Sub driver circuit
+5V
FXTHL
FXTHU
Figure 6-201
CANON 660/2100 REV.0 FEB. 1999 PRINTED IN JAPAN (IMPRIME AU JAPON)
DC controller PCB
M-CPU
IC202
3130
BUS
Expansion
I/O
FXUON
21
FXUONS
22
FXLON
23
FXLONS
24
IC203