Canon 1000 Service Manual page 223

2. Controlling the Fixing Roller Temperature
The upper fixing roller and the lower fixing roller are each heated by a fixing heater (H1: 700W, H2:
500W). The surface temperature of the upper fixing roller is monitored by the thermistor THM1, and the
surface temperature of the lower roller is monitored by the thermistor THM2.
If the surface temperature of the fixing roller is too high,
→ The resistance of the thermistor decreases.
→ The voltage of the fixing roller surface temperature detection signal (THM1, THM2) lowers.
Based on the voltage value, the CPU on the DC controller PCB uses the upper fixing heater drive signal
(UHON) and the lower fixing heater drive signal (LHON) to control the fixing heaters so that the surface
temperatures of the upper roller and the lower roller will be specific values.
• Upper/lower fixing roller (common)
Copying
During STBY
During pre-heat
Relay (RL1: NO)
Fixing lever
Power switch
Switch
(SW2: NC)
(SW5: NO)
+24V +24V
DC power supply
PCB (DCP1)
Upper fixing web
COPYRIGHT © 2001 CANON INC.
controlled to 180°C
controlled to 180°C
controlled to 180°C
Thermal switch
(TP1)
Upper fixing heater (H1)
Thermal switch (TP2)
Lower fixing heater (H2)
Lower fixing
web motor
M30
Lower fixing
heater triac (TR1)
Upper fixing thermistor (THM1)
H1
TP1
H2
TP2
Lower fixing thermistor (THM2)
Lower fixing roller surface temperature detection signal (THM2)
Lower fixing web
CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
REF.
AC driver
PCB
Upper fixing heater drive
signal (UHON)
Lower fixing heater drive signal
Current
(LHON)
detection
circuit
Triac error detection signal (TERR*)
Triac
short-circuit
Lower fixing web motor drive signal
detection
(M30D)
circuit
Upper fixing heater triac (TR2)
Upper fixing roller surface temperature detection signal (THM1)
Oil applying roller
Upper fixing roller
Lower fixing roller
Power to DC controller PCB
Power-off signal (PWOFF*)
Figure 3-647
3. OPERATION AND TIMING
When the fixing lever is shifted to
draw out the fixing assembly, the fix-
ing lever switch (SW5) cuts off
power to the fixing heater.
J2213H-10
J2213H-11
J2213H-9
J2213H-6
J2209A-9
J2209A-8
J2209A-10
J2209B-12
DC controller
PCB
3-179