Circuit - Canon LBP-2000 Service Manual

3. Fixing heater safety circuit
To prevent malfunction of the fixing heater, the Printer monitors the readings of the main thermis-
tor and the sub thermistor at all times in relation to the ASIC and the high-temperature detection
circuit found on the DC controller PCB.
In the event of an error, the Printer causes the relay drive signal (RLYDRV) to go Low, thereby
turning off the fixing heater drive rely (RL1) found on the power supply PCB to cut the AC power to
the fixing heater (H101).
AC
DC
SW1
CB
NF
P1
Relay

circuit

RL1
Power supply PCB
F1
NF
Low-voltage
power supply PCB
Zero-cross circuit
Heater drive circuit
Fixing heater
activation
detection circuit
Heater
trigger circuit
Fixing
assembly
J915
-1 -1
-3 -3
Figure 2-2-6
+3.3V, +5V, +24V
J1201
-3 /ZEROXI
J1201
-5 RLYDRV
-4 /FSRDRV
-1 /HEATDT
GND
GND
TH2
GND
TH1
THCNCT -1
J913
TH101 TH101
THSW101 H101
CHAPTER 2
DC controller PCB
J105
CPU
-33
J105
-31
-32
ASIC
-35
J103
-6
High-temperature
detection circuit
-5
-4
High-temperature
detection circuit
-3
-2
Connector
detection
circuit
2 - 15