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CHAPTER 2
2 - 8
B. Fixing Control Circuit
1. Fixing Temperature Control
The fixing film unit of the printer contains a plate-shaped fixing heater to heat up the fixing film.
The fixing heater temperature is detected by the thermistor (TH701) on the fixing heater. When the temperature
rises, the resistance of TH701 drops and the voltage of the FIXING HEATER TEMPERATURE DETECTION signal
(FSRTH) decreases.
The CPU (IC201) on the engine controller PCB outputs the FIXING HEATER DRIVE signal (FSRD) based on the
FSRTH signal voltage to bring the fixing heater temperature to the specified value.
The fixing heater temperature is controlled by the following three modes:
1)
Initial temperature control: Increases to the normal target temperature after the pickup command is input to the
engine controller.
2)
Normal temperature control: Maintains the normal target temperature (about 190°C) during printing.
3)
Between-page temperature control: Controls at low temperature in order to prevent the temperature rise at the non-
feeding areas between pages on the fixing film.
Figure 2-2-4
2. Fixing Heater Safety Circuit
This circuit is installed on the engine controller PCB and always monitors the abnormal rise of the fixing temperature.
When the output voltage from the thermistor falls below about 0.67V (244°C) due to the elevation of the fixing
heater temperature, the output of the comparator (IC302) becomes “L” and the relay (RL101) goes OFF, cutting off
power to the fixing heater.
Fixing heater
(H701)
IC201
FSRTH
CPU
27
FSRD
38
Pressure roller
(TH701)
Thermistor
Fixing film unit
J102-2
J102-1
+3.3V
+3.3V
+24V
INL101
FU101
IC302
SSR101
/RLYD
Engine controller
PCB
Thermal fuse
(FU701)
35
+3.3V
+3.3V
RL101
+24V
J206-1
J206-2
Fixing heater safety circuit
Summary of Contents for Laser Shot LBP-1120
Page 4: ...PREFACE P 2 ...
Page 54: ...2 35 CHAPTER 2 Figure 2 6 1 4 1 3 2 J1 2 1 20 19 J2 IC2 IC1 IC3 IC4 ...
Page 107: ...APPENDIX A 2 ...