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3: Operation
Colorwriter LSR 2000 Printer
Service Guide
3-99
Figure 3-78
Fixing temperature control
The fixing temperature is detected by the thermistor (TH) on the
fixing lower roller surface. As the surface temperature of the fixing
lower roller rises, the resistance value of TH lowers and the voltage
of the fixing temperature detect signal (THI) sent to the IC102 in
the DC controller and the safety circuit in the power supply unit
decreases.
When the DC controller outputs pulses as the fixing temperature
control enable signal (/FXENB) to the fixing heater safety circuit, it
controls the fixing temperature. The microcomputer (CPU) on the
DC controller controls the fixing heater drive signals (/FXUON and
/FXLON) so as to maintain the fixing temperature at the specified
value based on the voltage of the THI signal.
The fixing temperature varies depending on the image gloss modes.
This printer starts rising the fixing temperature while it is in the
WAIT period, and when it reaches the target value the printer enters
the STANDBY state.
Fixing heater
safety circuit
Fixing heater drive circuit
Power supply unit
RL
+24V
+5V
+5V
Mechanical
controller
PCB
DC controller PCB
/FXENB
/FXUON
/FXLON
IC101
THI
THSEL
TH
IC102
T2
Thermoswitch
Fixing
lower
roller
TP1
TP2
TH
Thermistor
Fixing upper
roller
CPU
Fixing unit