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3: Operation
Colorwriter LSR 2000 Printer
Service Guide
3-103
While the power is turned on, the CPU (IC101) sets the off-
timer charge signal (/TCCHG) to be output to IC102 to “L” to
charge C106. After the power is turned off, C106 begins to
discharge.
When the power is turned ON again, the CPU detects the voltage
of C106 with the off-time sense signal (OFTMR), and sets the
TCCHG signal to “L” and charges C106 to the specified voltage.
Then the off-timer discharge signal (TCDIS) is set to “H” and
C106 is forcibly discharged to the voltage level measured at the time
of power-on, and the required time is measured. Based on this
measured time, the time during which the power was turned off is
calculated.
Figure 3-80
Off-timer circuit for fixing heater errors
•
Changing the thermistor sensitivity
The sensitivity of the thermistor differs between its high and low
temperature ranges. In order to increase the detection accuracy
in either range, the CPU in the DC controller uses the
thermistor sensitivity select signal (THSEL) to switch the
thermistor sensitivity between the mode in which the detection
accuracy is higher at low temperatures and that in which it is
higher at high temperatures. When the THSEL signal becomes
“H,” the thermistor is put in the low temperature detection
mode, and when “L,” in the high temperature detection mode.
DC controller PCB
CPU
/TCCHG
TCDIS
OFTMR
IC101
IC102
C106
5V
Off-timer circuit