Canon iR1200 Series Service Manual page 108

Chapter 3
transfer charging roller, and fixing film. Of these, the application of DC bias is controlled based on the readings of
the humidity around the machine (checked by the humidity sensor) of the primary charging roller, developing
cylinder, and transfer roller.
This mechanism of control is used to increase the bias level in a low humidity environment, thereby improving the
reproduction of images.
In a medium to high humidity environment, on the other hand, it serves to save on the level of toner consumption.
Drive Control Block
The drive control block controls the main motor, pickup solenoid, and fan.
Sensor Detection
The sensor condition of the printer block and the various pickup block are checked to monitor the drive mechanism
and to detect the presence/absence of the cartridge, collection of waste toner, presence/absence of the toner bottle,
and the relative humidity around the machine.
Image Processor PCB Interface block
The image processor PCB interface block sends the horizontal sync signal (BD0*) to the image processor PCB. It
also returns a state signal in response to a command signal (serial) from the image processor PCB, thereby
communicating the state of the printer block to the image processor PCB.
Laser Control Block
The laser control block controls the drive of the laser diode of the laser scanner unit according to the image signals
(VD0, VD0*) from the image processor PCB. Also, it controls the intensity of the laser diode (auto power control)
for each line of print data.
Horizontal Sync Signal Control
When the laser beam reaches the horizontal print start position, the laser beam detection signal (BDI*) from the laser
scanner unit is detected, and the horizontal sync signal (BD0*) is sent to the image processor PCB. Also, the
horizontal sync signal (BD*) is monitored for frequency of output.
Scanner Motor Control
The scanner motor is controlled so that the horizontal resolution of the print image is 600 dpi. Also, the laser beam
detection signal (BDI*) from the laser scanner unit is detected to monitor the rotation of the scanner motor.
Cartridge Detection Mechanism
In wait state, the CPU on the DC controller PCB measures the voltage level of the cartridge detection signal
(CRGSNS) a specific number of times to check the presence/absence of the cartridge when an AC bias is applied to
the primary charging roller.
Toner Level Detection Mechanism
While the machine is in wait state, the toner level detection signal (ADDTNR; based on the comparison of the
developing bias output and the antenna output inside the cartridge) occurring when the developing AC bias is
detected during normal rotation to monitor the toner level inside the cartridge.
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