Fixing Control Circuit - Canon CLBR 460ps Service Manual

CHAPTER 2
B. Fixing Control Circuit
1. Outline
The fixing unit contains the upper and lower fixing rollers. Each roller has a halogen heater, a
thermoswitch, and a thermistor.
The fixing unit temperature is controlled by the D-CPU on the DC controller PCB. The fixing
heater is driven by the drive circuits (relay circuit, fixing heater drive circuit, fixing heater safe-
ty circuit, and fixing unit abnormality circuit) in the power supply unit.
The D-CPU detects whether the fixing unit is installed or not by checking FIXING UNIT
DETECTION signal (/FXSET). If the fixing unit is installed, /FXSET signal is "L" and D-CPU
assumes the fixing unit is installed in the printer. If it is not installed, /FXSET signal becomes
"H."
When it detects that the fixing unit is not installed, the D-CPU reports it to the video con-
troller.
Upper fixing roller
Thermoswitch
Fixing unit
Halogen
heater
Lower
Thermistor
fixing roller
2 - 14
Power supply unit
Relay
circuit
Fixing heater
drive circuit
Fixing heater
safety circuit
Fixing unit
abnormality
detection circuit
FIXING TEMPERATURE DETECTION signal (THRL, THRU)
FIXING UNIT TYPE DETECTION signal (FXTYP)
FIXING UNIT DETECTION signal (/FXSET)
Figure 2-2-10
FIXING HEATER DRIVE signals
(FXUON, FXLON, FXUONS, FXLONS)
FIXING TEMPERATURE signal (THI)
RELAY DRIVE signal (FXROF)
FIXING HEATER DRIVE ENABLE signal
(FXENB)
STATUS signal (FXSTS)
DC controller PCB
D-CPU
IC1001