Fuser Control Circuit; Configuration - Toshiba e-STUDIO555 Service Manual

(9) Fuser roller front thermistor (THM1)
This thermistor cannot be used for the temperature control of the fuser roller. It detects a
temperature abnormality at the side area of the fuser roller where the paper does not pass
through.
(10) Fuser roller center thermostat (THMO1) and Fuser roller side thermostat (THMO2)
These thermostats cut off the power supply to the IH coil (IH-COIL) when the fuser roller
becomes abnormally hot as the result of a problem such as a thermistors (THM1, 2 and 3)
malfunction. The thermostats (THMO1 and 2) of this equipment are used to prevent abnormal
operation, and when any abnormality is detected, they must be replaced altogether with the other
damaged parts of the fuser unit.

13.4 Fuser Control Circuit

13.4.1

Configuration

A forcible power OFF circuit is embedded in this equipment. This circuit detects the overheating of the
fuser unit with the thermistors installed on it. When the surface temperature of either the fuser roller or
the pressure roller has exceeded the specified value, the circuit sends the relay ON signal in order to
shut off the power supply throughout the unit.
Side thermostat
Front thermistor
LGC board
Main CPU
+5VB
Temperature
control circuit
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Center thermostat
Center
thermistor
IH coil
Pressure roller thermistor
+5VSW
Power supply for photocoupler
Switching signal of power setting
ASIC IH status signal
IH coil energization permitting signal
Duty ratio changing signal
+5VSW
Fig. 13-2
13 - 3
Rear thermistor
Fuser roller
Pressure
roller
IH board
Coil output N
IH power source / drive circuit
Photocoupler
Control circuit
including CPU
AC line
DC line
Power cable
Noise
filter
Breaker
Switching regulator
+5VSW
Relay
L AC input
Fuse
e-STUDIO555/655/755/855
FUSER UNIT
13