Toshiba 4560 Service Manual page 159

Surface temperature of heat roller: 200°C (Thermistor resistance value: about 3.2 kΩ)
Reference
1. A value other than 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 is never written in the C40 counter.
• At power ON, if the heater is not turned ON and the copier goes into the C40 CALL SERVICE, check
the C40 counter to see if it is 2 or more. If it is 2 or more, be sure to check the thermistor and heater
lamp, and after repair, reset the C40 counter (08-code 89) to 0 and then turn ON the power switch.
• If the value of the C40 counter is more than 10 (11, for example), it may be possible that BC-RAM or
the data in it have been destroyed by charger leaking, etc. In this case, check the guide bias, high-
voltage transformers, charger wires, etc. for any defects. Also, all the data inside BC-RAM need to be
rechecked.
2. Relationship between the output voltage and the fusing temperature.
• 200°C corresponds to approx. 2.5V and 0.078 V corresponds to approx. 40°C.
3. Relationship between heat roller surface temperature and thermistor-1 resistance.
Temperature
Less than 200°C
200°C
More than 200°C
Warm-up
°C
200
Heat roller
temperature
distribution
4. Temperature control at heat roller ends
During multicopying, the temperature at each end (no paper-contact area) of the heat roller normally tends
to rise higher that the controlled temperature of the paper-contact area. Therefore, the circuit is so devised
that if the temperature in the no paper-contact area rises to 245°C, the second thermistor detects this,
causing the heater to be turned OFF immediately regardless of the temperature in the paper-contact area.
Nov. 1997 © TOSHIBA
Thermistor resistance
More than 3.2 KΩ
3.2KΩ
Less than 3.2 KΩ
Standby (200°C)
Heater lamp
OFF ON
ON
Heater lamp state
ON
Maintains previous status
OFF
OFF ON OFF ON OFF
12 - 5
Copying (200°C)
ON
ON
4560/4570 FUSER